Weed Control & Harvest Desiccation in Sorghum – 2014
Statewide
Quick Guide for Weed Control & Harvest Desiccation in Sorghum – 2014
For producers across Texas, regardless of the stage of their grain sorghum, the “Quick Guide for Weed Control & Harvest Desiccation in Sorghum-2014” is a summary of relevant herbicides labeled for grain sorghum in Texas. This document was originally developed for the High Plains, but we have expanded it to include grain sorghum statewide. Though this document is not a substitute for labels, it does contain some of the ‘first hand’ information you need for weed control decisions such as application rates that reflect soil texture, whether you need a seed safener (there are herbicides with active ingredients similar to s-metolochlor, e.g. Dual/Dual Magnum that require it), and rotation restrictions to common crops.
The document is currently available online here.
High Plains
Grain Sorghum & Glyphosate-Resistant Palmer Ameranth
With the recent rains since Memorial Day weekend, we are seeing an explosion of pigweed species in the Texas High Plains. Glyphosate-resistant pigweed is widely prevalent now, but if you are growing grain sorghum don’t miss the opportunity to use herbicides that work well on the resistant Palmer Ameranth species if you are out of cotton for 2014. Huskie herbicide is one common means of addressing this problem weed in your cropping system. For an AgriLife Extension summary of Huskie herbicide, click here.
Grain Sorghum Harvest Aids
Statewide
This tip was provided by Dr. Ronnie Schnell, Cropping Systems Specialist, Texas A&M AgriLife Extension, College Station.
Harvest aids can be used in grain sorghum to potentially accelerate harvest and provide uniform and more favorable harvest conditions as well as effect late-season weed control. Sodium chlorate, glyphosate and carfentrazone (Aim EC) are labeled for pre-harvest or harvest aid use in grain sorghum. Sodium chlorate is a burn down chemical that acts as a defoliant, whereas glyphosate (technically labeled for weed control) kills the entire plant, which aids in drydown. Carfentrazone can be used as a harvest aid in grain sorghum to kill and dry down troublesome broadleaf weeds (glyphosate resistant), including morningglory and various waterhemp and pigweed species. Aim EC is labeled for grain sorghum for grain and cannot be applied to sorghum grown for seed. For seed milo growers, diquat dibromide is also labeled (under various product names). For all products, consult and follow all herbicide labels for rates, timing, specific adjuvants, protective gear and safety precautions. Although limited Texas A&M AgriLife research has not demonstrated yield differences among treated and untreated grain sorghum, the ability to manage and potentially accelerate harvest can have significant advantages in Texas, especially when humid conditions slow drydown.
The primary physiological criteria for application include seed moisture below 30% AND physiological maturity, which is best determined by identifying black layer in the seed (Figure 1). Remember that kernels near the base of the head mature last. Also, tiller heads will likely mature later than primary heads and may contribute significantly to yield. Applying products too soon can reduce grain yield and quality. There are restrictions for harvest intervals when using harvest aids. In addition, harvest must be completed in a timely manner due to lodging concerns, especially when stalk rot diseases are present. Do not treat more area than can be harvested if lodging or fall storms are a concern.
A summary of grain sorghum harvest aids and their uses can be found at: http://www.agrilifebookstore.org/product-p/el-5435.htm
Changes for Huskie Herbicide Label in Grain Sorghum – 2014
Statewide
Huskie herbicide (active ingredients: pyrasulfotole + two formulations of bromoxynil) from Bayer Crop Science has generated a lot of interest due to lower potential injury to grain sorghum compared to dicamba and 2,4-D products, which also have volatility drift issues to nearby cotton. Though leave burn is expected, sorghum grows out of it with little apparent long-term effects.
We first reviewed Huskie for “Sorghum Tips” April 2012 (see http://texassorghum.org/sorghum-tips/page/4). Huskie use continued in 2013 with largely good results in numerous sorghum fields across Texas. Reports of good control of Huskie, especially on pigweed species including glyphosate-resistant Palmer ameranth, are common especially when applied to smaller weeds (Fig. 1).
Fig. 1. – Huskie control of pigweed species in grain sorghum seven days after application, Nazareth, TX, 2012 (1 pint/A Huskie + 1 pint/A atrazine + AMS). Photo courtesy Russ Perkins, Bayer Crop Science, Lubbock, TX.
