The introduction of legumes into the cotton cropping system improves the N nutrition of the cotton following the legume crop. N fertilizer rates for cotton can be reduced by up to 50% when preceded by well-grown legume crops that can efficiently fix atmospheric N. The most effective N fixing legumes identified within this project include soybeans, lablab, faba beans, field peas and forage legumes, particularly vetches. While most growers aim for some financial return from their rotation crops, substantial benefits can be gained from green-manuring most legume crops, even those which have little value as seed crops (lablab and vetch). Where legume crops have preceded cotton the maximum yield attained has been consistently 4-5% higher than the maximum yield attained where non-legume rotation crops were used. This is probably a result of improved soil structure (tilth) enabling better root development, which is reflected in improved crop nutrition and soil water relations. Yield improvement and saving in N fertilizer application are typified in Figure I.