Sorghum Tips

Sugarcane Aphid Management Suggestions & Resources

This tip was provided by:

Calvin Trostle, Extension Agronomy, Lubbock, 806-746-6101, ctrostle@ag.tamu.edu

Texas High Plains

Sugarcane Aphid Management Suggestions & Resources

This edition of Sorghum Tips deals with SCA management in the Texas High Plains.  The information may also be relevant for the Concho Valley and Rolling Plains, though the information presented here was not developed in those regions.  There are differences in the High Plains recommendations vs. what we published in the March 3, 2016 Sorghum Tips for South & Central Texas (see http://texassorghum.org/sorghum-tips for Extension’s Dr. Robert Bowling’ comments).

Instead of reproducing here the details of current SCA recommendations for Texas High Plains grain sorghum, I refer you to the direct writings of Texas A&M AgriLife Extension’s High Plains entomology group led by Dr. Pat Porter, Lubbock.  Consult the Texas Sugarcane Aphid News blog at http://txscan.blogspot.com/  The March 2 posting is the first installment of advice with the topics:

  • Sugarcane aphid will most likely return at some level for renewed infestation of High Plains grain sorghum, so be prepared and plan for it.
  • Beneficial insects cleaned up the overwintering aphids in 2016, but what does this mean (or not mean) for 2017?  Read about early observations on the level of current beneficial insects observed in wheat.
  • What about 2017?  Certainly, early planting remains a primary consideration.  Late planting in 2015 was also a good strategy, but that didn’t hold in 2016.
  • Seed treatments are cheap insurance.  It appears that 45 days of protection can be obtained with neonicotinoid seed treatments.  This is especially helpful for seedling sorghum, but all sorghum regardless when planted, should use this strategy.
  • “Resistant” or “Tolerant” grain sorghum hybrids are still susceptible.  No grain sorghum hybrids have been shown to be able to keep SCA numbers below treatment thresholds, but they can slow the rate of SCA population increase.  All of these hybrids require scouting.
  • Additional information for SCA will be posted to the Sugarcane Aphid Network blog soon for the Texas High Plains.  Further topics will include initial treatment thresholds, insecticide rates and efficacy, and economic thresholds for a potential second spray.  Remember, High Plains SCA thresholds are lower than South Texas based on research to date.

Sugarcane Aphid Management Videos for the Texas High Plains

The Texas A&M AgriLife Extension entomologist team working on grain sorghum (Porter, Bynum, Reed Kesheimer) posted nine videos ranging from 3 to 8 minutes in their February 20 update.  See them all at http://txscan.blogspot.com/  Topics include early planting, “resistant” hybrids, thresholds, timing, insecticides to prevent sticky harvest issues, SCA effects on forage stalk quality, etc.

Sugarcane Aphid: Update, Outlook, and Early Season Thoughts on Management

This tip was provided by:

Robert Bowling, Extension Entomology, Corpus Christi, (316) 946-0329, robert.bowling@ag.tamu.edu

South Texas

Sugarcane Aphid: Update, Outlook, and Early Season Thoughts on Management

Sugarcane aphid is building populations on overwintering hosts from the Lower Rio Grande Valley up through the Coastal Bend of Texas.  Dry conditions and unusually high temperatures in the Valley have allowed farmers to get a big jump on seeding the 2017 sorghum crop.  Sorghum seeded early in February has emerged and conditions are favorable for rapid growth—also favorable for an early-season infestation by SCA.  This may be a harbinger of things to come for south Texas sorghum producers.

It is too early to say with certainty SCA will pose more an issue for sorghum producers in the Valley (and for south Texas) in 2017 than in 2016, but it is always a good idea to scout sorghum early and often for early aphid detection.  An insecticide seed treatment will provide approximately 30 to 50 days of protection from the planting date against SCA.  Start monitoring sorghum about three weeks after planting for early detection of SCA, for early season infestations which usually start on field edges especially where overwintering hosts such as volunteer sorghum or Johnsongrass are present. Always check field borders for SCA.

