Soil Fumigation Research Articles

Microbial Fertilization Improves Soil Health When Compared to Chemical Fumigation in Sweet Lily.

Lanzhou Lily(Lilium davidii) var. unicolor, which is also known as sweet lily in China, is used as a type of food. This lily is distributed in narrow regions, propagates asexually, cultivates perennially, and cultivates commonly in serious consecutive replant problems (CRPs). Soil fumigation is commonly used to control soil-borne disease to alleviate crops’ consecutive replant problems (CRPs). However, due to the improper fumigation application, it is common to cause chemical hazard to crops. In this study, we designed a two-factor experiment to explore the bacterial and fungal community structure and some specific microbial groups in the lily rhizosphere soil after chemical versus bacterial fertilizer treatments, by using a metagenomic analysis of the treated soils. The results showed that metham-sodium soil fumigation (SMF treatment) significantly decreased plant growth, as well as it significantly decreased both soil fungal diversity and abundance at the OTUs levels, while Special 8™ microbial fertilizer supplement (MF treatment) significantly improved plant growth and increased fungal diversity and abundance. Under FM treatment, Chao1 richness and Shannon’s diversity increased by 6.70% and 35.09% compared to CK (no treatment). However, the bacterial diversity and abundance were not significantly changed among these treatments. The fungal and bacterial community structure were different in all treatments. In SMF treatment, the pathogenic fungal species Fusarium oxysporum increased compared to CK, but it significantly decreased in MF treatment; in MF and MMF treatments, some beneficial bacteria groups such as the bacterial phylum Proteobacteria and its member genus Sphingomonas, as well as the fungal genus Mortierella, increased compared to CK and SFM treatments, but the harmful bacterial genera Gemmatimona was decreased, as well as the harmful fungal genus Cryptococcus. Thus, we concluded that under chemical fumigation conditions, both fungal diversity loss and overall microorganism reduction, which impair multiple ecosystem function, in conjunction with the increase of harmful fungal species such as Fusarium oxysporum, are causes for soil degradation. On the other hand, under microbial fertilizer supplement, it was the fungal diversity increase, as well as these beneficial microorganisms groups’ accumulation, together with those harmful groups’ depletion, played important roles in restoring and improving soil health that suffered from the chemical fumigant hazard. In addition, the bacterial phylum Proteobacteria and its member genus Sphingomonas are involved in soil health recovery and promotion. The results also emphasized that whether soil is chemically fumigated or not, beneficial microorganism supplementary is effective in ensuring soil productivity.

Toward a holistic view of orchard ecosystem dynamics: A comprehensive review of the multiple factors governing development or suppression of apple replant disease.

Replant diseases are a common occurrence in perennial cropping systems. In apple, progress toward the development of a universally effective disease management strategy, beyond the use of broad-spectrum soil fumigants, is impeded by inconsistencies in defining replant disease etiology. A preponderance of evidence attributes apple replant disease to plant-induced changes in the soil microbiome including the proliferation of soilborne plant pathogens. Findings from alternative studies suggest that the contribution of abiotic factors, such as the accumulation of phenolic detritus from previous orchard plantings, may play a part as well. Engineering of the resident soil microbiome using resource-based strategies is demonstrating potential to limit activity of replant pathogens and improve productivity in newly established orchards. An understanding of factors promoting the assembly of a disease-suppressive soil microbiome along with consideration of host factors that confer disease tolerance or resistance is imperative to the developing a more holistic view of orchard ecosystem dynamics. Here, we review the literature concerning the transition of orchard soil from a healthy state to a replant disease-conducive state. Included in the scope of this review are studies on the influence of soil type and geography on the apple replant pathogen complex. Furthermore, several tolerance and innate resistance mechanisms that have been described in apple to date, including the role of root chemistry/exudates are discussed. Finally, the interplay between apple rootstock genotype and key resource-based strategies which have been shown to “reshape” the plant holobiont in favor of a more prophylactic or disease-suppressive state is highlighted.

