Carbon and Nitrogen Distribution in Aggregates from Cultivated and Native Grassland Soils

Summary

This field study investigated how long-term cultivation affects soil aggregate structure and carbon and nitrogen distribution in grassland-derived soils. Using wet sieving and chemical dispersion, the authors separated aggregates by size and quantified organic matter fractions, finding that native grassland soils exhibited greater aggregate stability than cultivated soils, and that no-till management was more effective than bare fallow or stubble mulch at preserving macroaggregates and accumulating wheat-derived particulate organic matter. The data link the loss of soil structural stability from cultivation directly to losses of organic carbon and nitrogen from the labile particulate organic matter pool.

Regional applicability

Although conducted in the United States, the findings are likely transferable to United Kingdom arable systems, particularly in regions with historic grassland conversion. The relative benefits of reduced and no-till cultivation over bare fallow for soil aggregate stability and organic matter retention are relevant to UK soil management guidance and regenerative farming practice.

Key measures

Aggregate size distribution by wet sieving, organic C and N content in aggregate fractions, particulate organic matter (POM) mass and C/N ratio, aggregate stability under slaking, proportion of macroaggregates

Outcomes reported

The study quantified the distribution of organic carbon and nitrogen in different soil aggregate size fractions under native grassland, bare fallow, stubble mulch, and no-till management. It related losses in structural stability from cultivation to losses of organic carbon and nitrogen from the particulate organic matter fraction.

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