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West Texas Production Guide

  1. Growth Stages
  2. Hybrid Selection
  3. Planting
  4. Irrigation
  5. Fertilization
  6. Weed Control
  7. Insect Management
  8. Disease
  9. Harvesting
  10. References
  11. Appendices

Welcome to the United Sorghum Checkoff Program's West Texas Production Handbook. We have integrated research from various sources to produce an easy-to-use guide that can help farmers manage their crop more efficiently. Sorghum has tremendous potential to return a profit to your farm and the work of the Sorghum Checkoff will only improve that potential over time. As you manage your sorghum, keep these tips in mind:

By following a few guidelines, you'll be amazed at what this crop can do for you. We strive to help you make sorghum more profitable for your operation. But remember, every situation is a bit different so contact your local county extension office, land-grant university or other area sorghum farmers to help you get the most out of this water-sipping crop.


Produced and edited by:
United Sorghum Checkoff Program
Produced and Edited by:
Jeff Dahlberg Ph.D
USCP Research Director
Earl Roemer
USCP Research Committee Chair
Jeff Casten
USCP Research Committee
Gary Kilgore
USCP Research Committee
James Vorderstrasse
USCP Research Committee
Authored By:
Dr. Calvin Trostle
Texas ArgiLife Extension Service Agronomist
Dr. Brent Bean
Agronomist & Weed scientist,
Texas AgriLife Extension Service Agronomist
Dr. Roy Parker Texas AgriLife Extension Entomologist
Nicholas Kenny Texas AgriLife Irrigation Specialist
Dr. David Drake Texas AgriLife Agronomist
Dr. Todd Baughman Texas AgriLife Extension Agronomist & Weed Scientist
Dr. Tom Isakeit Texas AgriLife Extension Plant Pathologist
Dr. Pat Porter Texas AgriLife Extension Entomologist
Funded By:
United Sorghum Checkoff Program
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4201 N. Interstate 27,
Lubbock, TX 79403
806-687-8727
Sorghum Checkoff
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Growth Stages

It is important to understand the various developmental stages of sorghum since this understanding will assist in making irrigation and management decisions. The stages are based on key stages of sorghum growth that are used to describe sorghum from planting to maturity (Figure 1).

Another common scale that is used among sorghum researchers is a more simplified growth scale. GS1 would equate to stages 0-5 (vegetative stage) in this system. GS2 would represent from stages 5-10 (reproductive stage), and finally, GS3 would be from stage 10 to 11.5 (flowering stage).

Comprehensive grain sorghum growth and development guides are available, such as Kansas State How a Sorghum Plant Develops (currently being revised with your Sorghum Checkoff dollars) and Texas AgriLife How a Sorghum Plant Grows. Both of these guides provide pictures of different growth stages, graphs of cumulative nutrient uptake relative to growth stages (KSU), or approximate heat unit requirements (base temperature 50°F, maximum 100°F) for attaining a particular growth stage (Texas AgriLife). Cool or wet weather early in the season or an early planting date can significantly slow growth early in the season adding a week or even two weeks to the time to half bloom.

Growth Stage
Growth Stages

A summary of sorghum growth and develop-ment is outlined below including:

Growth StagesDescription and Management Tips
EmergenceColeoptile visible at soil surface. Coleoptile is the first leaf and is shorter than the later emerging leaves and has a rounded tip (leaf #1).
3-LeafCollar of 3rd leaf is visible (once a leaf 's collar forms the leaf no longer expands). This stage occurs ~10 days after emergence, depending on soil tempera- ture, moisture, planting depth, etc. Slow emergence may lead to more injury from pre-emerge herbicides. Insects: Corn earworm (whorlworm) and corn leaf aphids may infest the whorl and greenbugs may infest the leaves although not likely.
4-LeafCollar of 4th leaf is visible ~15 days after emergence.
5-LeafCollar of 5th leaf is visible ~20 days after emergence. May have lost 1st leaf (coleoptile) by this time. Plant ~8-10 inches tall. Cool soil and air temperatures coupled with sunny days to this point may trigger more tillering especially for stands less than 3 plants per row-foot.

Growing point differentiation (GPD)

This key growth stage and its importance are largely unrecognized and unappreciated by producers. The stage occures 30 to 35 days after emergence, perhaps a few days longer for fullseason hybrids, and sooner for early maturity hybrids. It generally corresponds with the 7 to8 leaf stage. Sorghum can tolerate significant stress from drought, hail, and even freezing temperatures prior to this stage; however, stress at this stage can significantly impact yield. Growing point is now above the soil surface, and the plant is 12 to 15 inches tall. The plant may have lost one to three leaves from the bottom of the plant and is entering a period of rapid growth.

The maximum potential number of spikelets and seeds per spikelet is a major component of maximum yield potential and are determined over a period of seven to 10 days.

Management: When applying midseason nitrogen (N) in one application, ideally the N should be available in the root zone by GPD, and irrigation, if available, is recommended to ensure that the growing point is not subject to moisture stress during GPD. Both good fertility and moisture enhance GPD and the subsequent yield potential. Dryland producers can enhance GPD by applying N early and ensuring that plant population is modest so that each plant has sufficient moisture for good spikelet and seed set.

A note about brace roots, sorghum standability, and possible cultivation: Brace roots are key to sorghum's standability. If it appears brace roots are having trouble entering the soil (likely more common for sorghum planted on top of beds where the soil is hotter and drier), then cultivation may be needed to move soil around the base of the plant. If this must be done, ensure that any pruning of the expanding root system is minimized after 30 days.

>Flag leaf visible

Boot

Management: Maximum water use occurs at this stage. Crop will respond very favorably to irrigation at this stage. Historically, this stage of growth is the optimum time to apply limited irrigation if crop is stressed. If you delay up to 20% of N past GPD, the final N should be applied within 60 days of planting or mid-boot, whichever comes first.
Insect: Corn leaf aphids begin to decrease. Greenbugs may be approaching an economic threshold.

Heading

Insects: Greenbugs may be at economic threshold levels.

Flowering

Insects: Greenbugs may continue as a proble, and mummies may be present. Begin checking for headworms. Sorghum midge potential should be evaluated.

Soft dough

Insect: Greenbugs may continue as a problem. Mummies should be increasing. Continue to check for headworms.

Hard dough

Insect: Greenbugs and headworms should be on the decline.

Black layer

Management: If harvest aids are used, label guidelines target application no sooner than black layer and grain moisture are less than 30%. Modified from 'Sorghum development and key growth stages.' Brent Bean, Extension agronomist, and Carl Patrick, Extension entomologist (retired), Texas AgriLife Extension Service, Amarillo.

Determining Leaf Stage Grain sorghum is numbered by the fully sized leaves that have a developed collar. If the seventh leaf (rounded coleoptile leaf is number one) has a collar, even though two to three other newer leaves may be visible, the plant is at leaf stage 7. Some herbicide labels cite leaf stage fortiming, usually a limitation of further herbicide applications. The lower leaves may be crumbling and even missing, but by counting back from the last fullyformed collar as leaves alternate from one side of the plant to the other, one can usually determine leaf stage, at least within one leaf.

Grain Sorghum Yield Components Sorghum yield is based on three factors: number of heads, head size, which includes the number of seed, and seed size and test weight. Although these factors may compensate for each other, for both irrigated and dryland production, the number of seeds per head is the greatest component of yield. This does not mean that having as many seeds as possible per acre gives the best yields. Rather, individual heads with fertility and adequate moisture (even if there are not a lot of heads), have the best yield potential for the environment.

Tillering is often left out of the discussion on yield potential, and its expression can significantly enhance yield in many instances, but tillering mayactually limit yield when drought stress is significant, diminishing the size and yield potential of the primary head. For this reason, reduced tillering hybrids have often performed better in dryland conditions.

Freeze Damage & Hail Injury Grain sorghum is occasionally hit by a late freeze that may damage leaves, but sorghum may face hail damage in the spring andearly summer. Early freeze injury often has little effect on sorghum as the growing point remains below the soil surface for several weeks after germination. Early hail-damaged sorghum has surprisingly little loss in yield potential provided the plants remain healthy. For example, a 50% leaf removal five weeks after germination (near growing point differentiation) reduces yield potential about 5%. Losses are substantially higher for older plants.

Additional grain sorghum production information resources for South and Rolling Plains,
Amarillo.tamu.edu
Lubbock.tamu.edu
Varitytesting.tamu.edu
Sorghum Producers
Sorghum Checkoff

For further information on these conditions consult Texas AgriLife Extension's "Assessing Hail and Freeze Damage to Field Corn and Sorghum," B-6014 (http://agrilifebookstore.org, or your county Extension office).


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Hybrid Selection

The initial criteria most producers make in choosing a grain sorghum hybrid in West Texas is maturity. Once an appropriate maturity range is decided upon, yield is paramount. Long maturity hybrids on dryland in this region will exhaust available moisture before maturity, and thus have reduced yields and even crop failure. This happens even in dry years for medium maturity hybrids. Extension does not recommend any sorghum hybrid maturity longer than medium maturity anywhere in West Texas. Just as important, grain sorghum production in the High Plains faces the task of reaching adequate maturity prior to the onset of cold nighttime temperatures, which are often more detrimental to a sorghum crop than when an actual killing frost occurs. This reverses the potential yield benefit of longer maturity hybrids.

Sources for Hybrid Yield Data

The Texas AgriLife Research Crop Testing Program conducts performance tests in West Texas and, when combined with additional sites begun in 2009 funded by United Sorghum Checkoff Program, trials are conducted at three irrigated and up to seven dryland test sites in West Texas. In most cases, companies enter the hybrids they think will perform best at each site. These independent tests collect a variety of data including days to half bloom, lodging, test weight, and yield. Trial results are published at http://varietytesting.tamu.edu, and producers may choose test sites and then review several years of results, looking for hybrids that have good consistent results over years and locations.

Producers should also consult individual companies for their recommendations. Company data is not considered independent in the manner that public tests are conducted; however, these tests can still be an excellent source of information, particularly when comparing yields among hybrids from the same company.

Additional Hybrid Selection Criteria

In addition to maturity and yield, the following hybrid parameters have a potentially major impact on sorghum performance in West Texas.

Tillering

Hybrids express differences in tillering. Early planting and low populations foster increased tillering. Although tillering enables sorghum hybrids to adapt to their environment, Extension recommends producers emphasize low-tillering hybrids for dryland cropping where drought stress is expected. This reduces the possibility that early favorable conditions lead to increased tillering, which leads to drought and heat increase.

Lodging

Standability is important for grain sorghum. Companies rate their own hybrids for lodging resistance, but significant lodging only occasionally shows up in Texas AgriLife hybrid trials. though it is often not even reported. Dryland sorghum producers should be concerned about lodging potential in drought conditions.

Lesser sorghum hybrid considerations include the following:


Stay-green

Grain sorghum hybrids maintain prolonged leaf and stalk integrity after flowering and are associated with post-flowering drought resistance. This trait can assist grain fill, take better advantage of late rains, and maintain stalk health later in the season (which may reduce lodging).

Greenbug tolerance

Many hybrids note resistance to Biotype C and E greenbugs, but these biotypes have been gone from West Texas for many years. Biotype I is now predominant, but only a few hybrids offer resistance. A small amount of Biotype K is also present. With the advent of numerous insecticide treatments, there is little emphasis placed on greenbug resistance.

Grain color and plant color

Red, bronze, cream, yellow, even white grain hybrids are marketed. Unless you are pursuing a specialty market (food sorghum, chicken feeding, etc.) where white grain is desired, there is little reason to choose a hybrid based on seed coat color. Yield considerations generally override any considerations of grain or plant color (purple, red, tan).

Panicle (head) type

Loose panicle hybrids (in contrast to tight, compact heads) that are fast growing and dry down rapidly may be preferred in areas with higher humidity and greater panicle feeding pressure from insects.

Plant Disease Resistance

Though some hybrids may have tolerance of certain diseases, this consideration is largely ignored by producers. If you have a particular disease that has affected your crop in many years, consult your Texas AgriLife Extension plant pathology experts or your seed dealer for possible suggested hybrids that may reduce disease injury potential.

Herbicide Tolerance

Although these technologies are now in the testing phase with seed companies and are not currently available, two major non-GMO herbicide tolerant traits will likely become important selection criteria once the traits are bred into competitively yielding commercial hybrids. These include ALS-herbicide or sulfonylurea tolerance (metsulfuron, nicosulfuron, rimsulfuron, e.g., Ally) and ACC-ase herbicide tolerance (quizalofop, e.g. Assure II).

Duration of Hybrid Bloom and Physiological Maturity

Hybrid ratings of the same hybrid may vary among companies. Days to half bloom and physiological maturity will depend greatly on weather since maturation is driven by heat accumulation. Texas High Plains Crop Testing results, mostly representing planting dates from late May to late June, demonstrate that medium maturity hybrids advance more quickly (often a week or more) to half bloom under dryland vs. irrigated production. This is just one example of the complexities of projecting the days to maturity as planting date and climate affect growth and development.

Guideline for late planting grain sorghum:
A typical sorghum planting date should allow the sorghum to reach black layer 1 to 2 weeks before your area's average killing frost (or since that data is harder to find, 2 to 3 weeks prior to the average first freeze). This allows for sorghum maturation without significant risk to yield or test weight if a frost/freeze occurs up to 10 days earlier than average.

Maturity ratings may vary by several days among companies. Knowing maturity range and days to half bloom are key to effective sorghum management strategies in terms of late planting dates or split-pivot irrigation scenarios (see the Agronomy section).

The following table provides the approximate range of days to half bloom and physiological maturity. This is in contrast to harvest maturity, which can be up to several weeks later depending on weather conditions and drying.

General company
maturity rating
(# of leaves)
Production
system
Expected
mid-range half
bloom
Expected
physiological
maturity
High Plains
half bloom
(2006-2009)
Days
Early (~`15)Dryland≤5880-9550-55
Medium-earlyDryland59-6390-10053-60
Medium (~17)Dryland64-6895-10556-64
Medium (~17)Irrigated64-68100-11065-70
Medium-longIrrigated69-73105-11568-74
Long (~19)Irrigated≥74110-12071-80

Cheap Seed

Because cost of seed when prorated per acre is relatively low for grain sorghum, particularly compared to just about all other crops, selecting seed based on price alone is a poor choice. Low-priced seed probably does not represent the best yield potential and proven genetics you would like to have for your farm. Shop hybrid maturity and yield potential, scour the yield trial data, narrow your choices, and find your best price for those hybrids on your short-list. Do not fret paying $2 per acre more in dryland to plant the hybrid of your choice.

The Bottom Line of Hybrid Selection

When extension staff surveys the means by which many producers choose their hybrids for planting grain sorghum, for irrigated and dryland West Texas producers could improve their yields 10% or more overnight by planting hybrids that have a track record of better performance. Depending on your production area, extension has compiled informal Picks' lists based on Texas AgriLife Research Crop Testing Program. Consult your county agent or regional specialist for hybrid suggestions.

Early maturity hybrids are frequently criticized for their lower yield potential and higher lodging potential. Yet these hybrids have their place when time is short. Some producers accept the increased risk of planting a medium-maturity hybrid in exchange for greater yield potential knowing that late planting dates in some years will encounter cold and frost and reduce yields. If a producer wishes to avoid early maturity hybrids, management for early planting is required.


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Planting

Site and seedbed selection

Sorghum often benefits by being planted low in the landscape profile. Most sorghum was planted with buster style planters into the 1980s. Buster planting patterns fit sorghum well because the plants were low in the landscape, brace roots were easily covered, and sorghum stood well. The possible drawbacks were the two-fold risk of a large rain either burying the sorghum or washing and concentrating atrazine in around the plant.

Today, most of the dryland sorghum in South Plains and much of the Rolling Plains and Concho Valley is planted on top of the bed. This is essentially the reverse of historical plantings. The listing of fields, particularly dryland, controls wind erosion and blowing soil. Furthermore, these raised beds give the producer the opportunity to knock off the top of the bed to get to planting moisture, and the raised position may also offer warmer soil temperatures; however, raised beds are likely to be detrimental for sorghum production. Sorghum brace roots and standability are compromised by planting on top of the bed:

Sorghum does not have to be planted as deeply as the traditional buster planters will place seed, and most planters today can do a modest job of placing sorghum below the average level of the field to still benefit in the manner of buster planting. The key for producers is they need to reconsider how they manage the field to take advantage of sorghum's potential when planted lower in the landscape. If this is done, then subsequent cotton planting is a good bet between the sorghum rows (still elevated) with the stalks providing wind protection.

