Soil Disinfestation Research Articles

Anaerocolumna chitinilytica sp. nov., a chitin-decomposing anaerobic bacterium isolated from anoxic soil subjected to biological soil disinfestation.

An obligately anaerobic bacterial strain (CTTWT) belonging to the family Lachnospiraceae within the class Clostridia was isolated from an anoxic soil sample subjected to biological or reductive soil disinfestation. Cells of the strain were Gram-stain-positive, short rods with peritrichous flagella. The strain was saccharolytic and decomposed polysaccharides, chitin, xylan and β-1,3-glucan. Strain CTTWT decomposed cell biomass and cell-wall preparations of an ascomycete plant pathogen, Fusarium oxysporum f. sp. spinaciae. The strain produced acetate, ethanol, H2 and CO2 as fermentation products from the utilized substrates. The major cellular fatty acids of the strain were C16 : 1 ω7c dimethylacetal (DMA), C16 : 0 DMA and C18 : 1 ω7c DMA. The closely related species of strain CTTWT based on the 16S rRNA gene sequences were species in the genus Anaerocolumna with sequence similarities of 95.2-97.6 %. Results of genome analyses of strain CTTWT indicated that the genome size of the strain was 5.62 Mb and the genomic DNA G+C content was 38.3 mol%. Six 16S rRNA genes with five different sequences from each other were found in the genome. Strain CTTWT had genes encoding chitinase, xylanase, cellulase, β-glucosidase and nitrogenase as characteristic genes in the genome. Homologous genes encoding these proteins were found in the genomes of the related Anaerocolumna species, but the genomic and phenotypic properties of strain CTTWT were distinct from them. Based on the phylogenetic, genomic and phenotypic analyses, the name Anaerocolumna chitinilytica sp. nov., in the family Lachnospiraceae is proposed for strain CTTWT (=NBRC 112102T=DSM 110036T).

Stationary soil steaming to combat invasive plant species for soil relocation

AbstractEradication of alien invasive species in the soil with steam as an alternative to chemical fumigation may allow contaminated soil to be reused. We have investigated steam disinfestation of soil to combat invasive plant species in three experiments including different temperatures and exposure durations using a prototype stationary soil-steaming device. The experiments included effects on seed germination of bigleaf lupine (Lupinus polyphyllusLindl.), ornamental jewelweed (Impatiens glanduliferaRoyle), and wild oat (Avena fatuaL.; one population from Poland and one from Norway), as well as effects on sprouting rhizome fragments of Canada goldenrod (Solidago canadensisL.) and Bohemian knotweed (ReynoutriaxbohemicaChrtek & Chrtková). In Experiment 1, we tested four different soil temperatures of 64, 75, 79, and 98 C with an exposure duration of 90 s. In Experiments 2 and 3, we tested exposure durations of 30, 90, and 180 s and 90, 180, and 540 s, respectively, at 98 C. Seed pretreatment of 14 d cooling forL. polyphyllusandI. glandulifera, no seed pretreatment and 12-h moistening forA. fatuapopulations, and 5- and 10-cm cutting size forR. xbohemicawere applied. Our results showed germination/sprouting was inhibited at 75 C forI.glandulifera(for 90 s) and 98 C for the other species; however, longer exposure duration was needed forL.polyphyllus. While 30 s at 98 C was enough to killA.fatuaseeds andS.canadensisandR. xbohemicarhizome fragments, 180-s exposure duration was needed to killL.polyphyllusseeds. The results showed promising control levels of invasive plant propagules in contaminated soil by steaming, supporting the steam treatment method as a potential way of disinfecting soil to prevent dispersal of invasive species.