Many sorghum producers are moving toward sorghum hybrids with ‘high tolerance’ to sugarcane aphid.  Many of these hybrids in multi-state university testing programs have demonstrated their value when compared to an SCA susceptible hybrid.  Sugarcane aphids can be found on ‘highly tolerant’ sorghum hybrids, but their population growth is much slower than growth on susceptible hybrids.  Regardless, all sorghum should be routinely scouted for SCA.  Check with your seed rep before purchasing any sorghum hybrid.  They will have the knowledge of each product’s performance potential and placement not only within a region but within fields on your farm.  A list of sorghum hybrids for 2017 that have been identified as having sugarcane aphid tolerance is posted by United Sorghum Checkoff Program, http://www.sorghumcheckoff.com/farmer-resources/grain-production/hybrid-selection (From the 2016 list of 21 hybrids, 15 remain, six have been deleted, and 12 new hybrids were added for 2017, as of Feb. 28.)

Keep in mind that you are paid on pounds of grain produced and not the tolerance of your hybrid to sugarcane aphid.  We would not suggest abandoning a high performing SCA susceptible hybrid for an unproven hybrid with SCA tolerance.  Remember that SCA management is highly dependent on early detection and routine weekly or twice weekly scouting to treat when populations reach an economic threshold of 50 to 125 aphids per leaf (average of sampled plants; remember, this is a South Texas threshold, the threshold for the High Plains is lower).  Treatment must be applied within 3 to 5 days of reaching a threshold to prevent populations from reaching economically damaging levels.  Remember that carrier volume is extremely important to maximize penetration of the insecticide into the canopy (10-15 gallons/A by ground and 5 gallons/A by air).

Fungal Infection of Sugarcane Aphid, South Texas, 2016

I recently wrote about an epizootic fungus occurring in an insecticide efficacy trial in 2016 which colonized sugarcane aphids.  The fungus responsible was Lecanicillium lecanii.  Is this possibly a means of managing SCA?  Although epizootic fungi are highly effective for SCA (and other pests) management, their occurrence is very dependent on very specific parameters.  At this time, our observations on this fungus are limited to a small area of Texas in 2016.  It remains to be seen if it will be present let alone have an impact on Texas sorghum in 2017.  Currently, it is not clear if the fungus could be managed by producers for control of SCA.  For further reading on the fungus, see newsletters 1.7 & 2.1 at http://betteryield.agrilife.org/newsletters/

For more information on sugarcane aphid and other sorghum pests in South Texas please visit our website at http://betteryield.agrilife.org.

Planting Grain Sorghum: I. Row Spacing Width

This tip was provided by:

Calvin Trostle, Extension Agronomy, Lubbock, 806-746-6101, ctrostle@ag.tamu.edu

Statewide

Planting Grain Sorghum:  I. Row Spacing Width

The average Texas grain sorghum field has narrower row spacing than 20 and 30 years ago.  The impetus to do so incudes better understanding of plant growth response, improved sorghum shading of the soil for reducing evaporation and suppressing small weeds, more conservation tillage, and in some cases the desire to push for higher yields with more uniformly spaced plants.  And finally, when sorghum producers (as well as corn, cotton, and other crops) push for higher yields there is a common belief that higher plant populations may enable you to realize that most years.  But as any Texas farmer knows, weather varies from year to year, and a crop will not respond the same way each year.  Higher plant populations can limit your sorghum’s ability to respond to environment, especially rainfall.

Whether a farmer moves from 40” rows to 30” rows in the High Plains, from 36” or 38” rows to 30” in South Texas, or to 15” or 20” row spacing anywhere in the state, there is tendency to increase seed drop thus resulting in a higher population.  I tend to believe this increased seed drop is a neutral to negative effect in most Texas sorghum fields because many farmers are in fact already at the upper end—or beyond—what seed drop they should be using (see below where to get AgriLife suggestions).  I recommend that farmers initially do not increase seed drop when they reduce row spacing width.  Instead, let the more uniform spacing of plants in the field be your friend and potentially increase your yield.  That alone is likely an improvement in agronomic practices.

