Organic and conventional management effect on biologically active soil organic matter pools

Summary

This 10-year field trial at the Rodale Institute compared how organic and conventional farming systems influenced biologically active soil organic matter pools. Organic management—particularly cover-cropping—accumulated more labile and stable SOM with higher total C and N, whilst conventional cash-grain farming accumulated no SOM and exhibited the lowest soil respiration and N supply rates. Particulate organic matter assays were identified as the most reliable indices for assessing SOM quality and quantity across these contrasting management systems.

Regional applicability

The study was conducted at a United States research centre and may have limited direct applicability to United Kingdom soil types, climate, and cropping systems. However, the methodological findings regarding particulate organic matter as a SOM quality indicator and the comparative benefits of organic practices with cover-cropping over conventional management are potentially transferable to temperate arable systems in the UK, provided local soil and weather contexts are considered.

Key measures

Soil CO₂ evolution, available inorganic N pools, N mineralization rates, water-dispersible organic carbon (WDOC), particulate organic matter (light fraction), total soil C and N

Outcomes reported

The study compared biologically active soil organic matter (SOM) pools across organic animal-based, organic cash-grain, and conventional cash-grain rotations over 10 years, measuring soil CO₂ evolution, nitrogen mineralization, water-dispersible organic carbon, and particulate organic matter. Both organic treatments accumulated biologically active carbon, whilst conventional management did not accumulate SOM and showed the lowest biological activity.

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