Microbial community responses to multiple soil disinfestation change drivers

Soil continuous cropping obstacles lead to yield and economic losses in agriculture. Reductive soil disinfestation (RSD) is an effective technology for alleviating it. However, the key factors influencing microbial community composition and how do they promote functional transformation of core microbes under RSD practice remain poorly understood. Hence, a short-term field experiment was performed integrating real-time polymerase chain reaction, average well color development (AWCD), and MiSeq pyrosequencing to investigate relationships between environmental factors and microorganisms in five different disinfestation treatments, i.e., untreated monoculture soil (CK), soil with high temperature heating (HT), soil with dazomet (DZ), RSD with sugarcane bagasse (SB), or with bean dregs (BD). The results showed that compared to non-RSD treatments, both RSD treatments significantly increased soil microbial abundance and soil available K and organic matter (OM). Further analysis found that available K and OM were the key factors inducing microbial community change. Additionally, relative to non-RSD treatments, the relative abundances of phyla Proteobacteria, Acidobacteria, Rokubacteria, and Ascomycota were higher, whereas those of Actinobacteria, Gemmatimonadetes, and Basidiomycota were lower in RSD treatments. Changes in microbial diversity and abundance led to variation of soil microbial community functions. AWCD and community function prediction showed that, in contrast with non-RSD treatments, soil metabolism activity significantly increased, bacterial community functions including terpenoids and polyketides metabolism, signal transduction and cell motility increased, and the number of saprotroph fungi increased under RSD treatments. Overall, RSD incorporated with sugarcane bagasse or bean dregs efficiently improved soil fertility, and considerably increased soil microbial activity and function, which may benefit future sustainable agriculture production. Key points • Reductive soil disinfestation can alleviate continuous cropping obstacles by improving soil fertility. • Organic matter and available potassium as the key factors affected microbial community reconstruction and function. • Reductive soil disinfestation can improve soil metabolic activity and functional diversity by altering microorganism community.

Amendment Properties Affect Crop Performance, Leaf Tissue Nitrogen, and Soil Nitrogen Availability Following Soil Treatment by Anaerobic Soil Disinfestation

Efficacy of anaerobic soil disinfestation (ASD) for soilborne plant pathogen suppression is strongly influenced by soil environment and organic amendment attributes. At the same time, these factors influence soil nutrient availability, crop nutrition, and crop performance, but published information on ASD amendment property effects, including carbon to nitrogen (C:N) ratio and C substrate bioavailability, on crop performance and soil nutrient availability is limited. We evaluated ASD amendment effects on soil N availability, crop N status, and solanaceous crop performance in a series of trials: (1) greenhouse/growth chamber study of amendments (primarily molasses/soybean hulls and wheat bran) formulated at 10:1, 20:1, 30:1 and 40:1 C:N ratios (4 mg C g−1 soil), (2) field study with molasses/soybean hull-based amendments at equivalent C:N ratios/C rates (3) on-farm study with molasses/soybean hull-based amendments (4 mg C g−1 soil) compared to grower-standard control, and (4) field study of labile to recalcitrant amendment substrates at 30:1 C:N ratio (~3.4 mg C g−1 soil). ASD amendment C:N ratio strongly influenced soil inorganic N and the lowest (10:1) ratio was associated with highest soil inorganic N at ASD treatment termination in both trials 1 and 2, which often persisted into the cropping phase. Accordingly, the lowest amendment C:N ratio was also associated with the highest biomass (trail 1), leaf tissue N (trial 2), and crop yield (trials 1, 2) among treatments, even with application of recommended fertigation rates to all treatments in the field study. In trial 3, ASD treatment induced higher soil inorganic N and crop yield than the control, but no differences were observed in plant tissue N. In trial 4, more decomposable ASD substrates reduced soil inorganic N at ASD treatment termination, with the highest soil inorganic N associated with the most recalcitrant amendment, but there was no effect on crop yield. ASD amendment C:N ratio, and to a lesser extent, amendment decomposability, exert a strong influence soil inorganic N and crop performance. Optimization of ASD treatments for disease management will require simultaneous optimization of crop nutrition practices to facilitate more holistic, less confounded assessment of crop performance and to facilitate recommendations for grower adoption.

Root-Associated Microbiomes, Growth and Health of Ornamental Geophytes Treated with Commercial Plant Growth-Promoting Products.

