Sunn hemp is a warm-season legume that requires good drainage, and tolerates poor, sandy, droughty soils. It is a high biomass crop and can also fix high levels of nitrogen. This is a tall herbaceous shrubby annual 3-9’ tall. It has a strong taproot with many well-developed lateral shoots and numerous branched, lobed nodules up to 1” in diameter with stems up to ¾” in diameter. Warm temperatures with moderate humidity are best. It is less demanding of soil fertility than cowpea. It can produce over 5,000 pounds of biomass and over 100 pounds of nitrogen per acre in 8-12 weeks of frost free growth. It tolerates soil pH levels from 5 to 7.5.
In the central plains it has been successfully seeded up to 2-2.5” deep. It looks to be a natural fit between two wheat crops, or preceding corn the following year. Possibly cotton, grain sorghum and sunflowers could be added to that list. Sunn hemp suppresses weeds, slows soil erosion, and reduces root-knot nematode populations.