I will cover in-row spacing in a future Sorghum Tip.

What if I am drilling my grain sorghum?
Some Texas sorghum farmers, at least in the High Plains, may even drill their grain sorghum.  Compared to 30” rows or even 40” rows, should they increase their grain sorghum seeding rate?  I usually say ‘no.’  First, it is hard to set drills to plant a targeted seed drop.  They are designed to plant seed in volume, like wheat.  You may not be able to get a sorghum seeding rate low enough without taping off 1 in 3 drill rows, or even 1 in 2 drill rows.  Again, let the spacing of your seed and the subsequent plant be your friend.  I will concede, though, a 10% increase in seeding rate if drilling due to the inferior ability of a drill to place seed like a planter does.  If the ground is rough and thus seedbed planting conditions are less than desirable, I might increase seeding rate 20%, but know that if you get the rain you hoped for, all the seed could germinate, and you are immediately overpopulated.

What grain sorghum seeding rates should I be using?
In some areas of the state we truly don’t have good data, or it may be 30 or more years old.  We don’t discount the data from the distant past, but as hybrids have changed some, tillering ability may be different, etc. it would be good if AgriLife could bring you recent multi-year and multi-site data for each region of the state.  For our current general suggestions see the United Sorghum Checkoff Program pocket grain sorghum production guides at http://www.sorghumcheckoff.com/farmer-resources/grain-production/  There are three editions that cover Texas (South & Central Texas; South Plains/Concho Valley/Rolling Plains (the West Texas edition), and a third edition that covers the Texas Panhandle.  The former two guides were prepared by Texas A&M AgriLife staff, the Panhandle edition was a joint effort between Texas A&M and Kansas State.

Preplant and Preemerge Herbicide Options in Grain Sorghum

This tip was provided by:

Ronnie Schnell, Cropping Systems – Statewide, College Station, ronschnell@tamu.edu

Statewide

Preplant and Preemerge Herbicide Options in Grain Sorghum

Early competition from broadleaf and grass weeds in grain sorghum can result in yield loss. Use of soil active herbicides applied before planting or before sorghum emergence is critical for effective weed management. Below is a partial list of herbicide options and approximate cost at low and high labeled rates. Prices are for planning purposes only. Actual cost may vary. Always read and follow label directions for specific rates and timing. EPPS = early preplant surface, SPPI = shallow preplant incorporate, PRE = after planting but before crop emergence.

  1. atrazine – (AAtrex, Atrazine 4L)                                                                           $5-10/A
  • 1-4 pts/A, PRE only (TX Gulf Coast & Blacklands only)
  • Lower rates (1-2.5 pts/A) for Pigweed control in other regions.
  • Supplemental Label can be found at:http://www.cdms.net/ldat/ld280000.pdf
  • Good control of broadleaves and some grasses.
  • Do not apply to coarse textured soils or soil with less than 1% organic matter.
  • Be aware of rotation restrictions.
  1. saflufenacil (Sharpen)                                                                                             $6-14/A
  • 1-2 oz/A EPPS or PRE
  • Burndown herbicide with some residual activity
  • Good activity on broadleaves.
  • 2-4 weeks of residual, some hybrids may be sensitive.
  1. dimethenamid-p – (Outlook, Establish)                                                                   $11-23/A
  • 12-21 oz/A based on soil texture, EPPS, SPPI, PRE
    • Seed Safener (Concep) Required.
    • Good control of grass and broadleaf weeds.
  1. s-metolachlor – (Brawl, Medal, Dual II Magnum, Brawl II, Cinch, Medal II)                       $10-28/A
  • 1-1.6 pts/A applied EPPS, SPPI, PRE
  • Seed Safener Required.
  • Good control of several annual grasses.
  1. acetochlor – (Warrant)                                                                                           $13-27/A
  • 1.5-2.5 qt/A SPPI, PRE
  • Seed Safener Required.
  • Annual grass control and some broadleaves.
  1. mesotrione – (Callisto)                                                                                           $36-39/A
  • 6-6.4 oz/A EPPS or PRE
  • Good broadleaf control.
  • Add a surfactant or crop oil for control of emerged weeds