The microbial community inhabiting a plant’s root zone plays a crucial role in plant health and protection. To assess the ability of commercial plant growth-promoting products to enhance the positive effects of this environment, two products containing beneficial soil bacteria and a product containing plant extracts were tested on Zantedeschia aethiopica and Ornithogalum dubium. The products were tested in two different growing media: a soil and a soilless medium. The effects of these products on Pectobacterium brasiliense, the causal agent of soft rot disease, were also evaluated in vitro, and on naturally occurring infections in the greenhouse. The growing medium was found to have the strongest effect on the microbial diversity of the root-associated microbiome, with the next-strongest effect due to plant type. These results demonstrate that either a single bacterial strain or a product will scarcely reach the level that is required to influence soil microbial communities. In addition, the microbes cultured from these products, could not directly inhibit Pectobacterium growth in vitro. We suggest density-based and functional analyses in the future, to study the specific interactions between plants, soil type, soil microbiota and relevant pathogens. This should increase the effectiveness of bio-supplements and soil disinfestation with natural products, leading to more sustainable, environmentally friendly solutions for the control of bacterial plant diseases.

Non-Chemical Soil Fumigation for Sustainable Strawberry Production in Southern Italy

In intensive strawberry production, monoculture is a common practice worldwide; however, prolonged replanting can cause plant disorders and jeopardize profitable cultivation of this highly valuable crop. To mitigate replanting problems, the strawberry industry is still highly dependent on chemical fumigation. Given the increasing regulatory restrictions and concerns about human and environmental risks from fumigants use, there is a growing interest in the adoption of effective, non-chemical alternatives. Two non-chemical soil fumigation practices, i.e., anaerobic soil disinfestation (ASD) and bio-fumigation with biocide plants (BIOFUM), were tested against chemical fumigation by chloropicrin + 1,3-dichloropropene mixture (STANDARD) and untreated (UNTREAT) control in a 2-year trial established in a commercial strawberry farm in Southern Italy (40°25′ N, 16°42′ E). Overall, the alternative practices provided consistently better results than UNTREAT; whereas, compared to STANDARD, their performance was significantly different in the two years: in 2018/19 season the alternative practices registered a 20% (ASD) and 39% (BIOFUM) marketable yield loss compared to STANDARD, while in the 2019/20 season yield differences were not significant. Although both practices appear promising as eco-friendly alternatives to chemical fumigation, in this short-term trial ASD performed better than BIOFUM both in terms of yield and fruit size, resulting in a more advanced stage for practical adoption.

Impact of Soil Disinfestation on Fungal and Bacterial Communities in Soil With Cucumber Cultivation.

Soil treatment with disinfectants has been used for controlling soilborne phytopathogens. Besides suppressing specific pathogens, how these disinfectants impact soil health, especially soil microbial communities, is yet to be systemically determined. The objectives of this study were to examine the effects of three representative disinfectants, including the dazomet fumigant, fenaminosulf fungicide, and kasugamycin antibiotic on chemical properties, enzymatic activities, and microbial communities in soil for cucumber cultivation. Results showed that 14 days after soil treatment with these chemicals, residual content of dazomet and kasugamycin quickly declined in soil and were undetectable, while fenaminosulf residues were found at 0.48 ± 0.01 mg/kg. Total nitrogen and total carbon increased in soil after dazomet treatment. Urease and sucrase activities were significantly restrained after disinfectant application. The disinfectants did not significantly change the taxon of predominant bacteria and fungi but altered the relative abundance and diversity of soil microbiome, as well as microbial interspecific relationships. Moreover, cucumber cultivation enhanced the overall soil microbial diversity and enzymatic activities, which diminished the difference of soil microbiome among four treatments. The difference in soil microbial diversity among the four treatments became smaller after planting cucumber. Thus, soil microbial communities were affected by soil disinfectants and gradually recovered by cucumber application.

Anaerobic Soil Disinfestation Efficacy Against Fusarium oxysporum Is Affected by Soil Temperature, Amendment Type, Rate, and C:N Ratio.

