Soil carbon dynamics and productivity of rice–rice system under conservation tillage in submerged and unsubmerged ecologies of Eastern Indian Himalaya

Abstract

Intensive tillage practices along with improper residue management in a rice (Oryza sativa)–rice system (RRS) contributed to soil fatigue and declining productivity in South Asia. Therefore, a 3-year (2013–2015) field study was conducted to assess tillage modification effects on productivity and soil C sequestration under RRS at ICAR- RC for North Eastern Hill Region, Tripura, India. The experimental site represented two different ecologies: unsubmerged (ECO 1) and submerged (ECO 2), with three tillage practices: conventional tillage (CT), reduced tillage (RT) and no-till (NT). Results showed that the cultivation of RRS under RT produced significantly higher grain (8.6–9.4 Mg ha−1) and straw (11.8–12.9 Mg ha−1) yields under both ecologies over those under CT and RT, in addition to recycling the maximum biomass. Soil under RT had lower bulk density (ρb), the highest soil organic carbon (SOC) concentration, pool, sequestration, accumulation, carbon retention efficiency, soil microbial biomass carbon and dehydrogenase activities under both ecologies as compared to CT. A total amount of 1.34 Mg C ha−1 was accumulated under soils of RT over 3 years. The rate of SOC sequestration ranged from 133.6 kg ha−1 year−1 under soils of CT to 444.7 kg ha−1 year−1 under RT in RRS. Thus, cultivation of RRS under RT with effective residue recycling is recommended for higher system productivity and C sequestration under both rice production ecologies of the NEH region of India.