How agricultural management impacts the soil food web: comparing the effects of two different soil management treatments.

Soil analysis is fundamental to optimise nutrient management, fertiliser use and promote sustainable farming. The main method of soil analyses interpretation is an index system of available nutrients. An alternative approach is the use of the base-cation saturation ratio (BCSR) which theorises that balancing these ratios will optimise the uptake of nutrients by plants. Soil fauna are pivotal in nutrient decomposition and cycling within the soil and may be affected by these different management strategies. Here we try to assess the differences between faunal communities under two soil nutrient management strategies at a farm scale and attempt to link these effects to soil nutrient availability. Three replicate 3 ha plots of each treatment, one based on the ‘mineral balancing’ BCSR, the other a standard ‘sufficiency level’ N, P, K fertiliser system (DEFRA RB209) as a control; were established in September 2009. Soil biology samples were taken twice yearly in the spring and autumn; and included soil mesofauna, nematodes, earthworms, and microbial biomass carbon. Analysis of the results over the three year period, proved there to be minimal differences between the two treatments over this timescale for total invertebrates, Collembola, mites, earthworms, nematodes or microbial biomass carbon. However, there were significant differences related to time for all these organisms. Our results indicate that the perturbation of ploughing and reseeding has a greater effect on the soil biology than the perceived differences in nutrient managements. Nonetheless, potentially the two nutrient managements needed longer establishment times for soil biology differences to be distinguished. This was exemplified by the trend in earthworm numbers which appear to be diverging over time for the two treatments.