tailieunhanh - Soil aggregate stability and aggregate-associated carbon fractions under different tillage systems of rice-wheat rotation in North India

The influences of tillage systems on soil carbon (C) stocks have been studied extensively, but the distribution of soil C within aggregate fractions is not well understood. This review study was to determine the influences of various tillage systems on soil aggregation and aggregate-associated C under rice-wheat rotation in North India. The NT and RT treatments significantly increased the proportion of macro-aggregate fractions (>2000 and 250-2000μm) compared with the MP-R and MP+R treatments. Averaged across all depths, mean weight diameters of aggregates (MWD) in NT and RT were 47 and 20% higher than that in MP+R. The difference of total SOC stocks between NT and CT decreased with soil depth, confirming that the SOC benefits of NT are concentrated to the immediate topsoil still subject to direct seeding. The topsoil achieved maximum SOC stocks after about 10 years of NT. In surface soil, the maximum () and minimum () proportion of total aggregated carbon was retained with >2 mm and – mm 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 ( g kg-1soil with the highest stratification ratio of SOC (). A considerable proportion of the total SOC was found to be captured by the macro-aggregates (>2– mm) under both surface () and sub-surface layers () leaving rest amount in microaggregates and silt + clay sized particles. However increasing the quantity of C input could enhance soil C sequestration or reduce the rate of soil C loss, depending largely on the local soil and climate conditions. | Soil aggregate stability and aggregate-associated carbon fractions under different tillage systems of rice-wheat rotation in North India