Can sustainability of maize-mustard cropping system be achieved through balanced nutrient management?

Abstract Information on optimization of nutrient management (NM) protocols for maize-mustard cropping system to achieve sustainability with regards to crop yield, nutrient use efficiency, soil quality, energy balance and profitability is limited. We evaluated NM practices for maize-mustard cropping system in a comprehensive manner using five criteria such as i) crop yield response, ii) recovery efficiency of plant nutrients, iii) soil quality index, iv) energy efficiency, and v) profitability of cultivation for acidic soils under subtropical conditions of northeast India. Eight NM treatments comprising of organic [farmyard manure (FYM)], inorganic fertilizers including micronutrients (Zn, B) and some of their combinations were tested using randomized complete block design with three replications for five consecutive maize-mustard cropping sequences during 2010–2015. Yield and yield related characters of the crops were recorded and nutrient concentration in representative plant parts was analysed for determination of their uptake, harvest index and use efficiency at each harvest. The initial and post-harvest (after fifth cropping sequence) soil samples were collected at 0-0.20 m depth from each of the experimental plots and analysed for physical, chemical and biological soil quality attributes. Energy and economic efficiency of the cropping systems was computed using fertilizers, seeds, plant protection chemicals, farm machineries for tillage and irrigation and human labor inputs and crop yield outputs. Yield and yield related characters, plant nutrient uptake and use efficiency, energy and economic variables of cultivation and soil properties were subjected to analysis of variance. Balanced supply of nutrients including micronutrients (Zn, B) through integration of organic and inorganic sources was proved to be sustainable in respect of crop productivity, economic viability and maintenance of environmental health. This helped improve recovery efficiency of applied nutrients as well as soil quality by increasing soil organic C, microbial biomass C and plant available nutrient content. Integrated use of 120-35-50-5-1 kg N-P-K-Zn-B with 10 Mg FYM ha −1 was proved to be the best due to significantly higher crop yield (5.80 Mg kernel and 1.22 Mg grain ha −1 for maize and mustard, respectively), recovery efficiency of applied nutrients (average recovery efficiency 64.5%), soil quality index (2.0), energy efficiency (energy gain 234,530 MJ ha −1 ) and economic return (marginal rate of return 3.5) as compared to the other NM treatments. Application of 120-35-50-5-1 kg N-P-K-Zn-B ha −1 or its combination with reduced rate of organic manure (5 Mg FYM ha −1 ) can also achieve sustainability with minimum conciliation with yield, nutrient recovery, environmental quality and economic benefit. Supply of nutrients only through organic sources (e.g., FYM) will not be sustainable for maize-mustard cropping system.