A meta-analysis of anaerobic soil disinfestation (ASD) efficacy against Fusarium oxysporum and F. oxysporum f. sp. lycopersici was conducted emphasizing effects of environment and organic amendment characteristics and pot and field studies conducted on ASD amendment C:N ratio and soil temperature effects on F. oxysporum f. sp. lycopersici inoculum survival. In a pot study, two organic amendments, dry molasses-based or wheat bran-based, applied at 4 mg of C/g of soil, with 40:1, 30:1, 20:1, and 10:1 C:N ratios, were evaluated against F. oxysporum f. sp. lycopersici at 15 to 25°C. This study was followed by a pot study with temperature regimes of 15 to 25°C and 25 to 35°C and two C:N ratios (20:1 and 40:1), and a field study at 40:1, 30:1, 20:1, and 10:1 C:N ratios, a 30:1 C:N ratio at a lower C rate (2 mg of C/g of soil), and an anaerobic control. Soil temperature >25°C and more labile amendments increased ASD suppression of F. oxysporum/F. oxysporum f. sp. lycopersici in the meta-analysis. In pot studies, F. oxysporum f. sp. lycopersici survival was reduced for molasses-based mixtures at 20:1 and 30:1 C:N ratios compared with wheat bran-based mixtures but not compared with the anaerobic control. At 25 to 35°C, all ASD treatments suppressed F. oxysporum f. sp. lycopersici relative to controls. In the field, all ASD treatments reduced F. oxysporum f. sp. lycopersici survival compared with the anaerobic control, and 4 mg of C/g of soil amendment rates induced higher anaerobic conditions and higher F. oxysporum f. sp. lycopersici mortality compared with the 2 mg of C/g of soil rate. Although amendment C:N ratios from 10 to 40:1 were similarly suppressive of F. oxysporum, lower temperatures reduced ASD effectiveness against F. oxysporum/F. oxysporum f. sp. lycopersici and further work is warranted to enhance suppression at soil temperatures <25°C.

Effects of reductive soil disinfestation during low-temperature stubble free period on the control of watermelon Fusarium wilt

In order to clarify the controlling effect of reductive soil disinfestation (RSD) during low-temperature stubble idle period on watermelon Fusarium wilt, we conducted a pot experiment, containing control (CK), flooded control (FCK), and RSD treatments incorporated with 2% (w/w) alfalfa meal (AL), 0.25% acetic acid (AC), and AL+AC. Real time PCR and Illumian Miseq sequencing were used to determine the abundances of fungi and Fusarium oxysporum as well as fungal community composition. The disease incidence and yield of watermelon were measured. Results showed that the abundance of Fusarium oxysporum and the ratio of Fusarium oxysporum to fungi significantly decreased in the FCK and three RSD treatments, and the disinfestation effects of these treatments ranged from 86.1% to 94.6%. The yield and disease incidence of watermelon significantly increased and decreased in all of the RSD treatments, respectively. There was no significant diffe-rence between FCK and CK treatments. The control efficiencies of Fusarium wilt in AL, AC, and AL+AC were 63.2%, 73.7%, and 94.7%, respectively. The compositions of fungal community in the AL and AC treatments were significantly changed, whereas FCK did not affect fungal community. The relative abundances of dominant fungal genera, such as Zopfiella, Pseudeurotium, Geotrichum, Ascobolus, Westerdykella, and Guehomyces, increased in the RSD treatments. Most of those genera were significantly and negatively correlated with the abundance of Fusarium oxysporum, the ratio of Fusarium oxysporum to fungi, and the disease incidence. In conclusion, RSD treated in the low-temperature stubble free period could effectively control watermelon Fusarium wilt by reshaping fungal community composition.

Analysis of Environmental Variables and Carbon Input on Soil Microbiome, Metabolome and Disease Control Efficacy in Strawberry Attributable to Anaerobic Soil Disinfestation.

