This work provides information relevant to the nitrogen (N) management strategy of multiple cropping in upland systems in the humid tropics of the transmigration areas of Sumatra, Indonesia. The experiment was conducted on a red yellow podzolic (orthoxic palehumult) soil at Kota Bumi in Lampung Province, Indonesia, where the annual rainfall of 2430 mm allows three consecutive crops per year to be grown. Two sequential systems were studied—rice-soybean-cowpea and rice-corn-cowpea. For each crop, crop residues and fertilizer applied to subplots were labelled with 15N so that the crop N uptake for the planted crop and subsequent crops could be partitioned into that derived from N fixation (legume only), fertilizer, crop residues and soil. The experiment was conducted over two years (6 crops).