Introduction: Soil solarization (Sol) and biosolarization (BioS) are hydrothermal, organically acceptable alternatives to agricultural soil fumigation with synthetic chemical toxicants. Returning on- or off-site crop residues to decompose in soil as amendments in BioS can aid in promoting a circular agroeconomy.Materials and methods: Onion crop residue amendment and soil temperature/covering regimens were evaluated in a feasibility study for their effects on survival and activity of phytoparasitic root-knot (Meloidogyne incognita = RK) and root-lesion (Pratylenchus neglectus = LN) nematodes, and their impact on winter squash (Cucurbita moschata cv. Waltham Butternut).Results: In laboratory microcosms, residue-amended (2% w/w) and irrigated soil reduced RK survival at diurnally maximum soil temperatures of 25 and 39 °C. In an on-farm trial, 35 days of Sol, but not exposure to onion amendment, reduced RK and LN numbers to near-undetectable levels, which persisted at least 23 days after setting squash transplants. However, following crop harvest, no differences in RK and LN numbers remained. Post-harvest plant ratings showed that both Sol and onion BioS provided reductions in RK root galling up to 76% (p < 0.05). Regardless of treatments or nematode presence, squash harvest was relatively robust, with extrapolated fresh yields of ~20 t/ha. Number of marketable fruits ranged from 27 (control) to 39 per plot (Sol).Conclusions: These tests indicated that both Sol and BioS using onion are feasible soil pest control and circular agroeconomy measures, and further studies are encouraged. Yield data agreed with previous reports that C. moschata squash may have some natural tolerance to phytoparasitic nematodes.

Soil biosolarization (SBS) is an alternative technique for soil pest control to standard techniques such as soil fumigation and soil solarization (SS). By using both solar heating and fermentation of organic amendments, faster and more effective control of soilborne pathogens can be achieved. A circular economy may be created by using the residues of a given crop as organic amendments to biosolarize fields that produce that crop, which is termed circular soil biosolarization (CSBS). In this study, CSBS was employed by biosolarizing soil with amended tomato pomace (TP) residues and examining its impact on tomato cropping under conditions of abiotic stresses, specifically high salinity and nitrogen deficiency. The results showed that in the absence of abiotic stress, CSBS can benefit plant physiological performance, growth and yield relative to SS. Moreover, CSBS significantly mitigated the impacts of abiotic stress conditions. The results also showed that CSBS impacted the soil microbiome and plant metabolome. Mycoplana and Kaistobacter genera were found to be positively correlated with benefits to tomato plants health under abiotic stress conditions. Conversely, the relative abundance of the orders RB41, MND1, and the family Ellin6075 and were negatively correlated with tomato plants health. Moreover, several metabolites were significantly affected in plants grown in SS- and CSBS-treated soils under abiotic stress conditions. The metabolite xylonic acid isomer was found to be significantly negatively correlated with tomato plants health performance across all treatments. These findings improve understanding of the interactions between CSBS, soil ecology, and crop physiology under abiotic stress conditions.

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 degrees 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.

Soil biosolarization (SBS) is an alternative technique for soil pest control to standard techniques such as soil fumigation and soil solarization (SS). By using both solar heating and fermentation of organic amendments, faster and more effective control of soilborne pathogens can be achieved. A circular economy may be created by using the residues of a given crop as organic amendments to biosolarize fields that produce that crop, which is termed circular soil biosolarization (CSBS). In this study, CSBS was employed by biosolarizing soil with amended tomato pomace (TP) residues and examining its impact on tomato cropping under conditions of abiotic stresses, specifically high salinity and nitrogen deficiency. The results showed that in the absence of abiotic stress, CSBS can benefit plant physiological performance, growth and yield relative to SS. Moreover, CSBS significantly mitigated the impacts of abiotic stress conditions. The results also showed that CSBS impacted the soil microbiome and plant metabolome. Mycoplana and Kaistobacter genera were found to be positively correlated with benefits to tomato plants health under abiotic stress conditions. Conversely, the relative abundance of the orders RB41, MND1, and the family Ellin6075 and were negatively correlated with tomato plants health. Moreover, several metabolites were significantly affected in plants grown in SS- and CSBS-treated soils under abiotic stress conditions. The metabolite xylonic acid isomer was found to be significantly negatively correlated with tomato plants health performance across all treatments. These findings improve understanding of the interactions between CSBS, soil ecology, and crop physiology under abiotic stress conditions.

