Sorghum Tips

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.

Lingering Issues from Wet Fields in 2015 & 2016? Soil Compaction and Management

Wet field conditions during 2015 and 2016 disrupted many field operations and forced many activities to be performed when soil conditions were less than ideal. Traffic from tillage, planting, fertilizing, spraying and harvest activities can lead to soil compaction when soils are too wet. Soil compaction is the compression of soil volume, reducing the amount of pore space between soil particles. Reduced pore space limits movement and volume of air and water in the soil profile. Soil compaction can restrict root penetration, reduce water infiltration, reduce water and nutrient uptake and reduce yields for years. Yield loss can range from 5-30% depending on severity.

There are four types of compaction: surface crusting, surface compaction, tillage pan and deep compaction. Surface crusting is caused by the impact of raindrops on soils with weak aggregates. Surface compaction occurs near the surface within the normal tillage depth and is caused by any pressure applied to the soil surface. Surface crusting and surface compaction can generally be alleviated through normal tillage practices such as chisel plowing. Tillage pans and deep compaction develop below the normal tillage depth. Tillage pans develop when the same tillage depth is used year after year. Deep compaction is caused by axle load of field traffic (Figure 1). The severity of deep compaction is influenced by equipment weight, tire and axle number, tire inflation, soil moisture and number of passes. High axle loads from combines and grain carts can cause severe compaction.

The best approach is to prevent soil compaction from occurring. Tips for preventing compaction include:
• Avoid field activities if possible when soils are too wet.
• If working on wet soils, frequently empty combines and grain carts to reduce axle loads.
• Minimize traffic from tractor-trailers or other vehicles with high inflation pressure and small footprint.
• Reduce tire pressure, use floatation tires or tandem axles.
• Use smaller/lighter equipment when possible.
• Reduce axle loads below 10 tons.
• Control traffic patterns.

Alleviating deep soil compaction can be expensive and results are not guaranteed. Subsoiling may be required if compaction is obviously limiting yield. Subsoiling refers to tillage at a depth of at least 14 inches. Subsoiling should be performed to 1 inch below the compacted zone. Subsoiling should occur when the soil is dry enough for the compaction zone to be fractured. Subsoiling when it is too wet will not fracture the compacted layer. Excessive tillage or subsoiling can destroy soil structure making soil more susceptible to compaction in the future. Plans for preventing compaction are critical following subsoiling activites.

Wrapping up Grain Sorghum Crop In-Season Management Decisions for 2016

This tip was provided by:

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

Statewide

Wrapping up Grain Sorghum Crop In-Season Management Decisions for 2016

Grain sorghum across Texas ranges from harvested several months ago in South Texas to pre-bloom in the lower Texas High Plains.  The further northwest in Texas the more likely there are still significant management decisions remaining in the cropping season.  Here are three remaining in-season management issues for finishing the Texas grain sorghum crop:

  • Sugarcane aphid.  Activity in the High Plains is mixed as some fields have hit thresholds with significant potential damage whereas other fields seem to have a prolonged duration of low levels of SCA that have not taken off.  Recent rains and cooler temperatures may be slowing SCA development, but as noted in earlier Sorghum Tips, this is no time to be complacent. Remember, all grain sorghum hybrids are susceptible to SCA at some level.  To review recent SCA information from Texas A&M AgriLife, re-visit the information and web links in the May 25, 2016 Sorghum Tip by entomologist Dr. Ed Bynum, see http://texassorghum.org/avoiding-complacency-about-sugarcane-aphid.html
  • Irrigation termination.  With recent rains over most of the Texas High Plains irrigation needs to make yield goals have lessened, and later maturing dryland sorghum is in better shape provided N fertility is available to make yield.  Typically irrigation termination occurs by early soft dough if some soil moisture remains.  For a brief review of late-season grain sorghum irrigation see the Sorghum Tip from August, 2012, at http://texassorghum.org/irrigation-termination-for-high-plains-grain-sorghum.html
  • Harvest aids.  We reviewed information for grain sorghum harvest aids in September 2015.  Evaluate cost of treatment and your yield potential and apply your assessment of A) lodging potential, and B) your ability to harvest in timely fashion rather than letting the crop sit for a long time in the field if you get busy with corn harvest, wheat planting, and cotton harvest.  See the prior information at http://texassorghum.org/harvest-aids-in-grain-sorghum-a-review.html

