Understanding the process of soil organic carbon (SOC) sequestration and mineralization in aggregates is pertinent to mitigate climate change and minimize risks of soil degradation. The NT system increased the proportion of >2 mm aggregate fraction and reduced the proportion of 0.25 mm macro-aggregate fraction also significantly increased in the 0.00-0.5 m layer in NT system. However, those within the 2.00-0.25 mm aggregate fraction were significantly reduced in the 0.05-0.200 m layer under NT system. Straw incorporation increased not only the SOC stock in bulk soil, but also the proportion of macro-aggregate, aggregate associated with SOC and humic and fulvic acids concentration within the aggregate. Compared to conventional tillage, the percentages of >2 mm macro-aggregates and water-stable macro-aggregates in rice-wheat double conservation tillage (zero-tillage and straw incorporation) were increased 17.22% and 36.38% in the 0–15 cm soil layer and 28.93% and 66.34% in the 15–30 cm soil layer, respectively. Furthermore, the large macro-aggregates (> 2 mm) with the highest proportion of size distribution represented the major pool of SOC stock (47.3–51.2%) and mineralization amount (38.2–43.6%) in the 0–30 cm layer, followed by that in the small macro-aggregates (0.25–2 mm), regardless of tillage practices. However, the mineralization quotient (mineralization per unit SOC concentration) of macro-aggregates (> 0.25 mm) was lower than that for the other size classes. The NTS enhanced the macro-aggregate formation in the 0–20 cm layer and associated SOC concentration in the 0–10 cm layer. Furthermore, NTS decreased total potential mineralization in the 0–30 cm layer compared with the other tillage practices, attributed to decrease in the large macro-aggregates (30.0–51.4%) with low particulate organic carbon (POC) concentration. Zero tillage and straw incorporation also increased the mean weight diameter and stability of the soil aggregate. In surface soil (0–15 cm), the maximum proportion of total aggregated carbon was retained with 0.25–0.106 mm aggregates, and rice-wheat double-conservation tillage had the greatest ability to hold the organic carbon (33.64 g kg−1). In the NPK + FYM treatment, LOC was ∼16% significantly higher in topsoil than the sub-surface soil. Aggregate size of > 2000, 250–2000, 53–250 and 2000 to < 53 μm. Plots with fertilization of 50% NPK + 50% GM (1.8 t ha−1) had significantly higher total soil organic C (TOC), LOC, macro-aggregate-associated C concentrations, and soil aggregation than other treatments. These collected review demonstrated that conservation agriculture that integrates application of nutrient management, tillage and crop residue is crucial for improving soil health and sustainability of farming systems in Northwest IGP.

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