Comparison of soil biosolarization with mesophilic and thermophilic solid digestates on soil microbial quantity and diversity

Abstract

Soil biosolarization (SBS) is a pest control technique that combines passive solar heating and fermentation of amended organic matter. The extreme soil conditions generated during SBS could decrease microbial biomass and restructure the soil microbiome, which could impact soil quality. Digestates from anaerobic digesters may harbor microbial communities tolerant of the oxygen, moisture, and temperature stresses encountered during SBS as these conditions may also occur in digesters.Digestate microbial communities may contribute to soil fermentation during SBS and affect organic matter turnover in soils treated with SBS. The objective of this study was to assess the effect of SBS on soil microbial diversity and quantity when solid digestates from thermophilic (TD) and mesophilic (MD) anaerobic digesters were used as soil amendments. In the soils amended with TD, communities showed the greatest divergence from the initial soil state whereas MD amendment resulted in a microbiome more similar to the non-amended soil. The microbial biomass of the biosolarized soils was significantly greater than the non-amended, solar-heated soil. The microbial biomass in the biosolarized soils was dominated by K-strategic or "native" species.Solar heating of the non-amended soil mainly affected "native" species, leading to conditions where other opportunistic species become more dominant. Further studies are needed to elucidate whether the persistent microbes in the soil are benign or pathogenic and to understand their roles in pest inactivation and nutrient cycling during and following SBS.

Effect of management of organic wastes on inactivation of Brassica nigra and Fusarium oxysporum f.sp. lactucae using soil biosolarization

“…Amendment addition positively affected the OM and K content after the solarization process, as observed in prior studies . In addition to these specific impacts, other studies also observed that organic amendments followed by solarization led to higher values of total N, total P, several enzyme activities, microbial biomass C, potentially mineralizable N, water‐soluble organic C and microbial functional diversity when compared with non‐amended soils . Biosolarization studies using thermophilic and mesophilic digestates showed a significant decrease in EC after solarization .…”

“…In addition, it has been observed that native microbial communities in the soil contribute to the suppression of Fusarium spp. 44 As SBS has been shown to have a significant impact on the soil microbial community, 45 future studies are needed to determine how SBS-induced changes to the soil microbiota affect long-term FOL suppression. Amendment addition positively affected the OM and K content after the solarization process, as observed in prior studies.…”

The initial soil microbiota impacts the potential for lignocellulose degradation during soil solarization

“…Several studies have reported the presence of Firmicutes and Proteobacteria in biosolarization systems (Fernandez‐Bayo et al . ) and in GW and municipal solid waste composts (Vaz‐Moreira et al . ; Pankhurst et al .…”

“…However, the same treatment using 1Á5 wt% mesophilic digestate did not significantly increase B. nigra mortality compared to the control treatments (Fernandez-Bayo et al 2017b). It is possible that differences in performance were due in part to compositional differences in the amended substrate and micro-organisms involved in the biotransformation of substrates to biopesticidal compounds (Fernandez-Bayo et al 2017a).…”

“…It is possible that differences in performance were due in part to compositional differences in the amended substrate and micro‐organisms involved in the biotransformation of substrates to biopesticidal compounds (Fernandez‐Bayo et al . ).…”