Biosolarization restructures soil bacterial communities and decreases parasitic nematode populations

Abstract

Biosolarization is a soil disinfestation technology that combines passive solar heating and organic amendments to generate multiple pest-inactivating stressors. The objectives of this study were to assess the performance of almond (Prunus dulcis) processing residues in biosolarization to control infestations of root lesion (Pratylenchus vulnus) and ring nematodes (Mesocriconema xenoplax) during the pre-planting period of an almond orchard. The broader effects on soil microbial community composition were assessed by 16S rRNA gene sequencing immediately before and after biosolarization, as well as two months after treatment ended. Soil organic acids with nematicidal activity peaked after 9 days in biosolarized plots. Temperatures in biosolarized plots and solarized control plots reached maximum values 9–12 °C higher than untreated control plots. Biosolarization and solarization also enriched for specific Firmicutes, Actinobacteria, and Proteobacteria taxa associated with nematode suppression, some of which remained enriched two months post treatment. Biosolarization led to 100% mortality of P. vulnus in the upper 0–30 cm soil layer by 9 days of treatment. In contrast, reductions in plant-parasitic nematode densities between non-amended, solarized treatments and untreated controls were not observed until day 41 of treatment.