Charcoal rot and Fusarium wilt, caused by Macrophomina phaseolina and Fusarium oxysporum f. sp. fragariae, respectively, are major soil-borne diseases of strawberry that have caused significant crop losses in California. Anaerobic soil disinfestation has been studied as an industry-level option to replace soil fumigants to manage these serious diseases. Studies were conducted to discern whether Gramineae carbon input type, incubation temperature, or incubation duration influences the efficacy of this disease control tactic. In experiments conducted using ‘low rate’ amendment applications at moderate day/night temperatures (24/18 °C), and carbon inputs (orchard grass, wheat, and rice bran) induced an initial proliferation and subsequent decline in soil density of the Fusarium wilt pathogen. This trend coincided with the onset of anaerobic conditions and a corresponding generation of various anti-fungal compounds, including volatile organic acids, hydrocarbons, and sulfur compounds. Generation of these metabolites was associated with increases in populations of Clostridium spp. Overall, carbon input and incubation temperature, but not incubation duration, significantly influenced disease suppression. All Gramineae carbon inputs altered the soil microbiome and metabolome in a similar fashion, though the timing and maximum yield of specific metabolites varied with input type. Fusarium wilt and charcoal rot suppression were superior when anaerobic soil disinfestation was conducted using standard amendment rates of 20 t ha−1 at elevated temperatures combined with a 3-week incubation period. Findings indicate that anaerobic soil disinfestation can be further optimized by modulating carbon source and incubation temperature, allowing the maximum generation of antifungal toxic volatile compounds. Outcomes also indicate that carbon input and environmental variables may influence treatment efficacy in a target pathogen-dependent manner which will require pathogen-specific optimization of treatment protocols.

Reductive soil disinfestation attenuates antibiotic resistance genes in greenhouse vegetable soils

Reductive soil disinfestation (RSD) is an emerging technique that ameliorates soil degradation, but its effects against antibiotic resistance genes (ARGs) were unclear. Here, we examined soil properties, ARG types and numbers, and ARG profiles, and bacterial community compositions following 4 soil treatments: control; straw addition (SA); water flooding (WF); and RSD, both straw addition and water flooding. The results showed that the numbers of ARG types and subtypes decreased by 10.8% and 21.1%, respectively, after RSD, and the numbers of ARGs decreased by 18.6%. The attenuated multidrug, beta-lactam, macrolide, and phenicol resistance genes in the RSD soil corresponded to a decreased relative abundance of ARG subtypes (i.e., adeF, mdtM, TypeB_NfxB, mecA, nalC, OXA-60, and cmlA4). Taxa in phyla Proteobacteria, Actinobacteria, and Deinococcus-Thermus were the main hosts for dominant ARG subtypes and were inhibited by RSD. The selected bacterial genera and soil properties explained 83.4% of the variance in ARG composition, suggesting that the improved soil properties and the reduced potential ARG hosts produced by the interactions of straw addition and water flooding are likely responsible for ARG attenuation by RSD. Therefore, RSD has the potential to mitigate ARG pollution in soils.

Two Distinct Soil Disinfestations Differently Modify the Bacterial Communities in a Tomato Field

Reductive soil disinfestation (RSD) and soil solarization (SS) were evaluated based on environmental factors, microbiome, and suppression of Fusarium oxysporum in a tomato field soil. Soil environmental factors (moisture content, electric conductivity, pH, and redox potential (RP)) were measured during soil disinfestations. All factors were more strongly influenced by RSD than SS. 16S rRNA amplicon sequencing of RSD- and SS-treated soils was performed. The bacterial communities were taxonomically and functionally distinct depending on treatment methods and periods and significantly correlated with pH and RP. Fifty-four pathways predicted by PICRUSt2 (third level in MetaCyc hierarchy) were significantly different between RSD and SS. Quantitative polymerase chain reaction demonstrated that both treatments equally suppressed F. oxysporum. The growth and yield of tomato cultivated after treatments were similar between RSD and SS. RSD and SS shaped different soil bacterial communities, although the effects on pathogen suppression and tomato plant growth were comparable between treatments. The existence of pathogen-suppressive microbes, other than Clostridia previously reported to have an effect, was suggested. Comparison between RSD and SS provides new aspects of unknown disinfestation patterns and the usefulness of SS as an alternative to RSD.

