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1.
实验室条件下威百亩及异硫氰酸甲酯在土壤中的降解特性 总被引：1，自引：0，他引：1
在实验室条件下,利用高效液相色谱研究了威百亩及其降解产物异硫氰酸甲酯在土壤中的降解特性及影响因素。结果表明:威百亩在土壤中的降解与土壤绝对含水量、环境温度和土壤有机质含量均密切相关。25 ℃下,威百亩在绝对含水量为0、20%、40%、60%的土壤中的半衰期分别为5.0、1.2、4.1和4.3 d,绝对含水量约为20%的土壤最有利于其降解。威百亩的降解速率还随温度的升高和土壤有机质含量的增加而加快。异硫氰酸甲酯的降解趋势与威百亩基本相同。研究结果可为威百亩的田间安全、合理施用提供参考。 相似文献
2.
土壤环境条件对威百亩熏蒸防治黄瓜枯萎病的影响 总被引：2，自引：0，他引：2
为探究威百亩在不同土壤环境条件下的消毒效果,采用离体和活体方法研究施药量、覆膜熏蒸时间、土壤相对含水量及土壤温度对威百亩熏蒸防治黄瓜枯萎病的作用效果。结果表明,25℃条件下,威百亩12 mg(a.i.)/kg土壤熏蒸消毒,对尖孢镰刀菌Fusarium oxysporum的抑制率为78.82%,对黄瓜枯萎病的防治效果为87.03%,且对作物安全无药害;威百亩对尖孢镰刀菌的熏蒸抑制作用随着熏蒸时间的增加而增强,土壤熏蒸10 d后对尖孢镰刀菌的抑制率为95.21%;土壤相对含水量为30%和50%时,威百亩对黄瓜枯萎病的防治效果分别为72.32%和82.14%,含水量过高或过低均不利于药效的发挥,而且还会对作物产生药害反应。威百亩的熏蒸效果随着土壤温度的升高而增强,在25、30、35℃时对黄瓜枯萎病的防治效果分别为80.18%、98.20%和100.00%。表明威百亩结合日光消毒温度大于25℃、土壤相对含水量为30%或50%、熏蒸10~15 d可有效控制土壤中尖孢镰刀菌引起的黄瓜枯萎病。 相似文献
3.
灌水方式对轻度盐化土壤玉米生长及土壤水分的影响 总被引：4，自引：0，他引：4
以盆栽玉米为研究对象研究了直接浇灌、滴灌、微润灌等3种灌水方式下玉米的生长、叶绿素含量和光合速率、蒸腾速率等生理生态指标及土壤水分垂直分布的特征,结果表明:灌水方式对玉米生理生态指标有较大影响,苗期滴灌玉米生长较快,拔节前期,微润灌条件下玉米生长最为迅速,滴灌次之,直接浇灌生长最慢;滴灌条件下叶绿素含量最高,拔节期需水旺季时微润灌叶绿素含量最低.三种灌水方式对玉米光合速率的影响为:微润灌＜滴灌＜直接浇灌.土壤水分特征表明:微润灌稳定后土壤水分主要分布在10～ 30 cm土层,滴灌主要分布在10～ 40 cm土层;苗期、拔节期灌水后取样测定的土壤含水率表明,作物根系层内微润灌与滴灌均大于直接浇灌时的土壤含水率. 相似文献
4.
菌核净在植烟土壤及烟叶中的消解动态 总被引：2，自引：0，他引：2
为了探明菌核净的残留污染风险,在室内模拟和田间试验条件下,采用气相色谱法研究了菌核净在贵州植烟土壤及烟叶中的消解动态及其在土壤中消解的影响因子。 结果表明:在供试条件下,土壤微生物对菌核净在土壤中的消解起着重要作用,其在灭菌土壤中的半衰期为未灭菌土壤的3.5倍;土壤类型、温度、含水量和菌核净浓度对其消解也有影响,在贵州5个地区植烟土壤中的消解速率由高到低依次为花溪土壤>黔南土壤>凯里土壤>遵义土壤>毕节土壤;土壤中菌核净的消解速率随土壤温度和含水量的增加而加快,随施药剂量的增加而减慢。田间试验结果表明,菌核净在烟叶和土壤中的半衰期分别为5.8和8.2 d。 相似文献
5.