 

Pre-Mixes (products requiring safener (Concep) in red)

  1. dimethenamid + atrazine (Establish LITE, G-Max LITE)                                             $11-23/A
  2. s-metolachlor + atrazine (Bicep II Magnum, Charger Max ATZ, Cinch ATZ) $16-26/A
  3. saflufenacil + dimethenamid (Verdict)                                                              $18-34/A
  4. s-metolachlor + mesotrione (Zemax)                                                               $42/A
  1. s-metolachlor + mesotrione + atrazine (Lumax)                                                           $51/A

Still “Free” Nitrogen for Grain Sorghum Production: Revisiting Soil Profile N

This tip was provided by:

Calvin Trostle, Extension Agronomy, Lubbock, 806-746-6101, ctrostle@ag.tamu.edu

Statewide

Still “Free” Nitrogen for Grain Sorghum Production:  Revisiting Soil Profile N

It has been almost five years since I first mentioned this topic in Sorghum Tips. What has changed?—Nothing! Across Texas crop consultants, producers, AgriLife staff, etc. continue growing awareness of the potential for accumulating nitrate-nitrogen (NO3-N) in the soil. This nitrogen has value for your sorghum and other crops. “Profile N” is readily available nitrogen accumulating below standard soil sampling depths (most often 6”). This accumulation is due to over fertilization (or underutilization in years when production is sub-par) with N, and the majority of the time producers are not aware of the presence of this N in the soil. Historically this N is not accounted for in supplying crop nutrient requirements, but it should be—all of it!

The level of N accumulation can vary greatly due to fertilization practices, downward percolating moisture from rains which carries the soluble and mobile nitrate, soil type, etc. Sometimes substantial N is found even below 3’ in the soil, but only deep rooted crops can tap that N. Texas A&M AgriLife’s Soil, Water, and Forage Testing Lab has updated their “Profile Soil Sample Information Form” (SP17) for 2017. This form pairs your standard 0-6” soil sample (analyzed for multiple nutrients including N, P, etc.; routine analysis is still only $10, the same as in 2012) with a second soil sample from below 6” to as deep as 24”. This paired soil sample is analyzed for nitrate-N only, $4/sample. The submitter marks the depth so a proper calculation of nutrient requirements can be made by the soil test lab

Is profile nitrate-nitrogen down to 24” deep 100% available to grain sorghum?

Yes. Even slightly deeper N is largely available. The Profile Soil Sample form for N credits all nitrate N at 6-24” to your crop requirement thus reducing fertilizer costs. Extension recommends that producers include at least some profile soil N sampling to establish whether there might be deeper N present.

Some producers disagree with crediting all nitrate-N in the 6-24” range to grain sorghum. In Texas across the state for different soil types, and yes, different crops, for all practical purposes you can credit all measured nitrate-N to your crop requirement. Many producers have never heard this. When I conduct Extension educational programs on this topic, I ask for a show of hands “How many of you think you can fully credit 100% of soil nitrate-N in the top 24” to your crop requirement?” (I deliberately emphasize ‘fully’ and ‘100%’). Normally about 10% of attendees say you can, and 20-30% say you can’t, and the rest are sitting on the fence. Yes, as noted above, “for all practical purposes…” Perhaps a producer is truly uncomfortable with this idea; if so, then credit 2/3 or ¾ of you soil test profile N—this is still a potentially significant cost savings. What do other states do in their soil testing labs do? They generally credit 100%, and in fact several states including Kansas now recommend a 24” soil sampling for all nutrient analyses.

The soil test lab I prefer doesn’t offer a profile soil test for N. What do I do?

Most labs in fact don’t have a separate form for nitrate-N only soil profile test. If you like the concept you can still submit your samples to that lab, just fill out one form for each sample then you will need to total the sum of nitrate-N. for all samples (above 3’) by your own hand.