Skip-Row Sorghum

Some fields are planted in a 2-inch/1-out skip-row pattern for cotton, which is thought to enhance yield in dry years by giving individual plants more rooting area to procure moisture. Small savings might be realized in crop insurance or the application of insecticides if using a ground rig.

A similar approach to grain sorghum production also views skip row planting as potentially favorable. However, research conducted by Texas AgriLife shows that long-term yields for grain sorghum are higher in solid planted fields vs. skip row provided that the per acre populations are not increased from the skip row pattern. For example, if you plant three sorghum seeds per foot on 40 inch rows (26,000 seeds per acre) in skip row, then a solid planted field should reduce to two seeds per foot and maintain the same 26,000 seed drop per acre. This spaces the plants out, provides more shading for weed suppression, and reduces potential moisture evaporation.

The combined results of two multi-year Rolling Plains studies found that solid planted grain sorghum yields averaged 3,195 lbs. per acre, but the skip-row pattern yielded 2,709 lbs. per acre, a yield decrease of 15 %. Similar results have been reported in the distant past for the South Plains, as well.

Is furrow diking still a good idea for dryland or irrigated sorghum?

Yes, in both cases, but if you have greatly reduced tillage, moved to no-till, or now maintain a residue cover as much as possible, then furrow diking may be difficult to implement and have reduced potential benefit. Research results from furrow diking in conventional tillage systems have long showed distinct yield advantages.

Dryland-Rolling Plains results found that in multi-year tests, conventionally tilled grain sorghum averaged 1,979 lbs. per acre, but with furrow dikes, the yields increased to 2,619 lbs. per acre (+32%). Other studies have shown similar benefits though not quite as much increase. Furrow dikes implemented long before planting provided the most benefit.

Irrigated-Furrow dikes are an essential component of alternate furrow LEPA irrigation using drag hoses with socks. Water is ponded in the diked furrow and remains in place wetting only 40 % of the soil surface, which allows deeper downward moisture percolation. Although dikes in sandy loam and loamy sands may not last the season or survive well with slopes greater than 2%, they are still beneficial as long as they last.

Although many producers have moved to less tillage and residue, it is more difficult to dike, because it adds to soil disturbance and may mean another pass over the field. Furthermore, the presence of stubble on the surface may diminish the expected benefit. If dikes can readily be installed, Extension recommends that producers implement this time-proven practice.

Seed Treatments

Many companies now treat all their seed with Concep III, which enables a producer to use the preferred method of grass control in grain sorghum, s-metolachlor (e.g., Dual Magnum) herbicides, This usually costs $10-15/bag.

Insecticides and fungicides-Gaucho and Poncho for insects may cost about $30/bag, but generics are inexpensive and may enable some greenbug control for cents per acre. Advanced combination insecticide/fungicide treatments like CruiserMaxx, etc. may double the cost of a bag of seed. Most seed is treated with a simple fungicide like metalaxyl as standard practice.

Due to low seeding rates used in dryland, even the cost of an expensive seed treatment, particularly for insecticide, is still a relatively small per-acre cost. A producer might actually be able to justify the cost better on dryland, where you may be reluctant to apply an insecticide versus irrigated, where if a problem develops, you are more willing to undertake control measures.

Having said this, the majority of Texas AgriLife studies in West Texas have not documented a consistent benefit among insecticide treatments. However, there is some peace of mind knowing that you may have some protection.

Planting Date

Grain sorghum's practical planting date throughout the region is three months wide in southern regions to about two months in the northwest South Plains. Possible outcomes are provided for what we can expect from sorghum if planted early or planted late.

Early-Season Planting
Planting early in the South Plains, particularly for dryland, is questionable unless ample deep soil moisture is available and soil temperatures are up. For dryland in the South Plains and Rolling Plains, if deep soil moisture in the spring is three inches or less, consider delaying planting until mid- or late June in hopes of storing deep moisture from May and June rains. This delay, however, is questionable for Concho Valley dryland sorghum and possibly the lower Rolling Plains due to sorghum midge potential on later planted fields. In general, yields in the South Plains and northern Rolling Plains are higher for later planting.

Rules for early grain sorghum planting:

  1. Target grain sorghum no earlier than a minimum of two weeksafter your last average spring freeze (see Table X).
  2. Delay Rule #1, especially in the South Plains, if the average soil temperature has not reached a five-day average of at least 60°F at a two inch depth although an ideal temperature for quick germination and establishment of grain sorghum is a 10-day average minimum of 62 to 65°F @ the four inch depth. If you plant early contact your seed dealer for any hybrids that may have better cool soil germination and vigor. You can view local soil temperatures at
  3. http://txhighplainset.tamu.edu
  4. http://www.mesonet.ttu.edu
  5. Your nearest National Weather Service regional website
  6. If 1 and 2 are satisfied, but there is a major cold front predicted in a few days then consider delaying planting.
LocationLast Avg Spring
Freeze
Earliest Planting Based
on Spring Freeze
First Avg Fall Freeze
Muleshoe4/175/110/21
Tulia4/144/2810/24
Floydada4/84/2210/30
Plains4/64/2010/29
Lubbock4/54/1911/1
Lamesa4/34/1711/5
Snyder 4/14/1511/7
Vernon4/24/1611/6
Haskell3/314/1411/8
Ballinger/San Angelo3/284/1211/11

Last Recommended Planting Dates-South Plains

In general, Extension suggests the following guidelines as criteria for the last recommended planting dates for sorghum maturity classes in the South Plains region. These dates reflect a combination of slowing heat unit accumulation in the fall, first freeze dates, elevation, etc. If your county is on the north and west edge of a planting date zone (e.g., for example the northwest portion of Parmer, Yoakum, Hockley Counties), you should take this into account and perhaps move planting forward a few days.

Texas
Counties
LongMed.
long
MediumMed.
early
Early
Parmer
Castro
Swisher
Briscoe
Bailey
Lamb
Cochran
6/106/186/256/307/5
Hale
Floyd
Hockley
Lubbock
Crosby
Yoakum
Terry
6/156/236/307/57/10
Lynn
Garza
Gaines
Dawson
Borden
Scurry
Andrews
Martin
Howard
Mitchell
6/206/287/57/107/15

Planting Dates and Late-Season Risk

Planting hybrids a week after its LRPD for your county will provide satisfactory results most years, but extension recommendations protect against unnecessary risk and complacency. In all cases, if you can plant a few days earlier than the LRPD, there is an occasional year that would make a nice difference.

Planting Date Summary for the Rolling Plains

(Summarized from Dr. Ed Clark, deceased)
Sorghum can be planted from early April through early July in the Rolling Plains. Based on 16 years of tests, it should be planted from April 1 through April 20 or from June 20 through around July 7. There was a significant advantage for late plantings versus early plantings in yield tests conducted at Chillicothe. Although mid-season plantings can sometimes produce higher yields than early plantings, they rarely, if ever, produce higher yields than late plantings at Chillicothe. It is generally recommended to plant in the late window for yield, but in practical terms, the subsequent late season sorghum harvest poses some problems:

This harvest issue may favor early planted sorghum for a farmer planting any number of acres. Early planting also fits better with your other spring cropping work. Sorghum is planted before cotton planting and wheat harvest, and likewise, sorghum harvest occurs before fall wheat planting and cotton harvest.

We recommend irrigated production. Follow Dr. Clark's suggestions on planting dates to avoid the worst of potentially damaging summer heat during peak water use, flowering, and early grain development.

Planting Date Summary for the Concho Valley

In contrast to the South Plains region where low spring stored soil moisture merits delaying planting until mid-June, high sorghum midge potential makes Concho Valley grain sorghum risky for fields which have not completed bloom around June 30. By this date research suggests about five percent midge damage increasing with delayed flowering. In this case we recommend that a medium maturity grain sorghum hybrid on dryland should be seeded by about April 20-25 (earlier for longer maturity hybrids under irrigation; earlier hybrid maturities planted by approximately May 5). Otherwise, similar to the Rolling Plains, sorghum likely should not be seeded again until late June to minimize the effect of summer heat on the crop. Any late plantings-primarily in the case of cotton hailout-will face substantial sorghum midge potential even if flowering occurs after early September.


Late planted sorghum in the Concho Valley otherwise should follow the LRPD guidelines for the lower South Plains in the table above

Restricting Sorghum Plantings to Avoid Bloom in July and August Heat

This is a particular consideration for dryland in the Rolling Plains and Concho Valley, but also for the South Plains. Temperatures consistently near 100°F or more may lead to sterility during flowering. The heat alone also makes for reduced efficiency of limited water. Planting a medium maturity hybrid by approximately April 20-25 in the Rolling Plains and Concho Valley should avoid significant flowering in July, whereas later planting near the end of June will reduce the potential for hot conditions that remain in August. This is also a consideration in the South Plains for any late planting, a rain and ideal planting conditions may move June planting forward to take advantage of the moisture. This is less of a concern for irrigated production in the South Plains where absolute heat is less of an issue if irrigation can be provided.

Consider these TIPS to ensure success:

Sorghum is the most common option after failed cotton in West Texas. Note these general guidelines:

Ensure that you adequately address cotton herbicide concerns-do not plant sorghum if Staple herbicide has been applied and consider the needed degree of buster planting to protect from trifluralin and other yellow injury. For further information on planting grain sorghum after cotton hail out, consult the annually updated "Alternative Crop Options after Failed Cotton & Late-Season Crop Planting for the Texas South Plains."

Planting: Seeds per Acre vs. Pounds per Acre

Texas AgriLife has long recommended that sorghum producers base planting on seeds per acre rather than pounds per acre. Grain sorghum seed can vary widely in seed size, often 12,000 to 18,000 seeds per pound, with 13,000 to 16,000 being most common. If you have to assume a seed number per pound, choose about 14,500 or 15,000. If you assume 14,500 seeds per pound, but the seed was actually 16,500, you have effectively increased the seeding rate 14 % (germination and emergence will probably be similar).

Calculating seeding rates can be done two ways.

Seeding Rate
43560ft2           12in              seeds
--------  X    -----------     X   ---------   =  seeds per acre
  acre       row spacing(in)      foot of row
Seeds per foot
target seeding rate        row spacing(in)        
  -----------        X       -----------    =  seeds per foot of row
   43560ft2                      12in.     

TIP: Texas AgriLife found that grain sorghum seeding rate varied by roughly 20% on individual rows of an air-vacuum planter. Even a new planter had significant differences in seed drop that needed correction. Before planting season, check your seed drop at both low and high rates to ensure you are planting your target seeding rate. Use the above table to help determine an approximate seed drop for each row over a pre-determined length such as 50 feet.

The accompanying table summarizes row spacing, seeds per acre, and the resulting seeds per foot. For air vacuum planters, your planter book lists both the seeds per acre and resulting seeds per foot in combination with the needed planter settings to achieve your targeted seed drop.

PlanterLinearTarget Seeding Rate per Acre for West Texas
RowRow
WidthFeet20,00026,00032,00040,00050,00060,00070,00080,000100,000
(inches)per acreSeeds per Foot of Row
4013,0681.52.02.43.13.84.65.46.17.7
3813,7561.51.92.32.93.64.45.15.87.3
3614,5201.41.82.22.83.44.14.85.56.9
3017,4241.11.51.82.32.93.44.04.65.7
2026,1360.81.01.21.51.92.32.73.13.8
1534,8480.60.70.91.11.41.72.02.32.9
1052,2720.40.50.60.81.01.11.31.51.9

Texas South Plains Seeding Rate General Guidelines

BENEFIT: Less is More! This principle has long guided grain sorghum seeding rates, especially for dryland. Lower seeding rates can produce higher yield when droughty conditions prevail and you're begging for a rain. Lower plant populations are suited to these drought conditions, preserving more moisture per individual plant, thus reducing the plant's stress level. Moisture and yield potential are conserved as less moisture is used to produce unneeded steams and leaves while the crop is better able to wait extra days until that next rain you are hoping for.

Dryland

For most dryland sorghum production in the Texas South Plains, when soil profile moisture is high (five or more inches of available soil moisture), a good target is 30,000-35,000 seeds per acre. A seed drop of 32,000 seed per acre is commonly cited for a wide range of production conditions because it is two and a half seeds per foot on a 40 inch row. Likewise 26,000 seeds per acre is commonly cited as well (two seeds per foot) when soil moisture is reduced. These seed drops have been shown to provide the best results under a wide range of conditions. This is a high enough seeding rate and resulting population to not limit yield, while, under extreme dry conditions, the sorghum will be less likely to burn up compared to a higher population.

If soil moisture is lower (2 to 3 inches), a seed drop of 24,000-28,000 per acre is advised. For any dryland situation with poor soil moisture, especially as plantings approach July 1, consider as little as 20,000 seeds per acre.

A common mistake often made by producers is applying an excessively high seeding rate. Keeping seeding rated down enables the crop to handle drought, retain modest yield potential, and still take advantage of a good year.

Irrigated

Producers in the South Plains who plan limited irrigation on grain sorghum frequently cite a target irrigation level of six to eight inches. In this scenario:

For full irrigation levels of 15 inches or more, cap target seeding rates at no more than 80,000 seeds per acre by early June, but by July (which requires a reduction in hybrid maturity) consider 100,000 seeds per acre for non-tillering hybrids and 80,000 to 90,000 seeds per acre for tillering hybrids. Several producers report, however, that even 60,000 seeds per acre is adequate to achieve grain sorghum yield potential of 10,000 lbs. per acre if planting long and medium-long maturity hybrids by June 1.

CAUTION: Low sorghum prices and high irrigation pumping costs cause some irrigated sorghum growers to cut back on irrigation after they plant a longer-season hybrid at a higher seeding rate. This hurts the crop and will diminish yield through no fault of the hybrid. If you are uncertain how much you might irrigate, be conservative with your seeding rate and cautious about long-season hybrids.

AvailableProjectedSuggestedProjected poten-Projected
stored soilirrigationseedingtial yield forN fertilizer
waterlevelrate targetplanning purposes#target^
(inches in top 3-4')(inches)(seeds/A)(lbs./A)(lbs. N/A)
020,0004008
<1428,0001,80036
837,0003,20064
1247,0004,60092
1657,0006,000120
024,0001,20024
2432,0002,60052
842,0004,00080
1252,0005,400108
1662,0006,800136
028,0002,00040
4437,0003,40068
847,0004,80096
1257,0006,200124
1667,0007,600152
032,0002,60052
≥6442,0004,00080
852,0005,400108
1262,0006,800136
1672,0008,200164

TIP: Wherever you farm in West Texas, if you are having doubts about whether you need to increase your seeding rate, do not. It is rare to see a South Plains sorghum field that is too thin for its production environment.

Rolling Plains Seeding Rate Guidelines

Although the higher rainfall in the northern Rolling Plains supports the idea of higher seeding rates, the excessive heat-the worst of which is avoided by April or late June/early July plantings-suggests we remain conservative in our recommendations. In lieu of any recent grain sorghum seeding rate trials with current hybrids, we suggest the following:

For April plantings with potentially lower establishment due to cool conditions.
For late June/early July plantings with moderate establishment.

These suggested seeding rate targets reduce the 1980s Rolling Plains recommendations by about half. If you have used the older higher seeding rates but have doubts about dropping the seeding rate this much, at least plant pass through the field at one or two lower seeding rates and watch the performance. For irrigated grain sorghum in the area, we suggest you start with the above then follow the relative recommendations for the South Plains based on projected irrigation level. These recommendations generally increase seeding rates by approximately 2,500 seeds per acre per inch of projected irrigation.

Concho Valley Seeding Rate Guidelines

This production area faces more pronounced heat than the South Plains but with one to two inches higher median rainfall during the growing season for any three-month period. Hence, heat and moisture balance each other out. We recommend that producers follow the above seeding rate guidelines for the South Plains. The southwest South Plains has sandier soil and less water holding capacity. As a result, there is a strong probability that grain sorghum seeding rates established populations well above the carrying capacity of sandy soil (and its lower inherent fertility), irrigation, and climate.