Soil biosolarization (SBS) is a pest-control technique that could come into wider use as a sustainable alternative to highly toxic soil fumigants such as 1,3-D and chloropicrin. SBS induces biohydrothermal inactivation of soil pests by covering moist soil with clear plastic tarp to promote passive solar heating. In addition, microbial activity supported by organic soil amendments can complement the heat stress by releasing biotoxic organic acids (OAs) and other chemical decomposition compounds, enhancing pest inactivation. In California, the use of SBS is still limited to organic production, mainly due to challenges related to treatment of deeper soil layers or deployment in cooler seasons or regions. However, as the release of OAs is related to the biodegradability of the organic amendments, less stable organic amendments are expected to significantly improve SBS efficacy. We have performed a wide range of studies with organic amendments of differing stability degrees on various pests. Our results have confirmed that the lower the stability of the organic amendment (indicated by the cumulative CO2 evolution rate), the greater the release of OAs and pest inactivation. These promising results promote SBS not only as a valid alternative to chemical fumigation but also as an organic waste management practice and a tool to improve soil health via addition of organic matter.

Biosolarization is an integrated pest management strategy that combines soil solarization with organic amendment application. In the present study, soil samples were taken after biosolarization using tomato pomace and green waste compost (GWC) amendments and analyzed to elucidate changes to the soil microbiome, including both fungal and bacterial communities. Following a field trial wherein soil mesocosms were biosolarized for 8 days, the effects of soil depth and soil amendments were assessed via sequencing and bioinformatic analysis of 16S rRNA gene and ITS2 amplicons generated from soil microbial genomic DNA. Structural and network analyses were used to quantify differences in microbiota between treatments and these results were correlated with measured levels of volatile fatty acids in the soils. The results showed that biosolarization had a stronger impact on the bacterial community relative abundance profile than on the fungal community at the phylum and order levels. However, at the operational taxonomic units (OTUs) level, biosolarization treatment had a significant impact on both fungal and bacterial communities, across soil depth and GWC addition. Co-occurrence microbial network analysis revealed a unique circular network consisting of 8 discrete clusters. Correlation between the clusters and soil volatile fatty acid (VFA) production suggested that the bacterial Clostridium, Weissella and Acetobacter genera tolerate, and perhaps drive, VFA accumulation. Notable fungal community effects included significantly reduced relative abundance within genera known to contain plant pathogenic members, such as Gibberella, Haematonectria, Fusarium, Aspergillus and Alternaria.

Regulatory pressure along with environmental and human health concerns drive the development of soil fumigation alternatives such as soil biosolarization (SBS). SBS involves tarping soil that is at field capacity with a transparent film following amendment with certain organic materials. Heating via the greenhouse effect results in an increase of the soil temperature. The organic amendments can promote microbial activity that can enhance pest inactivation by depleting oxygen, producing biopesticidal fermentation products, and competing with pests. The properties of the organic amendments can heavily influence the type and magnitude of these effects. This study evaluated the viability of chitin as a novel SBS soil amendment to influence soil fungal and bacterial microbial communities, including control of the plant pathogen Fusarium oxysporum f.sp. lactucae (FOL). Changes to FOL and the broader soil microbiota were monitored in response to biosolarization using 0.1% (by dry weight) amendment with chitin (Rootguard). FOL suppression was only observed in chitin amended soils that were incubated at room temperature, not under solarized conditions. Conversely, it decreased solarization efficacy in the upper (0-10 cm) soil layer. The presence of chitin also showed increase in FOL under anaerobic and fluctuating temperature regime conditions. Biosolarization with chitin amendment did exhibit an impact on the overall soil microbial community. The fungal genus Mortierella and the bacterial family Chitinophagaceae were consistently enriched in biosolarized soils with chitin amendment. This study showed low potential FOL suppression due chitin amendment at the studied levels. However, chitin amendment showed a higher impact on the fungal community than the bacterial community. The impact of these microbial changes on crop protection and yields need to be studied in the long-term.

