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Annual Crops for Forage

Annual crops can be used for mid- to late-summer forage production. Several of these are described here, and species, seeding rates, and seeding dates are given in the able below.

Sudangrass and Forage Sorghums
Sudangrass and forage sorghums are used sparingly on New York dairy and livestock farms. These annual grasses fit best in summer feeding programs, where they can supply ample yields of silage and green chop while perennial grasses are slowing down or going dormant. Thick stemmed and hard to dry, they make poor hay crops. As silage crops, they rank below corn in feeding value, unless they have the brown-midrib trait.

Sow sudangrass and forage sorghums in late May or early June. Choose land with drainage adequate for corn. These crops do not perform well in poorly drained fields or wet
spots. Fertilize as for corn. Nitrogen can be plowed down, disked in, or top-dressed. See Table 4.11.1 for weed control guidelines.

You can harvest these crops once in late summer or early fall, or more frequently for pasture or green chop. One cut at season’s end brings highest yields but gives up the unique value of these crops for midsummer feed.

Forage sorghums are widely grown in the south and west but have not done well in New York tests. Forage sorghums can be high yielding but are normally coarser stemmed than either sudangrasses or sorghum-sudangrass hybrids and have less regrowth potential in green chop or pasture situations. Forage sorghums do best for silage but rarely equal corn for this purpose in New York. Brown midrib varieties have higher digestibility and so may offer promise as late-planted or emergency silage crops.

Brown midrib varieties develop less lignin in stems and leaves and have higher digestibility.

Planting date: The seeds do not like cold soils. Soil temperature must be over 60ºF for rapid emergence and growth. BMR SxS planted as late as July 15th can still produce one cutting. However, little or no regrowth can be expected with late planting dates, especially when the first cutting is taken after September 1st.

Seeding rate: 65-70 lbs/acre of seed will give 2.5-3 tons more yield than lower seeding rates and shade the ground sooner to control weeds.

Weed control: Under proper growing conditions BMR SxS will beat the weeds and not need herbicide. A stale seedbed system (tilling the field 10 days before planting, letting small weeds emerge, and then harrowing before planting) will kill most weeds. Minor weed infestations are corrected by harvesting. If annual grasses get started, they will destroy the BMR SxS crop. Broadleaf weeds can be controlled by herbicide if needed.

Planting depth: Shallow, 1/2 to 3/4 inch deep for the Northeast. Deeper seed placement has resulted in significant stand loss and complete stand failure. Drills set to plant shallow will do an excellent job. Cultipacker seeders leave excessive seed on top. Broadcast with fertilizer gives uneven stands. Premixing fertilizer with seed, even for a short time, could be toxic and has resulted up to 90% stand loss. “Air truck seeding” can work if the roller has corrugations of less than 2 inches. Older rollers with 3-4 inch corrugations will bury the seed too deeply. Rolling with teeth down or light disking incorporation has resulted in stand failure.

Fertilizer: Apply P and K similar to corn silage (based on soil test levels). BMR SxS should be fertilized more like an intensively managed perennial grass than a corn crop. Research is ongoing to refine N recommendation for this crop, but current guidelines are to add 100-135 lbs N/acre at planting with the same amount top-dressed immediately after each cutting. This investment in N fertilizer is returned through higher yield and protein. Fertilizer rates need to be decreased when manure is in the system. Assume that similar amounts of N from manure will become available to BMR SxS as with corn.

Stand height at harvest: For double the protein of corn silage, and energy levels equal to corn silage, harvest at 36-48 inch stand height. At this stage, and with sufficient N, crude protein is usually 15-16%. As yields increase, energy holds at modest levels and protein drops at taller heights, but moisture removal becomes much more of a challenge. If the crop is light yellow – indicative of N deficiency – harvest at 30 inch height, then correct the yield limitations with proper N fertilization.

Harvest interval: It will take approximately 40 days to reach re-growth level for the next harvest. The crop needs to be watched closely. Under optimum conditions it has grown 12 inches in 3-4 days for harvest in 3-4 weeks.

Sorghum species usually contain a substance that can release the poison prussic (hydrocyanic) acid. To avoid poisoning animals, graze green forage when plants of sudangrass are 18 to 20 inches or taller and forage sorghum or sorghum-sudangrass hybrids are 24 to 30 inches or taller. Do not graze new regrowth that develops after a frost or a period of dry weather. This regrowth often contains high levels of prussic acid. Green plants that are frozen should be completely dried before grazing or ensiled for several weeks before feeding. If sorghums are properly fermented, prussic acid from any harvest is not a problem.

*Do not graze horses on sudangrass or sorghum-sudan hybrids. These crops cause cystitis syndrome, a serious condition in horses.*

As with corn, sorghums can accumulate nitrates under certain conditions (high N fertilization and extended periods of dry weather). When fermented, and if mixed with other feeds (not the sole forage), nitrates are not a problem. If in doubt, run an inexpensive forage nitrate test.

Japanese, German, Hungarian, and Siberian millets will all grow in New York but are generally lower yielding than other grain crops and well below sudangrass and sorghum-sudan in forage production. Sudangrass and sorghum-sudan are better choices unless there is some special reason for growing millet.

For best-quality hay, cut millet plants at the boot stage. Curing is somewhat slow because of the thick stems. For grazing, it is usually best to begin about six to eight weeks after planting or when the plants are 6 to 12 inches tall. After this stage, the nutritive value of millet for grazing decreases.

When these crops are planted in early spring and grazed or chopped early, they will regrow sufficiently for an additional harvest. Normally, they can be pastured five to seven weeks after planting. For silage, harvest at the boot stage. Once the head is emerged, small grain forage will contain more than 55 percent neutral detergent fiber. Late summer planting can provide some grazing during September and October. Oats grow well during periods of cool temperatures, which restrict the growth of sorghum or sudangrass.

Spring triticales have drawn attention as a silage crop. Triticales or oats mixed with field peas can produce more  protein per acre than small grains alone but may not be worth the added seed costs. Triticale-pea mixtures should be planted by May 1 because both crops grow well at cool temperatures but perform poorly under warmer temperatures.

These crops can provide grazing in the fall and early spring and green chop or silage in late May or June. If grown for grain, these crops can be grazed in fall and early spring until shortly before plants begin to grow erect or stems begin to elongate. Grazing after stems elongate will severely reduce grain yields.

Rye and triticales are best for fall and spring pasture because they are not damaged by Hessian flies when planted early; also, they grow at cooler temperatures and provide later fall and earlier spring pasturage than do other winter grains. With proper management, winter triticales can produce forage with estimated milk/ton levels equal to high quality corn silage.