Knowing and valorizing the effect of agricultural practices on soil biology is a promising way to progress towards more sustainable cropping systems. This study was conducted to gain a better understanding of the effect of legumes on soil biology. Its aim is to determine whether the presence of legumes has a specific effect on soil biology, by assessing this effect using a bioindicator: the soil nematofauna. To achieve this objective, we tested four plots, including three with legumes as a preceding effect and after-effect (TNLt1C, TLt0PC, TLT0V) and one control plot (TT) with a non-leguminous preceding. Soil samples were taken from these plots for physico-chemical analysis. The results thus obtained revealed significant differences in soil biological activity between leguminous and non-leguminous soils, with the control (TT) showing a population of 389.74 NN/100ml, followed by the TLT0V field with a population of 265.81 NN/100ml, TNLt1C with 205.13 NN/ml and TLT0PC with 185.47 NN/100ml. The fact that we obtained an average result for the effect of legumes on soil biology (through a more or less low abundance of nematodes) in no way proves that they do not have this power;