Anaerobic Soil Disinfestation Research Articles

Decline of charcoal rot in strawberry by anaerobic soil disinfestation: reduction of propagules and/or induction of soil suppressiveness

Decline of charcoal rot in strawberry by anaerobic soil disinfestation: reduction of propagules and/or induction of soil suppressiveness

Optimizing anaerobic soil disinfestation for high tunnel specialty crop production systems in the U.S. Mid-Atlantic region

Optimizing anaerobic soil disinfestation for high tunnel specialty crop production systems in the U.S. Mid-Atlantic region

In situ 15N labeling reveals high soil N2 emission during anaerobic soil disinfestation period in a greenhouse vegetable production system

In situ 15N labeling reveals high soil N2 emission during anaerobic soil disinfestation period in a greenhouse vegetable production system

Paenibacillus spp. may facilitate anaerobic soil disinfestation at low temperatures

We screened for bacteria that may facilitate the suppressive effect on Ralstonia pseudosolanacearum at temperatures < 30 °C after anaerobic soil disinfestation (ASD) with 1% v/v ethanol. Among 22 isolates grown anaerobically, we selected three that significantly suppressed R. pseudosolanacearum population after ASD at 25 °C. Based on the 16 S rRNA sequences, two isolates were inferred as Paenibacillus polymyxa and the other as Paenibacillus sp. Using qPCR primers designed for these strains, we found that all strains increased in the soil after ASD at 25 °C. After ASD with 1% v/v ethanol and with or without soil inoculation with these three strains in a concrete frame in the field at mean temperature of 26.3 °C, the R. pseudosolanacearum population was significantly lower in the inoculation treatment at a depth of 10 cm. These results suggest that these Paenibacillus strains have the potential to promote the ASD effect using 1% ethanol at low temperatures.

Sustaining Soil Health in High Tunnels: A Paradigm Shift toward Soil-centered Management

This review was conducted to synthesize current knowledge, learn producer and Extension specialist perspectives, and identify gaps in understanding of the role of soil health in sustaining production in high tunnel (HT) systems. This synthesis includes findings from scholarly resources related to soil health in HTs, including research and Extension-based literature, perspectives from experienced HT producers and technical assistance providers, and the direct observations of a broad network of university research and Extension personnel working with HTs. Findings are intended to identify knowledge gaps and additional research and Extension resource needs of greatest priority to the HT producer community and technical assistance providers that support them at the time of publication. A review of 68 research articles and 58 Extension resources was conducted. Focus group interviews were conducted with small groups of experienced HT farmers in four regions of the eastern half of the United States, with in-depth farm case studies conducted in individual farmers in three of these regions. Growers across regions identified soil fertility management, soilborne diseases, soil compaction, and lack of consistency of soil analyses specific to HTs as the greatest soil-related challenges to HT production. Research and resources for technical assistance providers on mitigation strategies to remediate yield-limiting HT soil conditions, such as excessive soil salinity and high pathogen populations, were also lacking. As such, process-based research on techniques such as leaching, soil steaming, solarization, and anaerobic soil disinfestation in tunnels that consider short- and long-term costs, benefits, and effects on soil and plant productivity should be prioritized in the future when considering the impact of HT production on soil health. Interviews also indicated a need for networking opportunities for technical assistance providers across agencies (e.g., Natural Resources Conservation Service, Extension, nongovernmental organizations). Despite a high and increasing rate of adoption, there is currently a lack of information about maintaining HT systems. Given that HTs play a critical and growing economic role for specialty crop growers throughout the eastern United States, comprehensive intervention across the research–Extension spectrum to sustain productivity in HT systems is recommended.