The current Texas A&M AgriLife Extension Profile Soil Sample form is found at http://soiltesting.tamu.edu/files/profilesoil.pdf

Grain Sorghum Hybrid Trials & Selection for 2017

I attended the Amarillo Farm Show on Wednesday. I have about 10 seed company catalogs that include grain sorghum hybrids. At first glance you would not know where to begin if you didn’t have your own track record of preferred grain sorghum hybrids—there are almost two dozen hybrids listed in some catalogs. Many of these catalogs are “national” in that they list all hybrids the company markets, including what you might plant in Nebraska, Missouri, Georgia, or Texas, for example. In most cases, however, I visited with company representatives and have circled in my catalogs their primary choices for dryland and irrigated hybrids for my region.

Texas A&M AgriLife Research is publishing every week additional 2016 grain sorghum hybrid trial results here (also note the “Archive” link for results from 2015 and previous years on the same page). None of the current trials have any data on sugarcane aphid observations.

As producers across Texas consider grain sorghum hybrids for 2016, your recent experience will color greatly the value you place on potential grain sorghum SCA tolerance. Producers in South & Central Texas have not had as much trouble the past two years as was probably feared after the first two years that SCA appeared. In contrast, in much of the Texas Panhandle and the northwest South Plains, growers in 2016 faced tremendous damage in this area of the state where SCA arrived the latest.

For hybrid trials that various states set up to test hybrid performance in the presence of sugarcane aphid, there are several types of data that you may find as these trials are published over the next 2 to 3 months. This data will include:

  • SCA counts of aphids per leaf (including lower and upper leaves) and a reporting of how soon initial SCA infestation occurred and perhaps SCA counts at different growth stages throughout the season.
  • Reductions in stand of younger plants if SCA killed seedlings (although it is likely it can’t be assumed that all trials had uniformity of planted seed having a seed treatment insecticide; most hybrids planted in these trials probably do).
  • SCA damage ratings (likely on a scale of 0 to 9 or 0 to 10) taken later in the season.
  • Percentage of lodged plants.
  • Head exsertion (how far the heads emerged past the flag leaf; heavily damaged plants may not have the energy to push the head out very well).
  • Yield—but not just regular yield. Yield is the bottom line, and the best trial results will compare yield of grain sorghum hybrids with and without SCA control. This enables comparisons of the total impact of SCA on hybrid performance.

Watch for trial reports that were conducted specifically to evaluate hybrid performance in response to sugarcane aphid. Texas A&M AgriLife has several forthcoming trials, and we will be interested in the same types of trials from surrounding states. United Sorghum Checkoff Program’s Dr. Brent Bean will be compiling numerous reports across states. I will let you know when these reports are reported.

A note about Sugarcane Aphid in South Texas—Robert Bowling’s 2016 Summary

Dr. Robert Bowling, Texas A&M AgriLife Extension entomologist, Corpus Christi, published his season-ending newsletter on Monday, Nov. 28. He discusses the “head scratcher” observations, e.g., sudden collapse of numerous SCA populations observed in many fields in 2016, as well as a potential fungal pathogen of the sugarcane aphid. See his most recent “Rolling with Bowling” post here.

Sugarcane Aphid Tolerant Grain Sorghum Hybrids

This tip was provided by:

Ronnie Schnell, Cropping Systems – Statewide, College Station, ronschnell@tamu.edu

Statewide

Sugarcane Aphid Tolerant Grain Sorghum Hybrids

Seven commercially available grain sorghum hybrids were evaluated for tolerance to sugarcane aphids (SCA) at five locations in Texas during 2016. All were compared to a susceptible public check (Tx399 x Tx430). Late plantings (mid May) were used to increase the chance of pre-bloom SCA infestations. Given the late planting, yield from SCA trials were low and are not provided in this report. Results from College Station and Greenville have been reported.