 

Bushland/Amarillo Forage Sorghum Field Day, September 8

Dr. Jourdan Bell, extension agronomist, Amarillo, will showcase the Texas A&M AgriLife forage sorghum hybrid research trials near Bushland on September 8, 9:00 AM-12:00 PM.  The tour will convene at the plots north of Bushland, plots north of Bushland at the intersection of Jim Line and Blessen Roads (35.205836, -102.041460).  This trial of commercial hybrids is among the largest of any kind in Texas—101 hybrids in 2016—and provides excellent multi-year data.  For further information contact the Amarillo AgriLife Center at (806) 677-5600, or e-mail Dr. Bell, jourdan.bell@ag.tamu.edu

“Feed Grain Outlook”—A Newsletter of AgriLife Extension Agricultural Economics

This tip was provided by:

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

Statewide

“Feed Grain Outlook”—A Newsletter of AgriLife Extension Agricultural Economics

For this edition’s regular Sorghum Tip I am reminded that growing grain sorghum is not all about planting date, hybrid choice, seeding rate, your fertility program, and managing weeds and pests.  Your economics assessment of sorghum via your budget and market prospects are important, too.

Dr. Mark Welch, Texas A&M AgriLife agricultural economist, specializes in the study and reporting of grain markets and their trends in production, usage, pricing, and supply.  He captures this information in his weekly newsletter Feed Grain Outlook.  Dr. Welch perspective on the markets includes his experience as a farmer in the High Plains as well as a feedlot operator.  Though the majority of Dr. Welch newsletter discusses corn, grain sorghum is also a significant part of the newsletter.  Readers can review recent data for feed use, carryover stocks, the proportion of the grain sorghum crop going to ethanol (and what proportion of ethanol production is from grain sorghum vs. corn), and China sales.  Much of the information Dr. Welch discusses is from USDA.

If you would like to receive a weekly e-mail with the Feed Grain Outlook newsletter, e-mail Dr. Welch at jmwelch@tamu.edu (office phone 979.845.8011) to be added to the distribution list.  You may view recent editions of the newsletter at http://agecoext.tamu.edu/resources/market-outlook/feedgrain-outlook/

Some of this information may also be reported by Texas Grain Sorghum Association or National Sorghum Producers, but Dr. Welch adds an additional dimension in his weekly analysis.  He welcomes your inquiries and interest in grain sorghum across the state.

Stalk Rots and Harvest

This tip was provided by:

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

Statewide

Stalk Rots and Harvest

Stalk rots can occur in sorghum and often go unnoticed until significant lodging occurs. Yield loss can result from severe lodging but also from reduced head size and poor grain fill.  Two common stalk rots are charcoal rot and fusarium rot. Each are caused by different fungal pathogens. The fungus invades the plant through the crown roots and then continues to colonize and destroy (shredding) the tissue of the lower nodes. Fusarium rots will cause tan to reddish colored shredding while charcoal rots will cause grayish to black shredding. Often the tissue at the second or third node above the crown roots become so weak the plant will eventually lodge.

Moisture stress is a common contributor to the development of stalk rots although crop nutrition, insect damage and plant populations will contribute as well. Some hybrids are more susceptible than others but no hybrid is immune. Lower plant populations can help in two ways; reduce stress due to interplant competition for resources (water and nutrients) and greater stalk diameter. Larger stalks will stand better than thin stalks, especially when disease is present.

As harvest approaches, the presence of stalk rots should be considered when making decisions about harvest timing and use of harvest aids. Presence of the disease can be easily checked using a pinch test. Simply pinch the stalk between your thumb and index finger at nodes just above the brace roots. If the stalk tissue is soft, stalk rot is likely present. You can split the stalk open to confirm. The degree to which the fungus has destroyed the tissue will affect standability. Shredding across multiple nodes will increase the susceptibility to lodging. Harvest as soon as possible to avoid yield loss due to significant lodging. Additionally, dry down after harvest aids are applied can exacerbate lodging. Severely infected plants will likely fall regardless of application of harvest aids.

For information on grain sorghum or sorghum forages for your area, or for specific questions you have on sorghum, contact your local county agricultural Extension agent, an Extension crop specialist, Dr. Ronnie Schnell (ronschnell@tamu.edu) or Dr. Calvin Trostle, extension agronomist, Lubbock at (806) 746-6101, ctrostle@ag.tamu.edu  Your question will be relayed to the appropriate Texas A&M AgriLife staff as needed.

