Also consider using a cover crop to hold the soil and increase the organic matter content of the soil. Small gains such as wheat should be seeded at 3/4 to 1 pound of seed per 1,000 square feet from mid-September to late October. Spring oats can also be seeded until mid-September but the rate should be 2 to 4 pounds per 1,000 square feet. Spring oats will winter kill and can be tilled under in the spring.
Legume cover crops such as hairy vetch, alfalfa and sweetclover provide an additional benefit by ‘fixing’ nitrogen, thereby increasing fertility of the soil. Each of these should be seeded at about 1/4 to ½ pound of seed per 1,000 square feet of garden. Sweetclover should be seeded from August to early September and hairy vetch and alfalfa from mid-August to late September. (Ward Upham)