Spatial and Temporal Changes of Soil Microbial Communities in Field Tomato Production as Affected by Anaerobic Soil Disinfestation

Anaerobic soil disinfestation (ASD) has been demonstrated as an effective alternative to pre-plant chemical soil fumigation (CSF) commonly used to control soilborne pathogens. However, the ASD effects on spatial and temporal changes in soil microbial communities remain poorly understood in production systems with low soilborne disease pressure. The objective of this study was to assess the influence of ASD treatments on soil microbial community composition at different soil depths during the spring tomato production season in Florida. Soil treatments included ASD using 6.9 m3 ha−1 of molasses with 11 Mg ha−1 of composted poultry litter (CPL) (ASD0.5), ASD with 13.9 m3 ha−1 of molasses and 22 Mg ha−1 CPL (ASD1.0), and chemical soil fumigation (CSF) using a mixture of 1,3-dichloropropene and chloropicrin. Soil microbial community composition was measured at soil depths of 0–15 and 15–30 cm using phospholipid fatty acid (PLFA) analysis at 0, 36, 76, and 99 days after transplanting (DAT). Fatty acid methyl esters were categorized into biomarker groups including total microbial biomass (TMB), G+ bacteria (G+), G− bacteria (G−), actinomycetes (Actino), arbuscular mycorrhizal fungi (AMF), protozoa, and general fungi (F). Soil concentrations of G+, Actino, F, AMF, and the ratio of F:bacteria (B) were significantly impacted by a soil treatment × soil depth × sampling time three-way interaction. All the microbial biomarkers were significantly affected by soil treatment × sampling depth two-way interactions except for protozoa and F:B ratio. Concentrations of TMB, Actino, AMF, F, G+, and G− bacteria were significantly increased in ASD treated soils at both 0–15 and 15–30 cm soil depths across different sampling times compared with CSF. In addition, the concentrations of G+ and G− bacteria, AMF, F, and TMB were higher at 0–15 vs. 15–30 cm soil depth under ASD treatments, whereas no soil depth differences were observed in CSF. Discriminant analysis further confirmed that soil microbial community composition was distinctly different in CSF compared with ASD treatments. The soil microbial profile was well-differentiated between the two soil depths under ASD treatments but not in CSF, while the enhancement of PLFA biomarkers by ASD decreased with increasing soil depth.

Mechanism of the antifungal action of chloropicrin fumigation against Panax notoginseng root rot caused by Fusarium solani

Fusarium root rot caused by Fusarium solani severely damages the roots of Panax notoginseng (ginseng) seedlings eventually leading in most cases to the total loss of this valuable crop. Soil fumigants are generally better at controlling soil-borne diseases such as F. solani than fungicides which provide unacceptable control. Therefore, this study aimed at evaluating the efficacy of fumigant chloropicrin (Pic) against F. solani in both laboratory and field. Ultrastructural changes in the mycelia of F. solani in each treatment were indicative of structural changes at the cellular level by transmission electron microscopy (TEM). Bacterial and fungal communities and diversity were targeted for Illumina high-throughput sequencing. Results indicated that chloropicrin inhibited F. solani mycelial growth completely at a concentration of 1.2 μg/l. In addition, ultrastructural studies showed that Pic caused plasmolysis and plasma leakage, indicating that the cell membrane of F. solani was disrupted. In the field trials, Pic at 45 g/m2 yielded an excellent long-term control of target pathogens, and treated plots allowed P. notoginseng plants to maintain vigorous growth compared with the untreated controls. Illumina MiSeq sequencing results revealed that bacterial communities were affected more seriously by Pic than fungi. The beneficial microbes (such as Trichoderma and Chaetomium) gradually increased, and the harmful microbes (such as Fusarium) decreased in fumigated soil. Together, the promotion of beneficial microorganisms and the direct inhibition of F. solani by chloropicrin were the main mechanisms for the prevention and control of soil-borne diseases. Our results provide useful information understanding chloropicrin fumigation against soil-borne disease.

