What is it: 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 funny name comes from the fact that it is a hybrid, a cross between sorghums grown for forage and a type of grass called Sudangrass.
Seeding rate and planting tips: Seed Sorghum-Sudangrass at a rate of 40-50 pounds per acre if broadcast, 35 pounds per acre if drilled. Plant after frost threat has passed in spring, but before July 15 in the Northeast for maximum growth potential. Soil temperatures of at least 60 degrees F are required for this cover crop to germinate. Repeated mowing can increase Sorghum-Sudangrass' 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.
Why use it: Sorghum-Sudangrass 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. And the first frost will kill it - so it's great to leave over winter as a dead residue to protect from soil erosion. Sorghum-Sudangrass is also excellent at penetrating compacted subsoil, improving the structure of the soil. It's often recommended to follow Sorghum-Sudangrass with a legume cover crop, such as clover, to restore soil health.
Sorghum-Sudangrass adds a lot of biomass to the soil, partly because it grows so tall - 5 to 12 feet, with stalks up to a half-inch thick.
When to kill it: As mentioned above, maintain by mowing several times during the season before the crop seeds. Just prior to a killing frost, mow Sorghum-Sudangrass, finely chop it and then immediately till into the ground while still green. Due to the presence of weed-suppressing compounds in the freshly mowed crop, wait several weeks before planting crops.