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Dimethyl disulfide (DMDS), a promising alternative fumigant, has been highly desirable for excellent management of soil pests and diseases. However, high volatility and moderate toxicity of this sulfide limit its application. To address these issues, a novel controlled release formulation of DMDS was proposed employing multiple emulsions and polyurea microcapsules (DMDS@MEs-MCs). The successful combination of the two technologies was revealed by confocal laser scanning microscopy, scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared. According to the multiple encapsulation structure, the encapsulation efficiency decreased by only 3.13% after thermal storage, compared with a 15.21% decrease of microcapsules made with only a monolayer film. DMDS@MEs-MCs could effectively control the release of active ingredient, which increased applicator and environmental safety during application. Moreover, it could be facilely used by spraying and drip irrigation instead of a special fumigation device. The innovative formulation exhibited better control efficacy on soil pathogens (Fusarium spp. and Phytophthora spp.) and root-knot nematodes (Meloidogyne spp.) than DMDS technical concentration (DMDS TC). In addition, it did not inhibit seed germination after 10 days when the plastic film was removed from the fumigated soil. This method appears to be of broad interest for the development of safe and handy fumigant application.

A highly chemoselective and enantioselective cyclization of γ-chloroenals and ketimines has been developed to synthesize enantiopure 3,4-2H-pyrindin-2-ones as major products. It is proposed that the intermediate enone IV reacted with an enamine to proceed with a [3 + 3] cyclization, thereby affording 3,4-2H-pyrindin-2-ones as major products. Interestingly, the addition of LiCl promoted the formation of the enamine and accelerated the [3 + 3] cyclization. In contrast, the [4 + 2] cycloaddition reaction between the intermediate vinyl enolate VIII and an imine offered 5,6-2H-pyrindin-2-ones as minor products. This protocol represents the exceptional potential of N-heterocyclic carbene (NHC) catalytic reactions in accessing biologically active 3,4-2H-pyrindin-2-one derivatives in good yield with high chemoselectivities and excellent enantiomeric purities.

The soil phosphorus (P) cycle and P transformation are largely driven by the soil bacterial microbial community. However, little is known about the effects of dazomet (DZ) soil fumigation on soil P and soil microbial communities associated with P transformation. This research investigated P released from three farm soils as a result of DZ fumigation and changes in enzyme activity, gene abundance, and the encoding alkaline phosphatase PhoD microbial community. After DZ fumigation, we observed a briefly significant increase in the available P and the active P fractionation. The soil ALP activity, 16s rRNA abundance, and the phoD gene decreased significantly after DZ fumigation. The abundance and diversity of phoD-harboring microbes also decreased shortly after fumigation, increased significantly 14-28 days later, and then decreased again toward the end of the experimental period of 86 days. The shared OTUs between treatments became fewer with increasing time after fumigation. The changes in available P and the active P fractionation after DZ fumigation were significantly correlated with the abundance of the dominant phoD-harboring microbes. DZ fumigation promoted P mineralization in these farm soils and changed the composition of phoD-harboring microbial communities, which will benefit crops able to absorb and use P.

The prevention and control of root-knot nematode disease is a worldwide challenge and there are not many varieties of pesticides for nematode control. To meet the huge market demand, the development of new nematicides is urgently needed. The lethal effects of soil fumigant dimethyl disulfide (DMDS) mixed with the chemical compounds copper sulfate (CuSO4) and ammonium bicarbonate (NH4HCO3) on Meloidogyne incognita were tested using the immersion method. The results showed that the LC50 of DMDS, CuSO4, and NH4HCO3 on the second stage juveniles (J2) of M. incognita were 19.28, 187.42, and 213.49 mg/L, respectively. The lethal effect on J2 were enhanced with the combination of DMDS and CuSO4 or NH4HCO3. The compound uses of DMDS (2.5 mg/L) and CuSO4 (46.58 mg/L) or NH4HCO3 (80.25 mg/L) have obvious synergistic effects on the control of M. incognita, with corrected mortalities of 97.09% and 94.00%, respectively. The synergistic effect of fumigant and chemical compounds on M. incognita was investigated to provide a new concept for the control of root-knot nematode disease.

Soil fumigants aim to control soil-borne diseases below levels that affect economic crop production, but their use also reduces the abundance of beneficial microorganisms. Previous studies have shown that adding various types of fertilizers to soil after fumigation can reshape the soil microbial community and regulate crop growth. We fumigated soil with dazomet (DZ) that had been cropped continuously for more than 20 years. After fumigation we applied silicon fertilizer, potassium humate organic fertilizer, Bacillus microbial fertilizer or a mixture of the last two. We studied the effects of different fertilizers treatments on the soil's physicochemical properties, enzyme activities, key soil pathogens and beneficial microbes. We found that fertilizers applied after fumigation promoted soil beneficial microorganisms (such as Fimicutes, Chloroflexi, Bacillus and Actinomadura) restoration; increased Fusarium and Phytophthora pathogen mortality, the content of ammonium nitrogen, sucrase enzyme activity; and increased strawberry fruit yield. A significant increase in strawberry yield was positively correlated with increases in beneficial microorganisms such as Gemmatimonadota, Firmicutes, Bacillus and Flavisolibacter. We concluded that organic fertilizer applied after fumigation significantly increased the number of beneficial microorganisms, improved the physicochemical properties of the soil, increased soil enzyme activities, inhibited the growth of soil pathogens to increase strawberry fruit yield. In summary, organic fertilizer activated soil beneficial microorganisms after soil fumigation, promoted soil health, and increased strawberry fruit yield.

