Impact of varieties and organic nutrient sources on productivity, soil carbon stocks and energetics of rice-ratoon system in Eastern Himalayas of India

Abstract

Abstract Cultivation of rice (Oryza sativa L.) varieties having ratooning potential under adequate organic nutrient sources (ONSs) could improve system productivity, soil organic carbon (SOC) stock and energy use efficiency in the eastern Indian Himalayas. A 6-year study was conducted to evaluate the impact of four varieties (Shahsarang-1, Lampnah, IR-64 and Krishna Hamsha) under five ONSs [pig manure (PM), farmyard manure (FYM), vermicompost (VC), in situ paddy straw (PS) recycling and farmers’ practice] on productivity, soil health and energetics of a rice-ratoon system in a mid-hill (950\u2009m asl) subtropical climate. Organic manures were applied on an N-equivalent basis. The 6-year average grain yield of main rice was significantly highest for Shahsarang-1 (4.40\u2009Mg ha−1) followed by IR-64. Shahsarang-1 (2.58\u2009Mg ha−1) and IR 64 also produced higher ratoon crop yields, leading to higher total annual productivity (main\u2009+\u2009ratoon crops) than other varieties. Rice grown with PM produced the highest average rice productivity of main crop, followed by FYM. The highest total N, P and K uptake by the rice was obtained under PM followed by FYM. After six cropping cycles, the maximum SOC stock and available N and P were observed under PM, whereas available K was highest under PS recycling. The highest gross energy output, net energy and energy intensity were registered with PM, whereas energy use efficiency and energy productivity were the highest under control. Thus, cultivation of either Shahsarang-1 or IR-64 using PM/FYM is appropriate for enhancing productivity, soil health and conservation of energy in the study region and similar eco-regions elsewhere.