BENEFIT-Dryland Seeding Rate Summary:
Seeding to obtain a modest plant population is agronomically and economically less risky than seeding a higher plant population under droughty conditions.

Row Spacing

Historically, sorghum and cotton producers in the Southern Great Plains considered 40 inch row widths as standard which in fact traced back to animal power. With hybrid sorghum becoming commonplace new and more efficient planting patterns were tested by experiment stations and put into practice by creative and progressive producers across the sorghum belt. Using twin rows and narrow rows (30 inches or less) these top growers quickly added 10% or more to their yields. To the contrary increasing seeding rates rarely had an advantage and could often be deleterious,especially with limited moisture.

Most of the region is on 40 inch rows, with some on 30 inch rows especially in the northern South Plains. We recommend you do not make significant changes in seeding rate if on narrower rows. If using a drill follow these guidelines:

TIP: Older plate planters have difficulty achieving the low seeding rates needed for dryland production You may use an old worn out buster planter to plant deep in the landscape, but it is still necessary to try to get the seed drop reduced. Short of getting a new planter, possible fixes include:

TIP: Watch for crusting and especially baking conditions that brick moist soils, especially sandy loams and loamy sands prevent emergence or trap roots inside the hard seed furrow sidewall from the disk opener. Having a rotary hoe available to enable good sorghum emergence is much better than changing a seeding rate.


Back

Irrigation

Sorghum's water use characteristics make it an excellent crop for a wide range of irrigation scenarios in the Southern Great Plains. Sorghum yields reliably under dryland conditions in many semi-arid environments (greater than 15 inches annual precipitation) can be managed to reach significant yield potential under full irrigation. Because of sorghum's water use versatility, it fits well into many cropping and irrigation patterns, a valuable trait considering current trends of declining groundwater and pending regulatory water use limitations.

As with all grain crops, sorghum yield is most directly related to available water during the cropping season. The total available moisture (TAM) a sorghum crop uses is a combination of applied irrigation water, stored soil water and in-season precipitation. Individual TAM inputs can be managed to optimize the grain yield return per unit of water available.

Evapotranspiration

Identifying the amount of water to be applied to a crop is one of the most important management contributions that a sorghum producer can make. Evapotranspiration (ET) is the preferred method for measuring and estimating the total crop water use and the irrigation demand of a crop. ET is a comprehensive measure of crop water use in a production setting, because it measures water evaporated from the soil, plant surface, and plant's leaves during photosynthesis. Irrigation demand is the difference between the ET value and the water available from precipitation and/or the soil storage. ET values for sorghum can be obtained locally through Extension services and, in most agricultural regions, online through weather station networks such as TXhighplainset and Texaset.tamu.edu Also, the northern Rolling Plains may use nearby weather information in Oklahoma at AgWeather

Over the 10-year period from 2000 to 2009, the peak daily grain sorghum ET was approximately 0.33 inches at the USDA Conservation and Production Research Laboratory at Bushland, Texas. This value will slowly increase the further you move south into the South Plains, Rolling Plains, and Concho Valley. For May-June plantings, water use commences at planting, peaks during late July and early August, and continues through harvest. Early or late planted sorghum can avoid these peak ET times and shift the sorghum's peak water use away from the hottest time of year. Under fully irrigated conditions, seasonal sorghum ET is approximately 27 inches.

Figure 1:10-year Average sorghum Daily ET at Bushland, TX (10 miles west of Amarillo).
Evapotranspiration

Irrigation

In the Southern Great Plains, an irrigated sorghum crop will receive approximately half of its water through irrigation. Irrigation water is the one controllable crop water source and, when managed properly, can optimize the quality and yield returns of all crop inputs, including soil water and in-season precipitation.

Pre-Irrigation

Irrigation immediately following planting is generally recommended for sorghum rather than pre-irrigation. Research has shown that up to 60% of water applied as pre-irrigation is not available in the soil at the time of planting, especially close to the soil surface near sown seeds. In dry conditions, sorghum establishment nearly always improves with a inch irrigation applied at planting.

Growth Stages & Optimum Irrigation Timing

Following plant establishment, key water use periods occur 30 to 35 days after emergence during the formation of the seed head, during the boot stage, and during early grain fill. Sorghum reaches its maximum daily water use requirement during heading and early grain fill. The most significant sorghum yield response from irrigation occurs during sorghum's rapid growth stage, or the 40- to 50-day period encompassing the 4-leaf stage through the boot stage. The more visible process of sorghum seed set occurs at flowering after the end of this rapid growth stage based primarily on climatic factors and, to some extent, nutrient and water availability as the sorghum plant is transitioning from reproductive growth to grain filling. The unseen process of defining potential seed number, however, is determined many weeks earlier than seed set, usually about 5-6 weeks after germination when the growing point differentiates. The sorghum plant is also establishing leaf mass and area throughout the rapid growth stage in preparation for nutrient transfer that will occur during grain fill. A producer targeting maximum yield should be prepared to irrigate 6 to 8 inches during this period, depending on seasonal rainfall.

In deficit or low capacity irrigation scenarios, which are likely in the South Plains, Rolling Plains, and Concho Valley, preference should be given to irrigation applications just prior to the boot stage. Stresses caused by lack of water prior to and during the boot stage will define lower yield capacity that cannot be overcome with adequate or excess water later in the growing season.

The reproductive stage, a 40-day period following the boot stage, is critical in actually harvesting the potential yield established during the rapid growth stage. A producer targeting maximum yield should be prepared to irrigate 5 to 6 inches during this period. Adequate water should be available completely through the soft dough stage. Since sorghum water consumption declines as the plant reaches physiological maturity, preference should be given to earlier water application during this growth stage.

Grain Sorghum Water/Irrigation Requirements in Relation to Heat Unit Accumulation

When a deficit irrigation strategy is implemented, either due to limited water or as part of a producer's overall agronomic approach, irrigation water should be applied during the priority periods of rapid growth and reproduction. Smaller, timely applications are recommended for sorghum under deficit irrigation to encourage uniform growth conditions. As little as 6 inches of timely irrigation water on sorghum in the Southern Great Plains has shown to greatly increase yields and profitability.

Sorghum ET and recommended Irrigation at typical dates and growth stages.
Approx. DateCrop StageDays after Planting Heat Unitsafter PlantingET per Stage (Inches)Irrigation Per Stage (Inches)
1-JunSeeded001.11.0
9-JunEmerged82002.20.0
Rapid Growth Stage
21-Jun3 Leaf205000.61.0
24-Jun4 Leaf235750.80.0
28-Jun5 Leaf276601.62.0
6-JulGPD359253.33.0
20-JulFlag491,2902.82.0
30-JulBoot591,5501.81.0
Reproductive Stage
7-AugHeading671,7101.41.0
10-AugFlower701,8503.52.0
25-AugSoft Dough852,2102.72.0
7-SepHard Dough982,5101.8None
17-SepBlack Layer1082,7003.9None
15-OctGrain Harvest1363,100None

Water and Grain Sorghum Productivity

These two considerations involving water affect the potential yield that can be produced in a particular field given its soil, water, and climatic conditions:

  1. The amount of water needed for initial grain production. An approximate amount, a minimum of water-stored soil moisture, rainfall, or irrigation-is required for a grain sorghum crop to achieve initial grain production. For a low plant population field (likely <20,000 plants per acre, and furthermore a crop with few tillers) with a hybrid maturity of medium or less, crop water use may be as little as 5 inches of equivalent moisture. In contrast, a typical field in the South Plains planted for modest irrigation levels resulting in 40,000 to 50,000 plants per acre might require 7 to 8 inches of moisture before initial grain yield, and plant populations of 70,000 or more plants per acre might require as much as 10 inches of moisture before any significant yield is produced. This readily demonstrates why we emphasize modest seed drop in West Texas. When population is modest, less water is wasted on unneeded stems and leaves, but instead, can go toward making grain.
  2. The amount of sorghum grain yield per one incremental inch of water. Texas AgriLife Research and Texas Tech University data from the South Plains suggests that once the above threshold is met that each incremental inch of rainfall or irrigation is generally worth about 350 to 425 lbs. of grain yield. In hot, dry weather, expect the lower end of the range. As one moves toward the Texas Panhandle, we more likely expect the incremental yield to surpass 425 lbs. per acre. In the South Plains, some field tests on drip irrigation suggest incremental yields over 500 lbs. per acre per inch.

Ceasing Irrigation

Irrigation cut-out will most likely occur no later than hard dough stage. The sorghum seed will proceed through grain development from watery ripe to milky ripe to mealy ripe then begins to firm at soft dough on to hard dough. If good soil moisture is still available to the plant (at least 2 inches) terminate irrigation as sorghum moves past soft dough. It is not reliable to base irrigation termination on grain color. A final irrigation may be applied during hard dough only if soil moisture storage is completely depleted or drought conditions are severe enough to hinder stalk quality at harvest.

When examining the head for seed maturation, be sure to check many heads and the whole head. Some difference in maturity will be observed on each head as seeds at the tip could easily be seven days older than seeds at the bottom of the head or primary tillers.

Can I use the color of the grain sorghum head to determine irrigation termination?

Not reliably. You still need to hand-check the heads and seeds. Furthermore, turnrow observations of sorghum fields do not tell you how much soil moisture is still available. Head coloration varies depending on hybrid. Some red sorghums are not as red as others, and many hybrids have grain color of orange, yellow, crème and white that never do give the sharp impression of distinct color change.

In general, when the seed in the head begins to take on an orange or reddish tint, the seed is most likely at the milk stage. As a field turns color, do not base the decision to irrigate again on the changing sorghum heads. Check for available soil moisture and the stage of seed maturity. Extension staff notes that little to no increase in yield is likely after a general red color appears over the field but an additional late season irrigation might help maintain stalk quality for harvest.

Does Sprinkler Irrigation Diminish Seed Set on Blooming Grain Sorghum?

This question occurs among producers in West Texas. When a grain sorghum producer looks at the blasting effect of sprinkler irrigation under pressure and it is possibly knocking anthers off the head, there is concern that sprinkler irrigation on blooming sorghum could be detrimental. Texas AgriLife sorghum breeders and physiologists do not believe this is likely. Sorghum is largely self pollinated, which means that by the time you see the anther protruding from the floret the seed embryo is likely already fertilized. Farmers may be inclined to associate possible blanking in the heads with the timing of sprinkler irrigation, and admittedly, there may not appear to be any other plausible explanation if the weather conditions at bloom were not hot and dry. If producers remain worried about this issue, consider using LEPA irrigation with drag hoses and take advantage of the increase in irrigation water use efficiency for sorghum.

Irrigation System Efficiency

Irrigation efficiency is defined as the percentage of water delivered to the field that is beneficially utilized by the crop. Factors such as wind drift, leaching, evaporation, and run-off all lead to decreased irrigation efficiency. To determine the depth of water to be applied during an irrigation event, irrigation system efficiency should be accounted for by using the following equation:

                   Irr. Demand
Irr. Depth   =    -------------
                  Irr. System Eff.

With rising energy and water costs and declining water levels, wasted or underutilized water has the potential to directly impact sorghum profitability. To maximize the return on water and pumping cost inputs, it is recommended that irrigated producers make use of high efficiency irrigation systems such as subsurface drip (SDI) and low elevation center pivot sprinklers (LESA and LEPA) wherever feasible. To reach sorghum yield potential, an SDI, LESA, or LEPA irrigation system should be designed or nozzled at four gallons per minute per acre (GPM/acre) or higher. At lower system capacities, irrigation should begin earlier in each crop stage to ensure that soil moisture reserves are present to buffer sorghum water needs during the rapid growth and reproductive stages.

Depth of irrigation water applied at various irrigation system capacities.

GPM/ AcreDailyWeekly30 Days45 Days60 Days90 Days
Inches Applied
2.00.110.743.24.86.49.5
2.50.130.934.06.08.011.9
3.00.161.114.87.29.514.3
3.50.191.305.68.411.116.7
4.00.211.486.49.512.719.1
4.50.241.677.210.714.321.5
5.00.271.868.011.915.923.9
6.00.322.239.514.319.128.6
7.00.372.6011.116.722.333.4
8.00.422.9712.719.125.538.2
9.00.483.3414.321.528.643.0
10.00.533.7115.923.931.847.7

Efficiencies for agricultural irrigation systemsunder optimal field conditions.

Irrigation MethodPotential Application Efficiency
Surface50 - 80%
Common Flood50%
Land Leveled60%
Row65%
Alternate Furrow70%
Surge80%
Center Pivot70-92%
LESA85%
LEPA90%
Drag Hoses92%
Drip90-95%
Above Ground92%
Subsurface (SDI)95%

Irrigation Costs

In most sorghum regions, the most significant portion of irrigation cost is related to the energy consumed during pumping. Historically, natural gas and electric pumping plants offer the lowest cost per unit of water pumped, typically by a significant margin. Where natural gas pipelines or electrical service are not available, diesel is the lowest cost pumping option. Although gasoline and propane engines offer the same thermal efficiency as the natural gas engines, they are traditionally more expensive to operate due to the higher cost of fuel on an energy basis (BTU) and should be avoided except in very specific situations. Regardless of energy source, the following operational practices universally promote lower irrigation water costs:

Pump Cost for One Inch of Water

Unfortunately, most producers do not have an approximate answer to this question. This is particularly important when grain prices are low. If grain sorghum is $5 per cwt, and you figure your production at 400 lbs. per acre-inch, the gross return is $20 per acre-inch. Grain sorghum has both lower input costs per unit of return and better suitability to limited, timely irrigation.

Soil Water

In addition to providing necessary structure and nutrients to crops, soil serves as a holding reserve for water. Each soil has a certain holding capacity for plant available water (PAW), or water that a plant can successfully extract from the soil. Coarse soils with rapid infiltration rates hold a minimal amount of water within the plant root zone, but nearly all of the water is available for plant use. Conversely, fine textured soils hold a significant amount of water within the root zone, but a lesser percentage of the stored water is available for plant use.

Available soil moisture by soil texture class. Soils with higher clay content hold a great amount of total water, but increasingly it is less available to plants.
Soil TextureInches of Water (3' Root Zone)
Coarse Sand1.50
Fine Sand2.75
Loamy Sand3.50
Sandy Loam4.00
Fine Sandy Loam5.25
Silt Loam6.75
Silty Clay Loam5.75
Silty Clay5.00
Clay4.00

Soil moisture is generally considered most valuable to a sorghum crop when it has been captured prior to planting. Field preparation following the crop previous to sorghum is vitally important in capturing off-season precipitation in preparation for the coming sorghum crop. Low impact, minimum tillage operations are recommended to minimize evaporation and surface run-off while maximizing soil water infiltration and sub-surface organic matter to assist in water holding capacity.

Capturing off-season precipitation through soil storage is a recommended agronomical strategy that helps early season plant growth, buffers drought stresses throughout the season, and saves costs associated with pumping and delivering irrigation water. Ideally, water from soil storage should be exhausted at the end of the season during grain drying.

In-Season Precipitation

Depending on location and weather patterns, in-season precipitation is typically a part of the water budget of irrigated sorghum, despite seasonal variations in quantity and timing. Although difficult to manage, the return on in-season precipitation can be optimized. In areas where in-season precipitation is probable, a portion of soil water capacity should be maintained to provide sufficient room to capture and contain water from small to moderate rainfall events. In addition to increased seasonal water and reduced pumping costs from holding and utilizing in-season precipitation, run-off and erosion are reduced, leaching effectiveness is increased, and in many cases, nitrogen is supplemented.

In regards to irrigation scheduling, in-season precipitation should be evaluated on an "effective rainfall" basis. Research has shown only a portion of the water received during a precipitation event will actually become useful to the sorghum crop. To avoid overestimating water received from precipitation, a producer should only credit precipitation events greater than 0.30 inch, or the peak daily sorghum ET. Consideration should be given to forgoing or delaying irrigation only if a precipitation event is larger than the scheduled irrigation depth or exceeds soil holding capacity. The benefit of in-season precipitation can often be redeemed at the end of growing season by terminating irrigation earlier with sufficient water stored in the soil profile.

