Integrated Soil Fertility and Plant Nutrient Management in Tropical Agro-Ecosystems: A Review

The greatest challenge for tropical agriculture is land degradation and reduction in soil fertility for sustainable crop and livestock production. Associated problems include soil erosion, nutrient mining, competition for biomass for multiple uses, limited application of inorganic fertilizers, and limited capacity of farmers to recognize the decline in soil quality and its consequences on productivity. Integrated soil fertility management (ISFM) is an approach to improve crop yields, while preserving sustainable and long-term soil fertility through the combined judicious use of fertilizers, recycled organic resources, responsive crop varieties, and improved agronomic practices, which minimize nutrient losses and improve the nutrient-use efficiency of crops. Soil fertility and nutrient management studies in Ethiopia under on-station and on-farm conditions showed that the combined application of inorganic and organic fertilizers significantly increased crop yields compared to either alone in tropical agro-ecosystems. Yield benefits were more apparent when fertilizer application was accompanied by crop rotation, green manuring, or crop residue management. The combination of manure and NP fertilizer could increase wheat and faba bean grain yields by 50%-100%, whereas crop rotation with grain legumes could increase cereal grain yields by up to 200%. Although organic residues are key inputs for soil fertility management, about 85% of these residues is used for livestock feed and energy; thus, there is a need for increasing crop biomass. The main incentive for farmers to adopt ISFM practices is economic benefits. The success of ISFM also depends on research and development institutions to provide technical support, technology adoption, information dissemination, and creation of market incentives for farmers in tropical agro-ecosystems.