Emmalea Ernest, Extension Fruit & Vegetable Specialist; emmalea@udel.edu
As spring and early summer crops are harvested, vegetable farms may have a fallow period in June and July before later season crops are planted. Growing warm season adapted cover crops during this period can provide soil health and weed management benefits.
Sorghum, sudex, buckwheat, sunn hemp, and cowpea are some of the potential summer cover crops for Delaware vegetable farms.
Sorghum and Sudex (Sorghum-Sudangrass)
Sorghum and Sudex are summer annual grasses that provide excellent weed suppression and have potential for high biomass production if nitrogen is available. Both are heat and drought tolerant and will regrow after mowing.
Buckwheat
Buckwheat is an extremely fast-growing cover crop that can be used to outcompete weeds during short fallow periods. However, buckwheat is not as heat and drought tolerant as the other species mentioned here. Risk of reseeding is high. To avoid mature seed production, buckwheat should be terminated within 7 days of flower initiation. Because of its short time to flowering/seed production, it should not be included in mixes if reseeding is a concern.
Sunn Hemp
Sunn hemp is a tropical legume with high nitrogen fixation potential. It is tolerant of heat and drought. Because of its tall, upright growth habit, it performs well in mixes with sorghum/sudex. Sunn hemp will tolerate high mowing.
Cowpea
Cowpea is tolerant of heat and drought once established. It grows quickly during hot weather and provides good weed suppression. As a legume, it has potential to fix nitrogen if inoculated with Rhizobium. Risk of reseeding is low, year to year. Larger seeded vine and runner types are less likely to reseed in the subsequent crop compared to types developed for cover crop/forage use.
The Northeast Cover Crops Council has developed a useful web based Species Selector Tool that can help you determine the best cover crops for your specific location based on plant hardiness zone, soil type, crop rotation, and goals. The tool also provides details on growth traits, location specific establishment windows, recommended termination methods and pollinator benefits.