Understanding the legacy effect of previous forage crop and tillage management on soil biology, after conversion to an arable crop rotation

The soil ecosystem provides a habitat for numerous and diverse fauna which hold a pivotal role driving decomposition and nutrient cycling. However, changing land use or management can alter population dynamics, changing soil biology within the system. The implementation of different field management can improve soil fertility, whilst natural variations in plant species growth and root system may create changes to soil structure and properties. All plant species create a legacy effect within the soil to some extent; changing the environment either physically or through remaining plant residues. The impact of this legacy effect is difficult to perceive and only by monitoring will determine the change in soil faunal populations. An experiment investigated the hypothesis that previous forage cropping and establishment method would alter the diversity and abundance of soil fauna, during crop rotation. Four replicate plots of either perennial ryegrass (Lolium perenne), red clover (Trifolium pratense), white clover (Trifolium repens) or chicory (Cichorium intybus) (crop 1) were grown in a randomised block design (2009-2013), before becoming part of a crop rotation. These plots were split in spring 2013 and winter wheat (Triticum aestivum) established, either by ploughing or direct drilling; and harvested autumn 2013 (crop 2). Winter barley (Hordeum vulgare) was established using the same methodology in autumn 2013; and harvested autumn 2014 (crop 3). Soil fauna abundance after each crop rotation, including microfauna (nematodes), mesofauna (mites) and macrofauna (earthworms), showed legacy effects. Abundance of both earthworms and nematodes were affected by the original forage within crop 2; although after crop 3 the legacy effect began to diminish. Crop establishment method also affected abundance, although these were fauna dependent, with earthworm numbers being detrimentally affected by ploughing whilst nematode abundances increased with ploughing. Overall, the effect of perturbations and the consequences on biodiversity dynamics and function may have an important impact on crop sequence choices within agroecology.