 

 

Avoiding Complacency about Sugarcane Aphid

This tip was provided by:

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

Central, North & High Plains 

Avoiding Complacency about Sugarcane Aphid

In his June 30 “Rolling with Bowling” entomology newsletter, Dr. Robert Bowling, Extension entomologist, Corpus Christi (361-265-9201, robert.bowling@ag.tamu.edu ) summarized 2016 sugarcane aphid dynamics (or lack thereof) in South Texas.  There was modest pressure in some area, but in many if not most instances SCA numbers though perhaps high early, these populations reduced greatly and were no longer an issue.  The newsletter will be posted shortly at http://ccag.tamu.edu/newsletters/ (call or e-mail if not yet posted).

Last year SCA showed up in the High Plains in late June.  This year there was overwintering SCA in three cages and a patch of Johnsongrass in the central and lower South Plains, but currently there are no reports of SCA any closer than the San Angelo area (which was a new discovery about a week ago).  Sorghum farmers everywhere, however, must not become complacent.  Scouting it still required.  Yes, an eventual report of SCA south and east of you 50 miles or 100 miles may help you understand movement and add impetus to your scouting, but SCA movement itself is hard to predict.   Tuesday night, July 5, I drove from Dallam Co. home to Lubbock in the face of a stiff south-southeast wind that was over 30 mph some of the time.  This is just the kind of wind for many hours that can enable airborne winged SCA adults to travel significant distances.

Please keep in touch with your local IPM agent, regional Extension entomology specialist, and networks like Texas Sugarcane Aphid News (http://txscan.blogspot.com) to keep abreast with up-to-date developments.

For a review of SCA and its management refer to the May 27 Sorghum Insider “Sorghum Tip,” available at http://texassorghum.org/2016-agrilife-extension-entomology-sugarcane-aphid-information.html

 

Last week, we received this comment from a reader regarding moisture levels in grain sorghum at harvest after posting our last Sorghum Tip:

It should be noted that most moisture and drying discounts reflect the loss in weight due to moisture in the grain and grain harvested at higher moisture ie 16% and dried to 14% or less will be prettier and grade better.  As you reflect in the article grain harvested at under 14% cost producers and it should be noted there is significant loss from cracks and lights being blown out of a combine at these lower moistures and this can cost producers significantly.  I think ideally a producer should start harvest where he can average 14% harvested grain at the finish.  Therefore starting at maybe 16% to know that when he finishes he will be at 14% and not 10% or 12% moisture.

Potential Income Losses in Harvesting Dry Sorghum Grain

This tip was provided by:

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

Statewide

Potential Income Losses in Harvesting Dry Sorghum Grain

The standard moisture for sorghum grain at harvest time is 14.0%.  If your grain sorghum moisture is above 14.0% you will be docked for the moisture.  If you are too much above standard moisture content for sorghum grain your delivery point may reject the grain, especially if they do not have drying capacity.

Common incentives that drive harvesting grain sorghum across Texas as soon as possible include minimizing potential storm and wind damage every day the crop remains in the field; muddy conditions that delay harvest if it rains again; risk of lodging; minimizing late-season weed issues; possible double-cropping scenarios where the sooner the next crop is in the more time it has for growth and maturation.

But there is another potential downside to harvesting dry sorghum—or any grain—when the crop remains in the field, further drying to well below standard moisture content.  Namely, the drier the grain, the more grain it takes to make a 100-lb., or cwt., pay unit.  In effect, being able to deliver sorghum grain as close as you can up to 14.0% enables you to “sell water.”  Conversely, as noted above, if grain moisture is above 14.0%, you don’t get paid—you get docked.

But how much is the potential income reduction in selling dry sorghum grain that perhaps you could have harvested sooner at somewhat higher moisture?  Is it a little?  Is it a lot?

Below is a table for sorghum grain with different moisture contents at a range of grain sorghum prices ($/cwt.) to help you understand what the potential for a reduction in your effective per-cwt. sorghum price is as you sell further and further below 14.0%.  A link to this table and a calculator, entitled “Sorghum Grain Moisture Calculator—Potential Income Loss” is posted on the sorghum page at

http://lubbock.tamu.edu/programs/crops/sorghum/ (and also soon in the Harvesting/Handling section at http://varietytesting.tamu.edu/grainsorghum/index.htm).

