Long-term effect of fertilizer application on rainwater use efficiency, soil fertility and sustainability of yield and profitability from sorghum and pigeonpea in semi-arid Vertisols

A long-term intercropping experiment with sorghum and pigeonpea was conducted during 1998 to 2008 under semi-arid Vertisols at Akola to identify a superior treatment for sustaining maximum rainwater use efficiency (RWUE), yield and monetary returns and maintaining soil fertility over years. The experiment was conducted with 9 fertilizer treatments with recommended dose of nutrients @ 80: 40: 0 NPK kg ha⁻¹ for sorghum. The treatments were: (i) T₁: Control; (ii) T₂: 100% recommended N; (iii) T₃: 50% recommended N; (iv) T₄: FYM @ 4 t ha⁻¹; (v) T₅: FYM @ 4 t ha⁻¹ + 10 kg N ha⁻¹; (vi) T₆: FYM @ 4 t ha⁻¹ + 20 kg N ha⁻¹; (vii) T₇: 2 t ha⁻¹ green leaf + 10 kg N ha⁻¹; (viii) T₈: 2 t ha⁻¹ green leaf + 20 kg N ha⁻¹ and (ix) T₉: FYM @ 4 t ha⁻¹ + 2 t ha⁻¹ green leaf. A common dose of P₂ O₅ @ 40 kg ha⁻¹ was applied to both crops and N was given to only sorghum. The soil was low in N, P and high in K. The study indicated a significant effect of treatments on soil nutrients, RWUE, yield and monetary returns over years. T₆ gave significantly higher sorghum equivalent yield of 4471 kg ha⁻¹ and RWUE of 6.47 kg ha⁻¹ mm. This treatment also gave maximum gross returns of 42291 ha; net returns of 25416 ha; benefit-cost (B: C) ratio of 2.51; apart from maintaining soil carbon of 6.7 g kg⁻¹; N of 255 kg ha⁻¹; P₂ O₅ of 28.9 kg ha⁻¹ and K₂ O of 339 kg ha⁻¹. Maximum sustainability yield index of 53% with lowest rank sum were attained by T₆. We conclude that the farmers could adopt treatment T₆ to attain maximum profitability, RWUE and maintenance of soil fertility under semi-arid Vertisols