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.

Anaerobic soil disinfestation (ASD), as a bio-fumigation technology, has been developed to control soil-borne pests. There is increasing evidence showing that carbon sources and cover tarps play an important role in the ASD suppression of soil-borne pests, but little is known about the effect of composted chicken manure (CCM) and totally impermeable films (TIF) against soil-borne pests in the strawberry production system. In experiments, the colonies of Fusarium spp. and Phytophthora spp., which are recognized to cause strawberry soil-borne diseases, decreased significantly after ASD. The soil promoted a significant increase in ammonium nitrogen, nitrate-nitrogen and organic matter, but a decrease in oxidation-reduction potential after ASD. Besides, the strawberry plant height, stem thickness and yield were significantly higher than in the non-amended soil. Compared to the untreated control, ASD, both at 6 and 12 ton/ha of CCM, significantly (p = 0.05) increased strawberry marketable yield and income. The economic benefit could be due to the suppression of soil-borne diseases and the improvement of soil nutrition. The soil bacterial and fungal diversity and richness increased after soil fumigation. The increased presence of biological control agents led to the suppression of soil-borne pathogens. In summary, ASD with CCM amendments could be applied in pre-plant fumigation to control strawberry soil-borne pests, strengthen soil fertility, improve crop yield and increase growers&rsquo, income.

A highly chemoselective and enantioselective cyclization of γ-chloroenals and ketimines has been developed to synthesize enantiopure 3,4-2

The soil phosphorus (P) cycle and P transformation are largely driven by the soil bacterial microbial community. However, little is known about the effects of dazomet (DZ) soil fumigation on soil P and soil microbial communities associated with P transformation. This research investigated P released from three farm soils as a result of DZ fumigation and changes in enzyme activity, gene abundance, and the encoding alkaline phosphatase

Chloropicrin (CP) is the most commonly used soil fumigant worldwide. Although CP effectively controls soilborne pathogens, it is also detrimental to beneficial soil microorganisms unless measures can be put in place to protect them from the effects of fumigation. In this study, we evaluated the ability of biochar made from the invasive weed Eupatorium adenophorum to mitigate the effects of CP fumigation on beneficial species. Our results showed that the addition of biochar to the soil effectively reduced the detrimental effects of CP on beneficial species and their ecological functions. Biochar added to CP-fumigated soil shortened the time to 28–84 days for microbial diversity and nitrogen cycle functions to be restored to unfumigated levels. At the same time, the inorganic nitrogen (NH4+-N, NO3−-N) content and N2O production potential level in CP-fumigated soil returned to unfumigated levels relatively quickly, which showed that nitrogen metabolism improved with the addition of biochar. The mitigation effect of biochar in CP-fumigated soil was more evident at higher biochar amendment rates. Our results suggest that the addition of biochar to CP-fumigated soil significantly reduced the impact of CP on beneficial species and their ecological functions, and significantly shortened the time for beneficial species to recover to pre-fumigation levels. Field research is required to determine biochar's ability to mitigate the impact of CP and other fumigants on beneficial species and to quantify its benefits on crop quality and yield.

The mechanism of N2O production following chloropicrin (CP) fumigation was investigated in this study. Our results showed that CP fumigation increased N2O production from 23 to 25 times in comparison with the control and significantly decreased the abundance of 16S rRNA and N-cycling functional genes. CP also decreased the soil bacterial diversity and caused a shift in the community composition. The N2O emissions in fumigated soil were significantly correlated with soil environmental factors (NH4+, dissolved amino acid, microbial biomass nitrogen, and NO3-) but were not correlated with the abundance of functional genes. Metatranscriptomes and dual-label 15N-18O isotope analysis revealed that CP fumigation inhibited the expression of gene families involved in N2O production and sink processes and shifted the main pathway of N2O production from nitrification to denitrification. These results provided useful information for environmental safety assessments of CP in China, to improve our understanding of the N-cycling pathways in fumigated soils.