There are new label changes for the 2014 cropping season:
- The original application window for Huskie has been expanded from 3-leaf stage to 12” tall to now include sprays to 30” tall grain sorghum, or initial flag leaf emergence, whichever comes first. Three potential caveats must be noted about the expanded window of application: 1) label guidelines still recommend weed size ≤ 4” in size, 2) Huskie applications after 12” tall must forego atrazine as a preferred tank mix (ATZ only labeled to 12” tall), and especially 3) the idea that you can save Huskie until later could deceive producers into making mistakes in regard to all-important timely weed control.
- The label now recommends that you do include AMS “under challenging conditions” (hot, dry) and “for optimal weed control in grain sorghum in arid environments, Huskie herbicide + 1 lb./A AMS can also be combined with 0.25% v/v NIS or 0.5% v/v HSOC (high-surfactant oil concentrate).”
AgriLife weed scientists in the High Plains on sandier soils continue to address the question about rotation back to cotton, which the label says “field bioassay.” For the first time in 2013 some apparent low levels of injury were observed in cotton and peanut after 2012 Huskie use in grain sorghum. This is being investigated further.
Bayer staff note that leaf burn appears to be reduced by the inclusion of iron (most likely iron chelate; less expensive iron sulfate has not been tested) in the spray solution.
Finally: Though Huskie appears to be a good choice for POST weed control in grain sorghum, I assert that your pre-plant/pre-emerge weed control strategy is still your most important weed control decision for grain sorghum. The expansion of the label application window may delude some producers into further relying on Huskie to fix their weed issues.
For an AgriLife Extension summary of Huskie herbicide, see http://lubbock.tamu.edu/files/2014/03/Huskie-Grain-Sorghum-Summ-Mar2014-Trostle-PDF.pdf
Grain Sorghum vs. Corn in Drought and Heat Conditions: Part VI (Final)
Statewide
This concludes a series of Sorghum Tips discussing production yield of grain sorghum vs. corn in relation to varying levels of available water as well as water use efficiency of grain sorghum vs. corn. All previous tips can be found at http://texassorghum.org/sorghum-tips. Previously Parts IV & V depicted simple corn/sorghum comparisons of 1) yield vs. seasonal water use (equal at about 18”) and 2) crop value vs. seasonal water use (equal at about 15” at current prices).
And finally…
• What is the relative net crop value among variable expenses (no fixed costs included) vs. seasonal water use?
One could also calculate the per-unit production costs and produce yet another graph.
To determine net crop value I used Texas A&M AgriLife Extension grain sorghum and corn enterprise budgets for the South Plains (you can find other crop budgets for your region of Texas at http://agecoext.tamu.edu/resources/crop-livestock-budgets/budgets-by-commodity/ )
Then using the same unit of sorghum or corn production per 1” of water (Tip IV) and the recent grain prices for determining the crop value per 1” of water, I used adjusted irrigation water (inches), yields (which automatically adjusts harvest costs), seeding rate, and N & P fertilizer inputs for corn and grain sorghum across a range of total crop water use up to ~38”. The results are noted in the Figure below.
We now see that the relative favorable comparison of grain sorghum in lower water conditions shifts back to the right, or more favorable, than corn at lower water. This is a combination primarily related to 1) the relative ability of grain sorghum to produce the first bushel of grain sorghum with several inches less water than corn, and 2) lower production costs than corn.
The “cross-point” (black arrow) has moved back to the right and is at 19” based on the budgets used. This suggests that in the South Plains a producer with less than 19” total moisture (projected irrigation, rainfall, stored soil moisture) available to the crop, the net income favors grain sorghum. Your farms may provide different results than this graph, and the calculations used can be no better than the budgets constructed by ag. extension colleagues, but this gives you the producer more information to consider when you are debating which fields, crop rotations, etc. should consider grain sorghum or corn.
The principles here apply to the Coastal Bend, Central Texas, Concho Valley, and the Panhandle as well (there are different budgets from Extension for those regions).
This concludes the Sorghum Tips on grain sorghum and corn water use.
In our next tip we will review the major changes in the Huskie herbicide label for grain sorghum.
Cold Temperatures & Sorghum Planting Dates
Cold Temperatures and Sorghum Planting Dates?
Tip provided by: Dr. Ronnie Schnell, Texas A&M AgriLife
Sorghum producers look to early plantings to avoid late season heat and moisture stress and to reduce the risk of midge. Yet, early plantings could encounter cool air and soil temperatures that can have adverse affects on sorghum emergence and growth.