SCA was present at both sites within 6 weeks of planting, although numbers remained below threshold (50 per leaf) through flowering. By Late July, the susceptible check had a mean number of SCA per leaf in excess of 200 and remained above 100 through harvest. In contrast, five commercial hybrids demonstrated consistent lower levels of SCA per leaf. DKS 37-07, AG 1203, BH4100, SP7715 and W7051 all remain below 50 SCA (mean per leaf) throughout the duration of the trial at College Station and Greenville. Performance of these hybrids at other locations is not available yet. Variation of timing, intensity and duration of SCA infestations may affect performance of these hybrids at other locations. However, these results suggest that these hybrids have some level of tolerance to SCA, which may reduce the number of insecticide applications or possibly the need for insecticide applications.

Is the maturity and yield potential of these hybrids appropriate for your farm? If so, including them among hybrids you plant may be appropriate. Maturity and yield information obtained from Texas A&M AgriLife trials in the Gulf Coast and Central Texas regions during 2016 are provided below. Yield differences for early maturing hybrids should be weighed against potential savings on insecticide sprays.

Sorghum Partners – SP7715

  • Medium-Full
  • Mean grain yield at Thrall, TX was 5,287 lbs/acre, +4% of trial mean yield.

Warner Seed – W7051

  • Medium-Full
  • No yield information available in the region for 2016.

BH Genetics – BH4100

  • Medium
  • Average yield from 4 trials in the Blacklands region of Central Texas was 4,708 lbs/acre, -3% of the regional trials mean yield.

Advanta – Alta Seeds AG1203

  • Medium-Early
  • Average yield from 15 trials in the Upper Gulf Coast and Central Texas region was 4,642 lbs/acre. Overall, was -5% of the trail mean yields.

Dekalb – DKS 37-07

  • Medium-Early
  • No yield information available in the region for 2016.

Grain Sorghum Hybrid Trials and Selection for 2017

This tip was provided by:

Calvin Trostle, Extension Agronomy, Lubbock, 806-746-6101, ctrostle@ag.tamu.edu

Statewide

Grain Sorghum Hybrid Trials and Selection for 2017

I attended the Amarillo Farm Show on Wednesday.  I have about 10 seed company catalogs that include grain sorghum hybrids.  At first glance you would not know where to begin if you didn’t have your own track record of preferred grain sorghum hybrids—there are almost two dozen hybrids listed in some catalogs.  Many of these catalogs are “national” in that they list all hybrids the company markets, including what you might plant in Nebraska, Missouri, Georgia, or Texas, for example.  In most cases, however, I visited with company representatives and have circled in my catalogs their primary choices for dryland and irrigated hybrids for my region.

Texas A&M AgriLife Research is publishing every week additional 2016 grain sorghum hybrid trial results at http://varietytesting.tamu.edu/grain-sorghum/  (also note the “Archive” link for results from 2015 and previous years on the same page).  None of the current trials have any data on sugarcane aphid observations.

As producers across Texas consider grain sorghum hybrids for 2016, your recent experience will color greatly the value you place on potential grain sorghum SCA tolerance.  Producers in South & Central Texas have not had as much trouble the past two years as was probably feared after the first two years that SCA appeared.  In contrast, in much of the Texas Panhandle and the northwest South Plains, growers in 2016 faced tremendous damage in this area of the state where SCA arrived the latest.

For hybrid trials that various states set up to test hybrid performance in the presence of sugarcane aphid, there are several types of data that you may find as these trials are published over the next 2 to 3 months.  This data will include:

  • SCA counts of aphids per leaf (including lower and upper leaves) and a reporting of how soon initial SCA infestation occurred and perhaps SCA counts at different growth stages throughout the season.
  • Reductions in stand of younger plants if SCA killed seedlings (although it is likely it can’t be assumed that all trials had uniformity of planted seed having a seed treatment insecticide; most hybrids planted in these trials probably do).
  • SCA damage ratings (likely on a scale of 0 to 9 or 0 to 10) taken later in the season.
  • Percentage of lodged plants.
  • Head exsertion (how far the heads emerged past the flag leaf; heavily damaged plants may not have the energy to push the head out very well).
  • Yield—but not just regular yield.  Yield is the bottom line, and the best trial results will compare yield of grain sorghum hybrids with and without SCA control.  This enables comparisons of the total impact of SCA on hybrid performance.

