Peer review

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. Full/partial CA improved soil physical condition and the productivity of rice?wheat systems in the Indo-Gangetic Plains.

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