Medium-term impact of tillage and residue retention on soil physical and biological properties in dry-seeded rice-wheat system in north-west India

Repeated puddling for rice cultivation and extensive tillage during wheat cultivation in the north-west of India has adversely affected soil health. Adoption of resource conservation technologies (RCTs) is required for long-term sustainability of conventional rice-wheat systems. However, the behaviour of these technologies is site-specific. A field study was conducted in 2016 to evaluate the medium-term impact of tillage and residue retention on soil physical and biological characteristics. Four treatments were imposed during 2011: conventionally-tilled (CT) rice followed by CT wheat all without residue retention (-M); zero-tilled (ZT) rice followed by ZT wheat and -M; CT rice followed by CT wheat and all with residue retention (+M); and ZT direct-seeded rice followed by ZT wheat and +M. In the surface layer (0-15 cm) of ZT, soil organic carbon (SOC) stock was higher by 15%, mean weight diameter (MWD) by 31.8% and bulk density (BD) by 4% compared to CT averaged across residue treatments. Irrespective of tillage, SOC stock was increased by 19% and MWD by 39% and BD decreased by 1.8% in +M compared with -M in the 0-15 cm soil layer. Infiltration rate was higher in +M than -M irrespective of tillage. Microbial biomass carbon, basal soil respiration and soil enzymatic activities were higher in ZT and +M than CT and -M respectively. Thus, medium-term adoption of RCTs such as ZT and residue retention enhanced soil physical and biological properties in this dry-seeded rice-wheat system. However, whether retaining wheat residue improves soil physical and biological properties requires further investigation.