The Evolution of Biological Soil Quality Under Long Term Agricultural Management

Abstract

Sustainable agricultural practices rely on the delivery of soil-based ecosystem services, which depend on processes mediated by the soil’s fauna. However, agricultural practices often have negative impacts on soil biota. What is still unclear is whether the impacts associated with agriculture lead to a soil community that is adapted to said impacts or whether the community continues to evolve under agricultural management, since there is a gap in studies of soil biology that include time as a covariate. Using time-series analyses, we investigate how and whether biological soil quality (as measured by the nematode community) has developed through time in cropping systems situated on two contrasting soil textures and under different management regimes in The Netherlands. We sampled two experiments (the Soil Health Experiment in Vredepeel (SHE) and the Broekemahoeve Applied Soil Innovation Systems experiment in Lelystad (BASIS)) and 20 commercial farms at several points in time. We found changes in the nematode community through time in all three systems, albeit not consistent across the systems or treatments. All treatments at the SHE showed an increase in nematode richness, abundance as well as the structure and enrichment indices over time. The nematode community in BASIS also showed an increase in richness through time in all treatments except for conventional management combined with conventional tillage. In commercial farms, however, we observed a decrease in the structure index and an increase in community specialisation. While we expect that the trends observed at the SHE are a result of change in the intensity of management at the beginning of the experiment, the trends observed in the commercial farms indicate a widespread decrease in the soil’s food-web structure, possibly associated with an increase in land use intensity. We observed that the nematode community continues to change over time, but whether the observed trend reflects an increase of the intensity of land management in time or that the effects of sustained agricultural land management continue to alter the nematode community over time remains uncertain.

Keywords: Nematode indicators, conventional management, organic management, tillage, conservation-tillage