Effectiveness of Anaerobic Soil Disinfestation for Weed and Nematode Management in Organic Sweetpotato Production

Weeds and nematodes are particularly problematic in organic sweetpotato production due to a lack of effective pesticides. Anaerobic soil disinfestation (ASD) has the potential to fit into current pest management practices as an alternative to pesticide application. Greenhouse studies were conducted at the Clemson Coastal Research and Education Center (CREC) in Charleston, SC, to investigate the impact of carbon source amendment and a no carbon source treatment, and soil type on cumulative anaerobicity, weed control, nematode population, and sweetpotato vigor. Microcosms were filled with one of three different soil types (Charleston—loamy/native; Blackville—high coarse sand content; and Clemson—high clay content) and were mixed with cottonseed meal (CSM) or no carbon amendment. The pots were then sealed with plastic totally impenetrable film (Tif) for 6 weeks, followed by the transplanting of sweetpotato (cv Bayou Belle) slips. The results suggested that the CSM-treated microcosms spent more time under anaerobic conditions than those treated with the no carbon amendment. The microcosms that experienced a longer duration of anaerobicity had a lower percent weed cover (49%), fewer nematode egg masses, and a lower gall index when compared to microcosms which experienced a shorter duration of anaerobicity. Significantly higher instances of leaf necrosis were observed in the sweetpotato slips sown in the CSM-treated microcosms. The addition of CSM as a carbon source to facilitate ASD resulted in similar above-ground biomasses of the sweetpotato plants compared to the treatments containing no carbon amendment. However, a significantly lower below-ground biomass of the sweetpotato plants was observed in the CSM-treated microcosms.

Anaerobic soil disinfestation: a biologically-based solution for sustainable crop production

Anaerobic soil disinfestation (ASD) is a novel, eco-friendly method to improve soil health. This method creates oxygen-free conditions by adding organic amendments as a carbon source, saturating the soil to field capacity, and then covering it with plastic. These anaerobic conditions reduce soilborne pathogens, enhance microbial diversity, and increase crop productivity. This review provides an overview of the different organic amendments used in ASD, their impact on managing soilborne pathogens, the role of beneficial microbiomes, and the challenges associated with adopting ASD. It also emphasizes the potential benefits of ASD and the innovative approach to advancing it for sustainable agriculture.

Impact of Anaerobic Soil Disinfestation Treatment on the Properties of Tomato Continuous Cropping Soil

Impact of Anaerobic Soil Disinfestation Treatment on the Properties of Tomato Continuous Cropping Soil

Unraveling the Interplay: Soil Biogeochemical Factors Shaping the Efficacy of Anaerobic Soil Disinfestation in Suppressing Fusarium Root Rot of Strawberry.

Nontoxic alternatives to chemical soil fumigants for suppressing soilborne pathogens such as Fusarium oxysporum (Fo), one causative agent of strawberry black root rot complex prevalent in the Southeastern United States, are urgently needed. A promising alternative is anaerobic soil disinfestation, in which soil is amended with labile organic materials, irrigated to field capacity, and tarped to induce anaerobic fermentation for a brief period before planting. Pathogen-suppression mechanisms of anaerobic soil disinfestation include anaerobic conditions and generation of reduced metal cations (Fe2+ and Mn2+) and volatile fatty acids (VFAs; e.g., acetic, n-butyric, isovaleric, and others). However, little is known about how the interaction between VFAs, reduced metals, soil texture, and liming influences suppression of Fo. We investigated Fo suppression by VFAs and reduced metal cations in both aqueous and soil-based incubation trials. Inoculum containing Fo chlamydospores was added to aqueous medium containing either 5 or 10 mmol/liter VFAs and either 0.01 or 0.05% (wt/wt) reduced metals. In soil-based incubations, chlamydospore-containing inoculum was applied to sandy, sandy loam, and silty clay soil saturated by solutions containing 10 or 20 mmol/liter VFAs with or without 0.05% (wt/wt) reduced metals. VFAs, particularly in combination with Fe2+ in aqueous solutions and Mn2+ in soils, significantly reduced Fo viability. At the same time, liming and higher soil clay content reduced the effectiveness of VFAs and reduced metals for suppressing Fo, highlighting the influence of soil pH and soil texture on anaerobic soil disinfestation effectiveness.

Optimization of anaerobic soil disinfestation against Verticillium wilt in strawberry cultivation using local agrowastes as amendments.