Chloropicrin (Pic) and dazomet (DZ) are effective soil fumigants that are often used to reduce soil-borne pathogens that would otherwise reduce crop yield. As Pic is scheduled to be banned, we investigated whether its consumption could be halved by alternating it with DZ. We observed that Pic alternated with DZ increased the soil NH4+-N content by 28.74–47.07 times, increased available potassium content by 40.80%−46.81% and increased electrical conductivity by 39.23%−85.81%. It generally improved the soil’s physicochemical properties. High-throughput DNA sequencing showed that Pic alternated with DZ changed the taxonomic diversity of bacteria and fungi by increasing the relative abundance of Bacillus and Firmicutes, and by decreasing Proteobacteria, Acidobacteria and Sphingomonas. Moreover, Pic alternated with DZ can inhibit key soil pathogens by more than 90% and significantly increased strawberry yield by 78.22%−116.12%. In terms of strawberry production, we recommend using DZ in the first year and Pic in the second year. Our results showed significant ecological benefit and yield benefit when Pic consumption was halved by alternating it with DZ.

Anaerobic soil disinfestation (ASD) is widely used to control soilborne diseases in organic crop production. The effect of ASD used different sealed films on soilborne pathogens and strawberry growth was evaluated in two laboratory studies and two field trials. Under maltose as carbon sources, 28 &deg, C temperature and 30% of soil moisture optimal conditions ASD decreased Fusarium spp. and Phytophthora spp. by 100%. ASD used maltose as an organic amendment and sealed with totally impermeable film (TIF) obtained the highest suppression (&gt, 96%) against Fusarium spp. and Phytophthora spp. (&gt, 91%). According to the laboratory results, the efficacy of ASD utilizing 6 or 9 t/ha maltose and sealing with TIF was evaluated and compared with reference treatment with chloropicrin (Pic) or solarization (Sol) in the field trials. Compared with the untreated soil, ASD treatments greatly reduced the pathogenic population of Fusarium spp. and Phytophthora spp., and successfully controlled the damage of fusarium wilt with evidence of lower mortality (6%). ASD significantly increased soil nutrition promoted plant growth and increased strawberry yield, which was similar as the Pic, but better than Sol treatment. The analyzed fungal and bacterial microbiota did not show significant differences in the taxonomic richness and diversity between the compared treatments. Nevertheless, the abundance of some bacterial and fungal taxa tended to change between treated. The evidence showed that adding maltose and sealing TIF for ASD has the potential to replace Pic for pathogen control in commercial strawberry production.

The mechanism of N

Dazomet (3,5-dimethyl-1,3,5-thiadiazinane-2-thione) is widely used as a soil fumigant for controlling soil-borne diseases and pests in China and other agricultural countries. The active ingredient of dazomet is its degradation product, methyl isothiocyanate. Little is known about the environmental conditions that affect the degradation of dazomet in soil. In this study, we conducted laboratory incubation experiments to test the effects of several environmental factors, including soil texture, water content, temperature, pH, and soil amendments, such as chicken manure or urea fertilizer, on the decomposition of dazomet. Results showed that dazomet degradation in soil is an abiotic process strongly dependent on soil texture, water content, temperature, and pH. Decomposition rates differed greatly in various soils, depending mainly on soil physicochemical properties such as pH and organic matter content. The degradation rate increased by 15 to 24 times and by 16 to 37 times when soil temperature increased from 5 to 45°C, and water content increased from 10 to 30%, respectively. Dazomet degraded faster in alkaline versus acidic soil. Both chicken manure and urea fertilizer moderately slowed dazomet degradation. Dazomet was degraded in soil mainly by hydrolysis. The results of our study contribute to a better understanding of the environmental behavior of dazomet, potentially leading to its more efficient, safe, profitable, and effective use by farmers.

The gelatin capsule (gel cap) formulation of 1,3-dichloropropene (1,3-D) is a new concept to reduce the environmental release, transport, and hazard potential of the use of 1,3-D to control soilborne diseases and nematodes. The objective of this study is to evaluate the biological efficacy of the 1,3-D gel cap formulation under laboratory and greenhouse trial conditions. Greenhouse experiments were carried out in suburbs of Beijing and Hebei Province of China in 2007 and 2008, focused mainly on tomato and Bellis perennis L. (daisy) crops. Results showed that 1,3-D gel cap application at a rate of 16.8 g of active ingredient m(-2) was as effective as 1,3-D liquid injection treatment. Crop yields in plots treated with 1,3-D gel cap and 1,3-D liquid were significantly higher than those in untreated control. The present study confirms that the 1,3-D gel cap formulation is a promising new formulation with good field efficacy.

Dynamics of a semiconductor laser subject to moderate optical feedback operating in the low-frequency fluctuation regime is numerically investigated. Multimode Lang-Kobayashi (LK) equations show that the low-frequency intensity dropout including the total intensity and sub-modes intensity is accompanied by sudden dropout simultaneously, which is in good agreement with experimental observation. The power fluctuation is quite annoying in practical applications, therefore it becomes important to study the mechanism of power fluctuation. It is also shown that many factors, such as spontaneous emission noise and feedback parameter, may influence power fluctuation larger than previously expected.