Biochemical pesticides and soil changes resulting from biosolarization with cover crop amendments

Biosolarization is an agricultural pest management technique that uses organic matter amendments and plastic mulch to control soil pests in a variety of cropping systems without harmful chemical fumigants. Biosolarization involves amending soil with organic matter, irrigating, and covering the surface with a clear tarp to suppress pests, combining stressors from increased temperature, reduced oxygen, and biochemical pesticide production. In particular, cover crops present a convenient, in situ amendment source for biosolarization. However, research is needed to evaluate the effectiveness of cover crops as soil amendments for biosolarization prior to large-scale applications. This study uses Brassica juncea (brown mustard) cover crop residues as biosolarization amendments to determine changes in soil properties contributing to pest suppression and crop growth. Specifically, a field trial was employed to quantify soil organic acid biochemical pesticide production, residual phytotoxicity, moisture content, pH, and electrical conductivity with B. juncea monoculture and B. juncea-Vicia villosa (hairy vetch) mixture cover crop amendments. Additionally, a simulated laboratory study evaluated changes in soil isothiocyanate biochemical pesticide concentrations during biosolarization with B. juncea cover crop amendments. Treatments were compared to non-biosolarized soil amended with cover crop residues, non-amended soil treated with solarization, and non-amended unheated soil controls. Results show biosolarization with cover crop residues increase the cumulative exposure to fermentative organic acid and plant-derived isothiocyanate compounds in soil by 314% and 28%, respectively, without causing persistent phytotoxicity. These findings highlight the potential for biosolarization with cover crop amendments to control soil pests without negatively impacting the growth of subsequent crops. • Biochemical pesticides were quantified from cover crop residue soil amendments • Cover crop soil amendments were studied with and without biosolarization treatments • Biosolarization with cover crop residues increased soil biochemical pesticides • Phytotoxicity from biosolarized soils was alleviated within eight days • Combining biosolarization with cover cropping practices may enhance pest control