Long and short term effects of solarization on soil microbiome and agricultural production

Soil solarization, a method of chemical-free pest treatment, is a practical and cost-effective way to treat organic farming soil. This method uses polyethylene sheets to capture solar irradiation that heats the soil. Together with heat generated during composting of fresh organic matter, this method can effectively treat many soil-borne pathogens. In this study we examined the effects of solarization with the addition of compost at three maturation levels, on soil microbial community structure and function along with plant performance. Similar hydrolytic activity among the treatments (as measured by FDA hydrolysis) was measured in the first year of solarization. High level of activity was obtained in soil amended with immature compost at the beginning of the second year, suggesting residual (carry-over) effects of previous-year treatments. Amplicon sequencing of 16S rRNA encoding genes was used to study soil bacterial community structure. Diversity and richness of bacterial communities were found to be negatively affected by solarization in all treatments. Interestingly, bacterial communities of solarized soils clustered together, regardless of compost amended and type, separated from the cluster of communities from non-solarized soils of all amendments. Specifically, long and short terms negative effects of solarization on the relative abundance of Alphaproteobacteria, Acidobacteria and Actinobacteria were noticed. In contrast, solarization positively affected Bacilli and Gammaproteobacteria abundance in both long and short term. Furthermore, solarization had long and short term positive effects on productivity of eggplant and wheat plants. This study is the first to describe in high details the combined effects of solarization and amendment of composts of different maturation levels.