Summary of "Top Tips" for Grain Sorghum Irrigation

Sorghum Production Scenarios with Shared Irrigation on Split Pivots

In the past several years as irrigation capacities have continued their decline, numerous South Plains farmers have become more interested in scenarios where grain sorghum shares pivot irrigation space and water with another crop, particularly cotton. By managing the planting date of grain sorghum as well as choosing the sorghum hybrid maturity producers can minimize, if not eliminate, the overlap of significant water requirements for either crop ultimately reducing the number of acres to be irrigated at one time.

Which crop has main emphasis? That is assumed to be cotton (unless you signed a pounds contract for grain) then the decision becomes regarding cotton (or corn or peanuts) to give it all you can in contrast to trying to grow a full circle of crop that needs irrigation all at once. Grain sorghum's positive role in this scenario with cotton, however, is growing a crop that can fit to lower input conditions while also providing all-important rotational advantages.

The dual crop/dual planting date scenarios for split pivot irrigation in different regions of the South Plains include several possibilities with grain sorghum:

Planting Dates and Physiological Growth

A particular planting date for either cotton or grain sorghum does not mean cotton cut-out or sorghum flowering will occur on a certain day or even within a few days. Heat and its accumulation drives physiological growth. For grain sorghum, cotton, or other crops these differences include:

Split Pivot Scenarios-Grain Sorghum & Cotton

Counties-Scurry/Howard/Dawson/Gaines/Lynn/Terry
Early cotton, late grain sorghum

Result-Early cotton, late grain sorghum: Early cotton is up to three weeks past cut out prior to sorghum flowering (~Sept. 5), and now has much lower moisture requirement. Sorghum enters peak water demand ~7 days after cotton cut out when cotton irrigation is greatly reduced. Sorghum maturity is near October 10-15 with added potential of Sept. rainfall assisting yield. Concentrate water to cotton early with one to two possible key waterings to sorghum (growing point differentiation, early boot) prior to flowering.

Early grain sorghum, delayed cotton

Counties-Hockley/Lubbock/Crosby/Floyd/Hale

Early cotton, late grain sorghum

Result-Early cotton, late grain sorghum: Cotton is up to two weeks past cut out and higher moisture requirement prior to sorghum flowering. Sorghum enters peak water demand about the time of cotton cut out but before end of cotton irrigation. Sorghum maturity is near October 5-10 with the potential of September rainfall assisting yield. Concentrate water to cotton early with one to two possible key waterings to sorghum (growing point differentiation, early boot) prior to flowering.

Early grain sorghum, delayed cotton

Parmer/Castro/Bailey/Lamb/Cochran
May 10 cotton, late grain sorghum-this scenario is harder to separate irrigation of the two crops than to the south and east

Result-May 10 cotton, late grain sorghum: Cotton is about 1 week past cut out before sorghum flowering (around Sept. 1) and cut-out is about 0 to 7 days after peak sorghum water demand begins. Sorghum maturity near October 5 to 10 (this is close to early frosts) with potential of September rainfall assisting yield. Concentrate water to cotton early with 1 to 2 possible key waterings to sorghum (growing point differentiation, early boot) prior to flowering.

Early grain sorghum, May 10 cotton (can't advocated delaying cotton in the northwest South Plains)

Parmer/Castro/Bailey/Lamb
Early corn, late grain sorghum

Result-early corn, late grain sorghum: The half circle of corn is essentially fully irrigated, but for grain sorghum one watering to establish stand (late June). Before corn is finished, a possible second water ~4 weeks after planting in advance of growing point differentiation (increase spikelet & seeds per spikelet set). Grain sorghum maturity October 5-10 (this is close to early freezes) with potential of Sept. rainfall assisting yield. Modest population for grain sorghum to better prepare the crop to wait until after corn irrigation is completed.

Gaines/Terry/Yoakum
Runner peanuts (late April-May 1), early grain sorghum

Result: Sorghum is at or past flowering (around June 30) before peanut enters peak water demand. Concentrate water to peanut after July 1 with only 1 possible additional watering to sorghum, especially if soil water is banked. Sorghum maturity by about August 5.


Back

Fertilization

Grain sorghum production in West Texas ranges from low input rain-fed production to high-input full irrigation. Hence soil nutrient status is highly variable. Crop rotation and the frequent producer practice to fertilize only when a certain crop is in rotation means that residual fertility may be more important. Likewise, tillage and fertilizer placement practices will affect the nutrient use efficiency of grain sorghum.

Soil Testing

Many producers do not realize the extent of research and testing that is behind the process of analyzing soil samples for nutrients and the subsequent recommendations they generate. A realistic goal for many producers is to take a soil sample every three years.

Different Philosophies of Soil Test Recommendations

There are two common approaches to soil fertility recommendations for the same crop and production conditions. Each has its own merits and can be used successfully although these approaches can generate recommendations that seemingly are at odds with each other.

  1. Provide what the crop needs for current-year production. Based on your yield goal, your current soil nutrient status and that nutrient's projected availability to your crop, add the level of nutrients needed to fertilize your crop for this year. This approach in terms of out-of-pocket expenses, costs less and also may reduce potential nutrient losses due to leaching or other means. This is most likely the approach that state labs take.
  2. Build-and-maintain soil nutrient status. Most likely this means fertilizing to maintain a higher long-term residual level of nutrients in the soil. Nutrient levels may be in excess of the crop's requirement, but also not at a luxury or wasteful level that squanders money. This approach, provided there are ample nutrients available, may guard against unexpected limitations in nutrient availability or higher crop demand if yields are higher than expected. This philosophy is more likely to be found among private labs.

TIP: If you have a fertilizer dealer, crop consultant or other third party collect and submit soil samples for you, be sure to obtain a sample of the soil test report itself. Understand what the report is saying, and keep it in your records for the farm or field for up to 15 years so that you may track changes in the soil over time.

Why are there differences between soil sample report recommendations?

Different methods of soil sample nutrient extraction and analysis

Have you ever submitted samples of the same soil to two different labs? You might have found different recommendations. Although, labs within a given region of the country tend to have uniform testing procedures, this is not always the case. For example, there are different tests for soil P (soil pH may dictate which one should be used). Labs may use a different extractant for the soil, or once they have obtained the extract for nutrient analysis may use a different method of measuring the nutrient in the extract which could be affected by other constituents in the sample. These differences lead to different test values of nutrients measured in your soil.

Different fertilizer recommendations

As noted above there are differences in the philosophy of soil testing. Provided the soil test value for a particular nutrient is the same, then build-and-maintain would likely have a higher fertilizer recommendation. This philosophy may be the normal approach to recommendations by a test lab. Apart from differences in philosophy the calibration curves plotting nutrient requirement for a unit of yield are not necessarily the same. One lab may recommend 2 lbs. of N per hundred weight of sorghum yield goal, whereas another recommends 2.5. Or, a particular lab's recommendations might include additions or deductions to their calculation that are not factored in by a different lab.

TIP: When your soil test lab, fertilizer dealer, crop consultant or other third party provides fertilizer recommendations, do the following:

Texas A&M University Soil Testing Lab

The College Station lab provides complete fee-based services for soil, plant tissue and water analyses. Texas AgriLife testing across Texas on grain sorghum (as well as other crops) forms the basis for soil test recommendations for samples. For more information on services, submittal forms (including the Soil Profile N form discussed below) and how to collect and submit representative samples visit http://soiltesting.tamu.edu/.

Yield
per Acre
Nutrient Uptake (cwt.)Nutrient Removal (cwt.)
(lbs.)NP2O5K2ONP2O5K2O
2,00060215530158
4,00012042110603016
6,00018063165904524
8,000240842201206032
10,0003001052751507540
A key soil test procedure that Texas A&M uses, which is now a common standard across many labs, is the Mehlich III extractant. Soil test numbers (but not necessarily the recommendations) using this method compared to other procedures will vary, especially for P. The Mehlich III test is better suited for the varied soil types across Texas. The test has been key to improving P recommendations for the state.

TIP: When choosing a soil test lab, inquire if the lab is accredited by a state agency or certification board, a participant in the North American Proficiency Testing program, or some other testing standard guidelines. This ensures that the lab meets recognized standards and practices that are foundational for providing you with good test values and recommendations.

TIP: If you already use or consider using a soil test lab that is far removed from the region or state where your soil was sampled, call them to ensure they can provide you with results based on suitable test procedures and recommendations for your soil type and your crop (especially if your crop is not grown in that state).

Sorghum Nutrient Requirements

"You Can't Get Something from Nothing for Very Long"

Occasionally in Texas, particularly where rainfall is lower (especially less than20 inches), farmers may fertilize grain sorghum minimally or not at all, even for nitrogen. To some extent this 'just-get-by' attitude resulted from low grain sorghum prices, but it may also reflect poor attitudes and the lack of success on the part of many producers due to too-high seeding rates and little thought in hybrid selection. Sorghum indeed responds to nitrogen.

Nitrogen(N) is by far the most important nutrient for sorghum to maximize production. For maximum yields relative to the available water, N should not be lacking or grain development will be reduced. The long-standing general N nutrient requirement for Texas grain sorghum is:

N requirement:

2 lbs. actual N (soil or fertilizer) per acre per 100 lbs. of yield goal

Thus a 5,000-pound grain yield would need about 100 lbs. of N per acre. In Texas this has often been presented-erroneously-to producers as the amount of N fertilizer to add without acknowledging available soil N. However, the Texas A&M University soil test lab recommends using the above rule but correctly deduct nitrate-N from a soil test in the top 6 inches as noted below.

Texas A&M Recommendation:

(Fertilize 2 lbs. actual N per acre per 100 lbs. of yield goal) - (soil N at 0-6 inches)

Hence for the same yield goal noted above, but with a soil test report showing 9 ppm NO3-N for a 6-inch deep sample (which is about2 million lbs. of soil), the calculated N fertilizer addition is:

Fertilizer N to add:
(2 lbs. N/acre) X (50 cwts./A yield goal) - (2 X 9 ppm) = 82 lbs. N per acre

This N recommendation, particularly when the soil N is deducted, is more conservative (lower) that what is normally generated in other states such as Kansas or Oklahoma which each use a more complicated formula or include other adjustments, but AgriLife Extension recommends Texas producers maintain the simple rule of thumb above. When soil test information is not available this rule will help producers at a minimum to be in the range of meeting the sorghum's N requirement for good yield.

Soil Profile N Test from Texas A&M-Sampling and Crediting Soil N Below 6 inches

Ideally soil testing for N would use a 24 inches depth sample (in contrast to 6 inches for P, which is largely in the surface, or the standard depth noted above in most soil tests). Research in several areas of Texas across several crops is frequently showing a significant amount of N below the surface 0-6 inches. One way to systematically assess for this potential deeper soil N is the use of the Soil Profile N Test from Texas A&M. In this testing protocol a producer collects and submits a paired soil sample, 0-6 inches for N, P, K, and other nutrients, and preferably a 6-24 inches for nitrate N analysis only. This test potentially captures extra N deeper in the soil. If soil test N is available for depths below 6 inches then credit that 100% N toward your N requirement thus reducing fertilizer N applications and their cost.

(Fertilize 2 lbs. actual N per acre per 100 lbs. of yield goal) - (PROFILE N at 0-24 inches)

The Texas A&M University Soil Testing lab has a special form for these paired samples at http://soiltesting.tamu.edu/files/profilesoil.pdf On the form you record the depth of soil collected below 6". In addition, crop rotations may affect residual N and often credits are assigned to soil N if the previous crop was a legume.

Nitrogen Applications after Sorghum Emergence

Side-dress N applications with knives or coulters should be made about 20-25 days after germination (4 to 5 leaf stage) to ensure good N fertility in advance of initial growing point differentiation (30-35 days after germination) while minimizing any root pruning. Later applications may excessively prune feeder roots and miss the potential benefits to GPD.

Under center pivot irrigation, N fertilizer may be applied several times during the early part of the growing season. Due to the convenience of pivot-applying N especially in the High Plains, up to 20% of N might be held back until after GPD, but Extension recommends that the final N be applied no later than boot stage which is about 60 days after germination for a full-season hybrid and no later than about 50 days for a medium maturity hybrid. About 70% of the needed N for a grain sorghum crop is already in the plant at boot stage.

Because N is relatively mobile in the soil, fertilizer placement is not as critical for N as it is for most other nutrients. Nitrate-nitrogen, NO3-N, the form most available to grain sorghum, will move with water and can be readily brought into contact with crop roots for quick absorption.

Ammonium-nitrogen (NH4, also available to plants) is positively charged and is held by negatively-charged clay and organic matter particles in the soil until converted by soil bacterial action into the nitrate form. The conversion from ammonium to NO3-N in the soil-nitrification-is most likely to occur when fields are arable. When fields are water-logged, nitrate can be converted to nitrogen gas-denitrification-and lost from the soil by volatilization.

Guidelines for Surface Applied N Fertilizer

Ammonium-based fertilizers are more susceptible to volatilization losses when applied to the soil surface if no rain or irrigation occurs. Three key factors reduce the effectiveness of the surface-applied N leading to volatilization losses, particularly when acting together:

Extension always recommends where possible that producers using broadcast N fertilizer apply to dry soil. Furthermore, applying N prior to a predicted rain or scheduled irrigation is particularly advantageous.

Starter Fertilizer and Salt Injury Potential-Suggestions for Grain Sorghum

Starter fertilizer application for sorghum is a sound practice in Texas. Even if soil tests like phosphorus (P) are in the "medium" range, one of the purposes of "starter" fertilizer for N and P is to "kick-start" or stimulate growth right after emergence. Starter fertilizer research, especially in Kansas has shown that rooting and early growth is promoted by starter fertilizer applications in the 2 inch x 2 inch configuration (from the seed, 2 inches to the side and 2 inches below). Starter fertilizer can be applied with the seed, the so-called "pop-up" fertilization, but at rates much less than the 2 inch x 2 inch placement. A common concern is potential salt injury and ammonia damage if the rate of starter fertilizer is too high.

Loamy-Clayey SoilSandy Soil
------------------------Row spacing (inches) ------------------------
Fertilizer
Placement
1520304015203040
Pop-up
(with seed)
10-158-125-8610854
2" X 2"
pattern
8060403040302015

More salt-forming N and K fertilizers can be applied to loamy and clay based soils than to sandy soils. Narrower row spacings allow more N and K as well. Pop-up starter fertilizer rates are much lower than starter fertilizer 2 inches from the seed. If the total amount of N fertilizer applied to your sorghum is 60 lbs. N and A, and you are on 20-inch rows, than the entire dose could be applied as a 2 inch X 2 inch starter on loamy and clayey soils. However, in most cases, the balance of the N fertilizer will have to be sidedressed. This can be as 32-0-0 either dribbled or knifed in 6 to 10 inches off the row without the threat of injury, applied through a pivot or using a broadcast spreader.

Some starter N fertilizers have potential for injury from ammonia (NH3) because they either contain NH3 or an N form that quickly converts to NH3 gas. This is primarily a concern with pop-up fertilization. For pop-up applications with the seed producers should avoid urea ammonium nitrate (32-0-0 or 28-0-0), mixtures of 32-0-0 and ammonium thiosulfate (28-0-0-5S), solid urea (46-0-0), mono-ammonium phosphate or MAP (11-52-0) and diammonium phosphate DAP (18-46-0).

For sample calculations as well as additional row spacings consult "Starter and In-Furrow Fertilizer & Salt Injury Potential," (Bronson) at http://lubbock.tamu.edu/sorghum

Phosphorus (P2O5)

It is difficult to gauge needed P requirements for grain sorghum or any crop without soil test information for P in the 0-6 inch depth. Table 7-3 notes soil test P levels and their relative designation such as very low, low and moderate (20-50 ppm, a very wide range). Soil test P levels above 50 ppm are high. Using the Mehlich III soil test method, the crop response in most of Texas to fertilizer P is inconsistent between 30 to 40 ppm (the transition zone of soil P response), and measurable yield differences are not demonstrated above 40 ppm soil P.

