Increasing farmer's income and water use efficiency as affected by long-term fertilization under a rainfed and supplementary irrigation in a soybean-wheat cropping system of Indian mid-Himalaya

Water and nutrient management are major corners in the improvement of productivity and sustainability of rainfed soybean-wheat cropping systems (SWCS). A nine-year-old (2006-2014-15) field experiment was started to explore the effects of recommended dose of farm yard manure (FYM) in SWCS, recommended dose of nitrogen, phosphorus and potassium fertilizers (RDF) along with FYM, FYM + 50% NPK, NPK, FYMsoybean + NPKwheat and without application of NPK and FYM (CK) under rainfed (I0) and supplementary irrigation (I1) situation in SWCS. Results from nine years continuous fertilization of NPK + FYM showed significantly highest grain yield of wheat (2.70 and 3.80 t ha−1) and soybean (2.50 and 2.74 t ha−1) under rainfed (I0) and supplementary irrigation (I1), respectively as compared to rest of treatments. Significant (p < 0.05) correlation (R2 = 0.50) was observed between seasonal rainfall and wheat grain yield. However, SWCS yield was also significantly (p < 0.05) higher with fertilization of NPK + FYM plots under both rainfed (I0) and supplementary irrigation (I1) situation. The mean water use efficiency (WUE) of wheat (9.70 and 9.60 kg ha−1 mm−1) was significantly higher as compared soybean (3.8 and 4.3 kg ha−1 mm−1) under rainfed (I0) and supplementary irrigation (I1), respectively. Meanwhile, in respective of treatments WUE of wheat (15 and 14 kg ha−1 mm−1) and soybean (5.7 and 6.2 kg ha−1 mm−1) were significantly (p < 0.05) higher in NPK + FYM plots under rainfed (I0) and supplementary irrigation (I1), respectively. Results showed that grain yield, irrigation and fertilizer interaction was significant (p < 0.05) positive for wheat, whereas it was non-significant for soybean. The net returns were significantly higher with fertilization of NPK + FYM under rainfed (I0) and supplementary irrigation (I1) in SWCS. Economic efficiency (EE) and production efficiency (PE) was also significantly (p < 0.05) higher with NPK + FYM fertilization in SWCS. Thus, we conclude that in the long-term fertilization (NPK + FYM) in SWCS under rainfed and supplementary irrigation situation, respectively is sustainable option for higher economic as well as production efficiency.