Small holder farmers have little access to capital and need high rates on return on their investments. Returns to investment in fertilizer varies with crop and nutrient applied. Six to 15 site-seasons of fertilizer  N, P, K rate research were conducted for maize, grain sorghum, upland rice, and dry bean, and only P and K for soybean and groundnut. Response curves were determined for each nutrient and each crop and the economically optimal application rates were determined. The returns to nutrient application were determined at different N cost to grain price ratios. For the current cost ratio, the returns to application of a starter dose of 10 kg ha^-1 N to dry bean gave the highest benefit:cost ratio, followed by P applied to groundnut, N applied to maize, and P applied to soybean. The information is being used to develop a tool for optimizing returns to fertilizer use for farmers with little investment capital.