Effects of Fertilizers on Yield, Sustainability, and Soil Fertility under Rainfed Pigeon pea + Rice System in Subhumid Oxisol Soils

A long-term field experiment was conducted at the research farm of the All-India Coordinated Research Project for Dryland Agriculture, Phulbani, Orissa, India, from 2001 to 2006 to identify the best integrated nutrient-use treatments for ensuring greater productivity, profitability, sustainability, and improved soil quality in pigeon pea + rice (two rows of pigeon pea followed by five rows of rice alternately) intercropping system. In all, nine treatments, eight comprising integrated nutrient-use practices, chemical fertilizer (CF), farmyard manure (FYM), and green leaf manure (GLM) to supply nitrogen (N) at 45 kg N ha–1 and one farmer's practice equivalent to 25 kg N ha–1 (FYM 5 t ha–1), were tested on a long-term basis. Results of the study revealed that 20 kg N ha–1 (FYM) + 25 kg N (CF) gave maximum mean rice grain yield of 1.52 t ha–1, followed by 20 kg N (GLM) + 25 kg N (urea) with grain yield of 1.51 t ha–1. In the case of pigeon pea, 30 kg N (FYM) +15 kg N (urea) gave maximum pigeon pea grain yield of 0.94 t ha–1, which was 34% greater than the sole application of chemical fertilizer. Pigeon pea grain yield tended to increase with increasing proportion of organic N in FYM + CF or GLM + CF combinations. Application of 20 kg N (FYM) + 25 kg N (urea) recorded maximum mean rice equivalent yield of 3.59 t ha–1 and sustainability yield index of 59%. While studying profitability, application of 20 kg N (FYM) + 25 kg N (CF) gave maximum net returns of US$168.94 ha–1. Impact of treatments on soil quality as assessed in terms of relative soil quality indices (RSQI) increased with increasing proportion of organic sources of N. Using an innovative and new approach, an index of integrated productivity–sustainability–profitability–soil quality performance index (I P,S,Pr,SQ) was computed to make a precise evaluation of the treatments. Based on this index, the order of performance of the treatments was T6 [20 N (FYM) + 25 N (CF)] (7.7) > T7 [30 N (FYM) + 15 N (CF) (6.9)] > T3 [20 N (GL) + 25 N (CF)] (6.8) > T5 [10 N (FYM) + 35 N (CF) (6.6)] > T9 [GL] (6.5) > T8 [CF] (6.2) > T4 [30 N (GL) + 15 N (CF)] (6.0) > T2 [10 N (GL) + 35 N (CF)] (5.7) > T1 [FYM at 5 t ha–1] (4.1). Thus, the results and the methodology adopted in this study using long-term data would be very useful to researchers, farmers, land managers, and other stakeholders not only in India but also across the world under similar climatic and edaphic situations.