Green manure from cover crops enhances pesticide degradation and soil biological health

Several biosolarization approaches have been investigated to reduce pesticide residues in agricultural soils, which can potentially affect soil health and microbial communities. This study explored biosolarization with green manures from fresh plant material (oats/vetch, mustard, radish, and red clover), previously used as cover crops, to degrade nine pesticide residues in soil. It also examined the effects on soil health indicators, such as basal respiration and microbial biomass. A pot experiment was conducted with pesticide-contaminated soil from SE Spain, amended to 10 % with green manure, during the summer in a greenhouse. Two control treatments without green manure were performed: untreated and solarized. Biosolarized soils exhibited significantly higher pesticide degradation (e.g., from 31 % for myclobutanil with radish) than controls (e.g., from 1 % for pendimethalin in untreated soil and from 7 % for myclobutanil in solarized soil). Basal respiration in biosolarized soils peaked at 15 days after amendment (5.5-11.2 mg CO₂-C kg-1 soil day^-1) compared to controls (1.7-1.8 mg CO₂-C kg-1 soil day^-1). Microbial biomass was four times higher in biosolarized soils than in the controls 15 days after amendment. The results demonstrate that biosolarization with green manure is a feasible tool for recovering pesticide-polluted soils while enhancing soil biological health.