6533b7d3fe1ef96bd126061c

RESEARCH PRODUCT

Effets du mode de travail du sol sur les microorganismes à l'échelle du profil cultural

subject

description

Soil tillage modifies the location of crop residues and soil structure and affects microbial populations and activities such as mineralization of soil organic matter. The aim of this work was to compare the effect of two tillage systems (traditional mouldboard ploughing, LT, and reduced tillage, TR) on crop residues distribution and soil structure as well as their consequences on soil microbial biomass (BM), the potential activity of C mineralization (Cmin) and soil bacterial community structure (through T-RFLP). In order to study simultaneously the effects of soil structure modifications and crop residues distribution on these microbial parameters we used a stratified sampling scheme based on a morphological characterisation of soil structure (figure 1 and 2). Compacted and non compacted clods (respectively named Δ and Γ clods) were distinguished and sampled at three depths : 0-7, 7-17 and 17-30 cm. BM and Cmin were homogeneously distributed in the soil profile in the LT treatment, whereas they showed a vertical stratification in TR (figure 3). Our sampling scheme pointed out that BM and Cmin were affected by both burying depth of crop residues and soil structure. They decreased with soil compaction, but this effect appeared only in soil layers where crop residues were buried, suggesting that these microbial parameters are modified firstly by organic matter availability and secondly by soil structure. Bacterial community structure was also modified by crop residues distribution and soil compaction (figure 4). Indeed, the bacterial community structure of the 0-7 cm soil layer differed markedly from the others soil layers, for LT and TR. However, the bacterial community structure exhibited a high spatial variability at the field scale and further studies are needed to investigate the effects of soil tillage on soil microbial communities.