Widespread deficiencies of sulphur, boron and zinc in dryland soils of the Indian semi-arid tropics

To characterize the fertility status of soils under dryland agriculture in the semi-arid regions of India, we collected 3622 soil samples from farmers' fields in watersheds, spread in several districts of Andhra Pradesh (AP; 5 districts), Karnataka (5 districts), Tamil Nadu (TN; 5 districts), Rajasthan (3 districts), Madhya Pradesh (MP; 2 districts), and Junagadh District, Gujarat. Results of the analysis of soil samples showed that almost all farmers' fields sampled were low in organic carbon and low-to-moderate in extractable phosphorus, but generally adequate in extractable potassium. The widespread deficiencies of sulphur (S) boron (B) and zinc (Zn) were most revealing; their deficiencies varied with nutrient, district and state. The deficiencies of S, B and Zn nutrients were more widespread in farmers' fields in AP, Karnataka, MP, TN and Gujarat than in the Rajasthan watersheds. Our results demonstrate that crops grown under rainfed agriculture in the semi-arid tropical regions of India not only face water shortages and deficiencies of major plant nutrients (nitrogen and phosphorus), but they also suffer from multi-nutrient deficiencies of S, B and Zn.