Soil-Test-Based Balanced Nutrient Management for Sustainable Intensification and Food Security: Case from Indian Semi-arid Tropics

In the semi-arid tropics (SAT), there exists large yield gaps (two- to four-fold) between current farmers’ yields and achievable yields. Apart from water shortages, soil degradation is responsible for the existing gaps and inefficient utilization of whatever scarce water resource is available. On-farm soil fertility testing across different states in Indian SAT during 2001–2012 showed widespread new deficiencies of sulfur (46–96 percent), boron (56–100 percent), and zinc (18–85 percent) in addition to already known phosphorus (21–74 percent) and nitrogen (11–76 percent, derived from soil carbon). Based on these results, a new fertilizer management strategy was designed to meet varying soil fertility needs at the level of a cluster of villages by applying a full nutrient dose if >50 percent fields were deficient and a half dose in the case of fields <50 percent deficient. Improved nutrient management significantly increased crop productivity in groundnut (Arachis hypogaea) (17–86 percent), sorghum (Sorghum bicolor) (30–55 percent), soybean (Glycine max) (10–40 percent), and maize (Zea mays) (10–50 percent) with favorable benefit-cost ratios (1.43–15.2) over farmers’ practice. Nutrient balancing improved nitrogen-fertilizer-use efficiency in respect of plant uptake from soil, transport into grain, use efficiency in food production, and grain nutritional quality. Balanced-nutrient-managed plots showed better postharvest soil fertility. Residual benefits of sulfur, boron, and zinc were observed in up to three succeeding seasons. Results of soil-test-based nutrient-management trials have sensitized policy makers in some states for desired policy orientation to benefit millions of smallholders in the Indian SAT.