Effects of Granule Size Ranges on Dazomet Degradation and Its Persistence with Different Environmental Factors

Pesticides are considered the most effective way to protect crops. However, irrational use has caused resources waste and environmental pollution. Dazomet (DZ) is a soil fumigant that has been used in many countries for decades, although it has caused occasional crop damage or insufficient control efficacy in some circumstances. In this study, the effects of DZ’s granule size and exposure to various environmental conditions on DZ degradation when used as a fumigant were demonstrated. The degradation rate of DZ was closely related to granule size. The half-life of larger DZ granules was longer than smaller granules with all studied environmental factors. The degradation rate decreased as the DZ usage (90–360 mg/kg) increased and different granule sizes showed the same variation trend. The half-life in each of the five granule size ranges tested decreased significantly as the temperature increased. DZ half-life decreased by 4.67–6.59 times as the temperature increased from 4 to 35 °C. Moreover, DZ usage and temperature affected the half-life of granules >400 and 300–400 μm in diameter significantly more than <100 μm granules. The half-life of all DZ granule sizes was reduced by 13.9–47.4% in alkaline compared to acidic conditions (pH from 9 to 5). Moreover, elevated temperatures could not only promote the production of methyl isothiocyanate (MITC) but accelerate its dissipation. The interactions between DZ granule size, dosage, temperature, and pH provide practical guidance on methods to improve DZ’s efficacy against pests and reduce the risk of phytotoxicity.

Efficiency of calcium cyanamide on the control of tomato soil-borne disease and their impacts on the soil microbial community

Soil-borne diseases resulting from continuous cropping are a huge problem for tomato producers around the world. In this study, differences in the efficiency of soil-borne disease control and the impact on the soil microbial community were investigated between two types of soil fumigation treatments, namely calcium cyanamide (CaCN2) and soil solarization with flooding (SS-F). Soil samples were taken at 0 days after transplantation (DAT), 60 DAT, 150 DAT and 220 DAT during the tomato season. The composition of microbiome after soil fumigation was assessed using heterotrophic plate counts, PCR and MiSeq high-throughput sequencing. CaCN2 and SS-F fumigation significantly reduced the disease incidences, at 4.98% and 11.41%, respectively, while the disease incidence of the CK was 26.62%. In addition, CaCN2 treatment significantly improved the tomato production by 21.65% compared to CK. Under CaCN2 fumigation, the soil microbial community was temporarily inhibited from 0 DAT to 60 DAT, while the bacterial and actinomycete communities recovered at 220 DAT. Remarkably, some potential beneficial microbial genera, e.g., Proteobacteria, Zygomycota phyla, Bradyrhizobium, Arthrobacter, Bacillus, Clostridium, Kaistobacter, Streptomyces, Gemmatimonadetes, and Mortierella, increased at 220 DAT after CaCN2 application. Nevertheless, the pathogenic Acremonium, Alternaria, Fusarium, Penicillium and Verticillium were significantly decreased. However, following SS-F fumigation, the relative abundance of non-soil-borne pathogenic Acremonium and Alternaria increased by 294.27% and 189.77%, respectively, compared to that in the CK. While the ratio of potential beneficial Trichoderma decreased, the bacterial composition of the SS-F soil at 220 DAT was nearly identical to that of the CK. In addition, a redundancy analysis showed that CaCN2 treatment increased the potential of hydrogen (pH) and the organic matter (OM), available phosphorus (AP), and available potassium (AK) contents, which were positively correlated with Bradyrhizobium, Rhodanobacter, Bacillus and Mycobacterium communities and negatively correlated with disease incidence. In conclusion, CaCN2 enhanced soil fertility, reduced the presence of soil pathogens, increased the relative abundance of potential beneficial bacteria and fungi and improved tomato yields.