Current agricultural soil pathogen control methods that rely on fumigation with toxic synthetic chemicals are not sustainable. Combining soil organic matter amendment with soil hydrothermal treatment via solarization is a biological pest control alternative to chemical fumigation. The application and bioconversion of readily-available organic amendment resources, such as green wastes (GW), have not been considered. The impact of compost inoculum on the bioconversion of GW to pesticidal volatile fatty acids (VFAs) in soil during solarization was investigated. Laboratory experiments showed a significant positive effect of compost inoculum at a rate >= 1% on aerobic and anaerobic decomposition of GW, but only when soils were heated. Field trials showed that GW induced conditions in soil that supported fermentation and resulted in accumulation of VFAs. When soil was inoculated with compost, VFA accumulation was enhanced at increasing soil depth. The results indicate that green waste bioconversion can be used to improve pest control conditions in soil during solarization. The findings have environmental implications on green waste management and use of toxic synthetic chemical fumigants.

Biosolarization utilizes organic amendments to produce biopesticide compounds in soil that can work in tandem with other stresses to inactivate agricultural pests. The prospect of using by-products from industrial almond processing as amendments for biosolarization was assessed. Soil mesocosms were used to simulate biosolarization using various almond by-products, application rates, and incubation times. Several potentially biopesticidal organic acids were identified and quantified in the soil, and the toxicity of soil extracts was evaluated for the root lesion nematode (Pratylenchus vulnus). It was determined that both almond hulls and a mixture of hulls and shells harbored several acids, the concentration of which was enhanced 1-7 fold via fermentation by native soil microbes. Organic acid concentration in the soil showed a significant linear relationship with the quantity of waste biomass amended. Extracts from soils containing at least 2.5% incorporated biomass by dry weight showed a 84-100% mortality of nematodes, which corresponded to acid concentrations 0.75 mg/g (2.0 g/L) or greater. This study showed that almond processing by-products-hulls and a hull and shell mixture-were suitable amendments for control of P. vulnus and potentially other soil agricultural pests in the context of biosolarization. (C) 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licensesiby-nc-nd/4.0/).

Aims Soil biosolarization (SBS) is a pest control technology that includes the incorporation of organic matter into soil prior to solarization. The objective of this study was to measure the impact of the initial soil microbiome on the temporal evolution of genes encoding lignocellulose-degrading enzymes during SBS. Methods and Results Soil biosolarization field experiments were completed using green waste (GW) as a soil amendment and in the presence and absence of compost activating inoculum. Samples were collected over time and at two different soil depths for measurement of the microbial community and the predicted lignocellulosic-degrading microbiome. Compost inoculum had a significant positive effect on several predicted genes encoding enzymes involved in cellulose, hemicellulose and lignin degradation. These included beta-glucosidase, endo-1,3(4)-beta-glucanase, alpha-galactosidase and laccase. Conclusion Amendment of micro-organisms found in compost to soil prior to SBS enhanced the degradation potential of cellulose, hemicellulose and lignin found in GW. Significance and Impact of the Study The type of organic matter amended and its biotransformation by soil micro-organisms impact the efficacy of SBS. The results suggest that co-amending highly recalcitrant biomass with micro-organisms found in compost improves biomass conversion during SBS.

