Most soils in the tropical region are highly weathered and infertile. A sustainable crop production system must adopt an ecological approach, using balanced nutrient inputs from inorganic, organic and biological sources. Achieving food security for a rapidly expanding population in the tropics means intensifying food production on existing cropland through enhanced nutrient input and recycling. While nitrogen may be generated through biological N fixation, other nutrients, especially phosphorus, must be supplied from external sources to achieve higher crop yields. The use of organic inputs is essential to maintain adequate physical, chemical and biological properties of soils. Features of nutrient management in large portions of the tropical region are as follows: (1) low nutrient reserves in arable soils, (2) a negative nutrient balance on cropland, (3) small family farms, and (4) multiple cropping with few or no external nutrient inputs. Acceptable technologies must be developed and implemented to ensure economically viable and ecologically sound nutrient-conserving cropping systems that integrate N-fixing plant species with food crops. Fuelwood and fodder production systems in an integrated watershed management approach will spare crop residues for use as mulching materials on cropland or for compost production. Phosphorus inputs are needed to sustain crop yields on highly weathered soils. Programs for integrating livestock and food crop production are needed for more efficient use of animal manure and household waste on cropland.