Sustainable Practices for Vegetable Production in the South
Dr. Mary Peet, NCSU
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Alfalfa has medium-high cold tolerance, good nitrogen-fixing capabilities, low-to-medium shade tolerance, and is deep rooting and drought tolerant. Alfalfa attracts many insects, both beneficial and pest. Perennial alfalfa is slow to establish and prefers a well-drained soil with a pH between 6.5 and 7.5. Annual alfalfa cultivars such as 'Nitro' have been developed with high nitrogen-fixing efficiency and more vigorous vegetative growth than perennial forms. Normal seeding rate is 10 pounds per acre. It can be planted in August at the latitude of Virginia and as late as October or November on the Gulf coast. Alfalfa will overwinter better if it has made some vegetative growth prior to the onset of cold temperatures.

Short-lived perennials

Hairy indigo prefers sandy, well-drained soil, is drought tolerant and nematode resistant, has poor shade tolerance and is killed by frost. Seed is drilled at 3 to 4 pounds per acre in the spring. Although not all seed germinates initially and establishment is slow, hairy indigo eventually grows into a 4-to-7-foot tall spreading bush. It produces large quantities of biomass (5 to 10 tons per acre) and fixes N at the rate of 90 to 130 pounds per acre. Although hairy indigo will reseed itself, the stand ard type is a very long season crop and is usually killed by frost before setting seeds. If seed set is desirable, or if a smaller plant is desired, early types exist which are less vigorous vegetatively, but will set seed as far north as central Georgia.

Red clover (legume)

Red clover is a short-lived perennial with moderate to high cold tolerance, good nitrogen fixing capabilities, and good shade tolerance. While it has low to moderate drought tolerance, it is not tolerant of flooded soil. Red clover prefers a soil pH of 6.2 to 7.0 and a loam to clay soil. Seeding rate ranges between 8 and 20 pounds per acre. Red clover can be seeded in the early fall or early spring. For an earlier start in the fall, it can be overseeded into vegetable crops after they are established (for example, sweet corn at tasselling and winter squash before the vines begin to run).