Assessment of using solid residues of fish for treating soil by the biosolarization technique as an alternative to soil fumigation

Organic food-waste is an ever growing environmental, economic, and social problem. One way to address this problem is to find new ways to valorise food waste in a circular economical manner. In this study, the concept of separating food from waste at its source in eateries was applied to obtain separated fish waste residues from the general waste of our university's canteen. This study is the first known attempt to use separated fish residues as soil amendments for soil biosolarization (SBS), a soil treatment method which is an environment-friendly alternative to chemical fumigation of soil. In this study a unique laboratory simulation system was used which mimics the conditions of field temperature, monitors the soil respiration and the follows the temporal profile of emitted volatile organic compounds. The fish waste residues were used as soil amendment in 2% wt. and the results showed elevated levels of aerobic soil respiration without unwanted CH4 emission. A different profile of volatile organic compounds (VOCs) was also identified in the soils treated with fish residues. The profile of volatiles found in the soil with fish residues included changes in the amounts of compounds such as: Dimethylsulfide, Methanethiol and C9-aldehydes that have been found to supress soilborne plant pathogens. This is the first indication that VOCs can be used as indicators for the SBS process. Greenhouse studies and analyses of soils treated by fish residues showed no soil residual phytotoxicity affecting later growth of lettuce seedlings while not hindering the herbicidal effect of SBS on unwanted Bidens (Bidens pilosa) weeds. These results indicate that fish waste residues can be used as a soil amendment in the SBS process.

Top-down and bottom-up estimates of anthropogenic methyl bromide emissions from eastern China

Abstract. Methyl bromide (CH3Br) is a potent ozone-depleting substance (ODS) that has both natural and anthropogenic sources. CH3Br has been used mainly for preplant soil fumigation, post-harvest grain and timber fumigation, and structural fumigation. Most non-quarantine and pre-shipment (non-QPS) uses were phased out by 2005 for non-Article 5 (developed) countries and by 2015 for Article 5 (developing) countries under the Montreal Protocol on Substances that Deplete the Ozone Layer; some uses have continued under critical-use exemptions (CUEs). Under the protocol, individual nations are required to report annual data on CH3Br production and consumption for quarantine–pre-shipment (QPS) uses, non-QPS uses, and CUEs to the United Nations Environment Programme (UNEP). In this study, we analyzed high-precision, in situ measurements of atmospheric mole fractions of CH3Br obtained at the Gosan station on Jeju Island, South Korea, from 2008 to 2019. The background mole fractions of CH3Br in the atmosphere at Gosan declined from 8.5±0.8 ppt (parts per trillion) in 2008 to 7.4±0.6 ppt in 2019 at a rate of -0.13±0.02 ppt yr−1. At Gosan, we also observed periods of persistent mole fractions (pollution events) elevated above the decreasing background in continental air masses from China. Statistical back-trajectory analyses showed that these pollution events are predominantly traced back to CH3Br emissions from eastern China. Using an interspecies correlation (ISC) method with the reference trace species CFC-11 (CCl3F), we estimate anthropogenic CH3Br emissions from eastern China at an average of 4.1±1.3 Gg yr−1 in 2008–2019, approximately 2.9±1.3 Gg yr−1 higher than the bottom-up emission estimates reported to UNEP. Possible non-fumigation CH3Br sources – rapeseed production and biomass burning – were assessed, and it was found that the discrepancy is most likely due to unreported or incorrectly reported QPS and non-QPS fumigation uses. These unreported anthropogenic emissions of CH3Br are confined to eastern China and account for 30 %–40 % of anthropogenic global CH3Br emissions. They are likely due to delays in the introduction of CH3Br alternatives, such as sulfuryl fluoride (SO2F2), heat, and irradiation, and a possible lack of industry awareness of the need for regulation of CH3Br production and use.

