When harvest aids are applied properly, harvest is made more efficient and combining is faster, with no reductions in grain weight. Grain from the entire field will have a uniform moisture content, resulting in few “hot” loads and price discounts. To keep the grain from losing weight, it is critical that growers apply the harvest aids at the proper time, which is once the grain reaches physiological maturity (cumulative growing degree units of 2,673 to 3,360) and the average grain moisture drops below 30 percent. If harvest aids are applied prematurely, both yields and grain quality will be reduced.
Physiological maturity can be determined by sampling grain with a grain moister tester and also looking at the kernels for a black layer which indicates that the crop is mature. Pictures of a black layer can be found in a publication L-5435 - “Harvest Aids in Sorghum,” that can be found at the following web address: http://sorghum.tamu.edu/gen_production/pdfs/L5435.pdf
There are only two products labeled for use as harvest aids: sodium chlorate (containing a fire retardant) and glyphosate. For satisfactory results, good spray coverage is needed for both products. Eight to 10 gallons per acre (GPA) of solution by ground or 3 to 5 GPA by air is recommended.
Sodium chlorate, which can cause fires if it is not mixed with a retardant, is a chemically active salt that desiccates the plant. Growers may apply up to 6 pounds per acre. This product is sold under various trade names and concentrations of active ingredient per gallon. For good desiccation, the weather must be hot and dry.
Glyphosate, a common herbicide, will kill the plant. Producers may make a single application of up to 2 quarts per acre. Since formulations can vary, be sure to check the product label for correct rates per acre. Once it is applied to sorghum, the plants move the glyphosate to the growing point over a 5- to 6- day period. Weeds that are actively growing when the product is applied will also be destroyed. Use a sprayable grade of ammonium sulfate at a rate of 17 pounds/100 gallons of water or a prepackaged sulfate formulation to condition the water and improve effectiveness. There is a 7-day waiting interval between application and harvest. The crop is usually ready seven to 10 days after application.
Growers should only treat those acres that can be harvested within 10 days to two weeks after application. Weather and storms in the Gulf should also be a consideration. To avoid any premature lodging, inspect the field before the application. Look for stalk degradation from diseases such as charcoal rot, which will cause premature lodging during natural dry down or after harvest aids are applied. Picture may be found on web at http://165.91.154.132/Texlab/Grains/Sorghum/sorcr.html
Conditions under which charcoal rot is favored include stressful hot soil temperatures and low soil moisture during the post-flowering period. Host plants are usually in the early-milk to late-dough stage when infection occurs. The fungus is common and widely distributed in nature. To check the plants before treatment, split the stalk lengthwise and look for a hollow stem or black rot just above the root crown. If the stalk is unhealthy, it will generally fall, whether or not it has been treated.
As always when using farm chemicals, read and follow label directions carefully before applying the product.