Screen Shot 2016-06-24 at 2.13.10 PM
Estimate your potential reduction in effective per-cwt. price for grain sorghum <14.0% moisture from the above table.  Access the calculator to determine reduction in potential income per cwt. with your actual %moisture and market grain price ($/cwt.).  Furthermore, with grain yield (actual or estimated) you can also calculate your potential reduction in income per acre and per field or farm.

Example:

You harvested grain sorghum at 11.0% moisture at a price of $6.50/cwt.  From the table (or the calculator in the online file) you find that you have effectively reduced your price $0.22/cwt. relative to 14.0% moisture.  At 5,000 lbs. per acre, this is a loss of potential income of up to $10.96 per acre.  And if you have 400 acres of sorghum, then you could have “sold water” and preserved up to $4,382 of income.

Weather, availability of harvest equipment, etc. will dictate when you can actually harvest grain sorghum, and no, you can’t hit 14.0% most of the time.  But if by more timely harvest you can sell grain sorghum at 12.0% moisture instead of 10.0% moisture, in the above example you can preserve some income (improve $0.14/cwt.; $7.05/acre; and $2,823 for this 400 acres of grain sorghum).  The difference is enough to factor in your harvest management decisions to put that money in your pocket.

High Plains

Late-Plant Grain Sorghum

For producers looking at late-planted grain sorghum in the Texas High Plains consult the updated guide “2016 Alternative Crop Options after Failed Cotton and Late-Season Crop Planting for the Texas South Plains.”  This includes needed information for grain sorghum and other crops for late planting, including last recommended planting dates based on your location, sorghum hybrid maturity, or other crops.

 

Wet Weather and Nitrogen Losses from Soil

This tip was provided by:

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

Statewide

Wet Weather and Nitrogen Losses from Soil

Nitrogen losses from soil following fertilizer applications to crops can be difficult to quantify after periods of wet weather. How much nitrogen was lost and how much does it vary spatially? If significant amounts are lost, yield reductions are likely. Answering these questions is critical when considering supplemental or “rescue” applications of nitrogen. Understanding nitrogen loss pathways will help to estimate nitrogen loss.

Nitrogen is lost from soil by four main pathways: denitrification, runoff, leaching and volatilization. When excessive rainfall and saturated soil conditions occur, denitrification and leaching are the greatest concerns. Many factors can affect denitrification and leaching losses, including soil texture, fertilizer type and rate, placement and timing, soil temperatures and the amount of rainfall received (duration of saturation).

Nitrate nitrogen (NO3-N) is required for nitrogen to be lost from soil by these two processes (leaching and denitrification). Understanding how much nitrate-nitrogen is in the soil is the first step to estimating potential losses. Fertilizer products may contain nitrogen in ammonium (NH4) and nitrate (NH3) forms. UAN (32-0-0) has about 25% of the total nitrogen as nitrate. Ammonium forms of nitrogen are rapidly converted (oxidized) to nitrate by soil bacteria in a process known as nitrification. The process is faster with warm soils. Most of the ammonium may be nitrified within several weeks under warm conditions. Nitrification inhibitors can be used to delay this process. Saturated soils (oxygen depleted) will also halt the nitrification process. Therefore, timing and source of nitrogen fertilizer plus the use of nitrification inhibitors will affect how much nitrogen is nitrate form. Nitrogen fertilizer applied several weeks or more before excessive rainfall without nitrification inhibitors is likely largely in nitrate form. This does mean it is lost but has the potential to be lost.

Coarse textured soils (sandy) are much more susceptible to leaching of nitrate below the rooting zone of the crop. Finer textured soils (clay) are susceptible to leaching and denitrification, although leaching potential is substantially lower compared to sandy soils. Low infiltration rates and ponding can result in extended periods of saturation. This will increase the potential for denitrification losses. As soil oxygen is depleted, some soil microbes will switch to nitrate for survival, releasing the nitrogen in gaseous forms that escape into the atmosphere. Some estimates suggest 2 to 5% of the soil nitrate-nitrogen can be lost per day of saturated conditions. The total loss will depend on nitrate available in soil, number of saturated days and temperature. Actual losses can vary widely depending on these factors.

