Effect of nutrient management practices on the productivity, economics and soil fertility of castor (Ricinus communis) - sorghum (Sorghum bicolor) cropping system in rainfed Alfisols

A field experiment was conducted for 6 years during 2005-10 to study the effect of nutrient management practices on the productivity, economics and soil fertility of castor (Ricinus communis L.) - sorghum (Sorghum bicolor (L.) Moench.) cropping system in rainfed Alfisols of southern Telangana region of Andhra Pradesh. Application of recommended dose of NPK for castor (60-40-30 kg/ha) recorded higher seed yield (1 614 kg/ha) which was comparable with NPK + 5 tonnes FYM/ha (1 589 kg/ha) and 75 % NPK + 25 % N through FYM (1 512 kg/ha). Whereas for sorghum, recommended NPK (60-30-30 kg/ha) + 5 tonnes FYM/ha recorded higher sorghum seed yield (3 147 kg/ha) which was comparable with the treatment, recommended dose of NPK (2 718 kg/ha) and 75% NPK + 25% N through FYM (2 696 kg/ha). Imbalanced application of N alone or NP or 50 % NPK and control plots recorded significantly the lowest seed yields of both crops. Response to zinc application was observed only in third crop cycle of sorghum. The system productivity in terms of castor equivalent yield (CEY) was the highest in NPK + 5 tonnes FYM/ha treatment (2 847 kg/ha) which was 84.3 % higher than the control (1 544 kg/ha). This treatment recorded the maximum gross returns (Rupees 71 175 /ha), net returns (Rupees 45 025 /ha)and benefit cost ratio (2.72). At the end of 3 cropping cycles (6 years), the treatment receiving NPK + 5 tonnes FYM/ha significantly improved the soil available N, P, K, organic carbon and micro nutrient (Fe, Mn and Zn) status compared to control or imbalanced fertilizer treatments.