When growing conditions are cool or wet early in the season, especially where producers might be planting early to minimize sorghum midge potential, seedlings may show temporary P-deficiency symptoms. This particular situation, as well as P nutrition in general, lends itself well to either banded or in-furrow application of P. Fertilizer P itself is not salt forming or toxic to plants at higher levels of P. See comments above on allowable banded and pop-up P fertilizer rates when N is a component of the P fertilizer.

Since soil P is relatively immobile or "fixed" in most Texas soils, placement in a concentrated form is particularly important in low to medium testing soils. Research has shown that plants obtain a higher proportion of their needed P from soil reserves. Only about 30% of applied P is used by the crop following fertilization in the current year, even though it may have been banded.

Yield Goal,bu/A (lbs./A)
Soil test Mehlich III40 (2,240)80 (4,480)120 (6,720)160 (8,960)200 (11,200)
(ppm)----------------------- Lbs. recommended P2O5/A* -----------------------
0-5 (Very low)35-4065-70808080
5-10 (Very low)30-3560-65808080
10-15 (Low)25-3050-60808080
15-20 (Low)20-2545-5070-808080
20-25 (Moderate)15-2035-4560-708080
25-30 (Moderate)15-2030-3545-6060-8080
30-35 (Moderate-High)---20-3035-4545-6060
35-40 (Moderate-High)------20-3530-4550
40-45 (Moderate-High)---------15-3030
*Table 7-3 P2O5 levels reflect Texas A&M Soil Test lab grain recommendations, however, regional Texas AgriLife soil research results in both West and South Texas suggests published recommendations may be slightly higher than needed, perhaps by 5-10 lbs. per acre for these regions. P2O5 rates are capped at 80 lbs. In severely depleted P soils, yield could potentially respond at higher rates of P. Visit with your Extension agronomist about severely depleted soil P conditions where a high yield goal is desired. West and South Texas soil research suggests that 30-40 ppm soil test P is a "transition level" at which yield responses to additional fertilizer P are inconsistent. §West and South Texas soil research suggests P fertilizer additions at this level of soil test P do not demonstrate measurable yield differences.

Texas AgriLife does not offer a general rule of thumb for P2O5 needs for grain sorghum like we do for nitrogen. However, when soil test P levels are very low, tables from several states' extension soil test guidelines cite a P2O5 requirement for fertilizer that is approximately 50% N (and 40% for low soil test P, 25% for moderate soil test P). This would reflect the fact that much P comes from residual sources.

TIP: If you do not know your soil P status, are without a soil test, but are willing to band P then consider a P2O5 rate that is about one-fourth to one-third of the N rate. Increase the target rate of P if you believe your residual soil P is low.

TIP: Fertilizer P applied in a band is more efficient than broadcast P. As a general rule of thumb producers may be able to reduce P applications by as much as 20% if fertilizer is applied in a band due to relative increased availability of P.

Potassium (K2O, or Potash)

Soil K levels in South and West Texas are generally high and unless soil K levels have been diminished greatly, it is likely that only top end grain sorghum yields would consider K additions. Texas A&M University soil test guidelines project the K requirement at 2 lbs. K2O/A per hundred weight, however, the soil test levels are normally sufficient (if not well in excess) to preclude fertilizing with potassium. Exceptions to this rule in most Texas sorghum production soils include sandy soils with low organic matter in the eastern third of the state, however, the acreage involved with this condition will be small.

Iron (Fe) and Zinc (Zn)

Two other important nutrients for grain sorghum production in South, Central, and West Texas are iron(Fe) and zinc(Zn). Zn is not commonly an issue in sorghum (it is for corn), but iron deficiency related to high pH usually pH ≥ 7.8, whether it be alkali spots in South Texas, carbonitic soils in the Blacklands or caliche soils in West Texas is a particular concern for sorghum. Soils that produce spotty yet heavy Fe deficiency across the field in South Texas or have more uniform chalky soils in the High Plains should probably never be used for grain sorghum production. It is prohibitively expensive to correct Fe deficiency. Many fields, however, simply experience some degree of iron deficiency, the classical condition of interveinal chlorosis where the veins of the younger leaves remain green and the leaves are yellow between the veins (Figure 6-1, Fe deficient sorghum). In the worst of cases, the leaves are almost completely bleached out and the plants do not grow. Iron deficiency can be induced temporarily due to water-logged conditions. When modest cases of iron deficiency occur as the root volume expands due to soil drying then iron deficiency usually diminishes.

Fe deficiency compared to N deficiency. Fe deficiency is normally expressed mostly on newest leaves, and Fe is immobile within the plant. When Fe becomes available again, newly emerging leaves will again be dark green. Older chlorotic leaves will not green up unless they receive a direct foliar feed. In contrast, N is mobile in the plant, and will move to the youngest leaves from older plant tissues (which may express N deficiency). There is no striping in N deficiency symptoms.

Most soil tests will flag Fe less than 4 ppm as deficient. Currently, there are no economical sources of soil-applied Fe available. Therefore, the only options for correcting Fe deficiencies are to apply foliar Fe sprays in-season or to apply manure for long-term correction. If Fe chlorosis has been observed during previous years in a field, Fe fertilizer materi­als may be applied preemptively to the foliage through multiple sprayings early in the season. Table S8-4 gives suggested foliar treatments to correct iron as well as Zn deficiencies.

DeficiencyProductProduct/100
gals water
Product/AcreTiming
IronIron sulfate
(20% Fe)

Iron chelate
(10% Fe)
20 lbs
(2.5% solution)

4-8 lbs.
(0.5-1%)
1 lb. then
2-3 lbs.

0.25-0.5 lbs
10-14 days after emergence - 5 gals/A
over crop row. Follow with 2 apps.
@ 10-14 day interval @ 10-15 gals/A
Same as above
ZincZinc sulfate
(30% Zn)
2 lbs.
(0.5%)
0.2 - 0.4 lbs10-20 gals/A in first 30 days
Zinc chelate
(9% Zn)
2 qts.
(0.1%)
1 pint10-20 gals/A in first 30 days
Include a surfactant or other wetting agent. Product composition may vary. Select similar products or adjust mixing ratios to achieve comparable rates of nutrient application.
Iron chelates range in concentration and chelate strength; consult label directions for actual recommendations as well as the cost compared to iron sulfate applications
Source: Updated information based on research results and recommendations through the Texas AgriLife Extension Service Soil, Water and Forage Testing Laboratory.

For further information about Fe consult 'Correcting Iron Deficiencies in Grain Sorghum' L-5155, from Texas AgriLife Extension (http://agrilifebookstore.org or contact your local county extension office).

Zn: Where soil P is 'very high' or 'high' and Zn levels are low then further P application may induce Zn deficiency particularly when soil pH is high. If soil test results indicate a possible Zn defi­ciency (less than one ppm Zn), Zn fertilizer may be broadcast and incorporated preplant with other fertilizers or ideally banded near the seed at planting. Chelates are up to five times more effective than inorganic sources, but price will determine which product is a better choice.

Other Nutrients in Texas Sorghum

Unless you have had a particular problem in the past with sulfur, calcium, manganese, etc., there is no fertility correction likely needed. Noting other nutrients and their levels in soil test reports is probably sufficient for keeping an eye on possible imbalances.

Foliar Feeding Major and Minor Nutrients

In general foliar feeding is expensive. Extension does not recommend that producers rely on foliar feeding for N due to the far higher per unit cost of N. A possible exception in Central and South Texas would be if a planned sidedress application of N could not be performed due to continued wet fields. Foliar feeding of micronutrients is more common, and many products will have a package of micronutrients and simply may be the most convenient means to use if you have a known deficiency with an individual nutrient. Otherwise, significant amounts of micronutrient sprays are used that probably provide little if any benefit ('feel good' or 'catch all' treatments). Micronutrient deficiencies other than iron are hard to diagnose without experience and/or a tissue test. Non-chelated sources if available and applied with a good sticking agent can be quite effective and perhaps a better buy.


Back

Weed Control

Weeds compete with grain sorghum for light, nutrients and soil water thus reducing yield and grain quality. In addition, they harbor insects and diseases that further impact yield and increase costs. Effective sorghum weed control first begins with identifying problem weeds in a given field and developing a control strategy. If there is any doubt about a particular weed, take it to your county agent or extension specialist for identification. Implement control strategies to first control those weeds that most affect yield.

Weed control in sorghum must begin in the months and days prior to planting. Eradication of weeds prior to planting is extremely important in sorghum production due to the limited number of herbicides available for selective post emergence control. This is especially true for weeds such as johnsongrass and perennial sharppod morningglory. Weeds left uncontrolled during any fallow period will use up valuable soil moisture that could otherwise be used by the sorghum crop. Control these weeds either by tillage or with herbicide application. The use of soil residual herbicides like atrazine can be particularly valuable prior to planting, reducing tillage and herbicide applications that might otherwise be necessary to control multiple flushes of weeds. However, make certain that any soil residual herbicide used is safe for planting sorghum.

The yield loss associated with sorghum due to weed competition is greater than that of most grain crops. Typical losses range from 30 to 50% but in extreme cases can result in complete crop failure. Depending on your region of South or Central Texas the most common weeds and weed problems include Texas panicum, pigweed (carelessweed) species, barnyard grass, smell melon, johnsongrass, shattercane and morning glory. Any of these can be the source of angst among producers is needed to avoid yield losses, but control as best we can, it can be achieved. Studies have shown that even one pigweed within 24 inches of grain sorghum across a field can reduce yield nearly 40%. And for each inch per acre of soil moisture used by weeds (not to mention nitrogen) can be worth 300-400 lbs. per acre of grain sorghum yield.

Annual grasses generally do not reduce yield as much as broadleaf weeds, but are more difficult to control. Yield loss will be the greatest when weeds emerge with the crop or soon afterwards. The most critical period for weed control is the first 4 weeks after planting. If weeds are controlled during this time, and control is maintained through the remainder of the season, little reduction in grain sorghum yield will occur. Yield reduction from weeds that emerge four weeks after planting is usually minimal. However, weed escapes can be a major interference with harvest. Large pigweed plants and morning glory vines can slow up harvest and damage machinery. Therefore, it is important to keep weeds such as these managed during the growing season and not let them become uncontrollable.

Broadleaf Weed Control

Most weed control strategies should consider the use of atrazine (and perhaps propazine if rotating to cotton) either applied prior to planting, at planting, prior to crop emergence or applied soon after crop emergence. Atrazine is relatively inexpensive and will control most broadleaf weeds. Restrictions and rates of atrazine use vary considerably depending on state and local requirements. Closely examine the label for use in any particular field. Generally, atrazine should only be applied prior to sorghum emergence in medium or fine textured soils at reduced rates, or crop injury can occur. The safest way to use atrazine is to apply the herbicide soon after the crop has emerged but before it reaches 12 inches in height. To control emerged weeds atrazine should always be applied with crop oil. The smaller the weeds, the better the control will be. If atrazine cannot be used or is ineffective on the weeds present, then other herbicides should then be considered.

Pigweed and common waterhemp MUST be controlled with preemergence herbicides or properly timed applications of 2,4-D or dicamba when the weeds are small (2-4 inches). If you miss them, there are few selective herbicide options left that will provide control of these species when they get large.

Other commonly used herbicides applied prior to sorghum and weed emergence are propazine, metolachlor, alachlor and dimethenamid (Table 7-1). These are sold under a host of trade names. Propazine is very effective on many broadleaf weeds and is safer on the sorghum crop than atrazine. The other three herbicides are more specific on which broadleaf weeds they will control and generally do not control the weeds for as long. Combining atrazine with any of the three improves overall control of broadleaf weeds.

Herbicide labels are constantly being updated. Before using any herbicide check the label for specific use under your conditions. Most state extension services provide updated herbicide lists and specific weed control recommendations. For a current summary of herbicides labeled for grain sorghum in Texas consult Brent Bean's "Quick Guide for Weed Control in Texas High Plains Grain Sorghum," http://amarillo.tamu.edu/programs/agrilife_programs/agronomy/agronomy_sorghum.php then click on the appropriate link, or contact your local extension office.

Atrazine (AAtrex, atrazine)Primarily broadleaf weed control. Long residual.
Propazine (Milo-Pro)
Metolachlor (Dual II Magnum, Cinch, Parallel,Me-Too-lachlor)
Dimethenamid (Outlook)
Alachlor (Micro-Tech)Good annual grass control with some broadleaf activity. Must use Concep III treated sorghum seed.
Atrazine + Metolachlor (Bicep II Magnum, Cinch ATZ)Atrazine + dimethenamid (Guardsman Max. G-Max Lite)Atrazine + alachlor (Bullet, Lariat)Broadleaf weed and grass control. Must use Concep IIItreated sorghum seed.
OthersSee state and local Extension service recommendations forother pre emergent herbicides.

Herbicides commonly used after crop and weed emergence are listed in Table 7-2 along with a brief description of their strengths and weaknesses. Check label for rates, application timing and other restrictions. All of these can be used in combination with each other. 2,4-D and dicamba have been used for decades for broadleaf weed control. However, these must be applied correctly or severe crop injury can occur. These should only be applied to sorghum that has not exceeded 8 inches in height. Drop nozzles that keep the herbicides out of the whorl of the sorghum can be used up to 15 inch sorghum. Care should be taken to minimize drift of 2,4-D and dicamba or damage to other broadleaf crops and ornamentals can occur.

Table 7-2. Popular broadleaf post-emergent herbicides byactive ingredient name (common trade names).
Atrazine (AAtrex, atrazine)Effective on most broadleaf weeds and will provide soilresidual control. Apply with crop oil.
2,4-D (2,4-D, Unison, Barrage, others)Will control most broadleaf weeds, crop injury can besignificant and drift to cotton fields is a concern.
Dicamba (Banvel, Clarity, Vision)Will control most broadleaf weeds, crop injury can besignificant and drift to cotton fields is a concern but safer than 2,4-D.
Prosulfuron (Peak)Must be applied to small weeds. Best to use with dicamba,2,4-D or atrazine.
Fluroxypyr (Starane)Weak on pigweed. Good on kochia, morningglory, anddevilsclaw.
Carfentrazone (Aim)Fast burn down. Effective only on small weeds (less than2inches).
Halosulfuron (Permit)Best product to use for nutsedge (nutgrass) control. Ineffectivewhen used alone on most broadleaf weeds.
OthersSee state and local Extension service recommendations forother post emergent herbicides.

Grass Control

There are no effective herbicides that can be used after the crop and grass has emerged in grain sorghum. Either metolachlor (Dual, Cinch, Parallel, Me-Too-lachlor), alachlor (Micro-Tech) or dimethenamid (Outlook) must be applied prior to crop and weed emergence. The sorghum seed must be treated with a herbicide seed safener (Concep III) or crop injury will occur. The effectiveness of control of annual grasses will depend on the specific grass species as well as other factors. However, these are the best products currently available for annual grass control. These three products are often sold in combination with atrazine and this combination is your best hope for control on Texas panicum. All herbicides applied pre-emergence require a minimum of 0.5 inches of rain or irrigation to move them into the soil. An alternative to rain or irrigation is to incorporate the herbicides with a rolling cultivator prior to grass emergence. However, care must be taken to avoid damaging the sorghum.

Perennial Weeds

Johnsongrass is the main perennial weed that causes the most problem having the potential to completely eliminate any significant grain sorghum yield. Bindweed is also a major problem in some Texas sorghum areas. Prevention is the best method of control with these weeds. Once johnsongrass or other local perennial weeds are found producers should do everything possible to prevent their spread. Do not run tillage equipment through isolated spots of these weeds (especially bindweed) as this will tend to spread them to other parts of the field. Diligent spot treating with glyphosate (Roundup) for Johnsongrass and dicamba, 2,4-D, glyphosate and even some soil sterilants for bindweed will be required to eradicate these two weeds. For Johnsongrass that is already widespread, the best control method is to allow the Johnsongrass to emerge prior to sorghum planting. Once the Johnsongrass has about 6 inches of growth treat it with glyphosate. Sorghum should then be immediately planted with as little disturbance of the treated Johnsongrass as possible. Although this will not provide season long control it, will allow the grain sorghum to grow with very little Johnsongrass competition during the critical 4 weeks after planting. Grain yield will be considerably better than if no control was attempted.