Watch for trial reports that were conducted specifically to evaluate hybrid performance in response to sugarcane aphid.  Texas A&M AgriLife has several forthcoming trials, and we will be interested in the same types of trials from surrounding states.  United Sorghum Checkoff Program’s Dr. Brent Bean will be compiling numerous reports across states.  I will let you know when these reports are reported.

A note about Sugarcane Aphid in South Texas—Robert Bowling’s 2016 Summary

Dr. Robert Bowling, Texas A&M AgriLife Extension entomologist, Corpus Christi, published his season-ending newsletter on Monday, Nov. 28.  He discusses the “head scratcher” observations, e.g., sudden collapse of numerous SCA populations observed in many fields in 2016, as well as a potential fungal pathogen of the sugarcane aphid.  See his most recent “Rolling with Bowling” post at http://betteryield.agrilife.org/files/2016/07/Updates-on-the-SCA-and-Fungal-Pathogens.pdf

Will Grain Sorghum Respond to Starter Fertilizers?

This tip was provided by:

Ronnie Schnell, Cropping Systems, College Station, ronschnell@tamu.edu

Statewide

Will Grain Sorghum Respond to Starter Fertilizers?

Stater fertilizer is defined as the application of small amounts of nitrogen (N) and phosphorus (P) near the seed at planting. In-furrow or “pop-up” applications apply small rates, usually less than 6 gallons per acre, directly in the seed furrow. Another option is to place the fertilizer about 2 inches to the side and 2 inches below the soil surface. This is referred to as a 2×2 application. Application rates can be increased for 2×2 placement due to greater separation from the seed. Rates may need to be adjusted (lowered) in sandy soils to prevent seedling damage.

Starter fertilizers have been investigated extensively for corn in northern latitudes. Results in corn have been inconsistent, many showing a positive yield response in less than 4 out of 10 years. Will grain sorghum respond to starter fertilizer in Texas? Limited information is available for grain sorghum. Research from Kansas in the 1990’s shows an 18% yield increase and 6- to 7-day reduction in bloom date with a 2×2 application of N and P compared to broadcast application of the same rate. Another study from Kansas in 2002 showed a 26% yield increase for starter fertilizers compared to no-starter checks and a 11-day reduction of days to mid bloom. Trials are underway in central Texas looking at starter fertilizers in grain sorghum in combination with nitrogen rate and timing. During the first year, grain yield was increased 14% with the 2×2 application (22-73-0/acre) compared to no starter or a lower rate in-furrow starter application (7-24-0/acre). Earlier flowering was observed with 2×2 starter application in Texas as well, although only a few days earlier than plots without starter. There certainly could be advantages to earlier flowering in Texas. However, more work is needed to determine the actual economic response to starter fertilizers in Texas.

Soil sampling should be conducted to determine P requirements for grain sorghum production. Soils with low levels of extractable P are more likely to see a response to starter fertilizers. Depending on soil test recommendations, in-furrow or 2×2 application of starter fertilizers are a convenient and efficient way to apply needed P. Also, there are many different sources of phosphorus fertilizer available today that can be used in starter fertilizer solutions. Polyphosphates, orthophosphates and various ratios of the two are found in many products today. Given current grain prices, using the product that provides the most nutrient for the best price is likely the best option.  Efficient timing, rate and placement will have greater impact than any particular source.