Conventional solarization and biosolarization with mature compost and tomato processing residue amendments were compared with respect to generation of pesticidal conditions and tomato (Solanum lycopersicum L.) plant growth in treated soils. Soil oxygen depletion was examined as a response that has previously not been measured across multiple depths during biosolarization. For biosolarized soil, volatile fatty acids were found to accumulate concurrent with oxygen depletion, and the magnitude of these changes varied by soil depth. Two consecutive years of experimentation showed varying dissipation of volatile fatty acids from biosolarized soils post-treatment. When residual volatile fatty acids were detected in the biosolarized soil, fruit yield did not significantly differ from plants grown in solarized soil. However, when there was no residual volatile fatty acids in the soil at the time of planting, plants grown in biosolarized soil showed a significantly greater vegetation amount, fruit quantity, and fruit ripening than those of plants grown in solarized soil.

BACKGROUND:Soil biosolarization is a promising alternative to conventional fumigation. Volatile fatty acids (VFAs) produced in the soil through fermentation of amended organic matter can affect pest inactivation during biosolarization. The objective was to determine how soil amended with organic wastes that were partially stabilized through either composting or anaerobic digestion affected the inactivation of Brassica nigra (BN; a weed) and Fusarium oxysporum f. sp. lactucae (FOL; a phytopathogenic fungus).RESULTS:The mortality of BN seeds in the biosolarized soil was 12% higher than in the solarized soil, although this difference was not significant. However, a significant correlation between BN mortality and VFA accumulation was observed. The number of FOL colony-forming units (CFU) in solarized samples at 5 cm was 34 CFU g-1 of soil, whereas in the biosolarized samples levels were below the limit of quantification. At 15 cm, these levels were 100 CFU g-1 for solarized samples and < 50 CFU g-1 of soil for the biosolarized samples. Amendment addition positively affected the organic matter and potassium content after the solarization process.CONCLUSION:The organic waste stabilization method can impact downstream biosolarization performance and final pest inactivation levels. This study suggests that organic waste management practices can be leveraged to improve pest control and soil quality. © 2018 Society of Chemical Industry.

The California tomato processing industry produced circa 388,856 t of tomato pomace in 2014. While currently used for animal feed, tomato pomace could be utilized for biosolarization. Primary Energy Demand (PED) and Global Warming Potential (GWP) equivalent emissions were calculated for two valorization pathways: (i) feed for cattle; and (ii) biosolarization. In order to make these two valorization pathways comparable three management options were analyzed whereby each part of the system was satisfied, i.e. a pest management sub-system and a cattle feed sub-system. The management options were (1) tomato pomace used for cattle feed and soil pest control using fumigant Telone II and herbicide glyphosate; (2) tomato pomace used for cattle feed and soil pest control using solarization; (3) alternative cattle feed (cottonseed, canola pellets and wheat straw) and soil pest control using biosolarization with tomato pomace. Options 2 and 3 result in a reduction of GWP and PED. Among management options, the GWP ranged from 64-98 kg CO2-e and 1502-2250 MJ for PED pert of pomace. The majority of impacts were beyond the tomato processors' immediate control, therefore encouraging the diversion of tomato pomace to biosolarization may be desirable. Total savings per annum for biosolarization could be as large as 7.7 M kg CO2-e and 203,000 GJ annually. (C) 2016 Elsevier Ltd. All rights reserved.

Combining soil solarization with organic amendments, as a tool for improved control of plant pests, represents a fusion of two separate approaches that were developed at different times under different circumstances. Organic materials of various kinds have traditionally been used to improve soil fertility, as well as to reduce soil pest infestation. Soil solarization is a later approach. The combination of soil solarization with organic amendments first received attention in the work of Ramirez-Villapudua and Munnecke, who demonstrated improved control of Fusarium cabbage yellows by the solarization of soil amended with cabbage residues. Above all, studies indicated that this chain of reactions results in improved control of soilborne pests, some of which were not effectively controlled by either method alone. The simple application of such a combination, together with the global trend toward reducing the use of soil fumigants, has boosted its commercial application in organic production as well as conventional farming.