Economical efficiency of disinfestation of soil in trichocephalosis of sheep

For the first time in the soil-climatic condition of the west region of Azerbaijan economical efficiency disinfestation of soil in trichocephalosis of sheep is found out. The use of solution sodium hypochlorite as disinfestational preparation in condition of bad trichocephalosis of sheep farm let it get more effective results using the least expenditure force and means. The efficiency of disinfestation is explained by high bioavailability of the preparation and optimal concentration of acting substance. It was identified that economical disinfestation of soil with the use of sodium hypochlorite is 22,30 azn (1 azn= 0, 022 ruble).

Potential inoculum sources of Fusarium species involved in asparagus decline syndrome and evaluation of soil disinfestation methods by qPCR protocols.

Asparagus decline syndrome (ADS), one of the most important diseases affecting asparagus crops, causes important yield losses worldwide. Fusarium proliferatum, F. oxysporum and F. redolens are among the main species associated with ADS. To explore their potential inoculum sources and the effectiveness of soil disinfestation practices for ADS management, molecular methods based on a quantitative real-time polymerase chain reaction (qPCR) were developed. qPCR-based molecular tools demonstrated advantages in the sensitive and specific detection and quantification of fungal pathogens in comparison with less-accurate and time-consuming traditional culture methods. F. proliferatum, F. oxysporum and F. redolens could be specifically detected and accurately quantified in asparagus plants, soil and irrigation water collected from asparagus fields with ADS symptoms by means of the designed TaqMan qPCR protocols. Furthermore, these molecular tools were successfully applied for evaluation of the efficacy of diverse soil disinfestation treatments. Chemical fumigation with dazomet and biosolarization with pellets of Brassica carinata contributed to a significant reduction in the inoculum densities of the three Fusarium species in treated soils, which was correlated with production increases. The capability to accurately detect and quantify the main Fusarium species involved in ADS in plants, soil and water samples by means of qPCR will allow identification of high-risk fields that can be avoided or managed to reduce yield losses. Quantification of pathogen densities in the soil may also provide essential insights into the effectiveness of soil disinfestation methods for ADS management. © 2021 Society of Chemical Industry.

Field scale application of Brassica seed meal and anaerobic soil disinfestation for the control of apple replant disease

Apple replant disease caused by a complex of soil-borne fungi, oomycetes, and nematodes causes stunting and reduced yields when apples are planted in locations previously cropped to tree fruit. Anaerobic soil disinfestation and bio-renovation using mustard seed meals have successfully mitigated replant disease in greenhouse trials and small field plots. The objective of this study was to examine the efficacy of Brassica seed meal and anaerobic soil disinfestation for the control of replant disease at a commercial scale in apples. At three 0.4 to 5 ha field sites in Washington, United States anaerobic soil disinfestation and Brassica seed meal bio-renovation were compared to non-treated and fumigation with 1,3-dichloropropene/chloropicrin controls. Brassica seed meal treatments significantly altered composition of the bulk soil and rhizosphere microbiomes and resulted in apple tree growth as great or greater than fumigated controls across all three study locations. Anaerobic soil disinfestation resulted in significant changes to composition of the rhizosphere microbiome and tree growth that was greater than the no-treatment control in three of four experiments. Our findings indicate that both methods may serve as biologically effective alternatives to soil fumigation for control of apple replant disease, though further modifications may be required to ensure their economic feasibility.

On-Farm Evaluations of Anaerobic Soil Disinfestation and Grafting for Management of a Widespread Soilborne Disease Complex in Protected Culture Tomato Production.