Determining potential nitrogen losses in-season is difficult. Deciding if and what amount of additional nitrogen to apply can be challenging. If you have reason to believe significant nitrogen has been lost, there are several considerations when planning supplemental nitrogen applications. First, ensure that plant stands/populations are adequate for expected yield goals. Next, consider the growth stage of the crop. Applying nitrogen closer to growing point differentiation will improve yield response (see previous tips). However, if panicle initiation has passed but conditions were favorable during this period, significant yield potential may exist yet.  Some yield loss can be expected with later applications (pre flowering) but it is important to capture yield potential that does exist. Finally, consider grain price and nitrogen cost in combination with expected yield response. Applying 100 lbs/acre of urea (46 units of N) will cost about $19/acre ($0.42/ lb of N) plus application cost. With grain at $6.50/cwt, you need about 300 lbs/acre of grain to cover the fertilizer cost. Yield response to N fertilizer under ideal conditions is 100 lbs of grain for every 2 lbs of available nitrogen per acre (over 2,000 lbs of grain per acre in this example). With late applied fertilizer, yield response will likely be lower but may be profitable yet.

If plants have been severely affected by wet conditions, this can result in damaged root systems, reduced or delayed tillering, lower leaf area and reduced yield potential. Response to additional nitrogen is unlikely. Extended periods of stress (saturated soils) at earlier growth stages (3-5 leaf) will have greater impact compared to later growth stages (post flowering). Carefully evaluate the crops recovery once soil conditions improve before considering supplemental nitrogen applications.

sorghum

Figure 1. Sorghum showing signs of nitrogen stress following excessive rainfall.

2016 AgriLife Extension Entomology Sugarcane Aphid Information

This tip was provided by:

This Sorghum Tip from Extension Entomologist Dr. Ed Bynum, Amarillo, directs sorghum growers in the Texas High Plains to AgriLife Extension entomologist guidelines developed for the region.  These efforts are coordinated by Dr. Bynum, Amarillo, (806) 677-5600, ebynum@ag.tamu.edu, and Dr. Pat Porter, Lubbock, (806) 746-6101, pporter@ag.tamu.edu  in conjunction with the five Extension IPM agents that each cover 2 or 3 counties in the South Plains (based in Lamesa, Brownfield, Levelland, Lubbock, and Plainview)

High Plains

2016 AgriLife Extension Entomology Sugarcane Aphid Information

The March 10 Sorghum Tip summarized sugarcane aphid control recommendations from Dr. Robert Bowling for SCA in South and Central Texas.  In this edition, High Plains sorghum growers are directed to a different set of SCA control recommendations for the High Plains region.  Compared to South & Central Texas guidelines, the initial action thresholds are lower for the Texas High Plains.

 If you have last year’s thresholds on hand in the High Plains, discard them and replace with the information resources below.

Since Dr. Bowling’s update, SCA has been confirmed to have overwintered on Johnsongrass in at least three counties in the High Plains (Dawson, Lubbock, Hale), but IPM agents based in Lamesa & Garden City currently have no reports of SCA on commercial sorghum.

You may access the current statewide AgriLife sugarcane aphid management guide at http://www.texasinsects.org/sorghum.html  In addition to information on SCA identification, scouting, and insecticides, note the High Plains specific information found on pages 4-5.  These High Plains specific guidelines are also published at http://lubbock.tamu.edu/files/2016/03/ENTO-047.pdf  (ENTO-047, “2016 Texas High Plains Sugarcane Aphid Management Guide”; you can get laminated cards from your county Extension office or order from http://agrilifebookstore.org )

Overall Texas High Plains AgriLife Extension entomology suggestions for managing SCA follow these six principles:

Primary Options to Reduce Potential SCA Damage on Grain Sorghum 

1)    Plant outside the normal window {Early planting, e.g. late April in the South Plains to reduce risk of infestation in whorl stage, late planting in mid-summer will have a higher risk of infestation in whorl stages, but beneficial insect populations may be increasing.}

2)    Use seed insecticide treatments.  {This might add up to ~$50/bag for seed, but that is still less than $2.50/acre in dryland.  Entomologists have noted that you should anticipate at least 30 days of some protection with any of the insecticide seed treatments.}

3)    Plant “resistant” hybrids (talk to companies).  {All sorghum hybrids are susceptible to SCA at some level, and AgriLife statewide has conducted little research yet on commercial hybrids.  (United Sorghum Checkoff Program has summarized a list of what companies believe is their most tolerant material, see http://www.sorghumcheckoff.com/newsroom/2016/03/28/sugarcane-aphid/ )}

4)    Spray promptly at threshold.  {IPM agent Kerry Siders has noted that a good first shot may eliminate the need for a second spray.}

5)    Re-spray the field as needed.