Effect of Biofumigation on Population Densities of Pratylenchus spp. and Verticillium spp. and Potato Yield in Eastern Canada

Biofumigation has been proposed as an alternative to soil fumigation to manage soil-borne diseases including potato early dying disease complex (PED). This study examined the potential of using brown mustard (Mustard juncea) biofumigation to manage PED under rain-fed potato production in New Brunswick, Canada in two trials between 2017 and 2020 in comparison with chloropicrin fumigation and a conventional barley rotation. Biofumigation increased yield in one trial, but not in a second trial where the potato crop experienced severe drought, whereas chloropicrin fumigation increased yield in both trials. Biofumigation was effective in suppressing root-lesion nematode (RLN, Pratylenchus spp.) counts in both trials, but was ineffective in suppressing V. dahliae population density. Chloropicrin fumigation was effective in suppressing RLN counts and V. dahliae population density only in the hill where injected, but the effect was short-lived as the population density of V. dahliae in the hill increased to the level of the control in one potato growing season. Biofumigation may be an alternative to chloropicrin fumigation in managing PED, particularly in fields with high RLN population but relatively low Verticillium population density. However, neither biofumigation nor fumigation used alone may be sustainable in the short-term potato rotations commonly used in New Brunswick, and additional beneficial practices are required to sustain productivity in the long-term.

Activation effect of soil available nitrogen, manganese and cobalt after addition of different fumigants

Soil fumigation is a well-established method for controlling soil-borne diseases. Better quantification of soil available nitrogen and trace elements may provide recommendations on the safe and effective application of soil fumigants. The effects of four fumigants on the available soil nitrogen and trace elements (including Mn, Co, Ni, Cu, Zn and Cd) were investigated in the laboratory incubation with agricultural soil. The results showed that soil fumigation increased soil mineral nitrogen and available Mn, Co, Ni. A significant increase of soil NH4 +-N and available Mn was observed in all fumigation treatments. Chloropicrin treatments showed the largest increase of soil NH4 +-N. In addition, chloropicrin and dazomet increased Mn and Co to a greater extent than dimethyl disulfide and 1,3-dichloropropene in soil. Available Mn content after chloropicrin fumigation has increased by 2.2 times compared with control treatments, and available Co content in dazomet treatments is also 2.8 times more than untreated control. In fumigated soil, the steady increase of soil available elements is beneficial to nutrient uptake by plants. Soil fumigation created an activation effect on soil mineral nitrogen and available trace elements, which may increase their bioavailability to plants and promote plant growth.

EVALUATION OF TRICHODERMA HARZIANUM AND SOLARIZATION FOR THE MANAGEMENT OF FUSARIUM WILT AND SOUTHERN BLIGHT DISEASES OF TOMATO

The efficacy of Trichoderma harzianum and soil solarization was determined solely and in combination for the management of fusarium wilt and southern blight diseases of tomato. The treatments comprised two concentrations of T. harzianum, (104 and 107 spore/ml), two levels of solarization, (one and two months), and the interaction between solarization and T. harzianum. Formaldehyde, a soil fumigant was the standard check and the control consisted of untreated soil. The causal pathogen of the diseases was separately inoculated at 106 spore/ml into wide surfaced (410mm diameter) plastic pots of 15 liters containing 15kg of soil. Clear transparent polythene of 0.05mm thickness was used to achieve solarization. Local tomato cultivar, Hausa scissors, was the test crop and it was sown in nursery tray on a sterile nutrient-rich soil, irrigated with equal water volume and transplanted after 21 days into the treated soil. The pots were placed in the open field throughout the growing season. The experiment was arranged in a randomized complete block design with three replications for each treatment. Data collected were subjected to statistical analysis and mean separation using Minitab software. The interaction of T. harzianum at 107 spore/ml and two months solarization significantly reduced the incidence and severity index of the two diseases, increased plant growth parameters, yield quality and quantity and enhanced fruit shelf life and may be recommended for the management of fusarium wilt and southern blight diseases of tomatoes than their application as sole management agents.

Biochar significantly reduced fumigant emissions and benefited germination and plant growth under field conditions

