The interest in long-term sustainability and reduction of environmental costs of agricultural ecosystems have led to an increased interest in C and N cycling. To achieve this interest, soil organic carbon (SOC) formation and decomposition processes need to be better understood and subsequently managed. Here, we focus on the influence of alternative farming practices (conservation tillage, organic farming and agroforestry) on the relationship between earthworm abundance/diversity and the incorporation plus long-term stabilization of residue-derived C in soils.

Earthworms play an important role in the process of litter decomposition and incorporation into soil aggregates. They ingest large amounts of organic matter, mix it with inorganic soil material, pass this mixture through their gut and excrete it as casts. It has been suggested that earthworms mediate aggregate formation and stabilization. However, the relevance of this process for the long-term C stabilization and short-term N and P cycling under field conditions remains unclear and how it is affected by agricultural management is also unknown. Earthworm abundance and diversity are generally greater in alternative farming systems compared to conventional farming systems. We therefore investigate the relationship between alternative farming practices, earthworm abundance and diversity, aggregate dynamics, C stabilization and N and P cycling. Our ability to predict farming system behavior and develop sustainable farming system management practices will rest to a large extent on our quantitative understanding of this relationship.

Results from our experiments will: 1) quantify under field conditions the effects of increased earthworm abundance and diversity in alternative farming systems on residue incorporation and stabilization of C, 2) increase our understanding of biological mechanisms controlling C stabilization and nutrient cycling within the soil matrix and, 3) contribute to the knowledge about the ecological functioning of alternative farming systems in temperate and tropical climates.

For more information contact Johan Six (jwsix@ucdavis.edu) or Steve Fonte (sjfonte@ucdavis.edu)