为明确完全不透性膜(totally impermeable film,TIF)对熏蒸剂在田间应用时散发和残留的影响,采用静态散发箱技术测定了TIF与聚乙烯膜(polythene film,PE)对氯化苦、1,3-二氯丙烯(1,3-dichloropropene,1,3-D)和棉隆施用后所产生的异硫氰酸甲酯(methyl isothiocyanate,MITC)大气散发的控制效果,并应用气相色谱法检测了揭膜后3种熏蒸剂在土壤中的残留情况。结果表明,在20 g/m~2(棉隆为15 g/m~2)剂量下,氯化苦、1,3-D及MITC透过PE的累积散发率为施用量的6.42%、7.37%和22.27%,透过TIF的累积散发率为施用量的0、0.65%和2.05%,表明TIF极大地降低了熏蒸剂向大气的散发量,可有效控制熏蒸剂向大气扩散。揭膜后氯化苦及1,3-D在各处理土壤中的残留量均低于0.30 mg/kg,说明TIF没有增加土壤中氯化苦和1,3-D的残留量;但MITC(15 g/m~2)在TIF下10~20 cm土壤中的残留量在3.28~3.41 mg/kg之间,高于在PE下的残留量(0.46~0.47 mg/kg),表明TIF能提高MITC在土壤中的持效浓度。 相似文献
6.
为探究威百亩对土壤硝化作用的影响及作用机制,通过理化分析和变性梯度凝胶电泳方法研究浓度为20、100和500 mg/kg威百亩熏蒸处理对土壤硝化作用及amoA型硝化细菌群落结构的影响。结果表明,威百亩熏蒸处理0、14、28 d后,3种浓度处理的土壤硝化率与对照差异不显著;处理56 d后,20、100和500 mg/kg浓度处理的土壤硝化率分别为81.15%、76.66%和94.08%,前两者与对照差异不显著,后者与对照差异显著;而处理84 d后,3种浓度处理的土壤硝化率与对照差异均不显著。与对照相比,3个浓度威百亩熏蒸处理不同时间后土壤amoA型硝化细菌群落的均匀度指数差异不显著。熏蒸处理14 d后,浓度20、100 mg/kg威百亩处理的土壤amoA型硝化细菌群落的香农多样性指数和丰富度指数分别为1.00、10.97和0.84、7.79,与对照的0.92和9.78均无显著差异;而浓度500 mg/kg威百亩处理的香农多样性指数和丰富度指数分别为0.59、5.77,显著低于对照。表明威百亩对土壤硝化强度的影响较amoA型硝化细菌群落延迟,说明土壤中硝化作用的强弱并非完全决定于土壤amoA型硝化细菌的作用。 相似文献
7.
通过对国内外46个乳油类农药以342ppm标准硬水稀释不同倍数、不同静置时间测定乳液稳定性,结果表明:若以硬水稀释20倍静置半小时分离出的乳膏不大于2毫升、静置2小时不大于4毫升为合格的条件,或以硬水稀释200倍静置1小时乳液无浮油、沉油或沉淀析出为合格的条件,则两个测定方法的测定结果基本相同。因此建议测定乳液稳定性在国内统一稀释200倍,在国际上也可用硬水稀释200倍的测定方法代替稀释20倍的测定方法。因前者方法简便、节省时间、易于观测。还表明用硬水稀释1000倍的测定方法,分离物不易观测,容易误检,是不适用的。还测定了乳液的表面张力、接触角和甘蓝、棉花叶片的润湿百分率。可以看出对水溶性较大的及施用时稀释倍数大的乳油类农药,为了充分发挥药效,在标准中除规定乳液稳定性外,还应增加润湿性指标。 相似文献
8.