Where severe infestations of Johnsongrass or other weeds are present, applications of Roundup through hooded or shielded sprayers may be warranted. Roundup may be applied through these devices after the sorghum is 12 inches tall. Extreme care should be taken to avoid herbicide contact with the sorghum plants. Refer to your specific glyphosate (Roundup) label for further instructions and precautions regarding this use.

The glyphosate treatment procedure outlined above can also be effective on bindweed. In addition, early in-season treatment of 2,4-D or dicamba should be considered. Another herbicide, quinclorac (Paramount), can be used alone or in combination with 2,4-D or dicamba. Quinclorac is safe on sorghum and can be very effective.

New Advances

Some very promising new herbicides for both broadleaf and grass control will soon be on the market. Continue to check with herbicide dealers and the extension service for information about new products. New grain sorghum hybrids will be available in the next five years that are tolerant to two classes of herbicides giving producers many more herbicide options. For the first time producers will be able to control Johnsongrass as well as annual grasses (including shattercane) with herbicides applied after the sorghum and grass has emerged.

Herbicides, Grain Sorghum and Crop Rotation Restrictions

Cotton Herbicides and Rotation to Grain Sorghum

Staple-NEVER plant grain sorghum in a cotton hailout or replant situation after Staple has been applied (label says do not plant in the year following an application). Even banded applications present a major concern. Though high irrigation or rainfall may diminish Staple residues, significant sorghum injury can still be expected the year after Staple was applied. Don't try to "get by" if Staple was applied, as it is highly risky. Furthermore, grain sorghum is not labeled for Staple the following year after application.

Trifluralin/Prowl-Growers are familiar with the risk associated with cotton failure and subsequent attempts to plant back to grain sorghum. Because trifluralin and similar herbicides do not move much in the soil, in contrast to Staple which is much more soluble and harder to predict where it could be. Buster planting can usually move the treated soil away from the sorghum with success.

Know, however, that the Treflan label states "In portions of Texas receiving less than 20 inches of rainfall or irrigation to produce a crop, unless crop injury is acceptable, do not plant sorghum (milo) for 18 months after an application of Treflan 4EC. In sorghum, cool, wet weather conditions during early growth stages may increase the possibility of crop injury. In areas that receive more than 20 inches of rainfall and irrigation, sorghum planting 12 months after spring application or 14 months after fall application is permitted." Prowl H2O restriction is 10 to 12 months for spring and fall applications.

Valor-In a cotton crop failure situation do not plant grain sorghum for one month.

Other cotton pre-emerge herbicides-Should be OK the next year. For example, the rotation restriction for diuron and Layby Pro is 8 months.

Wheat and Small GrainsCornPeanut or Soybean
Amber 75 DF {triasulfuron}, 14Nicosulfuron (Accent &
Stinger {clopyralid}, 10.5Steadfast), 10 or 18Cadre, 18
Maverick Pro {sulfosulfuron}, 22Pursuit (Clearfield), 18Pursuit, 18
Beyond (imazamox) (Clearfield), 9Corvus, 9 or 17Raptor, 9
Ally XP {metsulfuron methyl}, 10
Glean {chlorsulfuron}, 14-25
Finesse (Glean + Ally) {chlorsulfuron + metsulfuronmethyl}, 14-26
Olympus {propoxycarbazone-sodium}, 12
Olympus Flex, 9
Rave 59 WDG {triasulfuron + dicamba}, 14

Grain Sorghum Herbicides and Rotation to Cotton

Peak (prosulfuron)-22 month restriction

Atrazine and the many products that contain atrazine-The main labels for atrazine products state:

Propazine-Currently propazine is used sparingly in Central Texas, most likely on sandy soils often in Central Texas river bottom ground. Ironically, the label states that cotton must be planted at least 12 months after a broadcast application of 1.2 quarts per acre (the full rate) in West Texas, which would be medium and fine-textured soils. In contrast for other Texas sorghum regions the label states cotton, only after 18 months, even though propazine is rated as less risky to cotton than atrazine. This clearly tips the scales to atrazine since it is labeled for 12-month rotation to cotton in all of Texas not to mention atrazine costs much less. Nevertheless, because there is limited propazine use, details about its use and comparison to atrazine are noted in the table below.

Parameter

Propazine

Atrazine, 24(c) label

Cost

~2X of atrazine

Soil pH

No restriction

<8.5, no caliche, cuts, etc.

Organic matter

No restriction

Minimum, 1.0%

Soil texture exclusions

Loamy sand, sand (incorporate shallow on sandy loam soils)

Sandy loam, loamy sand, sand

Application timing

Not labeled for post-emerge

Pre-plant, pre-emerge, post- emerge?

Rotation to cotton

None

Yes, depending on application timing, rain + irrigation

Tank mixes

Many (see label)

Many (see full label)

Minimum carrier volume:

aerial

3 gal/A

Not listed on 24(c)

ground

10 gal/A

10 gal/A

Additional info.

50 mesh screens min. 30-40 psi agitate well

50 mesh screens min. 30-40 psi agitate well

The following reflect research observations, an analysis of producer experience, and potential limitations for propazine in grain sorghum weed control.

Atrazine

Propazine

Additional Considerations for Effective Weed Control in Sorghum

CAUTION: We reiterate that the misapplication of several herbicides whether early, mid or late-season can cause significant injury on grain sorghum. These herbicides include:

The potential problems with these chemicals are twofold: 1) chemical applications place too much of the herbicides on the plant or in the whorl, causing injury; 2) errors with both hooded sprayers and mis-directed drop nozzles, which may be due to defective equipment, ground speed too fast, drift within the row and operator error. None of these potential errors are without a solution; attention to detail can solve many of the concerns.

TIP: If you are frequently relying on 2,4-D, dicamba, paraquat or glyphosate mid-season to deal with weed problems, then we need to back up and re-evaluate our comprehensive weed control program to prepare for and attack potential weed issues earlier in the season.

CAUTION: Sprayer equipment, applicators-even labels!-are not perfect. We may be inclined to push the limit on:

  1. Herbicide rate (a little more per acre, especially on that sandy soil),
  2. Timing (a few days or a week later will not hurt-this leads to increased crop injury OR weeds that germinate or grow larger and become harder to control),
  3. Permitting too much herbicide or crop contact.
  4. If using 2,4-D in your sprayer equipment, due to the sensitivity of cotton to 2,4-D a separate spray system (not just the tank) is strongly recommended.

The result is too often disappointment, and the outcome when it proves to have been a mistake can not be undone.

Glyphosate Drift from Cotton to Grain Sorghum

Grain sorghum can tolerate low levels of glyphosate drift without long-term impacts but is susceptible to injury. A friendly reminder, however, to neighbors and local aerial applicators might increase awareness of the potential issue.

Your Weed Control Team-Improving Your Employees' Partnership

BENEFIT: The manner in which you train, supervise and verify your employees understanding and their herbicide application methods can pay large dividends. Consider these suggestions:

How you verify your staff's mixing and spraying of herbicides can reduce the possibility of a mistake leading to crop injury or worse. Consider these suggestions:

Any of these points could reduce the possibility that even just one time you might have a mistake that costs you $5,000, $10,000 or more. The training is worth it as a personal safety issue, but it can also pay off in the mistakes that never happened.

Where Can Producers Go Online to Identify Weeds?

The Texas Weed Information Group (TWIG) maintains a website at http://twig.tamu.edu. This website, however, works best if you already know the name of the weed then you can find pictures, etc. Additional weed ID links are provided that may help you initially identify the weed by name based on its appearance. To visually identify unknown weeds when you do not know the weed name, many Texas AgriLife workers prefer the book Weeds of the West (Western Society of Weed Scienc, 2006, http://www.wsweedscience.org) in contrast to attempting to guess at which pictures to open online when weeds are listed alphabetically and you do not know the weed's name.

Where Do the Weed Scientists Go for Quick Label Information?

Chemical Data Management Systems, http://www.cdms.net (click on 'Services,' then Labels/MSDS, then type in chemical brand name).

Greenbook, http://www.greenbook.net, may need to register for use. Allows searches by product or active ingredient. Often database is incomplete as a major chemical label is not found.

Chemical and Worker Safety

Safety with herbicide, fungicide and other chemical applications is paramount. For emergency medical treatment information by phone call 1-800-424-9300 (CHEMTREC) as well as your local 9-1-1. If you have an accident and must require examination and possible treatment take the chemical label with you.

Keys & Concerns for Weed Control in West Texas Grain Sorghum

The following weed scientists offer these suggestions regarding weed control tips, concerns, and common mistakes in West Texas grain sorghum.

South Plains
Wayne Keeling, Research Agronomist, Lubbock, (806) 746-6101, wkeeling@ag.tamu.edu South Plains and Panhandle
Brent Bean, Extension Agronomist, Amarillo, (806) 677-5600, bbean@ag.tamu.edu Rolling Plains
Todd Baughman, Extension Agronomist, Vernon, (940) 552-9941, tbaughma@ag.tamu.edu
  • Few herbicide options (2,4-D or dicamba options cannot always be used, and if planning on double cropping wheat behind sorghum then atrazine is out).
  • Pre-emergence applications:
  • Weeds
  • Timing weed control options to the appropriate grain sorghum stage of growth (common mistake is waiting until sorghum is too large thus more susceptible to herbicide injury).
  • Mistake—Unwillingness to run hooded sprayer: this tool indeed is an effective option to protect grain sorghum but still get many weeds knocked back.
  • Windmillgrass and marestail are becoming bigger issues on no-till ground
  • Most Common Weed Issues—Rolling Plains For more information view:

    Chemical Data Management Systems, http://www.cdms.net (click on 'Services' then Labels/MSDS, then type in chemical brand name

    Greenbook, http://www.greenbook.net, may need to register for use. Allows searches by product or active ingredient. Often database is incomplete as a major chemical label is not found.


    Back

    Insect Management

    Methods of Preventing Insect Pest Infestations

    Managing insect and mite pests of sorghum involves actions that prevent pests from increasing to high enough numbers to cause economic damage. These practices help avoid pests, reduce their abundance, slow their rate of increase, lengthen the time it takes them to reach damaging levels, and/or increase the plant's tolerance to the insect pest. These actions include:

    Sampling and Determining Economic Injury Levels

    Because sorghum insect pest levels can change quickly, it is beneficial to scout insects once a week, unless otherwise noted. The major exception is sorghum midge, which may require scouting daily during flowering so as not to miss a sudden increase in their number in the field. The full Texas AgriLife Extension sorghum insect guide contains further details on scouting and sampling techniques.

    Economic injury levels will vary based on the projected or contracted price of the grain as well as insecticide and application costs. Economic injury levels, however, should be regarded as in making decisions about pest insect control.

    Seed Treatments

    Seed treated with Gaucho® (imidacloprid), Poncho® (clothianidin), or Cruiser® (thiamethoxam) can be purchased to manage southern corn rootworm, greenbug, yellow sugarcane aphid, chinch bug, stink bug, wireworms, false wireworms, and grubs. Recently Extension has suggested the efficacy of these treatments may extend to about 45 days from planting. Texas AgriLife trials with many of these seed treatment products has produced varied results in part depending greatly on the insect and a particular region in Texas.

    Bottom Line: Consult your local IPM agents of regional Extension staff for trial results and observations in your area. Many of these insecticide active ingredients are now often packaged with seed fungicides as well (e.g., CruiserMaxx). See the hybrid selection section for comments about price considerations when purchased on your planting seed.

    Major PestsHigh Plains
    Rolling Plains
    Concho Valley
    Central Texas
    Coastal Bend
    South Texas
    Southern corn rootwormNoYes
    GreenbugsYesYes
    Yellow sugarcane aphidYesYes
    Corn leaf aphidMinorCommon, not severe
    Spider mitesYes?
    Sorghum headworms
    corn earworm and
    fall army worm
    YesYes
    Rice stink bugNoYes
    Sorghum midgeYesYes

    Major Soil Insect Pests of Texas Grain Sorghum

    Wireworms and False Wireworms

    Description: True and false wireworms are immature stages of click and darkling beetles. Wireworms generally are shiny, slender, cylindrical, and hard-bodied. Color ranges from yellow to brown.

    Time of attack: Primarily planting to a few days after germination.

    Damage: Wireworms feed on planted sorghum seed, preventing germination.To a lesser degree, they feed on seedling plant roots.

    Sampling: Two to three weeks before planting. Sift soil for wireworms or set up bait stations for examination before planting.

    Economic threshold: One wireworm larva per square foot (four inches deep) or two or more larvae per bait trap.

    Major suggested insecticides: Seed treatments - imidacloprid, clothianidin, thiamethoxam; at planting - terbufos.

    Southern Corn Rootworm

    Description: Southern corn rootworm is the larval stage of the spotted cucumber beetle. Rootworms are small, brown-headed and creamy white with wrinkled skin.

    Time of attack: Planting to mid-vegetative stage prior to boot.

    Damage: Larvae burrow into germinating seeds, roots and crowns of sorghum plants. Symptoms of rootworm damage include reduced stands, lower plant vigor, and the occurrence of "dead heart" in young plants. Plants may be more susceptible to lodging later in the season. Damage by southern corn rootworm is most likely to occur in the Texas Coastal Bend area.

    Major suggested insecticides: Seed treatment-clothianidin, thiamethoxam; at planting-chlorpyrifos, terbufos.

    Yellow Sugarcane Aphid

    Description: Usually lemon-yellow, but under some conditions are pale green. They are covered with small spines and have two double rows of dark spots on the back. Both winged and wingless forms live in the colony. They often feed on nearby Johnsongrass or dallisgrass.

    Time of attack: Seedlings and older plants to near whorl stage in Southern Texas. Yellow sugarcane aphid tends to be a later season pest on the High Plains; high numbers on seedling and whorl stage plants are seldom observed.

    Damage: Yellow sugarcane aphids feed on sorghum and inject toxin into leaves of seedlings and older plants. Aphids feeding on seedling plants turn the leaves purple and stunt growth. On more mature plants, leaves turn yellow. By the time discoloration symptoms are visible, plants have been injured significantly. Damage often leads to delayed maturity and plant lodging that may be worsened by associated stalk rots.

    Sampling: Determine presence soon after sorghum plants emerge. Purple-colored seedling plants are an indication of infestation. Scout sorghum by inspecting plants beginning the first week of plant emergence, then twice weekly until plants have at least five true leaves. As plants grow larger, they become more tolerant of aphid feeding. Very small seedling sorghum plants (one to three true leaves) often are significantly damaged after being infested for a week or less. Discoloration symptoms may be useful in assessing yield losses, and may be used in a decision to replant.

    Economic threshold: See Texas AgriLife sorghum insect guide for tables. Decision is based on the percentage of yellow sugarcane aphid-infested plants at 1, 2, or 3 true-leaf stage. There are no established thresholds for later infestations.

    Major suggested insecticides: Seed treatment-clothianidin, imidacloprid, thiamethoxam; foliar-dimethoate.

    Corn Leaf Aphid

    Description: This dark bluish-green aphid is oval-shaped, with black legs, cornicles and antennae. There are winged and wingless forms. Corn leaf aphids are found most frequently deep in the whorl of the middle leaf of pre-boot sorghum, but also found on the undersides of leaves, on stems or in grain heads.

    Time of attack: Most likely active from pre-boot sorghum to head exsertion.

    Damage: This insect rarely causes economic loss to sorghum and in fact may be considered helpful as they attract beneficial arthropods to grain sorghum, many of which feed on greenbugs and yellow sugarcane aphids. Corn leaf aphids often infest the whorl and undersides of sorghum leaves in great numbers. When feeding, corn leaf aphids suck plant juices but do not inject toxin as do greenbugs and yellow sugarcane aphids. These aphids are common, but their presence does not necessarily mean significant damage is expected. The most apparent feeding damage is yellow mottling of leaves that unfold from the whorl.

    Sampling: No procedure.

    Economic threshold: None. Often present, but rarely a pest.

    Major suggested insecticides: Rarely justified. Seed treatment-imidacloprid, thiamethoxam; at planting-phorate, terbufos; post-emerge/foliar rescue, several products.