Grain Sorghum Stubble vs. Planting a Cover Crop

This tip was provided by:

Calvin Trostle, Extension Agronomy, Lubbock, 806-746-6101, ctrostle@ag.tamu.edu

Statewide

Grain Sorghum Stubble vs. Planting a Cover Crop

In past Sorghum Tips I have outlined several points regarding our management and understanding potential benefits that sorghum stubble may afford.  Access some of the previous information at http://texassorghum.org/sorghum-tips (at the bottom of the page you can click on earlier pages, they are arranged in reverse chronological order).  Regarding sorghum stubble three of these posts include:

  • Grain Sorghum, Surface Residues, and Soil Organic Matter. July 24, 2012.  Grain sorghum stubble is a ‘blanket’ to protect the soil surface and minimize erosion.  Farming into stubble is increasingly a common practice across the U.S.  Learn how to manage the stubble and farm it with possible modifications to your equipment.  Tillage of sorghum stubble into the soil does not appreciably increase soil organic matter as some of the soil matter you already have is disturbed and lost (incorporating residues is an “exchange” of organic matter).  The best route to maintaining and improving stable long-term soil organic matter content is to leave the roots undisturbed.
  • Baling Sorghum Stalks:  I—Loss of Nitrogen ($) from the Field.  November 19, 2014.  When sorghum stalks are removed from the field, a modest but significant amount of N (roughly 1% of the biomass) is nitrogen, which has a replacement cost that is often not factored into the price you receive.  Grain harvest or grazing remove much less N and is not a concern.
  • Baling Sorghum Stalks:  II— Loss of Soil Cover Protection.  December 9, 2014.  Removal of sorghum stalks in baling means that you are selling an asset—and probably not getting compensated adequately for the intangible value of your “blanket.”

Cover cropping is a common topic across much of the U.S.  NRCS promotes cover cropping.  Several industry publications like No-Till Farmer and Dryland No-Tiller newsletter highlight producers using cover crop practices across the country.  I have attended several cover crop conferences, and I have some work on the topic myself in the Texas High Plains.  Much of the reporting on the successes of cover cropping come from regions of the U.S. that either have high rainfall (e.g. more than the annual crop requires) or lower evaporative demand (cooler conditions where 1” of moisture goes much further than it would in Texas).

A Cover Crop Caveat…

A caveat—and I assert a major one—is that outside of the areas noted above there is not a lot of data to date from universities, USDA Agricultural Research Service (in contrast to NRCS), etc. that clearly demonstrates value of cover cropping (and this type of data needs to be long-term to capture the potential benefits that can occur over time).  The primary concern in many drier areas, which would include much of Texas, is that there is not sufficient moisture to support investing some of your water resources in a cover crop.  This is a fair question though note that tillage practices are the culprit in significant potential moisture losses.

Cover crops have costs starting with the seed.  Some recommendations from seed companies can easily exceed $30/acre, usually for a multi-species blend.  For any area in Texas multi-species blends may be only 3 or 5 species (probably OK) vs. a shotgun approach with up to 15 species, several of which are quite possibly not well adapted and don’t grow (so why pay for them?).  Also, winter blends (think colder conditions of the Texas High Plains) will include a few legumes, but Texas A&M AgriLife observations are that most legumes don’t nodulate well (may not have a crop-specific Rhizobium or Bradyrhizobium inoculant) and if soils are cold there is little nitrogen fixation occurring—thus the purported benefit of adding N to the soil ecosystem is not realized.

Grain sorghum stubble vs. separate planting of a cover crop.  I believe this is an important consideration, especially in drier areas of Texas where grain sorghum is the only adapted summer annual crop you can plant that will generate much residue.  Do not overlook the value of this stubble.  It may preclude any need to consider costs associated with establishing a cover crop.  One selling point of cover crops is “A living root in the soil at all times” which fosters microbial activity thus contributing to nutrient cycling.  This is often mentioned as if to lead you and I to conclude that there is no biological activity if there is not a live root in the soil, and this is simply not true.  There is massive amounts of biological activity, and though it is somewhat less, soil microorganisms are busy decomposing root matter in the months after a root dies, and these populations of organisms will increase rapidly once live root matter returns to the soil.  Cover cropping may be viable for your farm, and I encourage Texas farmers to experiment.  But don’t overlook existing and “free” resources—like your remaining grain sorghum stubble—in terms of achieving some of the same goals that cover crops in principle may offer.

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