These are annual or biennial plants. There are two varieties, yellow and white. They form arbuscular mycorrhizal associations, attracts pollinators, moderate water use and fair salinity tolerance. Sweet clovers within a single season on even marginally fertile soils, can produce abundant biomass and moderate amounts of nitrogen as it pushes its taproot and branches deep into subsoil layers. Given fertile soils and a second season, it reaches its full potential for nitrogen and organic matter production. Early in the second year it provides new top growth to protect the soil surface as its roots anchor the soil profile. It is the most drought-tolerant of forage legumes, is fairly winter-hardy and can extract from the soil then release phosphorous, potassium and micronutrients that are otherwise unavailable to crops. It thrives in temperate regions wherever summers are mild.
Annual sweet clover is not frost tolerant, but can produce up to 9,000 pounds of dry matter per acre over a summer after being over sown into a grain crop or direct seeded with a spring grain nurse crop. Its taproot is shorter and more slender than that of its biennial cousins, but it still loosens subsoil compaction.
Subterranean clovers offer a range of low growing, self-reseeding legumes with high N contribution, excellent weed suppression and strong persistence in orchards and pastures. Most cultivars require at least 12 inches of growing-season rainfall per year. A dry period in the summer limits vegetative growth, but increases hard seed tendency that leads to self-reseeding for fall reestablishment. They generally grow close to the ground, piling up their biomass in a compact layer. There are many cultivars that can be selected from to fit your climate and cover crop goals. Sub-clovers can produce 3,000 to 8,500 pounds of dry matter per acre in a thick mat of stems, petioles and leaves. Denser and less viny than hairy vetch, it also persists longer as weed-controlling mulch. Subterranean clovers might be able to be utilized by planting them with cereal crops as a living mulch and nitrogen provider.
White clovers are a top choice for “living mulch” systems planted between rows of irrigated vegetables, fruit bushes or trees. They are persistent, widely adapted perennial nitrogen producers with tough stems and a dense shallow root mass that protects soil from erosion and suppresses weeds. Once established, they stand up well to heavy field traffic and thrive under cool, moist conditions and shade. Cultivars are grouped into three types by size. The lowest growing type (Wild White) best survives heavy traffic and grazing. Intermediate sizes (Dutch White, New Zealand White and Louisiana S-1) flower earlier and more profusely than the larger types are more heat-tolerant and include most of the economically important white types. The large (Ladino) types produce the most N per acre of any white types, and are valued for forage quality, especially on poorly drained soil. They are generally less durable, but may be two to four times taller than intermediate types.
White clover performs best when it has plenty of lime, potash, calcium and phosphorus, but it tolerates poor conditions better than most clovers. Its perennial nature depends on new plants continually being formed by its creeping stolons and, if it reaches maturity, by reseeding.
Red clover is a dependable, low-cost, readily available workhorse that is winter hardy in much of the U.S. Easily over seeded or frost seeded into standing crops, it creates loamy topsoil, adds a moderate amount of N, helps to suppress weeds and breaks up heavy soil. It’s most common uses include forage, grazing, seed harvest, plow down N and, in warmer areas, hay. It’s a great legume to frost seed or inter seed with small grains where you can harvest grain as well as provide weed suppression and manage N.
Berseem clover is a cool season annual legume. It is commonly known as Egyptian clover. It has fair salinity tolerance, low water use; forms arbuscular mycorrhizal associations and the flowers attract bees.
Closeup picture of Common Vetch showing the larger leaves and stems as compared to Hairy Vetch.
Field Peas are another very good option for the area. There are spring and winter options for these, as well as those bred more for grain or forage types.