Earthworm and enchytraeid co-occurrence pattern in organic and conventional farming: Consequences for ecosystem engineering

Abstract

Earthworms and enchytraeids are ecosystem engineers with an important influence on soil structure maintenance and nutrient cycling. We investigated if different agricultural managements produce a replacement of earthworms by enchytraeids, the magnitude of that replacement, and its effect on ecosystem engineering activities. Organic farming with plough tillage (ORG), conventional farming with plough tillage, conventional farming with no-tillage (NT), and unmanaged natural grasslands were studied. Earthworms and enchytraeids were sampled by means of extracting and hand sorting soil monoliths. Soil bulk density, mechanical resistance, organic matter content, and litter decomposition were measured as indicators of soil structure maintenance and nutrient cycling. A negative relation between earthworm and enchytraeid abundances was confirmed, not related to tillage intensity. Competitive interactions between them are suggested. Among agricultural systems, ORG had the highest earthworm abundance and NT had the highest enchytraeids abundance and the highest enchytraeid-to-earthworm ratio. Besides, intermediate abundances of earthworms and enchytraeids promoted by ORG were related to soil structure indicators' values similar to grassland and enhanced litter decomposition process. Despite a higher abundance of enchytraeids in NT, both soil structure maintenance and nutrient cycling indicators had worse values than those in ORG.