为探明以卵磷脂和维生素E为主要成分的安融乐对烯禾啶 (sethoxydim) 的增效作用及在烯禾啶胁迫下对谷子 Setaria italica 品种‘晋谷21号’药害的缓解作用,采用盆栽试验方法,以‘晋谷21号’和牛筋草 Eleusine indica (L.) Gaertn. 为研究对象,设置不同浓度烯禾啶和安融乐混合药液,于谷子和杂草3~5叶期于叶面喷施,于药后7 d测定谷子农艺性状及光合生理指标,于药后7、15和30 d调查添加安融乐后对烯禾啶防除牛筋草的增效作用。结果表明:施用烯禾啶单剂对‘晋谷21号’株高、叶面积、光合色素含量、叶绿素荧光均有显著抑制作用,且随浓度增加抑制作用加强;1/8倍推荐剂量 (推荐剂量为有效成分187.5 g/hm2) 的烯禾啶对‘晋谷21号’已经产生药害,1/2倍推荐剂量下谷子株高、叶面积均显著低于对照,分别比对照降低了23.41%和33.15%,此剂量下谷子光合色素含量及叶绿素荧光参数也均显著低于对照。添加不同稀释倍数的安融乐后,对低浓度烯禾啶胁迫的缓解作用不显著,对高浓度烯禾啶胁迫的缓解作用显著。其中安融乐稀释倍数为2500倍时,对1/2倍推荐剂量烯禾啶胁迫的缓解作用最好,谷子株高和叶面积比施用烯禾啶单剂分别增加16.76%和24.94%,光合色素含量及叶绿素荧光参数等生理指标均在此剂量下显著高于对照及其他处理。1/8倍推荐剂量烯禾啶对牛筋草防效较差,株防效几乎为0,但随着烯禾啶浓度的升高,对牛筋草的防效逐渐升高。1/2倍推荐剂量下药后30 d烯禾啶对牛筋草的株防效和鲜重防效分别为53.33%和73.10%,在此剂量下添加稀释倍数为2500倍的安融乐后,牛筋草株防效和鲜重防效分别上升至73.33%和84.65%。综上,添加稀释倍数为2500倍的安融乐可以提高烯禾啶对牛筋草的防效同时提高对谷子的安全性。 相似文献
9.
为探讨抗旱保水袋在废弃采石场造林中的应用效果,通过室内试验和室外盆栽试验研究了抗旱保水袋性能及对容器苗生长的影响。结果表明:大袋保水袋的吸水速率和吸水倍数比小袋保水袋分别增加1.4倍、1.9倍,在蒸馏水溶液下的吸水速率和吸水倍数比自来水分别增加0.6倍、0.1倍;大袋保水袋的保水率大于小袋保水袋;保水袋能显著增加渣土土壤体积含水量,比对照高1.29倍,苗高平均比对照增加2.36cm,成活率平均比对照增加69.5%,出现死亡天数平均比对照推迟12d。结论得出,抗旱保水袋是干旱、半干旱及半湿润地区废弃采石场困难立地提高造林成活率并促进植被恢复的一种有效方法。 相似文献
10.
不同施肥土壤对尿素NH3挥发的影响 总被引：10，自引：0，他引：10
经过6a长期不同施肥定位试验,使同一土壤形成肥力上的差异,对此土壤进行室内氨挥发模拟试验。研究结果表明,施用等量尿素条件下,不同施肥土壤氨挥发损失具有明显差异,长期施N土壤,可缩短氨挥发时间3～4d,并且可明显降低挥发损失量。长期施用P肥土壤也能降低氨挥发损失量。并且氨挥发损失量与土壤有机质含量显著相关。 相似文献
11.