Tomato production in Ohio protected culture systems is hindered by a soilborne disease complex consisting of corky root rot (Pyrenochaeta lycopersici), black dot root rot (Colletotrichum coccodes), Verticillium wilt (Verticillium dahliae), and root-knot (Meloidogyne hapla and M. incognita). In a survey of 71 high tunnels, C. coccodes was detected in 90% of high tunnels, and P. lycopersici (46%), V. dahliae (48%), and Meloidogyne spp. (45%) were found in nearly half of high tunnels. Anaerobic soil disinfestation (ASD) with wheat bran (20.2 Mg/ha) plus molasses (10.1 Mg/ha) and grafting onto 'Maxifort' or 'Estamino' rootstocks were evaluated in high tunnels on five farms. In post-ASD bioassays of trial soils, root and taproot rot severity were significantly reduced after ASD, and root-knot galling was also reduced by ASD. Soilborne pathogenic fungi were isolated less frequently from bioassay plants grown in ASD-treated soils than control soils. Similar results were observed in tomato plants grown in high tunnels. Root rot was significantly reduced by ASD in nearly all trials. Corky root rot severity was highest in nongrafted plants grown in nontreated soils, and the lowest levels of corky root rot were observed in 'Maxifort'-grafted plants. Black dot root rot severity was higher or equivalent in grafted plants compared with nongrafted plants. Root-knot severity was lower in plants grown in ASD-treated soils in high tunnels compared with plants grown in control soils, but grafting did not significantly decrease root-knot severity. However, soil treatment did not significantly affect yield, and grafting led to inconsistent impacts on yield.

Evaluation of Agricultural Byproducts and Cover Crops as Anaerobic Soil Disinfestation Carbon Sources for Managing a Soilborne Disease Complex in High Tunnel Tomatoes

Anaerobic soil disinfestation (ASD) is a viable option for disease management in tomato production and reduces damage due to a soilborne disease complex consisting of Pyrenochaeta lycopersici, Colletotrichum coccodes, Verticillium dahliae, and Meloidogyne spp. There are plentiful options for ASD carbon sources using byproducts of Midwestern United States agriculture or cover crops, yet these carbon sources have not been evaluated for use in Midwestern settings. Low (10.1 Mg/ha) and high (20.2 Mg/ha) rates of corn gluten meal, distillers dried grains, soybean meal, wheat bran, and dry sweet whey were evaluated as ASD carbon sources in growth chamber and greenhouse bioassays. Cover crops including buckwheat, cowpea, crimson clover, mustard, oilseed radish, sorghum-sudangrass, white clover, and winter rye were evaluated in similar bioassays with one amendment rate (20.2 Mg/ha). Reducing conditions developed in soils regardless of carbon source or rate. Use of high rates of corn gluten meal, distillers dried grains, soybean meal, and wheat bran led to the lowest levels of root rot severity compared to non-treated controls. The higher rate of any byproduct carbon source was always more effective than the lower rate in reducing root rot severity. Use of both rates of soybean meal or corn gluten meal and the high rate of distillers dried grains or dry sweet whey led to significant increases in dry root and shoot biomass compared to controls. For cover crops, ASD with crimson clover, sorghum-sudangrass, white clover, or winter rye amendments reduced root rot severity relative to the aerobic control, but not relative to the anaerobic control. Use of cover crops did not significantly impact plant biomass. A subset of three ASD carbon sources [distillers dried grains, soybean meal, and wheat middlings (midds), all 20.2 Mg/ha] were evaluated in five on-farm ASD trials in high tunnels. Soil temperatures were low during the application period, limiting treatment efficacy. Reducing conditions developed in all soils during ASD treatment, and a moderate but significant reduction in root rot severity was observed following ASD with the soybean meal or wheat midds compared to ASD with distillers dried grains. Tomato yield was not significantly affected by ASD treatment.

