Water-stable soil aggregation and associated carbon in a no-till Atwood silt loam soil with cover crops and poultry litter

Knowledge on integrating cover crops and poultry litter effects on soil aggregation and associated carbon remains uncertain. In this study, aggregate size fractions, aggregate stability, and aggregate-associated carbon were examined within the topsoil (0–5 cm depth) across five winter cover crops [no cover crop as a control, cereal rye (Secale cereale L.), winter wheat (Triticum aestivum), hairy vetch (Vicia villosa), and mustard (Brassica rapa) plus cereal rye (mix)] and three fertilizer sources (no fertilizer as a control, recommended inorganic fertilizers, and poultry litter) in a split-plot design in no-till upland Atwood silt loam soil. Results demonstrated that the aggregate size 0.25–0.053 mm was the most dominant, containing the largest soil organic carbon (SOC) stock, and contributing significantly to the bulk SOC in no-till upland Atwood silt loam soil. Among the cover crops, the mustard plus cereal rye cover crop increased SOC stock both in bulk soil (10.0 Mg ha−1) and in the 0.25–0.053 mm aggregates (7.1 Mg ha−1). The corresponding increases for poultry litter were 9.7 and 5.9 Mg ha−1, respectively. The highest values for aggregate stability index, mean weight diameter, and geometric mean diameter (56.8 %, 1.0 mm, and 0.6 mm, respectively) were obtained under winter wheat cover crop, while fractal dimension and soil erodibility factor were highest (2.8 and 0.14, respectively) under no cover crop. Multivariate analysis revealed the > 2 mm aggregates was the most dominant predictor for the stability of soil aggregates, suggesting its pivotal role in affecting soil aggregate stability. Aggregate-associated carbon positively correlated with aggregate stability index. Overall, integrating cover crops such as winter wheat and mustard plus cereal rye, along with poultry litter, can increase the stability of soil aggregates and improve SOC stock, which may further enhance the sequestration potentials of soil carbon and decrease the threat of soil degradation and erosion in agricultural systems.