    Greenbug

    Description: Adult greenbugs are light green, approximately 1/16" long, with a characteristic darker green stripe down the back. Usually, the tips of the cornicles and leg segments farthest from the body are black. Winged and wingless forms may be present in the same colony. Females produce living young (nymphs) without mating. Under optimum conditions, the life cycle is completed in 7 days. Each female produces about 80 offspring during a 25-day period.

    Time of attack: Greenbugs are active throughout the life of the plant. The greenbug may be a pest during the seedling, the boot, and the heading stages.

    Damage: The greenbug is an aphid that sucks plant juices and injects toxin into sorghum plants. Greenbugs usually feed in colonies on the undersides of leaves and produce honeydew. Infestations may be detected by the appearance of reddish leaf spots caused by the toxin greenbugs inject into the plant. The reddened areas enlarge as the number of greenbugs and injury increase. Damaged leaves begin to die, turning yellow then brown. Damage at the seedling stage may result in stand loss. Larger sorghum plants tolerate more greenbugs. Yield reductions during boot, flowering and grain-development stages depend on greenbug numbers, length of time greenbugs have infested the plants, and general plant health

    Sampling: Scout seedling sorghum, examining the entire plant and the soil around the base of the plant. Note the presence or absence of greenbugs and any damage to plants (yellowing, death of tissue). Usually only the undersides of lower leaves need to be examined, although in some cases greenbug colonies may be found first on the undersides of upper leaves. Greenbugs in a field can increase 20-fold per week, but the seasonal average is a 5- to 6-fold increase each week. Examine a minimum of 40 randomly selected plants per field each week. Greenbugs are seldomly distributed evenly in a field, so examine plants from all parts of the field; avoid examining only field borders. In fields larger than 80 acres, or if making a control decision is difficult, examine more than 40 plants.

    Economic threshold: When deciding whether to control greenbugs, consider the amount of leaf damage, number of greenbugs per plant, percentage of parasitized greenbugs (mummies), numbers of greenbug predators (lady beetles) per plant, moisture conditions, plant size, stage of plant growth and overall condition of the crop. It is important to know from week to week whether greenbug numbers are increasing or decreasing. Insecticide treatment is not justified if the recommended treatment level (based on leaf damage) has been reached but greenbug numbers have declined substantially from previous observations. See table below.

    Major suggested insecticides: Seed treatment-clothianidin, imidacloprid, thiamethoxam; at planting-aldicarb, chlorpyrifos, phorate, terbufos; post-emerge-chlorpyrifos, dimethoate, malathion, phorate.

    Plant sizeWhen to treat
    Emergence to about 6 inches20% of plants visibly damaged (beginning to yellow), with greenbugs on plants
    Larger plantto bootGreenbug colonies causing red spotting or yellowing of leaves and before any entire leaves on 20% of plants are killed
    Boot to headingAt death of one functional leaf on 20% of plants
    HeadingWhen greenbug numbers are sufficient to cause
    Hard DoughDeath of two normal-sized leaves on 20% of plants

    Whorlworms and Headworms-Corn Earworm and Fall Armyworm

    Description: Corn earworm and fall armyworm comprise the sorghum headworm complex. They infest the whorls and grain heads of sorghum plants. Larvae hatching from eggs laid on sorghum leaves before grain heads are available migrate to and feed on tender, folded leaves in the whorl.

    Newly hatched corn earworm larvae are pale in color and only 1/16" long. They grow rapidly and become variously colored, ranging from pink, green or yellow to almost black. Many are conspicuously striped. Down the side is a pale stripe edged above with a dark stripe. Down the middle of the back is a dark stripe divided by a narrow white line that makes the dark stripe appear doubled. Corn earworm larvae have small hairs (microspines) over much of the body. Fall armyworms and true armyworms do not, so the presence of microspines is one way to differentiate between corn earworm and fall armyworm or true armyworm. Fully grown larvae are robust and 1.5 to 2.0 inches long.

    Young fall armyworm larvae are greenish and have black heads. Mature larvae vary from greenish to grayish brown and have a light-colored, inverted, Y-shaped suture on the front of the head and dorsal lines lengthwise on the body. An important management tactic is to use sorghum hybrids with loose (open) grain heads.

    Time of attack: Whorl stage and then again from flowering into kernel development as late as hard dough. Infestations occur less often in early- than late-planted sorghum.

    Damage: Whorl-Damaged leaves unfolding from the whorl are ragged with "shot holes." Although this may look dramatic, leaf damage usually does not reduce yields greatly. The fall armyworm is more likely to cause significant damage since many more are often found on individual plants. Heads-corn earworm and fall armyworm larvae feed on developing grain. Small larvae feed on flowering parts of the grain head at first, then hollow out kernels. Larger larvae consume more kernels and cause the most damage. The last two larval stages cause ~80 percent of the damage.

    Sampling: Whorl stage-Pull the whorl leaf from the plant and unfold it. Frass, or larval excrement, is present where larvae feed within the whorl. Heads-Begin sampling for headworms soon after the field finishes flowering and continue at 5-day intervals until the hard dough stage. Scouting should also determine the percentage of corn earworm larvae separately from the percentage of fall armyworm larvae. Fall armyworms are often more difficult to kill with pyrethroid insecticides, and a treatable population that is mostly fall armyworm might require a different insecticide than one which is predominately corn earworm. This may be especially important if control is to be directed at a population that is composed of larger larvae.

    Economic threshold: Whorl-Larvae within the whorl are somewhat protected from insecticide. Control of larvae during the whorl stage is seldom economically justified, but insecticide application may be necessary if larval feeding reduces leaf area by more than 30 percent or is damaging the developing grain head or growing point within the whorl. It is very difficult to achieve good control of caterpillars in whorl stage sorghum because the larvae are sheltered from the insecticide while in the whorl. If control is needed, chemigation will provide better results than ground application, which in turn will provide better results than aerial application. Head-Determining the threshold will depend on the number of larvae per head and the size of the larvae. Consult the Texas AgriLife grain sorghum pest guide for instructions, calculations, and tables to help determine spray thresholds.

    Major suggested insecticides: Carbaryl, cyfluthrin, cyhalothrin, esfenvalerate, methomyl, zeta-cypermethrin. (Note: It is more difficult to kill fall armyworms with the pyrethroid class of insecticides.)

    Banks Grass Mite

    Description: Large numbers of Banks grass sometime occur on sorghum, especially in more arid areas of Texas. After feeding, these very small mites turn deep green, except for the mouthparts and first two pairs of legs that remain light salmon colored. Eggs, laid in webbing on the undersides of sorghum leaves, are pearly white, spherical, one-fourth the size of the adults, and hatch in three to four days. The life cycle requires about 11 days under favorable conditions.

    Hot, dry weather may lead to a rapid increase in mites. Also, mites in sorghum may respond as induced (secondary) pests after an insecticide application for a key insect pest such as greenbug. A rapid increase in spider mites after insecticide application may be due to tolerance of mites to some insecticides, the destruction of beneficial insects, and the dispersal of mites from colonies. Spider mites increase more rapidly on moisture stressed plants. Irrigation reduces the potential of mite population reaching damaging levels, but once mites are present, resuming irrigation will not diminish the injury potential from the mites.

    Time of attack: Present at low to moderate levels, but worst potential damage occurs after heading to early grain fill.

    Damage: Spider mites suck juices from the undersides of sorghum leaves, initially along the midribs of the lower leaves. Infested areas become pale yellow and reddish on the top surface, and the leaf may turn brown. As spider mites increase on lower leaves, infestation spreads upward through the plant. The undersides of heavily infested leaves may have a dense deposit of fine webbing. Increases in spider mite abundance generally occur after sorghum grain heads emerge. Large numbers of spider mites occurring early in kernel development can reduce the ability of sorghum plants to make and fill grain. After kernels reach hard dough, grain is not affected.

    Sampling: Inspect the undersides of lower leaves carefully. Mites occur in colonies, first along midribs of leaves. Later, they spread away from the midrib and up the plant to higher leaves. Webbing indicates the presence of mites. Mite infestations commonly begin along field borders and may spread quickly throughout a field.

    Economic threshold: Miticides produce varying degrees of success. Historically, insecticidal control of mites in sorghum has been erratic. Thorough leaf coverage is essential, especially since the mites live on the lower sides of the leaves. Ground application equipment with high gallons of water per acre is preferred. Insecticide application may be justified when 30 percent of the leaf area of most sorghum plants in a field shows some damage symptoms from mite feeding.

    Major suggested insecticides: Dimethoate, phorate, propargite.

    Sorghum Midge

    Description: The sorghum midge is one of the most damaging insects to sorghum in Texas, especially in the southern half of the state. The adult sorghum midge is a small, fragile-looking, orange-red fly with a yellow head, brown anten­nae and legs and gray, membranous wings.

    During the single day of adult life, each female lays about 50 yellowish white eggs in flowering spikelets of sorghum. Eggs hatch in two to three days. Larvae are colorless at first, but when fully grown, are dark orange. Larvae complete development in nine to 11 days and pupate between the spikelet glumes. Shortly before adult emergence, the pupa works its way toward the upper tip of the spikelet. After the adult emerges, the clear or white pupal skin remains at the tip of the spikelet.

    A generation is completed in 14 to 16 days under favorable conditions. Sorghum midge numbers increase rapidly because of multiple generations during a season and when sorghum flowering times are extended by a range of planting dates or sorghum maturities.

    Sorghum midges overwinter as larvae in cocoons in spikelets of sorghum or Johnson grass. When sorghum is shredded, spikelets containing larvae fall to the ground and are disked into the soil. Sorghum midges emerging in spring do so before flowering sorghum is available, and these adults infest johnsongrass. Sorghum midges developing in johnsongrass disperse to fields of sorghum when it flowers.

    Time of Attack: Early-season infestations in sorghum are usually below damaging levels. As the season progresses, sorghum midge abundance increases, especially when flowering sorghum is available in the area. Numbers often drop late in the season.


    Estimated latest sorghum flowering dates most likely to escape significant damage by sorghum midge.

    Damage: A sorghum midge damages sorghum when the larva feeds on a newly fertilized ovary, preventing normal kernel development. Grain loss can be extremely high. Glumes of a sorghum midge-infested spikelet fit tightly together because no kernel develops. Typically, a sorghum grain head infested by sorghum midge has various proportions of normal kernels scattered among non-kernel-bearing spikelets, depending on the degree of damage.

    Effective control of sorghum midge requires the integration of several practices that reduce sorghum midge abundance and their potential to cause crop damage. The most effective cultural management method for avoiding damage is early, uniform planting of sorghum in an area so flowering occurs before sorghum midges reach damaging levels. Planting hybrids of uniform maturity early enough to avoid late flowering of grain heads is extremely important. This practice allows sorghum to complete flowering before sorghum midge increases to damaging levels.

    Cultural practices that promote uniform heading and flowering in a field are also important in deciding treatment methods and in achieving acceptable levels of insecticidal control. To reduce sorghum midge abundance, use cultivation and/or herbicides to eliminate johnsongrass inside and outside the field. Where practical, disk and deep plow the previous year's sorghum crop to destroy overwintering sorghum midges.

    Multiple insecticide applications are used to kill adults before they lay eggs. Sorghum planted and flowering late is especially vulnerable to sorghum midge. To determine whether insecticides are needed, evaluate crop development, yield potential and sorghum midge abundance daily during sorghum flowering. Because sorghum midges lay eggs in flowering sorghum grain heads (yellow anthers exposed on individual spikelets), they can cause damage until the entire grain head or field of sorghum has flowered. The period of susceptibility to sorghum midge may last from seven to nine days (individual grain head) to two to three weeks (individual field), depending on the uniformity of flowering.

    Sampling: To determine if adult sorghum midges are in a sorghum field, check at mid-morning when the temperature warms to approximately 85 degrees F. Sorghum midge adults are most abundant then on flowering sorghum grain heads. Because adult sorghum midges live less than one day, each day a new brood of adults emerges. Sampling must be done almost daily during the time sorghum grain heads are flowering. Sorghum midge adults can be seen crawling on or flying about flowering sorghum grain heads.

    The simplest and most efficient way to detect and count sorghum midges is to inspect carefully and at close range all sides of randomly selected flowering grain heads. Handle grain heads carefully during inspection to avoid disturbing adult sorghum midges. Other sampling methods can be used, such as placing a clear plastic bag or jar over the sorghum grain head to trap adults.

    Because they are relatively weak fliers and rely on wind currents to aid their dispersal, adult sorghum midges usually are most abundant along edges of sorghum fields. For this reason, inspect plants along field borders first, particularly those downwind of earlier flowering sorghum or johnsongrass. If few sorghum midges are found on sorghum grain heads along field edges, there should be little need to sample the entire field.

    However, if you find more than one sorghum midge per flowering grain head in border areas of a sorghum field, inspect the rest of the field. Sample at least 20 flowering grain heads for every 20 acres in a field. Flowering heads are those with yellow blooms. Record the number of sorghum midges for each flowering head sampled and then calculate the average number of midges per flowering head. Almost all of the sorghum midges seen on flowering sorghum heads are female.

    Economic Threshold: The economic injury level for sorghum midge can be calculated from the following equation:

    Number of
    
    sorghum midges     (Cost of control as $ per acre) X 33,256
    
    per flowering   =   ________________________________________
                           (Value of grain as $ per cwt)
    head needed				X
    		        (Number of flowering heads)
    to trigger spray
    

    In the equation above, the control cost is the total cost of applying an insecticide for sorghum midge control and the grain value is the expected price at harvest as dollars per 100 pounds. The value 33,256 is a constant and results from solving the economic injury equation. The number of flowering heads per acre is determined as described above.

    Economic injury levels, as determined from the above equation, are shown in Table X for a range of typical treatment costs per acre, market values per 100 pounds of grain, and numbers of flowering heads per acre. Use the equation for estimating injury levels for your actual control costs, crop value and number of flowering heads per acre.

    Insecticide residues should effectively suppress sorghum midge egg laying 1 to 2 days after treatment. However, if adults still are present 3 to 5 days after the first application of insecticide, immediately apply a second insecticide treatment. Several insecticide applications at 3-day intervals may be justified if yield potential is high and sorghum midges exceed the economic injury level.

    Economic injury level-mean number of midges/flowering heads
    Control cost, $/acreCrop value, $100/lbs.Flowering heads = 18,000/aFlowering heads =45,000/aFlowering heads =67,500/a
    561.50.620.41
    571.30.530.35
    581.20.460.31
    661.80.740.49
    671.60.630.42
    681.40.550.37
    762.20.860.57
    771.80.740.49
    781.60.650.43

    Rice Stink Bug and Related Insects

    Rice stink bug is a pest of grain sorghum in South Texas and the Coastal Bend. It is one of several species of true bugs, primarily stink bugs, which may move in relatively large numbers from alternate host plants into sorghum during kernel development. Bugs infesting sorghum in Texas include rice stink bug, southern green stink bug, conchuela stink bug, brown stink bug, red-shouldered stink bug, leaf-footed bug and false chinch bug.

    Description: The rice stink bug is straw-colored, shield-shaped, and œ inch long. Females lay about 10 to 47 short, cylindrical, light-green eggs in a cluster of two rows.

    Time of attack: During sorghum kernel development.

    Damage: Rice stink bugs suck juices from developing sorghum kernels and, to a lesser extent, from other grain head parts. Damage depends on the number of bugs per grain head, the duration of infestation, and the stage of kernel development. Damaged kernels rarely develop fully and may be lost during harvest.

    Sampling: Grain head-feeding bugs tend to congregate on sorghum grain heads and sometimes within areas of a field. Using the beat-bucket method, count all bugs including fliers as well as those on leaves. Sample at least 30 plants from a field. Take at least one sample per acre in fields larger than 40 acres.

    Economic threshold: Determine the average number of bugs per sorghum head. Then multiply the average number of bugs per head by the plant density per acre to calculate the number of bugs per acre.

    Major suggested insecticides: Carbaryl, cyfluthrin, cyhalothrin.