In general, the earliest recommended planting date for a given region is about two weeks after the average last frost (Figure 1). Normally, soil temperatures have warmed to sufficient levels by this date for planting sorghum. Yet, late season cold fronts and associated cold air temperatures could reduce soil temperatures below optimum levels for grain sorghum germination and emergence. Cold soil temperatures during germination could significantly delay emergence, reduce stand and early season vigor.
Sorghum will germinate quickly with soil temperatures at 65-70°F but will also germinate at temperatures as low as 50°F (expect very slow growth). Planting should not begin until soil temperatures (2 inch depth) have reached an average of 60°F over a five day period. For example, the current (March 8-12) five day average 2-inch soil temperature at Bushland, TX is 47°F (Figure 2). Make sure to determine the soil depth that is used to measure soil temperature at various weather stations. For planting, measurements from a depth of 2 inches are most relevant. However, some stations may report measurements taken at a depth 6 inches or deeper. Shallow depths will respond more quickly and drastically to changes in air temperatures while deeper soil depths are buffered from large swings in temperature. For this reason, soil temperatures from deeper depths (> 2inch) do not reflect conditions within the planting zone.
Soil temperature information can be found at:
High Plains Region – http://www.mesonet.ttu.edu/soilobsframe.html
State Wide: http://www.wcc.nrcs.usda.gov/scan/Texas/texas.html
Temple: http://www.ars.usda.gov/SP2UserFiles/Place/62060500/temple/T2014.XLS
Figure 1. The average last freeze dates for Texas.
Figure 2. Soil temperature at depths from 20 to 20 inches over a 5-day period at Bushland, TX.
For further information, contact:
Dr. Ronnie Schnell, State Wide
(979) 845-2935
Dr. Calvin Trostle, Lubbock
(806) 746-6101
Grain Sorghum vs. Corn in Drought & Heat Conditions: Part V
Statewide
Grain Sorghum vs. Corn in Drought and Heat Conditions: Part V
This continues a series of Sorghum Tips discussing production yield of grain sorghum vs. corn in relation to dryland and limited water conditions as well as water-use efficiency of grain sorghum vs. corn. Previously in Part IV I demonstrated a relative albeit simplistic comparison of yield vs. seasonal water use for grain sorghum vs. corn which emphasized two points:
- What is the incremental change (increase) in yield per unit of available water?
- How much available water does it take to produce the first bushel of grain?
Although corn generally yields more per unit of water than grain sorghum—once sufficient water is present to achieve grain yield for each crop—the important consideration for grain sorghum, however, is that grain sorghum can produce grain yield at moisture levels (lower) that corn cannot. K-State Research & Extension frequently and generally notes in Kansas that when corn yields fall below 100 bu/A that sorghum generally becomes the more favorable cropping option.
But what about the price of the corn or grain sorghum you receive in the market (this Tip’s discussion)? And what about the cost to produce the corn or grain sorghum (the next TGSA Tip)? These factors will influence the simple comparison I portrayed in the Part IV tip, which was based only on yield.I have reconstructed the original graph in Part IV to now reflect crop value of grain sorghum and corn using the same yield per inch as before. I have used $4.50/bu for corn and $4.00/bu for grain sorghum (approximate High Plains contract prices as of February 2014), but of course these prices change: 1) in absolute value (prices per bushel go up and down), and 2) the price differential varies (and may be closer together on the Texas Gulf Coast?)
Remember, the above figure is based on crop value. Due to corn’s higher price and higher yield per unit of water, you can see that compared to the previous tip—which is yield only—the relative positioning of the lines on the graph favor corn over grain sorghum in that the “cross point” of crop value has moved to the left, from ~20” to ~15”. This is for our educational comparison. High relative prices for corn shift this red line to the left for corn. So strictly on crop value, corn is favored more.
But any Texas producer knows this is not the whole story! We know grain sorghum costs less to produce.
As noted before the above graph is another singular (and not the whole story) means to compare grain sorghum vs. corn. How may this relative comparison change significantly in favor of grain sorghum even though corn yield per 1” of water and corn grain prices are higher?
So stay tuned for my next Sorghum Tip considerations:
- What effect do production costs for corn and grain sorghum have in terms of profitability in response to water use?
- How would you portray the risks of growing corn vs. grain sorghum on this type of graph?
