In 1959, a long-term study was initiated at Louisiana Agricultural Experiment Station's Red River Research Station. This study was initiated to address concerns about the long-term effects of continuous cotton cultivation on native soil fertility and whether or not any negative effects of cultivation could be avoided or corrected by alternating a summer cotton crop with a winter cover crop. The study was also designed to compare the performance of different cover crops under Northwest Louisiana environmental conditions. Each year, data collected includes the amount of dry matter produced by each cover crop, the nitrogen contribution of each cover crop, effects on soil fertility, and cotton yield. 1998 marked the fortieth year of this study that has undergone only minor changes since its beginning in 1959. On average, over the 40 years of this study, cotton following hairy vetch has produced the greatest yields. In 1998, all treatments that included a winter cover crop had significantly greater organic matter at 0 to 6 inches than those that did not.