The study explores anaerobic soil disinfection as an alternative to soil fumigants for controlling Verticillium wilt in strawberry crops. For this purpose, two agrowastes close to the strawberry-growing areas of Huelva province were tested as potential amendments for the control of Verticillium wilt: rice bran and residual strawberry extrudate. Furthermore, two application rates were evaluated: 13.50 and 20.00 t/ha for the rice bran and 16.89 and 25.02 t/ha for residual strawberry extrudate. Amended and anaerobically disinfested soils were compared with a non-amended soil under anaerobic conditions, a soil treated with the chemical fungicide metam sodium and an untreated soil. One week before the start of disinfection treatment, these soils were artificially inoculated with 250 microsclerotia/g dry soil of Verticillium dahliae. After disinfestation treatments, pathogens were quantified, and strawberry plants were cropped in a growth chamber to further evaluate Verticillium wilt severity, which was measured with a symptom scale in the same potting soils. Measurements of the anaerobic condition, pH and microbial population densities were performed, and the results showed significant differences between the different amendments. In addition, the treatment with rice bran at 20 t/ha recorded the lowest population density of V. dahliae. Likewise, it was possible to achieve a reduction in foliar disease severity in all amended treatments in similar percentage to those obtained by chemical treatment. These results suggest potential application of this technique for the control of Verticillium wilt in the strawberry-growing area of Huelva, reducing the use of chemical fumigants.

Insights for Soil Improvements: Unraveling Distinct Mechanisms of Microbial Residue Carbon Accumulation under Chemical and Anaerobic Soil Disinfestation

Soil disinfestation has been widely used as an effective strategy to improve soil health and crop yield by suppression of soil-borne plant pathogens, but its effect on soil organic carbon (SOC), a crucial factor linked to climate change, remains unknown. A microcosm trial was conducted to evaluate microbial residue carbon (MRC) and its contribution to SOC under chemical soil disinfestation (CSD) with quicklime (QL) and chloropicrin (CP), as well as anaerobic soil disinfestation (ASD) with maize straw (MASD) and soybean straw (SASD). The SOC concentrations were increased by both CSD and ASD. Also, total SOC-normalized MRC concentration was enhanced, with a considerable increase in soil bacterial and fungal MRC, particularly evident under CP and SASD treatment. Due to broad-spectrum biocidal activities, decreased SOC-normalized microbial biomass carbon (MBC) was consistent with the reductions in bacterial and fungal phospholipid fatty acids (PLFAs), consequently increasing MRC accumulation under CSD. Similarly, ASD decreased fungal PLFAs while shifting bacterial PLFAs from aerobic to anaerobic taxa or from gram-negative to -positive taxa, both of which contributed to both MBC and MRC buildup. Collectively, the findings demonstrate that ASD can efficiently increase SOC concentration, with distinct mechanisms underlying MRC generation when compared to traditional CSD.

Anaerobic soil disinfestation rather than Bacillus velezensis Y6 inoculant suppresses tomato bacterial wilt by improving soil quality and manipulating bacterial communities

Continuous cropping leads to high incidence of soilborne diseases such as bacterial wilt caused by Ralstonia solanacearum, which poses a risk to agricultural production. Anaerobic soil disinfestation (ASD) and plant growth-promoting rhizobacteria (PGPR) are considered environmentally friendly methods to control bacterial wilt. However, the underlying mechanism of the improvement of soil health and the inhibition of bacterial wilt after ASD treatment and PGPR inoculation needs further exploration. This study evaluated the effect of ASD treatment on soil improvement at pre-planting of tomato, and the effect of ASD treatment combined with the application of Bacillus velezensis Y6 (BV) on soil quality, R. solanacearum abundance, and bacterial communities 90 days before harvesting of tomato. The results showed that ASD treatment reduced R. solanacearum abundance in soil by 17.6% pre-planting and 18.7% 90 days before harvesting, but BV inoculation did not influence R. solanacearum abundance. ASD and ASD+BV treatments effectively reduced the occurrence of bacterial wilt, improved soil nutrient status and increased soil microbial activity 90 days before harvesting. Principal co-ordinate analysis showed that the soil bacterial community was significantly influenced by ASD treatment both pre-planting and 90 days before harvesting. Further investigation found that ASD contributed to the enrichment of beneficial flora (Bacillus and Streptomyces). Moreover, pH was an important environmental factor affecting the abundance of R. solanacearum in soil. Co-occurrence network analysis showed that ASD treatment significantly increased network connection of bacterial communities and the proportion of beneficial microorganisms (Proteobacteria and Firmicutes), leading to complex soil bacterial co-occurrence networks both at pre-planting and 90 days before harvesting. Collectively, these results indicate that ASD treatment, but not microbial inoculation can enhance tomato plant resistance to bacterial wilt by improving soil quality and modulating the soil bacterial community.

