Farm Progress

Preparing sorghum for harvest

Jeffrey Stapper

June 29, 2010

3 Min Read

Corpus Christi, Texas--Our early planted, early maturing, grain sorghum hybrids have accumulated enough growing degree units to reach “black layer” or physiological maturity so harvest time is here and preparing grain for harvest is underway.

Grain sorghum growers can obtain higher prices if their sorghum meets market moisture specifications. To help meet those specifications, growers may apply harvest aids.

When harvest aids are applied properly, harvest is 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, when the grain reaches physiological maturity 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:

Only two products are 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 5 to 6 days. Weeds actively growing when the product is applied will also be destroyed. Use a sprayable grade of ammonium sulfate at a rate of 17 pounds per100 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.

This year most sorghum plants are healthy, and there should be no need to worry about crop lodging after harvest aid applications. Studies have shown that healthy sorghum treated with harvest aids will stand well for up to three weeks after treatment. After 30 days, lodging can be significant. Growers should only treat those acres that can be harvested within 10 days to two weeks after application. Also consider weather and storms in the Gulf.

To avoid any premature lodging, inspect the field before 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.

As always when using farm chemicals, read and follow label directions carefully before applying the product.

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