Sustainability Assessment of Rice-Wheat System Through Organic Fertilizers and Green Manuring in Sub-Tropical Humid Climate

The improved crop varieties and inorganic fertilizers played a key role in bringing the revolutionary change from insufficient to surplus food grains production. In the era of self-reliant in food grains production, the noxious impacts of long-term sole application of inorganic fertilizers on natural resources are being observed critically and climate vagary and its threat to agriculture sector makes such studies of prime importance. The present study was undertaken with a hypothesis to substitute the inorganic N (either partial or fully) with farm yard manure (FYM) in at least one crop under rice-wheat system. The experiment was conducted in a two-factorial randomized complete block design with different levels of FYM (0, 10 and 30 t ha − 1 ) in each crop to study the yield, soil health, quality, profitability and sustainability with a comparison to recommended dose of conventional inorganic fertilizers (CIFs). In all treatments, green manuring was done through the incorporation of Sesbania aculeata (Willd.) Pers crop prior to rice translating. The results of pooled analysis of seven-year data (2013–2014 to 2019–2020) revealed that application of 30 t ha − 1 FYM produced statistically similar (p > 0.05) rice yield but with a decline of 19.21% in wheat yield as compared to CIFs. The continuous application of FYM @30 t ha − 1 increased organic carbon content of soil to 1.24% in the upper soil layer which was 74.6% higher than that under CIFs. The substitution of CIFs with FYM brought significant (p < 0.05) increase in available N, P and K in the top layer of the soil. The available N was significantly higher (p < 0.05) along with slight improvement (p > 0.05) in organic carbon in the top layer of the soil under control treatment associated with Sesbania aculeata (Willd.) Pers incorporation over CIFs. The application of 30 t ha − 1 FYM produced similar net return and wheat equivalent yield as with CIFs. However, benefit-cost (B:C) ratio in CIFs (2.16) was significantly (p < 0.05) higher than those with FYM application (1.75–1.90) due to increase in transportation and labour cost in handling bulky FYM. The substitution of CIFs with FYM produced statistically similar sustainability value index (SVI) which indicates the similar stability of rice-wheat system and its sustainable nature as with CIFs. The results of present study suggest that CIFs can be substituted by green manuring + FYM application @30 t ha − 1 in rice crop under rice-wheat cropping system without any penalty on crop productivity and profitability while providing the multifarious benefits on soil health, which has been deteriorated through intensive cultivation of rice-wheat system, and overdosed and imbalanced inorganic fertilizers application in Indo Gangetic plains. Further, assured premium price of organic rice can escalate the adoption of such alternative fertilizers; however, high cost of FYM amidst declining cattle, increased transportation and labour cost in handling bulk volume of such fertilizers seems to be challenging factors.