Studies were conducted in Louisiana, USA, between 1987 and 2002 to determine the effects of tillage practices (no-till and surface till), cover crops (winter wheat, winter hairy vetch and volunteer winter native (fallow) vegetation) and nitrogen rates (0, 35, 70, 105 and 140 pounds per acre) under rainfed or irrigated conditions on cotton growth and yield. Following a cotton crop and without additional fertilizer, the native, vetch and wheat cover crops produced an average 1054, 2054 and 4045 pounds above-ground biomass per acre, respectively. Nitrogen concentration of the cover crop vegetation averaged 2.0, 4.0 and 1.5% in native, vetch and wheat, respectively. The total nitrogen in the cover crop biomass averaged across year, tillage regime and nitrogen rate was 27, 90 and 38 pounds per acre in native, vetch and wheat, respectively. Initially, lint yields in surface-till and no-till were similar but, after five years, no-till yields were higher. No cover crop + tillage treatment recorded the lowest yield. Savings in equipment and labour costs increased the returns for cotton grown with no-till practices. Cotton following vetch needed no nitrogen fertilizer. Cotton following wheat required high nitrogen rates for optimum yield. At the optimum nitrogen rate, all tillage cover crop regimes produced similar yields. Lint yields were lower in rainfed than irrigated conditions. Wheat cover crop was more beneficial to yield in rainfed than irrigated cotton. No-till + wheat cover crop recorded the highest yields and returns from rainfed cotton. No-till cotton produced yields similar to or higher than cotton planted in surface-till treatments.
