While the focus has always been on cotton and corn, other crops are included in the rotations. Oats were the winter grain and winter cover crop of choice after corn through the 1960s when cereal rye replaced oats. By the 1990s, soft red winter wheat varieties replaced rye. Cowpea was the summer legume of choice through the 1950s when soybean was introduced as a major crop in the Southeastern U.S. Today, soybean are double-cropped after wheat grain harvest in the 3-year rotation. Cultivars change from year to year but are always those that are popular and available to farmers.
The winter legumes of choice have always been crimson clover and/or hairy vetch. At times, common vetch was planted. Cultivars used have been those released through the Auburn University breeding program; these were developed for earliness and dry matter yield. Total nitrogen (N) fixed by the winter legume is periodically measured and ranges between 50 and 150 pounds N per acre.