Tillage and residue management effects on soil aggregation, organic carbon dynamics and yield attribute in rice–wheat cropping system under reclaimed sodic soil

Abstract

Conservation tillage and residue management are the options for enhancing soil organic carbon stabilization by improving soil aggregation in tropical soils. We studied the influence of different combinations of tillage and residue management on carbon stabilization in different sized soil aggregates and also on crop yield after 5 years of continuous rice–wheat cropping system on a sandy loam reclaimed sodic soil of north India. Compared to conventional tillage, water stable macroaggregates in conservation tillage (reduced and zero-tillage) in wheat coupled with direct seeded rice (DSR) was increased by 50.13% and water stable microaggregates of the later decreased by 10.1% in surface soil. Residue incorporation caused a significant increment of 15.65% in total water stable aggregates in surface soil (0–15cm) and 7.53% in sub-surface soil (15–30cm). In surface soil, the maximum (19.2%) and minimum (8.9%) proportion of total aggregated carbon was retained with >2mm and 0.1–0.05mm size fractions, respectively. DSR combined with zero tillage in wheat along with residue retention (T6) had the highest capability to hold the organic carbon in surface (11.57gkg−1 soil aggregates) with the highest stratification ratio of SOC (1.5). Moreover, it could show the highest carbon preservation capacity (CPC) of coarse macro and mesoaggregates. A considerable proportion of the total SOC was found to be captured by the macroaggregates (>2–0.25mm) under both surface (67.1%) and sub-surface layers (66.7%) leaving rest amount in microaggregates and ‘silt+clay’ sized particles. From our study, it has been proved that DSR with zero tillage in wheat (with residue) treatment (T6) has the highest potential to secure sustainable yield increment (8.3%) and good soil health by improving soil aggregation (53.8%) and SOC sequestration (33.6%) with respect to the conventional tillage with transplanted rice (T1) after five years of continuous rice–wheat cropping in sandy loam reclaimed sodic soil of hot semi-arid Indian sub-continent.