Anaerobic Soil Disinfestation and Vermicompost to Manage Bottom Rot in Organic Lettuce.

Rhizoctonia solani Kühn (teleomorph: Thanatephorus cucumeris [Frank] Donk) is an aggressive soilborne pathogen with a wide host range that survives saprophytically between crops, presenting a challenge for organic vegetable farmers who lack effective management tools. A 2-year field experiment was conducted at two organic farms to compare anaerobic soil disinfestation (ASD) and worm-cured compost (vermicompost) to manage bottom rot caused by R. solani subspecies AG1-IB in field-grown organic lettuce (Lactuca sativa). At each farm, four replicate plots of seven treatments were arranged in a randomized complete block design. Randomization was restricted by grouping treatments to evaluate ASD, and treatments to evaluate vermicompost in starter plugs. ASD experiment treatments were three different ASD carbon sources that are commonly used and widely available to local farmers in Vermont: compost, cover crop residues, and poultry manure fertilizer, as well as a tarped control. Vermicompost experimental treatments were vermicompost compared with two types of controls: a commercial biocontrol product (RootShield PLUS + G), and unamended (untarped control). This study demonstrated that the ASD method is achievable in a field setting on Vermont farms. However, neither ASD nor vermicompost produced significant disease suppression or resulted in higher marketable yields than standard growing practices. Given the laborious nature of ASD, it is likely more appropriate in a greenhouse setting with high-value crops that could especially benefit from being grown in plastic tarped beds (e.g., tomatoes and strawberries). This study is the first known attempt of field-implemented ASD for soil pathogen control in the northeastern United States.

Effects of Anaerobic Soil Disinfestation for Soilborne Disease and Weed Management on Baby Leaf Lettuce Performance in a High Tunnel Organic Production System

The use of high tunnels, which allows growers to extend their season and improve yields, is increasing in the Southeastern U.S., yet growers face challenges related to weed and disease management, particularly in organic systems. On-station experiments were conducted during fall 2021 and spring 2022 in a split-plot design to assess the efficacy of anaerobic soil disinfestation (ASD) in high tunnels for the organic production of direct-seeded baby leaf lettuce. Soil treatments (ASD, Compost, and Control) and lettuce types (romaine and oakleaf cultivars) were included in whole plots and subplots, respectively. The ASD-treated soils received molasses and granular organic fertilizer as carbon and nitrogen sources. The Compost treatment involved the application of yard waste-based compost and the same organic fertilizer, while the Control soils received organic fertilizer only. The ASD treatment period lasted 8 days rather than the typical 21-day period evaluated in Florida. Crop yield, biometrics (leafy dry matter content, specific leaf area, specific leaf weight), and lettuce quality attributes (leaf color, soluble solids content, total titratable acidity, ferric reducing antioxidant power, ascorbic acid content, total phenolics) were assessed following harvest. In both trials, numerical differences in lettuce fresh weight yield between soil treatments were evident, though not statistically significant. Differences in leaf quality attributes were driven by lettuce cultivar rather than soil treatments. Bottom rot incidence caused by Rhizoctonia solani was reduced by 93% and 87% in the ASD-treated plots compared with the Compost- and Control-treated soils during the spring 2022 trial. The ASD-treated soils had a reduced population density of broadleaf weeds in both baby leaf lettuce production trials. The current study presents novel evidence of the potential of integrating ASD into HT organic production systems without reducing the yield and quality attributes of direct-seeded baby leafy greens compared with common grower practices.

Evaluation of Anaerobic Soil Disinfestation to Reduce Soilborne Diseases in Soilless and Soil-Based Substrates for Specialty Cut Flower Production.