Soil fumigation continues to play an important role in soil disinfection, but tools to significantly reduce emissions while providing environmental benefits (e.g., biochar) are lacking. The objective of this study was to determine the effects of biochar products on fumigant 1,3-dichloropropene (1,3-D) and chloropicrin (CP) emissions, their distribution and persistence in soil, nematode control, and potential toxicity to plants in a field trial. Treatments included three biochar products [two derived from almond shells (ASB) at either 550 or 900 °C pyrolysis temperature and one from coconut shells (CSB) at 550 °C] at 30 and 60 t ha−1, a surface covering with a low permeability film (TIF), and no surface covering (control). A mixture of 1,3-D (∼65%) and CP (∼35%) was injected to ∼60 cm soil depth at a combined rate of 640 kg ha−1. All biochar treatments significantly reduced emissions by 38–100% compared to the control. The ASB (900 °C) at both rates reduced emissions as effectively as the TIF (by 99–100%). Both fumigant emission reduction and residue in surface soil were positively correlated with biochar's adsorption capacity while cucumber germination rate and dry biomass were negatively correlated with residual fumigant concentrations in surface soil. This research demonstrated the potential and benefits of using biochar produced from local orchard feedstocks to control fumigant emissions. Additional research is needed to maximize the benefits of biochar on fumigant emission reductions without impacting plant growth.

Variations of soil phosphatase activity and phosphorus fractions in ginger fields exposed to different years of chloropicrin fumigation

PurposeAlthough soil fumigation efficiently controls soil-borne diseases, the effects of repeated soil fumigation on soil phosphorus (P) cycling are still largely unknown.MethodsIn this study we conducted a field experiment to explore soil phosphorus availability in ginger fields with 0, 3, and 7 years (F0, F3, and F7) of annual chloropicrin (CP) fumigation history in Shandong Province of China. Soil samples (0–20 cm) were collected at four different times in 2019. Ginger yield, soil phosphatase (acid and alkaline) activities, and soil P fractions were measured.ResultsResults showed that ginger rhizome yield was similar in F0 and F3 (70.0 t ha−1), but significantly lower in F7 (37.5 t ha−1). The acid phosphatase (AiP) activity was significantly higher in F0, while alkaline phosphatase (AlP) activity was the highest in F3. There was no significant difference in the available P (resin-P + NaHCO3-P + NaOH-P) between F0 and F7, with 33.6 to 57.5% of total P (TP), while the available P was significantly lower in F3, being less than 30% of TP. Redundancy analysis (RDA) showed that the highest pH values in F3 contributed to the lowest soil P availability there. AiP activities showed highly positive effects on the soil labile P contents.ConclusionResults suggested that more P fertilizers are needed after 3 years of CP fumigation to avoid soil P deficiency for ginger growth. The death of ginger became the main limitation for ginger production after 7 years of CP fumigation, at which time, comprehensive agricultural practices should be considered to control ginger soil-borne diseases.

Organic fertilizers activate soil enzyme activities and promote the recovery of soil beneficial microorganisms after dazomet fumigation

Soil fumigation can reduce the impact of soil-borne diseases, weeds and insect pests on commercial crop production. Unfortunately, fumigation also kills beneficial microorganisms. In this study, we explored if dazomet fumigation could be used in combination with organic fertilizers (silicon fertilizer, potassium humate organic fertilizer, Bacillus microbial fertilizer, and mixtures of the last two) to reduce its impact on soil beneficial microorganisms. We evaluated the effects of adding these fertilizers after fumigation on the soil's physical and chemical properties and its enzyme activities, as well as its effects on the soil microbial communities under continuous production for >20 years. We found that fertilizers applied after fumigation increased the soil nitrate nitrogen content by 11.6%–29.4%, increased available potassium content by 5.6%–26.3% and increased organic matter content by 28.5%–48.8%. In addition, soil conductivity and water content increased significantly by 8.2%–26.5% and 8.0%–16.0%, respectively. The activities of soil catalase and soil sucrase were significantly increased by 6.2%–15.9% and 133.1%–238.5%, respectively. High-throughput DNA sequencing showed that fertilizers applied after fumigation increased the relative abundance of the phyla Proteobacteria, Actinobacteria and Ascomycota; and the genera Sphingomonas, Chaetomium and Mortierella. Silicon fertilizer applied after fumigation has the most significant promotion effect on soil micro-ecological health. The results showed that organic fertilizers applied after fumigation can improve the soil's fertility, activate soil enzyme activities and promote the recovery of soil beneficial microorganisms, which are all factors that improve crop quality and yield.

