Cover crops are plants that are grown to help the soil on a small farm. Benefits of cover crops may include improving the soil's structure, adding nitrogen, conserving moisture, preventing erosion, suppressing weeds, or even helping other crops by boosting disease- and pest-resistance. Sorghum-Sudan grass can offer all of these benefits as a cover crop.
What Is It?
Sorghum-Sudan grass, or sorghum-sudangrass, is a fast-growing cover crop with an extensive root system that thrives in the heat of summer. It excels at suppressing weeds. Its name comes from the fact that it is a hybrid, a cross between sorghums grown for forage and a type of grass called Sudan grass or Sudangrass, which is native to eastern Africa. Sorghum-Sudan grass grows well in most places in the United States. For growth, the soil temperature must reach 65 to 70 F for two months before frost. The crop is extremely drought-tolerant once established, but it does need rain or irrigation during early growth.
Seed Sorghum-Sudan grass at a rate of 40 to 50 pounds per acre if broadcast, or 35 pounds per acre if drilled. Plant after the threat of frost has passed in spring. However, for maximum growth potential, don't wait too long to plant, depending on your climate. In the Northeast, for example, it's best to plant before July 15th.
Soil temperatures of at least 60 F are required for this cover crop to germinate. Repeated mowing can increase the root system, leading to greater penetration in compacted soil. In fact, this cover crop should be mowed several times in the season to prevent it from setting seed.
Maintain your Sorghum-Sudan crop by mowing several times during the season before the crop seeds. Just prior to a killing frost, mow the grass to finely chop it, and then immediately till into the ground while it is still green. Due to the presence of weed-suppressing compounds in the freshly mowed crop, wait several weeks before planting new crops.
Sorghum-Sudan grass is a great cover crop for revitalizing worn-out, "farmed-out" soils because it adds a lot of organic matter and bulk to the soil. It grows so quickly, especially in temperate regions, that it creates a thick stand that cannot be penetrated by weeds. It's also very tolerant of heat and drought, making it hardy. In addition, Sorghum-Sudan grass is killed by the first frost so it's great to leave it to overwinter as a dead residue to protect against soil erosion.
Sorghum-Sudan grass is also excellent at penetrating compacted subsoil and improving the structure of the soil. It's often recommended to follow Sorghum-Sudan grass with a legume cover crop, such as clover, to restore soil health.
It will add a lot of biomass to the soil, partly because it grows so tall—5 to 12 feet—with stalks up to 1/2-inch-thick. Finally, Sorghum-Sudan grass is an excellent quick forage for pastured animals. Be aware that under certain conditions, such as frost or drought or after the grass is cut, Sorghum-Sudan grass can contain high levels of prussic acid, which can be toxic to cattle.