氯化苦在表层土壤的挥发运移实验及数值模拟

在土柱通风的挥发运移实验中,当孔隙流速为0.0131cm·s-1时,经2.5d后土壤熏蒸剂氯化苦在表层土的含量由200mg·kg-1降至一半,9d后基本不残留;将气速提高至0.0210cm·s-1后,挥发半衰期缩短为1d,共需5d即可全部挥发。本文通过一维传质模型的数值模拟可以预测挥发效果,在前期和中期与实验结果吻合较好,但在后期产生较大偏差。     

熏蒸剂对土传病原菌的防效和对土壤微生物群落的影响

为了明确熏蒸剂对2种土传病原菌的持续防效以及对土壤微生物群落的恢复影响,采用选择性培养基分离计数、土壤微生物量碳、土壤微生物量氮和BIOLOG的方法研究氯化苦(chloropicrin, PIC) 40 mg/kg、二甲基二硫(dimethyl disulfide, DMDS) 40 mg/kg以及PIC+DMDS(8+32) mg/kg对镰孢菌属(Fusarium spp.)、疫霉菌属(Phytophthora spp.)的长期抑制效果,以及对土壤微生物群落的影响。结果表明,恢复培养98天时,PIC 40 mg/kg对镰孢菌属和疫霉菌属仍然有很好的抑制作用,抑制率分别维持在98%、55%以上,而该处理对土壤微生物的影响已恢复到对照水平。与DMDS(40 mg/kg)相比,PIC+DMDS[(8+32) mg/kg]处理对镰孢菌属和疫霉菌属的持续抑制作用都有很大提高。在恢复培养28天时,PIC+DMDS[(8+32) mg/kg]处理对土壤微生物群落多样性的影响已恢复到对照水平。DMDS(40 mg/kg)处理对镰孢菌属和疫霉菌属的抑制效果较差,但该处理对土壤微生物量和土壤微生物群落影响也相应较小。     

Contrasting resilience of soil microbial biomass,microbial diversity and ammonification enzymes under three applied soil fumigants

Fumigation is a widely applied approach to mitigate the soil-borne diseases. However, the potential effects of currently applied fumigants on ammonification remain unclear. An 84-day incubation experiment was conducted based on nonfumigated soil(CK) and fumigated soil using three common fumigants, i.e., chloropicrin(CP), 1,3-dichloropropene(1,3-D), and metam sodium(MS). The results showed that, the three fumigants all decreased the microbial C, and the largest reduction(84.7%) occurred with the application of CP. After fumigation, the microbial diversity in the CP treatment rapidly recovered, but that in the 1,3-D treatment decreased and did not recover by the end of the experiment. The application of MS showed no impact on the microbial diversity during the assay, indicating that significantly different microbial diversity can be achieved by choosing different fumigants. Furthermore, the three fumigants showed divergent effects on the enzymes involved in ammonification. The analysis showed that the enzyme variation with CP application was mainly associated with the changed microbial C and N(P0.05), and not with the microbial community, which was different from the observed effects of 1,3-D or MS application. In addition, the soil quality index showed that CP was still significantly harmful at the end of incubation compared with the good resilience of MS, indicating that CP may not be a suitable fumigant.     

Effect of chloropicrin fumigation on microbial communities evaluated by community-level physiological profile and the resistance against fusarium wilt

Different microbial communities characterized by the Biolog pattern were developed in the rhizosphere of radish grown on a rockwool hydroponic system treated with chloropicrinfumigated and non-fumigated soil suspensions although no differences were observed in their viable counts. Different microbial communities also were developed in the rhizosphere and non-rhizosphere. After the development of microbial communities in the rhizosphere, bud cells of Fusarium oxysporum that causes vascular wilt of radish plants were inoculated, and disease symptoms were examined. Treatment with the non-fumigated soil suspension was much more effective than that with the fumigated one in controlling the disease, indicating that the Biolog method might be applicable to characterize microbial communities that control the disease caused by F. oxysporum.     