Quantifying the effects of anaerobic soil disinfestation and other biological soil management strategies on nitrous oxide emissions from raised bed plasticulture tomato production.

Soilborne pests are a major obstacle that must be overcome for the production of horticultural crops. Methyl bromide (MBr) was an effective preplanting soil broad-spectrum biocide, but its use has been banned due to its role in depleting the ozone layer. As a result, sustainable alternative methods for controlling soilborne pathogens and pests are needed. Nitrous oxide (N2 O) emissions are of concern in crop production due to the role of N2 O as a greenhouse gas. Agricultural lands are known sources for emission of N2 O into the atmosphere. Emissions are related to many environmental factors as well as fertilization and fumigation practices. This study evaluated the influence of different alternatives to MBr on N2 O emissions throughout a tomato production season in two locations representative of southern and northern Florida. We evaluated eight soil management practices, including (a) untreated controls; (b) chemical soil fumigation; (c) anaerobic soil disinfestation using molasses (M) + composted poultry litter and (d and e) M + composted yard waste (CYW, at two rates); (f) Soil Symphony Amendment (SSA), a commercially available mix of microbes and nutrients; (g) CYW alone; and (h) CYW + SSA. Nitrous oxide emissions were measured throughout the cropping season. Emissions were highest on the day of planting (Day 21), ranging from 213 to 1,878μg m-2 h-1 , likely due to the release of N2 O that had accumulated under the totally impermeable film when it was punctured for planting. However, statistical significance varied between sites. Estimated cumulative emissions of N2 O throughout the production season ranged from 1.3 to 4.8kg N2 O-N ha-1 .

Management of Chrysanthemum Verticillium Wilt through VIF Soil Mulching Combined with Fumigation at Label and Reduced Rates

Pre-plant soil fumigation for managing soilborne pathogens is practiced worldwide in several intensive ornamental and vegetable production areas. However, global regulations are currently implemented to minimize use of these chemicals. According to these policies, the efficacies of dazomet (DZ, Basamid Granulat®) applied alone to soil and under virtually impermeable film (VIF) at reduced (247.5 kg ha−1 a.i.) and label (495 kg ha−1 a.i.) rates were assessed in managing natural infections of Verticillium wilt and in reducing yield losses on greenhouse chrysanthemum plantations in two trials carried out in the 2012 and 2013 seasons. The performances of this fumigant at a lower rate combined with VIF application were also compared with standardized metam-sodium (MS, Divapan®) fumigation applied at 510 L ha−1 a.i. under VIF and application of dazomet at label rate alone to bare soil. Temperatures were monitored at 20-cm depth in plots covered (VIF) throughout the entire fumigation period. Although all fumigation treatments significantly reduced the infection level by V. dahliae on chrysanthemum, the performances differed among them. DZ and MS applied at label rates under VIF showed the most effectiveness in controlling Verticillium wilt of chrysanthemum. However, DZ applied to soil at a low rate under VIF mulching showed good performances, which were always better than application of DZ alone at label rate to bare soil. Moreover, when combining a reduced rate of DZ with VIF mulching, chrysanthemum yield losses were reduced in a similar manner to the label rate application under VIF. Based on these findings, DZ application at a reduced rate could be suggested on a large scale to prevent Verticillium attacks on chrysanthemum cultivated on a protected crop. Future studies should be performed to verify the ability of VIF application in inducing high temperatures in soil and above all in enhancing performances of soil fumigation at low rates performed with other natural and chemical sterilants.