Anaerobic soil disinfestation (ASD) is a nonchemical soil treatment where an easily decomposable carbon source is incorporated into soil, which is then irrigated to saturation and tarped to create anaerobic conditions, which prompts shifts in the soil microbiota from aerobes to anaerobes. ASD has been tested successfully for soilborne disease management in a variety of cropping systems but has not been sufficiently investigated in ornamentals. In this study, ASD was evaluated in soil-based and soilless substrates commonly used in specialty cut flower production using two model pathosystems: Rhizoctonia solani-Zinnia elegans and Phytophthora drechsleri-Gerbera jamesonii. Each substrate was mixed with pathogen-infested vermiculite and amended with either wheat bran, tomato pomace, or soybean meal as the carbon source. Amended substrates were incubated at 25°C for 4 weeks and used as growing substrates for the two crops mentioned above, which were monitored weekly for disease development for up to 5 weeks posttransplant. Additional experiments tested the effect of plant age and inoculum concentration in the substrate on ASD efficacy. Results showed that ASD has the potential to be deployed successfully for the control of Rhizoctonia stem rot in both substrates. Conversely, ASD was not effective at controlling Phytophthora crown rot on gerbera daisy in any of the experiments conducted in this study. More research is needed to understand the influence of carbon amendments, inoculum thresholds, and environmental conditions on ASD efficacy.

Agriculture against the wall: barriers and opportunities for agroecological transitions in California’s industrial agricultural landscapes

ABSTRACT Agroecology emphasizes a shift from low diversity, high chemical input farming to more biodiverse agroecosystems cultivated in conjunction with natural ecosystem processes and embedded in socially just relationships. Yet achieving such agroecological transitions presents enormous challenges in industrial agricultural landscapes dominated by consolidation and overproduction. We examine both the challenges and the opportunities for agroecological transition in one particular industrial agricultural context: the fumigant-dependent strawberry production of California’s Central Coast. We do so by exploring adoption of Anaerobic Soil Disinfestation (ASD), an agroecological alternative to fumigation which has shown considerable promise but has been historically underutilized. Building on previously identified “domains of agroecological transformation,” we characterize the enabling and disabling conditions for agroecological transitions in California’s agricultural landscape. Through semi-structured interviews with farmers, extensionists, and industry stakeholders we uncover significant regime lock-ins: most prominently insecure land tenure and unequal access to land, unequal systems of exchange, and a culture that favors silver bullet narratives and top-down knowledge transfer; as well as drivers of change. The case of ASD, we conclude, reveals that technology-led agroecological transitions will have difficulty succeeding unless they are embedded in broader efforts to transform the social and political relationships of industrial agriculture.

Effects of anaerobic soil disinfestation on antibiotics, human pathogenic bacteria, and their associated antibiotic resistance genes in soil

Despite the widespread use of anaerobic soil disinfestation (ASD) to improve soil health, its impact on soil antibiotics, human pathogenic bacteria (HPB) and antibiotic resistance genes (ARGs) remains unclear. To address this knowledge gap, we conducted an incubation study in manure-amended soil with three treatments: no treatment (CK), crop straw only (CS), and CS combined with water flooding and plastic covering (ASD). The results showed that ASD increased the concentrations of tetracycline by 27 % and β-lactam by 22 %, while depleting macrolide by 51 %. Furthermore, ASD increased the numbers of potential HPB species and genes by 4.1 % and 23 %, respectively. Co-occurrence network analysis demonstrated intensified cooperation and competition among HPB and HNPB (human non-pathogenic bacteria) species under ASD, favoring the prevalence of HPB species such as Escherichia coli, Streptococcus equi, Clostridium tetani, and Bacillus anthracis. Potential HPB species in Proteobacteria exhibited negative correlations with macrolide and β-lactam antibiotics, whereas those in Firmicutes showed positive correlations with tetracycline antibiotics, suggesting that specific bacterial taxa contributed to the production and degradation of antibiotics in response to ASD. Interestingly, CS mitigated the presence of ARGs in soil, while ASD further amplified this reduction, almost eliminating nalC, acrB, OXA-60, VIM-7, tetL, and tetQ. The variation in ARG profiles (91.7 %) could be explained by antibiotics, HPB, and HNPB species, indicating their collective contribution to reducing soil ARGs under ASD. Moreover, host prediction and network analysis revealed that, compared with CK, where potential HPB species were the main carriers of ARGs, soil ARGs were less frequently carried by potential HPB species after ASD, indicating a reduction in the collaborative dissemination of HPB and ARGs in manured soil. In conclusion, ASD provides a promising strategy for mitigation of soil biologic contamination, which can have profound significance for environmental safety and agricultural sustainability.

Optimization of the Use of Industrial Wastes in Anaerobic Soil Disinfestation for the Control of Fusarium Wilt in Strawberry.

