Ecotoxicological impact of conventional, organic and biodynamic viticultural systems and associated practices on soil microbiota in various French territories
Viticulture represents a strategic agricultural sector at an international scale, but conventional production (CV) still implies an intensive use of chemical phytosanitary products and strongly mechanised soil management, with dramatic negative outputs on soils and environmental quality. Although alternative organic (OV) and biodynamic (BD) systems have developed substantially, their impact on the soil biological quality is still poorly documented, and this limits our ability to design a sustainable viticulture. We characterised soil microbial abundance, diversity and interactions in 152 vineyard plots using molecular tools. The plots were distributed in three French viticultural territories (Alsace, northern Burgundy, southern Burgundy) and selected to balance the relative share of each production system in each territory (1/3 of CV, OV and BD). Significant differences between Alsace and Bourgogne were recorded for microbial biomass, diversity and interactions, mainly due the soil typology and viticultural practices. Variance partitioning of the cumulated microbial dataset from all three territories evidenced higher microbial biomass and bacterial richness in OV than in CV and in BD than in OV. Microbial co-occurrence networks showed an increase of microbial interactions of about 145% in BD compared to CV and a loss of about 37% in OV compared to CV. Regarding practices, we highlighted a negative effect of soil tillage on the soil molecular microbial biomass and fungal richness, and a positive one of vine shoot restitution on the soil microbial biomass. Altogether, our study stresses that organic or biodynamic systems could be a relevant alternative to improve soil quality but should be combined with better cover cropping and no till to reach the environmental objectives of a sustainable viticulture.