Grain Sorghum vs. Corn in Heat & Drought Conditions – Part IV
Statewide
This continues a series to examine production of grain sorghum vs. corn in relation to dryland and limited water conditions as well as water-use efficiency of grain sorghum vs. corn.
As noted in my previous Sorghum Tip, from an agronomic perspective, we want to know the following:
- What is the incremental change (increase) in yield per unit of available water?
- How much available water does it take to produce the first bushel of grain?
Research from several workers in Texas is summarized in the graph below for corn vs. grain sorghum. This graph is simplistic, but it is useful for explaining water use efficiency relationships for corn and grain sorghum. First note the yield relationship for both corn and grain sorghum here is portrayed as linear, and that is not the case as we move to higher water use, but rather it usually tails off some (less yield per 1” of water at the higher total water amounts). Second note that the graphs for each crop requires a minimal amount of water before the first bushel of grain is produced.
This data is mostly derived from irrigated research in the High Plains, but the principles are applicable across Texas. In this depiction, which originally reported corn and grain sorghum data prior to 2005, corn and grain sorghum yields are equal at about 20” of total seasonal water use. More recent data in the High Plains suggests the corn line (red) likely has a steeper slope meaning that the corn yield per unit of incremental water (after initial yield is obtained) has increased slightly and the “Equal Point” is at about 18”, likely the result of newer corn hybrids with new technologies in the seed (water use efficient, sometimes called ‘drought tolerant’ corn, of which there are several commercial names). This is all the result of hundreds of millions of dollars invested in corn seed and hybrid research (unlike grain sorghum) where corn has an advantage of a several dozen fold higher expenditures in developing new corn hybrids compared to grain sorghum.
In this depiction, corn is yielding 476 lbs. of grain per inch of water after initial grain yield is achieved, and grain sorghum yields 355 lbs. per inch. Other data suggests similar results between corn and grain sorghum so that in summary corn tends to yield up to 1/3 more grain per inch of available water—but only once initial grain yield is achieved. In Texas, with lower agronomic plant populations for corn it still takes 9 to 10 inches of water to get the first bushel of grain yield whereas for grain sorghum this number is much lower, as low as 5 inches of water to get the first bushel of grain yield (again, low plant population crop).
This matter of minimum water to achieve is initial grain production is a key consideration. This is why grain sorghum is a better fit for much of Texas than corn as potential grain yields are more for grain sorghum in limited water situations than for corn.
The above graph is one means to compare grain sorghum vs. corn. Two additional considerations will be noted in the next Sorghum Tip so stay tuned:
- What effect does grain price have on the corn vs. grain sorghum relationship per unit of water?
- What effect do production costs for corn and grain sorghum have in terms of profitability in response to water use?
Grain Sorghum vs. Corn in Heat & Drought Conditions – Part III
Statewide
This continues a series to examine production of grain sorghum vs. corn in relation to dryland and limited water conditions as well as water-use efficiency of grain sorghum vs. corn.
Water use efficiency (WUE) is debated frequently among research, educators, and producers. When you read reports in research and farm publications, sometimes either of two mistakes are made in the data and discussion—Results are given and discussed for:
- Total crop yield divided by total water
- Total yield divided by irrigation water applied
The flaw in each is, in the first case, there is a certain amount of water required (stored soil moisture, rainfall, irrigation) to achieve that first bushel of grain yield per acre. In the second case, the flaw dismisses the contribution of soil moisture and rainfall.
From an agronomic perspective, we want to know the following:
What is the incremental change (increase) in yield per unit of available water?
Again, from an agronomic perspective, we also often overlook this:
How much available water does it take to produce that first bushel of grain?
If you get an additional 2” of rain (one rain, or over the course of the season) on your crop, what is the increase in yield? If you use an additional 2” of irrigation, what is the yield increase due to that water?
In the first question corn grain yield is greater than grain sorghum, but in the second grain sorghum has a strong advantage over corn.
There are many factors to discuss, and I will begin that in our next Sorghum Tip.
Grain Sorghum vs. Corn in Drought & Heat Conditions: Part II
Statewide
This continues a series to examine production of grain sorghum vs. corn in relation to dryland and limited water conditions as well as water-use efficiency of grain sorghum vs. corn.
A producer posed a question this week. He knows full well about the ‘battle’ between corn and grain sorghum for acreage. He knows, too, that corn hybrid defense traits (insects, herbicide tolerance), so-called drought tolerant traits, and yield gains available in corn hybrids have exploded in the past 10 years or so—all improvements—so he asked:
“In your opinion, are current grain sorghum hybrids capable of producing higher yields than most farmers are getting? If so, why? Is it just the weather, or is it partly due to management factors?”