Following the route of veterinary antibiotics tiamulin and tilmicosin from livestock farms to agricultural soils

Veterinary antibiotics (VAs) are not completely metabolized in the animal body. Hence, when animal excretes are used as soil manures, VA residues are dispersed with potential implications for environmental quality and human health. We studied the persistence of tiamulin (TIA) and tilmicosin (TLM) along their route from pig administration to fecal excretion and to agricultural soils. TLM was detected in feces at levels folds higher (4.27–749.6 μg g-1) than TIA (0.55–5.99 μg g-1). Different administration regimes (feed or water) showed different excretion patterns and residual levels for TIA and TLM, respectively. TIA and TLM (0.5, 5 and 50 μg g-1) dissipated gradually from feces when stored at ambient conditions (DT50 5.85–35.9 and 23.5–49.8 days respectively), while they persisted longer during anaerobic digestion (DT90 >365 days) with biomethanation being adversely affected at VA levels > 5 μg g-1. When applied directly in soils, TLM was more persistent than TIA with soil fumigation extending their persistence suggesting microbial degradation, while soil application through feces increased their persistence, probably due to increased sorption to the fecal organic matter. The use of TIA- and TLM-contaminated feces as manures is expected to lead to VAs dispersal with unexplored consequences for the environment and human health.

The remediation effects of microbial organic fertilizer on soil microorganisms after chloropicrin fumigation

Soil fumigation with chloropicrin (CP) is an effective means of overcoming continuous cropping obstacles (CCO) in Panax notoginseng and improving its yield and quality. CP fumigation can change the microbial community of soil. Therefore, a key step after CP fumigation is the rapid restoration of soil microorganisms and the promotion of beneficial microorganism proliferation as the dominant flora. In this study, continuously cropped soil of P. notoginseng was fumigated with CP, and general organic fertilizer (GOF) or microbial organic fertilizer (MOF) was used to restore soil microorganisms after fumigation. Soil physical and chemical properties, soil microorganisms, and quality of P. notoginseng were investigated. The application of MOF and GOF after CP fumigation promoted increases in soil nitrogen (9.88% and 8.21%, respectively), phosphorus (21.39% and 11.57%, respectively), potassium (7.99% and 2.75%, respectively), and the quality of P. notoginseng; it also promoted the accumulation of saponins in the main roots (23.62% and 9.12%, respectively). Application of MOF and GOF can restore the diversity of microorganisms in the soil. MOF increased the relative abundance of the beneficial soil microorganisms Glomeromycota, Mortierellomycota, Humicola and Bacillus, thereby lowering the relative abundance of the harmful Ascomycota and Fusarium relative to GOF. In summary, CP fumigation reduces the diversity of microorganisms in the soil. The addition of organic fertilizer can promote microbial diversity and increase the relative abundance of beneficial species. Moreover, the promotion effect of MOF is better than that of GOF, thereby improving soil fertility and ultimately promoting the quality and yield of P. notoginseng.

Speciation of soil trace elements in different fumigated soils#

AbstractBackgroundSoil fumigation is widely used as an effective way to control soil‐borne diseases and increase crop yield. Fumigants may also affect the bioavailability and mobility of soil trace elements (STEs) due to the inhibitory and biocidal effects of soil microorganisms.AimsQuantification of STEs fractions after fumigation would help us in understanding the role of fumigants on soil environment and provide valuable evidence on the explanation of the “fertilizer effect” of soil fumigants. The overall objective was to quantify the effects of soil fumigation on three main chemical fractions of nine STEs.MethodsEffects of chloropicrin (PIC), dimethyl disulfide (DMDS), dazomet (DZ) on STEs were studied in three soils with standard and high dosages of fumigants. STEs fractions were detected using a modified Community Bureau of Reference three‐stage sequential extraction procedure.ResultsResults were evident in three farmland soils: (1) Among the nine elements, three fumigants had a significant impact on Mn and Co elements. Soils had a great complement to the bioavailable Mn and Co after fumigation. The content of Mn and Co in F1, the most available and transportable form for plants, significantly increased after fumigation with PIC, DMDS, and DZ. (2) Soil fumigation has an impact on Mn, Co, and other trace elements due to the process of Mn oxidation changed.ConclusionsOur study suggested that the complement of bioavailable Mn and Co could be an important factor to promote plant growth and increase crop yield after soil fumigation.

Bacterial Diversity Change after Soil Fumigation and its Effect on the Population of Root-Knot Nematode

Bacterial Diversity Change after Soil Fumigation and its Effect on the Population of Root-Knot Nematode