Chemical Soil Fumigation for Strawberry Nursery in Jalisco (Mexico): 2013–2014 Results of Semarnat/Unido Project

ABSTRACT

We evaluated the effectiveness of alternative fumigants on weed control and plant productivity in two nurseries located at high elevation and low latitude (Ciudad Guzman, Jalisco), during 2013 and 2014 at Driscoll’s and Lassen Canyon South nurseries. Treatments were: MB:chloropicrin (MB:CP); 1,3-dichloropropene:CP; CP alone; metam sodium (MS) alone; dimethyl disulphide (DMDS):CP; and sequentially applied CP and MS. A rotary spading machine was used for MS and CP followed by MS. All treatments produced similar pest suppression and runner-plant yields during 2013 and 2014. However, CP alone showed very poor control of the most abundant weed (barnyardgrass, Echinochloa crus-galli). Two years of work on MB alternatives were not sufficient to provide reliable recommendations on this critical need, therefore, the Methyl Bromide Technical Options Committee recommended critical use nomination for MB in 2015.     

Movement and biological activity of drip-applied 1,3-dichloropropene and chloropicrin in raised mulched beds in the southeastern USA

Movement and biological activity of 1,3-dichloropropene (1,3-D) and chloropicrin applied through drip irrigation in raised beds was investigated at three locations in the southeastern USA. Tests were conducted in fields with dense populations of nutsedge (Cyperus spp), with one location also having a high level of soil nematodes, both of which served as biological indicators of the distribution of effective concentrations of 1,3-D and chloropicrin. Objectives were (1) to gain a better understanding of 1,3-D and chloropicrin movement and the extent of biological activity outside of the wetted bed area, and (2) to examine the effect of application rate, application concentration and subsequent irrigation events on movement and activity of 1,3-D and chloropicrin. InLine, an emulsifiable concentrate containing 60.8% w/w 1,3-D and 33.3% w/w chloropicrin, was injected into polyethylene mulched beds through the drip tubes and water movement in the beds was visualized by adding a blue dye to the injection system. Gas concentrations of 1,3-D and chloropicrin in soil were measured using Gastec detection tubes at different positions relative to the drip tube at 1-4 days after InLine application. After one week, mulch was removed and nutsedge survival evaluated at different positions in the bed. High concentrations of 1,3-D and chloropicrin were measured at the bed center and midway between the bed center and the shoulder, but concentrations were low at the bed shoulder. Width of nutsedge control was significantly greater than width of water movement. Plant-parasitic nematodes were controlled over the entire bed width, but nutsedge re-emerged at the bed shoulders regardless of treatment. Higher application rates and concentrations of 1,3-D + chloropicrin resulted in higher fumigant concentrations in soil air. Irrigations subsequent to application reduced soil air concentrations of 1,3-D and chloropicrin and increased water movement, as did the use of two drip tubes instead of one. The data show that the pesticidal activity of 1,3-D + chloropicrin extends beyond the waterfront and indicate a significant degree of fumigant activity of emulsifiable 1,3-D + chloropicrin. However, unlike plant-parasitic nematodes, nutsedge could not be controlled over the entire bed width, regardless of rate, concentration and volume of water applied.     

1,3-二氯丙烯与氯化苦混用对土壤 微生物数量恢复动态研究

为了明确1,3-二氯丙烯与氯化苦混用对土壤微生物数量的影响,采用室内培养的方法,研究4种剂量熏蒸处理后,供试土壤中微生物数量变化。结果表明：混剂熏蒸土壤后,低剂量（25.78 mg/kg）对放线菌表现为＂抑制—恢复＂趋势,中高剂量（128.91 mg/kg,257.81 mg/kg和1289.06 mg/kg）表现为＂抑制—激活＂趋势,在试验后期（第112天）激活率为125.36%;细菌与放线菌表现的趋势相似,但是细菌出现激活的时间（第49天）较放线菌（第14天）的晚,且中高剂量在试验后期（第112天）接近对照水平;而对镰刀菌、疫霉菌及可培养真菌均表现出明显的抑制作用,但低剂量下镰刀菌、疫霉菌在第49天和可培养真菌在第28天恢复至对照水平,高剂量处理（1289.06 mg/kg）对其则表现出＂抑制—激活＂的趋势,并且在试验末期（第112天）激活趋势依然明显,激活率分别为99.19%、51.54%和225.64%。