Yes, hybrids are capable of producing higher yields than sorghum farmers may receive. The commitment to higher yielding grain sorghum production seems to have waned over the years. Statistics suggest U.S. grain sorghum yields have been only a little above flat for up to 30 years. The typical acre of grain sorghum production today, however, is likely on slightly more marginal ground than 20 and 30 years ago. Furthermore, producers have been more reluctant to put inputs into the crop in part because grain sorghum prices are lower than for corn—but these are inputs are lower, too.
The psychology of farming tends to focus on grossing the most money you can per acre rather than the net return or the risks you take. Yes, farmers may feel that the more income dollars they roll through their operation the better their management skill comes into play, and the more likely they can increase profitability.
Also, sorghum’s fit is more appropriate relative to corn where moisture is limiting (rainfall or irrigation), so grain sorghum tends to experience a more pronounced ‘limited irrigation’ or ‘deficit irrigation’ or ‘limited input’ production system (relative to corn).
Grain sorghum hybrid yield potential has improved, but higher yields—in contrast to more efficient yields—are not being realized on many farms. Perhaps we could argue that sorghum shouldn’t be gunning for higher yields on an absolute or maximum basis. For those producers who make the decision to favor heavier inputs on grain sorghum, modern hybrids will respond, but the days are largely gone when a farmer will pour 20” of irrigation or 250 lbs. N per acre or maximize some other input to grain sorghum.
Many producers in 2013 learned that their county T-yield for corn (especially if irrigated) were double or more that of grain sorghum. This represents a willingness to enhance inputs on corn for maximizing yield or income, but also ‘crappy farming’ when folks don’t take care of their grain sorghum, maybe irrigate it only a little if (if available) and perhaps didn’t apply any nitrogen at that—and used a too high seeding rate as if they were.
It is not the weather! Seed companies have been doing their best to increase yield potential, and markets move up and down like they always have, but I think we would all agree that farming is probably more risky than it used to be. And for this reason I believe sorghum has an essential role on many farms in Texas and beyond.
Grain Sorghum vs. Corn in Drought & Heat Conditions: Part I
Statewide
This begins a four-part series to examine production of grain sorghum vs. corn in relation to dryland and limited water conditions and water-use efficiency of grain sorghum vs. corn. Subsequent tips will discuss the amount of water needed for initial grain production as well as the results for grain production per one inch of water.
Here are some basics of grain sorghum vs. corn when available moisture is limited†:
- Heat unit accumulation: Corn HU are capped at 86°F whereas grain sorghum’s cap is 100°F. The corn HU cap should be re-examined in light of more recent corn developments, but it remains that grain sorghum is a more “heat efficient” crop than corn.
- Grain sorghum is self-pollinated (unless you grow a hybrid seedblock). Grain sorghum produces heads over a broader time period as tillers can be initiated and developed over several weeks. Thus short periods of drought are unlikely to seriously damage pollination and fertilization in grain sorghum. During prolonged drought, sorghum produces fewer, smaller heads but seed set is usually not impaired—you get grain. Corn is cross-pollinated and is especially vulnerable to heat and drought/ conditions at critical 2 to 3 days of silking which could lead to poor seed set. In contrast, grain sorghum flowering normally occurs over a 7 to 10 day period, so the crop is not nearly as vulnerable to a short hot spell.
- For good corn production the relationship between plants per acre and moisture supply availability is often critical but much less so with sorghum. With abundant soil moisture sorghum heads grow large and tillers that may produce heads are more likely developed. In drought conditions sorghum heads are small with a significant reduction in tillering or tiller head development as the plant adapts itself to the environment. Consequently, sorghum growers within limits can plant higher populations for potentially high yields (high plant populations for grain sorghum particularly in dry regions of Texas are too risky due to drought stress). Corn growers may choose between high populations for maximum yields or lower populations with less chance of serious loss from drought.
- Sorghum foliage resists drying. At equal moisture stress, corn leaves lose a greater percentage of water content than sorghum. Sorghum’s waxy coating on leaves and stems may be an important cause, the coating giving leaf sheaths a sticky, frosty appearance.
†Partially adapted from ‘Grain Sorghum,’ Alternative Crops Field Manual, Purdue Univ.