Anaerobic soil disinfestation (ASD) is proposed as an alternative to the use of chemical fumigants against Fusarium wilt in strawberry crops. Different residual wastes (rice bran, fishmeal, and residual strawberry extrudate) were assessed as amendments for ASD. Two different concentrations and two incubation durations were tested in growth chamber trials. The abundance of several microbial groups was noted before and after the treatments. Strawberry plants were grown in the treated soils to record Fusarium wilt disease severity. The population density of F. oxysporum increased after ASD in most amendments with rice bran and residual strawberry extrudate. Changes in Trichoderma spp., copiotrophic bacteria, and Streptomyces spp. populations were observed after anaerobiosis treatments and plant trials. A reduction in the disease severity was achieved in ASD-treated soils with 20 t/ha of rice bran at both 25 and 60 days of incubation, but not when using a 13.5 t/ha dose. Similarly, treatments using 19.3 t/ha of fishmeal for both incubation durations were able to reduce disease severity. In contrast, a severity reduction was only obtained in soils treated with 25.02 t/ha of the residual strawberry extrudate and incubated for 60 days in anaerobic conditions. Two of the three by-products tested were able to reduce Fusarium wilt symptoms in strawberry plants after an ASD-treatment period of only 25 days. Accordingly, the technique seems promising for strawberry growers in Huelva, Spain, and highly sustainable by giving value to residues produced in surrounding areas.

Brewer’s Spent Grain with Yeast Amendment Shows Potential for Anaerobic Soil Disinfestation of Weeds and Pythium irregulare

Anaerobic soil disinfestation (ASD) is a promising alternative to chemical fumigation for controlling soilborne plant pathogens and weeds. This study investigated the impact of brewer’s spent grain (BSG), a locally available carbon source, on various weed species and the oomycete pathogen Pythium irregulare in ASD. Two greenhouse studies were conducted using BSG and yeast at full and reduced rates in a completely randomized design with four replicates and two runs per study. In both studies, ASD treatments significantly decreased the seed viability of all weed species and the Pythium irregulare inoculum, while promoting higher cumulative anaerobicity compared to the non-treated control. The addition of yeast had a notable effect when combined with BSG but not with rice bran. When used in reduced carbon rates, yeast supplementation enhanced the efficacy of BSG, providing comparable control to the full rate for most weed species, including redroot pigweed, white clover, and yellow nutsedge. Interestingly, no ASD treatment affected the soil temperature. Furthermore, BSG treatments caused higher concentrations of volatile fatty acids compared to ASD with rice bran and the non-treated control. This finding suggests that the inclusion of yeast in ASD shows potential for reducing the carbon input required for effective soil disinfestation.

Effect of Anaerobic Soil Disinfestation on Tuber Vitality of Yellow Nutsedge (Cyperus esculentus)

Cyperus esculentus is considered the sixteenth worst weed in the world. The weed causes huge losses in arable crops. Current control strategies are based on combinations of chemical and mechanical methods, repeated over years, and aim to deplete the belowground bud bank. However, this is a slow process. Anaerobic soil disinfestation (ASD) using readily decomposable carbon sources may be a promising innovative method to quickly deplete the bud bank. This study investigated the effect of ASD with fresh grass clippings (dosage of 80 tonnes ha−1) differing in C:N ratio and Herbie® (consists of organic by-products from the food processing industry, dosage of 25 tonnes ha−1) on the vitality of small and large C. esculentus tubers buried at three depths (5, 15, and 30 cm) into two soils differing in soil type and soil moisture content. Their effects were compared with the effect of chemical soil disinfestation (CSD) with metam-sodium (153 kg ha−1). ASD with Herbie® showed at least equal performance compared with CSD with metam-sodium, with reductions in tuber vitality up to 97.5%. The performance of ASD with grass clippings was less consistent across soils and was affected by the C:N ratio of the grass. Both ASD and CSD showed the highest performance in moist, sandy soil and on small tubers. ASD is an effective and promising method to quickly deplete the C. esculentus bud bank, provided that the soil is sandy and moist, the carbon source has a C:N ratio of about 10, and the incorporation depth is at least 25 cm. To foster the implementation of ASD, future research should evaluate its performance consistency across environments and years.