Dynamics of soil aggregate-associated organic carbon based on diversity and high biomass-C input under conservation agriculture in a savanna ecosystem in Cambodia

No-till (NT) cropping systems have the potential to enhance soil aggregation, providing physical protection and C sequestration. The existence of discrepancies in impact tillage on aggregation sequestration warrants further studies, particularly for different crop rotations. We hypothesized following: a) NT biannual rotations tend be more effective restoring large macroaggregation concentrations organic (SOC), total N permanganate oxidizable (POXC) associated with macroaggregates than a one-year frequency pattern conventional (CT); b) continuous biomass-C inputs via residues under increase proportion aliphatic those CT. Therefore, objectives this study were: (i) assess changes aggregate size distribution levels aggregate-associated SOC, POXC (ii) characterize humic acid (HA) using 13C CP-MAS nuclear magnetic resonance (NMR) spectra 8- 19-mm class reference vegetation (RV) rice-, soybean- cassava-based (RcCS, SbCS CsCS, respectively) clayed Oxisol after rotation management. evaluated four treatments each system: 1) CT, 2) three randomized complete block design replicates. Soil samples were collected at depths 0–5, 5–10 10–20 cm. conversion RV agricultural land influenced classes, indices two surface layers. formation (8–19 mm) dominated relatively higher Across all depths, proportions fraction 59% (NV), 43% 47% (RcCS), 45% 53% (SbCS) 34% 37% (CsCS) CT systems, respectively. Among (NT2-Rice, NT2-Soybean, NT2-Cassava; NT3-Rice, NT3-Soybean NT3-Cassava) indicated better performance macroaggregates. Additionally, (0–5 cm) subsurface (10–20 layers, high rate (7.32 Mg ha−1 year−1) diversity [Pennisetum typhoides) (Pearl millet)/maize + Brachiaria ruziziensis (Brz), Stylosanthes guianensis (St)] reached highest lability SOC macroaggregate classes 0.25–0.5 8–19 mm, NMR measurement suggests that diverse NT, such as millet, maize, Brz, St Crotalaria juncea, tended CT; an opposite trend was observed aromatic C. revealed advance caused by association between quantity quality addition cultural discrimination composition tropical region.