    InsecticideApplication RateHarvestGraze
    Chlorpyrifos
    (Lorsban 4E)
    8 oz3030
    Cyfluthrin
    (Baythroid 2E)
    1.0-1.3ozSee Remarks14
    Cyhalothrin
    (Karate 1E)
    (Warrior 1E)
    1.92-2.56 ozSee Remarks
    Esfenvalerate
    (Asana XL)
    2.9-5.8 oz21-
    Malathion
    (Fyfanon ULV)
    8-12 oz77
    Methomyl
    (Lannate)
    2.4LV
    90WSP
    12-24 oz
    4-8 oz
    14
    14
    14
    14
    Zeta-cypermethrin
    (Mustang Max)
    1.28-4.0 oz1445
    Remarks:CyfluthrinIf one or two applications are made, green forage may be fed or grazed on the day of treatment. If three applications are made, allow at least 14 days between last application and grazing.
    Cyhalothrin Do not graze livestock in treated area or harvest for fodder, silage or hay.

    Tips & Concerns for Insects in Grain Sorghum

    West Texas

    Pat Porter, Extension entomologist, Lubbock (806) 746-6101, pporter@ag.tamu.edu

    Kerry Siders, Extension IPM agent, Hockley-Cochran Counties, (806) 894-2406, ksiders@ag.tamu.edu

    Central & South Texas

    Roy Parker, Extension entomologist, Corpus Christi, (361)265-9203, rd-parker@tamu.edu

    Policy Statement for Making Pest Management and Insecticide Suggestions

    Labels list product uses for grain sorghum grown for grain. When using products it is impossible to eliminate all risks and conditions or circumstances that are unforeseen or unexpected that could result in less than satisfactory results. Such responsibility shall be assumed by the user of this publication. Pesticides must be labeled for use by the Environmental Protection Agency. The status of pesticide label clearances is subject to change and may be changed since this guide was printed. The USER is always responsible for the effects of pesticide residues on his livestock and crops as well as problems that could arise from drift or movement of the pesticide. Always read and follow carefully the instructions on the container label. Pay particular attention to those practices that ensure worker safety. For information about the registration status of a product and product use, contact a local chemical company representative, a dealer representative, and/or your county Extension staff.

    The primary Texas AgriLife Extension Service resource for grain sorghum insects was updated in 2007 for insects, new treatment thresholds, and labeled insecticides. "Managing Insect and Mites Pests of Texas Sorghum" B-1220 and "Field Guide to Pests & Beneficials in Texas Grain Sorghum," B-6094 is available at http://agrilifebookstore.org or through your local county Extension office.

    Texas AgriLife Extension Entomology Staff

    Texas AgriLife has Extension entomologists with responsibility in grain sorghum located in Lubbock, Amarillo, San Angelo, Ft. Stockton, Stephenville, Dallas, Corpus Christi, Uvalde, and Weslaco. In addition, most of the sorghum acreage in the South Plains and Concho Valley as well as key production areas in Central Texas, the Coastal Bend, and the Rio Grande Valley are covered by county-based integrated pest management (IPM) Extension agents.

    Identifying Insects

    Contact your local county office or your nearest Texas AgriLife Research & Extension Center for assistance. If the insect still can't be identified then county or regional Extension staff can send a digital image or actual specimen to the Texas A&M University Department of Entomology for identification (instructions and submittal form at http://insects.tamu.edu/insectquestions/index.cfm; we recommend further ID be conducted through Extension staff rather than submitting directly yourself).


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    Diseases

    Disease: Stalk Rot
    Stalk Rot
    Cause: Macrophomina phaseolina (Charcoal Rot), Colletotrichum graminicola(Stalk Red Rot/Anthracnose)
    Symptoms: Stalk is spongy, and internal tissue (pith) shredded and often discolored. Plants sometimes turn grayish-green after jointing.
    Key Features:Fungi survive on crop residue. High plant population, high nitrogen and low potash can aggravate the diseases. Charcoal Rot is prevalent in hot, dry weather. Stalk Red Rot is prevalent during warm weather with alternating wet and dry periods.
    Management: Use hybrids resistant to Stalk Red Rotand tolerant to Charcoal Rot. Avoid excessive plant populations. Maintain proper soil fertility. Rotate away from sorghum for two or more years following a severe outbreak of eitherdisease. Avoid soybeans and corn for two or more years following severeoutbreaks of Charcoal Rot. Azoxys trobin is labeled for management of C. graminicola and Charcoal Rot.
    Disease: Head Smut
    Head Smut
    Cause: Sporisorium reilianum (syns. Sphac elotheca reiliana)
    Symptoms: At heading, large galls occur in place of the head. Head turns into mass of dark brown, powdery spores.
    Key Features:Infection occurs in seedlings from spores in the soil.
    Management: Use resistant hybrids.
    Disease: Leaf spots and blights
    Leaf Spot
    Cause: Setosphaeria, Collectotrichum, Cerco spora, Gleocercospera, Ascophyta
    Symptoms: Older leaves are infected first with round, oval, or rectangular leaf spots. Spots are tan, yellow, reddish or purple and sometimes have a darker margin.
    Key Features:These fungi survive in crop residue and spores are spread by air currents or by splashing rain. Normally, thesediseases do not hurt yields. If the upper leaves become infected, then severe yield losses can occur.
    Management: Use resistant hybrids, especially forno-tillage. Rotate away from sorghum or corn for 1 to 2 years. Control weeds that may be a source of the inoculum. Azoxystrobin is labeled as a foliar spray for Cercospora (Gray leaf spot)control in sorghum.
    Disease: Maize Dwarf Mosaic
    Dwarf Mosaic
    Cause: Maize Dwarf Mosaic Virus
    Symptoms: Irregular, light and dark green mosaic patterns on the leaves, especially the younger leaves. Tan stripes with red borders between the veins ("red-leaf ") occurs under cool conditions.
    Key Features:The virus lives in Johnsongrass rhizomes and other perennial grasses. The virus is transmitted by certain aphids.Late-planted sorghum is at greater risk.
    Management: Use tolerant hybrids and eradicate John songrass and other perennial grassy weeds.
    Disease: Root Rot
    Seedling Disease
    Cause: Periconia, Pythium, Rhizoctonia,Fusarium
    Symptoms: Stunting, sometimes leaf yellowing and/or wilting. Rotted roots are pink, reddish brown, or black.
    Key Features:Common fungi in soil, but not damaging unless plant is stressed. Common stresses include cool soils, poor drain age, or inadequate fertility. Vigorously growing plants are able to replacedamaged roots with new roots.
    Management: Use adapted hybrids. Plant in warm (above 65°F) moist soils at the proper depth and seeding rate. Place herbicide, fertilizer, insecticide and seed properly to avoid stress or injury to seedling. Azoxystrobin is labeled for in-furrow use for Rhizoctonia and Pythium diseases.
    Disease: Bacterial Stripe
    Bacterial Stripe
    Cause: Burkholderia andropogonis (syns.Pseudomonas andropogonis)
    Symptoms: Long, narrow brick-red to purplish red stripes, becoming tan when dry. Lesions are bound by secondary veins.
    Key Features:Bacteria survive in infected seed and in undecomposed sorghum residue. Warm, humid weather favors infec tion. Generally does little damage.
    Management: Use clean seed. Rotate away from grainsorghum for two years. Control weeds, especially shattercane (Sorghum bicolor). Use resistant hybrids, espe cially for reduced tillage and no-tillage fields.
    Disease: Fusarium head blight
    Fusarium Head Blight
    Cause: Fusarium moniliforme
    Symptoms: The head becomes infected first while stalk tissue at and immediately below the head become infected later. Cream to pink fungal growth can occur ongrain.
    Key Features:The fungus can occur in seed or crop residue. Spores are spread by air. Warm moist conditions provide a favorableenvironment for disease development.
    Management: Timely harvest of grain at propermoisture. Hybrids with pigmented seed coats are more tolerant grain mold. Hybrid with dense, compact heads could be more damaged.
    Disease: Sorghum Downy Mildew
    Downy Mildew
    Symptoms: Yellow-green stripes in leaves. "Downy" growth from fungal spores may occur on underside of leaf. Leavesbecome shredded as season progresses. Heads are partially or completely sterile.
    Key FeaturesThe fungus survives in the soil for many years. Spores germinate and infect roots, and colonize plants inter nally. Infected plants produce spores carried by the air to other plants. Alsoinfects corn and shattercane.
    Management: Use resistant hybrids. Use seed treatedwith metalaxyl. Control shattercane to reduce inoculum. Long-term rotation to soybeans, wheat or forages reduces inoculum in the soil. Avoid cornsorghum rotation where the diseaseoccurs.
    Disease: Charcoal Rot
    Downy Mildew
    Cause:A fungus, Macrophomina phaseolina
    Symptoms: External symptoms of charcoal rot are lodging and poor grain filling. The lower stalks of infected plants disintegrate internally and the small, black resting structures (microsclerotia) of the fungus are found in the rotted area of the stem
    Management: Charcoal rot is not a problem in irrigated sorghum. The disease develops only when temperatures are hot and plants are under drought stress. A high plant density or previous cropping with cotton may predispose plants to charcoal rot. Sorghum grown under rain‑fed conditions rarely develops charcoal rot if plant density is low. Plants that develop a good root system in response to dry conditions early in the season and then exposed to a prolonged dry period are less likely to become diseased than those with a shallow root system promoted by numerous, light rainfalls.



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    Harvesting

    Producers consider harvest aids to provide for easier threshing or to hasten harvest to meet a delivery/pricing deadline, make fields more uniform for harvest or dry out the late-emerging non-productive sucker-head tillers. Extension believes there is questionable economic benefit of sorghum harvest aids particularly when maturity is occurring during summer and early fall when days are still quite warm.

    Currently, sodium chlorate and glyphosate are labeled for application in grain sorghum. Paraquat is not labeled for use in sorghum drydown. Glyphosate is a preferred option among many producers, as additional late-season weed control benefits may be achieved, particularly in fields that have significant Johnsongrass. Both chemicals generally state that applications should be made once the field is generally mature (black layer) and seed moisture is below 30 percent. The Rolling Plains region, however, struggles to get late planted sorghum harvested because once maturity is achieved foggy, moist weather prevails and long delays are common. So harvest aids may still be a consideration although earlier planting (late June rather than early July) may be just as effective for fall drydown. Once a harvest aid is applied, it is imperative that timely sorghum harvest occurs.

    Harvesting & Drying

    Grain sorghum can be harvested once seed moisture drops below 20 percent, however, few elevators have significant capacity to dry grain. Thus, grain needs to be delivered at 14 percent moisture or less. When drying conditions are favorable (temperatures > 75°F, breezy, low humidity) grain may lose one percent moisture per day. The standard test weight for grain sorghum is 56 lbs. per bu. Nevertheless, there are a couple of key points that guide grain sorghum harvest:

    Economic "Loss" from Selling Low Moisture Grain Due to Excessive Harvest Delay

    Producers understand the need for timely harvest to minimize potential lodging and the reduction in yield. A hidden loss of gross income, however, comes from delaying harvest well beyond when sorghum can be cut and sold at 14 percent moisture. Your pay weight is not adjusted up for low moisture, so you don't get to sell water. Any moisture in the seed up to 14 percent adds to your pay weight.

    If Sorghum Fails, Grazing & Nitrate/Prussic Acid Issues

    When grain sorghum fails due to drought, grazing and baling are options to recapture some value from the crop. Nitrate accumulation in sorghum crops tends to occur only when drought stresses the crop to the point where little growth is occurring, particularly when significant N fertilizer has been applied. Even though the sorghum is not growing, nitrate accumulation is still occurring in the plants. Prussic acid normally would only be a possible issue for grain sorghum for a very late maturing crop that willnot reach sufficient grain yield for harvest. Once a killing frost occurs the crop should be left ungrazed for a minimum of one week before grazing.

    After Harvest-Preserving Grain Sorghum Stubble

    A few producers may bale the hay and sell it for profit. Keep in mind, however, that the sorghum has value in terms of soil tilth, erosion control, the protection of future cotton seedlings, and the fertilizer replacement cost of the nutrients that leave the field in the hay.

    For each ton of stubble removed from a field you are also selling nitrogen and other nutrients in the forage, which has a replacement cost when you purchase fertilizer. Nitrogen content of grain sorghum stubble is about 0.4-0.6 percent (or about 2.5-3.5% crude protein), so a ton of baled stubble removes about 8-12 lbs. per N. At a fertilizer replacement cost of $0.50 per lb. of N, then each ton contains $4-6 worth of N, as well as values of P and K. This must be factored in to the price of the hay. If a hay harvester offers to buy your standing grain sorghum stubble 'as is' in the field, it is still not 'free money.' The nutrient losses let alone the intangible value of the stubble for soil and erosion protection.

    Sorghum Stubble's Value for Erosion Protection & Reduced Tillage

    If you are committed to no-till or strip tillage, the opportunity to manage the stubble to optimize erosion protection and possibly replace cover crop small grains for cotton seedling protection should be carefully considered. Many more producers are now inclined to leave the stubble on the surface. Extension believes sorghum crops that produce a minimum of ~1,500 lbs. of grain provide sufficient ground cover to express benefits for erosion control. Furthermore, particularly with the advent of GPS guidance systems, producers are programming their planting pattern to offset the planting of cotton and sorghum rows in rotation to minimize the need to disturb the sorghum stubble.

    Leaving the sorghum stubble stand as long as possible offers the best soil protection in the long run. To our knowledge, producers have never had a problem with sorghum stubble interfering with cotton harvest. Standing stubble does, however, catch tumbleweeds and contain nutrients you might wish to have available to a future crop.

    Plowing sorghum stubble does not increase organic matter. In dry West Texas soils which are often quite sandy, there is little stability for organic matter due to heat and lack of moisture. Any tillage operation compounds this as it destabilizes the organic matter you have. Research conducted by USDA on a sandy loam in Wellman, TX demonstrated that one tillage pass after five or more years of no-till was enough to undo all the gains in organic matter that had been achieved. Tillage and deep breaking sorghum stubble may improve the condition of your land for a time, but it does not increase organic matter after you have completely disturbed the root system.

    Grain Sorghum and Conservation Tillage

    Properly managed sorghum residues can greatly reduce water and especially wind erosion particularly on the sandy soils of West Texas. Producers are encouraged to experiment with tillage options that grain sorghum rotation affords, especially in retaining much or most of the stubble above the surface. Stubble can reduce the amount of light and wind at the soil surface which leads to moisture loss. Much of West Texas relies far too much on tillage or cover crops to control wind erosion and damage to cotton seedlings. Both options lead to moisture losses, and dedicated cover crops are not viable for dryland. Keep in mind that achieving the benefits of the ultimate conservation tillage program-no-till-requires patience in both learning how to make the system work and having the patience to await for coarse soils to develop aggregation.

    Grain Sorghum Crop Budgets & Regional Custom Rates

    Texas AgriLife Extension Service agricultural economics staff have prepared templates for an extensive list of crops including grain sorghum. Specific budgets are available for the South Plains (D-2), Rolling Plains (D-3), and the Concho Valley (D-7) at http://agecoext.tamu.edu, then click on "Crop & Livestock Budgets" and select 'District' or 'Commodity' to access the information for your region. In addition, Extension compiles custom rates for a variety of field and transportation operations which are summarized by USDA at the above website, then click on "Custom Rates Statistics." Finally, comparative crop budgeting is available for the Texas South Plains region at http://southplainsprofit.tamu.edu This document is an interactive Microsoft Excel spreadsheet in which you may enter your own numbers and compare them with other crops.


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    References

    1. FAO. 2007. Global Production of Grain sorghum. Online. http://www.fao.org/docrep/T0818E/T0818E03.htm#Chapter%202%20-%20Production%20and%utilization
    2. U.S. Grains Council. 2008. Sorghum. Online. http://www.grains.org/sorghum
    3. National Grain Sorghum Producers Association. Online. http://www.sorghumgrowers.com/sorghum%20101.html
    4. Kansas Grain Sorghum Producers Association. 2008. Kansas Ethanol Production.Online. http://www.ksgrains.com/ethanol/kseth.html
    5. U.S. EPA. 2009. Crop Production. Online. http://www.epa.gov/oecaagct/ag101/printcrop.html
    6. Figure 2. Pocket Guide to Crop Development: Illustrated Growth Timelines for Corn, Sorghum, Soybean, and Wheat. 2003. University of Illinois Extension Publication #C1389.