Short-term dynamic responses of soil properties and soil fauna under contrasting tillage systems

Abstract Achieving sustainability is a worldwide current concern in agriculture that brings important challenges but also opportunities for rethinking agroecosystems. While many studies focused on tillage effects upon soil organisms, few of them have considered this into a temporal framework. In a study conducted in actual field conditions, we evaluated at short-term (7 months) the dynamic of several abiotic and biotic soil parameters under contrasting tillage systems. We hypothesised that (1) the reduction and especially the stopping of the soil mechanical perturbation lead overall to an improvement of the soil physical structure and the food resources available for soil fauna. (2) According to their specific ecological requirements, Collembola and Earthworms will show different dynamics of responses following alleviation of soil mechanical perturbation. (3) For a single group (either Collembola or earthworms), differences between tillage systems are dependent on the sampling period. We used a field set-up held on the INRA experimental station of Estrees-Mons (North of France). Three tillage systems were investigated: conventional tillage (with the soil inverted up to 25 cm depth) reduced tillage (limited to the first 7–8 cm depth) and no-tillage. Each treatment was replicated 4 times randomly (3 × 4 = 12 plots in total). Collembola and earthworms were sampled at each plot using standard methods. During the course of the experiment, two tillage operations were performed one in mid-March and one in mid-May. Samplings of soil fauna were performed on a regular basis according to tillage operation: 1 day before, and respectively 1; 7; 30; 49; 56; 104; 210 days after. Abiotic parameters (bulk density, SOC stock, Mean Weight Diameter (MWD) and aggregates size) and microflora (microbial and fungal biomass and their activity) were also monitored and used as explaining factors. Our findings showed that slightly reducing the intensity of soil mechanical perturbation, did not favour soil fauna. But, when stopping tillage, population sizes of earthworm and Collembola increased. This is related to the improvement of the distribution of, and accessibility to, organic matter as a basic food source (SOC stock, microbial and fungal biomass and their potential C mineralisation activity), the physical structure of the soil and the distribution of pore sizes as a space life (bulk density, MWD and aggregates size). Our kinetic study has shown that the different groups of soil fauna respond differently to mechanical soil disturbance. Overall, conservation tillage can foster one of the numerous services provided by the soil compartment, namely the soil biodiversity and therefore improve soil quality and health.