Linking legacy effects within crop rotations to the soil food web

Maintaining soil biodiversity and function is key to maintaining soil health particularly within agricultural systems, as soil fauna play a pivotal role within nutrient cycling and decomposition. Natural variations in grasses/forbs/legumes growth and rooting system will create significant changes to soil structure, properties and soil biology. The legacy effects of these different forages within a crop rotation are difficult to perceive and only monitoring how individual invertebrates are affected will indicate the impact of agricultural practice. An experiment was set up to test the hypothesis that previous forage cropping and establishment method would alter the diversity and abundance of soil faunal population, during crop rotation. Four replicate pure sward plots (12m × 7.5m) of chicory (Cichorium intybus), red or white clover (Trifolium pratense, T.repens) or perennial ryegrass (Lolium perenne) (crop 1) were grown in a randomised block design, 2009-2013, before becoming part of a crop rotation. These plots were split (12m × 3.75m) in spring 2013 and winter wheat established by ploughing, or direct drilling; and harvested autumn 2013 (crop 2). Winter barley was established using the same methodology as above in autumn 2013; and harvested autumn 2014 (crop 3). The findings presented here are the assessment of the soil faunal populations after these crop rotations; the soil fauna assessed included microfauna (nematodes), mesofauna and macrofauna (earthworms). Currently, we found for soil faunal groups across the three scales of sampling, that the influence of the original forage on the soil system continued to have legacy affects within crop 2, which in some groups started to diminish after crop 3. The effect of perturbations and the consequences on biodiversity dynamics and function may have an important impact on crop sequence choices within agriculture.