Anaerobic soil disinfestation with incorporation of straw and manure significantly increases greenhouse gases emission and reduces nitrate leaching while increasing leaching of dissolved organic N

Greenhouse vegetable production in China mostly involves excessive N fertilization and flood irrigation. This causes serious soil degradation and spreading of soil borne diseases. As a countermeasure against soil borne diseases anaerobic soil disinfestation (ASD) is applied during the summer fallow period. Current practices involve the incorporation of organic C sources, covering of the soil with plastic film and flood irrigation. However, farmers not only apply straw but also organic manure in ASD which may result in significant greenhouse gas emissions and N leaching. A field experiment was conducted in a greenhouse during the summer fallow period to test the impact of three ASD practices on soil GHG (N2O, CO2 and CH4) emissions and N leaching: 1) control (CK), bare soil, no ASD; 2) ASD without straw incorporation (ASD-S); 3) ASD plus straw incorporation (ASD+S) and 4) ASD plus straw and chicken manure incorporation (ASD+SM). Applying any form of ASD resulted in an increase in N2O emissions from approximately 1 kg N ha−1 month−1 to 10.7 (ASD)–47.0 (ASD+SM) kg N ha−1 month−1. Furthermore, N leaching from treatments of ASD ranged from 24.1–54.2 kg N ha−1 month−1, with highest values in ASD-S. However, while N leaching in ASD-S was solely in the form of NO3−, DON leaching was with approximately 12–20% a significant component of total N leaching in ASD+S and ASD+SM. Overall, ASD+SM showed the highest environmental N losses, which were dominated by N2O emissions. This highlights the need to advise farmers and policy makers to ban the incorporation of chicken manure instead of straw only during the ASD period and to optimize irrigation schemes instead of flood irrigation to reduce environmental N losses. Putting in more environmental sound ASD practices will certainly help to improve the sustainability of greenhouse vegetable production.

Integrating broccoli rotation, mustard meal, and anaerobic soil disinfestation to manage verticillium wilt in strawberry

Verticillium wilt, a disease caused by the fungus Verticillium dahliae, affects a vast range of crops, including strawberries. A field trial was established to evaluate the effect of broccoli in rotation prior to strawberries, anaerobic soil disinfestation (ASD), and mustard cake (MC) alone and in combination at suppressing V. dahliae. Broccoli, cauliflower and fallow plots were established in year 1, followed by strawberry, winter cover crop, and lettuce across all plots over the next two years. ASD and ASD + MC improved strawberry yields compared to the untreated control (UTC). At the end of the harvest season, V. dahliae infection rates in strawberry crowns were lower in the ASD and ASD + MC treatments compared to the UTC. After harvest of the lettuce crop, the number of V. dahliae microsclerotia in soil treated previously with ASD was lower than in the UTC. Broccoli residue incorporation had no effect and MC alone a limited effect on strawberry yields, V. dahliae in strawberry crowns, and soil microsclerotia levels at lettuce harvest. All rotations treated with ASD showed higher total net returns despite the higher cost of treatments. The ability of ASD to control V. dahliae and its persistent suppressive effect on soil microsclerotia levels have important economic implications for growers.

Evaluation of Broadcast Steam Application with Mustard Seed Meal in Fruiting Strawberry

Soil disinfestation with steam has potential to partially replace fumigants such as methyl bromide, chloropicrin, and 1,3-dichloropropene because it is effective, safer to apply, and has less negative impact on the environment. Here, we compared the efficacy of steam and steam + mustard seed meal (MSM) to chloropicrin on soil disinfection, plant growth, and fruit yield in a strawberry (Fragaria ×ananassa) fruiting field. The MSM was applied at 3368 kg·ha−1 before the steam application. Steam was injected into a 3-m-wide reverse tiller that was set to till 30 to 40 cm deep. Soil temperatures at depths of 10, 20, 25, and 35 cm were monitored. Steam and steam + MSM treatments reduced the viability of purslane seeds and nutsedge tubers, microsclerotia density of Verticillium dahliae, propagule density of Pythium ultimum, cumulative weed densities, and biomass compared with the nontreated control. Moreover, the steam application was as efficacious as chloropicrin on these pests. The growth and fruit yield of strawberries grown on soils previously treated with the steam and steam + MSM treatments were similar to those in the chloropicrin treatment and were higher than those in the nontreated control. Our study indicated that steam, steam + MSM, and chloropicrin are equally effective at suppressing weeds and soilborne pathogens. These results suggest that the steam and steam + MSM treatment can be a practical alternative for soil disinfestation in conventional and organic strawberry fields.