6)    Preserve biological control—your best friend.Screen Shot 2016-05-27 at 9.10.38 AM

 

Additional High Plains SCA management tip sections in ENTO-047 include:

  • First Detection:  Is the field at risk?
  • Sampling Decision
  • Control Options after First Application
  • Forage Sorghum Management

For further information on sugarcane aphid in the Texas High Plains and beyond follow the online Texas Sugarcane Aphid News at http://txscan.blogspot.com

Nitrogen Fertilizer Timing for Grain Sorghum

This tip was provided by:

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

Statewide

Nitrogen Fertilizer Timing for Grain Sorghum

In the last Sorghum Tip I discussed the nitrogen requirement for grain sorghum production, which is different than how much N fertilizer you may apply.  A field may have N credits, most likely from soil test nitrate-nitrogen, which a Texas A&M AgriLife soil test will credit 100% to you grain sorghum N requirement.

Nitrogen fertilizer timing for grain sorghum can involve pre-plant application, sometimes well in advance of cropping (especially if using anhydrous ammonia, which is often cheaper per unit of N) and pop-up fertilizer (in-furrow) or starter N (placed near the seed).  Each have their place though conditions like the potential for water-logged soils and the time before planting can reduce efficiency for pre-plant applications.  See the Texas sorghum production guides below for information about safe use of at-plant N to ensure that toxicity or fertilizer salts do not hinder germinating grain sorghum and seedling growth.

For in-season application of grain sorghum, the key reference point that guides timing of N application is the changeover of the growing point from producing another leaf to initiating the head (Fig. 1).  In wheat (the same botanic family of grasses as grain sorghum), this generally occurs just before jointing, which you can see in wheat.  But in grain sorghum there is nothing visual externally on the plant that signals this is occurring.  Generally, this occurs about 30 to 35 days after planting.

sorghumtip

Fig. 1. The growing point of grain sorghum after differentiation from leaf production to developing panicle, or head. This process initiates about 30 days or so after germination. In this image there is likely at most 2 days’ difference from left (early) to right. Spikelet number and potential seeds per spikelet—both important components of yield potential—are being determined for each head over a 7 to 10-day period.

Once growing point differentiation (GPD) occurs, the developing head must not be limited in needs for sufficient nitrogen (or water!), lest you cap your potential spikelets and seeds per spikelet, thus limiting your yield potential.  Once GPD concludes you cannot increase spikelet number and seeds per head.

Historical guidelines from Texas A&M, Kansas State Univ., etc. have suggested that side-dress N fertilizer applications be completed by about a month after planting to meet your crop’s targeted N requirement.  This can be a substantial amount of N for larger yield goals.  Though all remaining N is not needed right then at GPD, in-season N applications were generally only made once, so it was necessary to apply the remainder of your N fertilizer soon.

Today, particularly where N fertilizer applications may be conveniently supplied by dissolving in irrigation water, some producers may elect to withhold a portion of their in-season N fertility after GPD to spread out the N application and perhaps increase nitrogen utilization efficiency.  This could be up to 20% or so (an estimate on my part) of the N, but I would recommend that all remaining N be on the field by early boot stage.  This would be within 50 days of planting for a medium-early maturity hybrid and about 60 days for a medium-long maturity hybrid.  Kansas State Univ. research suggests that by the time late boot stage occurs 70% or more of grain sorghum’s required N will already be in the plant.

Further Information:
You can read additional information on several aspects of nitrogen fertility for Texas grain sorghum from the fertility sections of the West Texas and the South & Central Texas editions of United Sorghum Checkoff Program’s production guides, on the web at http://sorghumcheckoff.com/farmer-resources/grain-production/  The information is similar in both guides, which were prepared by AgriLife Extension staff.

Page 3 of 11«12345»10...Last »