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Topics : Species and Forage Variety Trials : Species Fact Sheets : Sorghum & Sudangrass

Species: Sorghum & Sudangrass

Additional sorghum & sudangrass information via the Forage Information System (FIS)

Sorghum & Sudangrass Harvest Management

Both the grain and forage sorghums are most frequently used for silage or green chop in a single cut system, although they can be grazed if desired. Silage should be cut when the grain is in the medium to hard dough stage. Generally, whole plant moisture should be near the desired level for ensiling at this time. In some cases, where maturity is delayed, a frost may be necessary to reduce whole plant moistures to an acceptable level. Under most conditions, corn silage will produce higher silage yields and quality. The sorghums will produce similar or higher yields than corn silage on droughty soils or in fields with significant deer damage. Deer will not graze the sorghums to the extent they will corn. Digestibility of silage made from the sorghums will usually be about 90-95% of well preserved corn silage.

The other summer-annual grasses can be used for grazing, green chop, silage or hay. When used for grazing, these grasses must be grazed at the proper stage of growth to reduce herd health problems and optimize production. The best time to graze is when the plants are between 18 and 30 inches tall (6 to 8 weeks after planting). Grazing when the plants are less than 18 inches tall will delay regrowth and increase the chances of prussic acid poisoning in sorghum, sudangrass, and sorghum-sudangrass hybrids.

Sufficient animals should be placed on the pasture area to graze the grass down in less than 10 days. Six or more animals per acre may be necessary to accomplish this rapid grazing. After grazing, clip the residue at about 8 inches high to eliminate old stems and insure high quality for the next grazing period. Do not graze or clip these grasses too close (less than 8 inches) because it will weaken and may kill the plants. It will normally take three to four weeks for sufficient regrowth before grazing again.

Grazing can continue on these grasses until frost, or even after frost if the plants are allowed to to turn brown (one week after a killing frost) before they are grazed. Do not graze frost damaged or stunted sorghum, sudangrass, or sorghum-sudangrass hybrids until they have been killed (turn brown) by the frost. If the plants begin to grow again after being frost damaged, they should not be grazed until the regrowth is 18 inches tall or the entire plant is killed by frost and turns brown.

Summer-annual grasses are ideal for green chop. Use the same harvest precautions when feeding as green chop as used when grazing to avoid prussic acid poisoning. Cut the plants down to about 8 inches. Green-chop harvesting should not begin until the plants are at least 18 inches tall, however, it should begin early enough to complete harvesting before the plants begin to head. Harvesting after the plants have headed will reduce dry matter intake and milk production in cows, and regrowth potential of the plants.

Sudangrass, sorghum-sudangrass hybrids, and millet should be harvested for silage when they are between 36 and 48 inches tall or in the boot to early- head stage, whichever comes first. At this maturity, they contain excessive moisture for proper ensiling and should be wilted (mowed and allowed to partially dry in the field) before ensiling.

Greatest hay yields are obtained if the annual grasses are harvested when the seed is in the soft- dough stage. However, proper drying is difficult at this stage. Therefore, harvest for hay is recommended during the vegetative stage before the heads emerge or the plant reaches a height of 4 feet. A hay conditioner should be used to mow and crush the stems for rapid, uniform drying. It is extremely difficult to field cure these grasses adequately for safe storage as hay.