A field experiment was conducted at Lucknow (26.5 degrees N, 80.5 degrees E, 120 m above mean sea level), India, during 1992-1995 to compare biomass productivity and crop yields in Sesbania aculeata (as green manure)-sugarcane-ratoon and rice-sugarcane-ratoon rotations at 0, 150 and 300 kg ha(-1) N through urea to sugarcane and 0, 75, 150 and 225 kg N ha(-1) applied to the subsequent ratoon crop with and without trash mulch. The Sesbania-sugarcane-ratoon rotation added 14.48 t ha(-1) biomass to the soil compared with 4.81 t ha(-1) by the rice-sugarcane-ratoon rotation because Sesbania yielded a significantly greater biomass (11.12 t ha(-1)) than did the residual rootmass of rice (1.68 t ha(-1)) and sugarcane (2.64-3.83 t ha(-1)). Soil organic carbon, however, tended to decline after green manuring with Sesbania but gradually increased after incorporation of rice-root residues. Trash mulching of the ratoon crop upgraded the level of soil organic carbon and mineral-N status compared to no mulching Sugarcane yields were significantly higher in the rice-sugarcane-ratoon rotation than in the Sesbania-sugarcane-ratoon rotation. A multiple linear regression model; Y=8.075+/-0.675 (PN)-22.45 (OC) + 0.671 (P); R(2)=0.965, showed that cane yields (Y) were influenced significantly by N uptake (PN), soil organic carbon (OC) and available P (P) status.