Short-term (5 years) impact of tillage and residue management practices on physical properties and organic carbon (OC) of a silty clay soil was evaluated in a rice-wheat rotation in the Indo-Gangetic Plains of Bihar. The experiment had three conservation agriculture (CA) practices: one full (direct-seeded rice (DSR)-no-tilled wheat (NTW)-no-tilled mung bean (NTMB); fCA) and two partial (puddled transplanted rice (PTR)-NTW-conventionally tilled mung bean (CTMB); pCA1 and unpuddled transplanted rice (UPTPR)-conventionally tilled potato+maize (CTP + M)-NTMB; pCA2), which were evaluated against full conventional practice (puddled transplanted rice (PTR)-conventionally tilled wheat (CTW); TA). Subsurface compaction reduced and soil aggregation improved under both full and partial CA. Macro-and water-stable aggregates increased to a large extent (26 and 11%, respectively) in full CA and to a lesser extent in partial CA, mostly due to increase in coarse macroaggregate (2-8 mm) contents in the 0-10 and 10-20-cm depth soil layers. Steady-state infiltration rate nearly doubled under full CA, with larger pore volume recorded in 10-20 and 20-30-cm depth soil layers. The CA increased OC associated with all size fractions of aggregates in the surface soil layer (0-10 cm), but a higher amount of C was associated with macroaggregates, indicating relative stabilization of OC in the soil under CA. Change in bulk soil OC was larger in the 0-10-cm depth soil layer in favour of CA, which also had an 11% increase in OC stock in the 0-30-cm depth soil layer. Improvement in soil physical condition did not effectively translate into increased rice or wheat yields, but the system productivity increased largely. Highlights • Conservation agriculture (CA) resulted in 11-12% higher macro-aggregation compared to conventional practice (CT). • Macro-and total pores reduced in the 0-10 cm depth soil layer but increased in the 10-20 cm depth soil layer under CA. • CA resulted in 27-35% higher aggregate-associated OC content and 11% increase in OC stock at 0-30 cm.

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