Emission of methyl isothiocyanate (MITC) from fields treated with metam‐sodium (sodium N‐methyldithiocarbamate) is a potential environmental and human safety hazard. Concentrations of MITC at three heights above four arable fields were measured following the application of metam‐sodium at a rate of 480 litre ha−1 (166 kg AI ha−1). Two of these fields were treated by injection into a center‐pivot irrigation system (chemigation), while in the other two fields the fumigant was applied through injection directly into the soil. Generally, higher MITC air concentrations were observed above chemigated than above injected fields. Maximum MITC air concentrations were 11.2 and 7.4 µg m−3 recorded 10 cm above ground 6–8 h following application and the minimum concentrations were 0.7 and 0.2 µg m−3 observed at 200 cm 30–35 h after application above chemigated and injected fields, respectively. The estimated MITC respiratory exposure a worker might encounter during the re‐entry period ranged between 1.37 and 0.03 mg day−1 in chemigated fields and between 0.35 and 0.02 mg day−1 in the injected fields. These results suggest that application of the fumigant through injection reduced MITC volatilization losses in comparison with the chemigation method, thus posing a relatively lower risk of exposure to MITC emissions. © 2000 Society of Chemical Industry 相似文献
12.
Catherine R Simpson Shad D Nelson Jerry E Stratmann Husein A Ajwa 《Pest management science》2010,66(6):686-692
BACKGROUND: Metam‐sodium (MS, sodium methyldithiocarbamate) has been identified as a promising alternative chemical to replace methyl bromide (MeBr) in soil preplant fumigation. One degradation product of MS in soil is the volatile gas methyl isothiocyanate (MITC) which controls soilborne pests. Inconsistent results associated with MS usage indicate that there is a need to determine cultural practices that increase pest control efficacy. Sealing the soil surface with water after MS application may be a sound method to reduce volatilization loss of MITC from soils and increase the contact time necessary for MITC to control pests. The objective of this research was to develop a preliminary soil surface water application amount that would potentially inhibit the off‐gassing rate of MITC. RESULTS: Off‐gassing rate was consistently reduced with increasing water seal application. The application of a 2.5–3.8 cm water seal provided significantly lower (71–74% reduction in MITC volatilization) total fumigant loss compared with no water seal. The most favorable reduction in MITC off‐gassing was observed in the 2.5 cm water seal. CONCLUSION: This suggests that volatilization of MITC‐generating compounds can be highly suppressed using adequate surface irrigation following chemical application in this soil type (sandy clay loam), based on preliminary bench‐scale soil column studies. Copyright © 2010 Society of Chemical Industry 相似文献
13.
Soil column studies were undertaken to investigate the influence of soil water content and irrigation on leaching, distribution and persistence of methyl isothiocyanate (MITC) in a sandy soil chemigated with the soil fumigant metam-sodium. No leaching was obtained from columns at low water content (0·042 or 0·074 cm3 cm−3). However, 8·4 (±2·8), 34·2 (±7·4) and 119·4 (±8·3) μg of MITC leached from columns at 0·105, 0·137 and 0·168 cm3 cm−3 water content, respectively. Increased leaching resulted from sprinkler application of 25-mm of water to columns at 0·137 cm3 cm−3 water content. Leaching of MITC constituted only a small fraction of the amount applied even in the worst case. Methyl isothiocyanate persisted in soil for 15 days at 2°C in varying amounts under the different water regimes. Relatively high amounts of MITC residues (8–12 mg kg−1 soil) were detected in the top 25-cm layer of all the soil columns. Degradation was the major pathway of dissipation for the chemical despite the soil water regime. 相似文献
14.
Wang D Fraedrich SW Juzwik J Spokas K Zhang Y Koskinen WC 《Pest management science》2006,62(3):263-273
Adequate concentration, exposure time and distribution uniformity of activated fumigant gases are prerequisites for successful soil fumigation. Field experiments were conducted to evaluate gas phase distributions of methyl isothiocyanate (MITC) and chloropicrin (CP) in two forest-tree nurseries. Concentrations of MITC and CP in soil air were measured from replicated microplots that received dazomet, metam-sodium and CP. Half of the plots were covered with high-density polyethylene tarp immediately after fumigation; the other half were not covered but received daily sprinkler irrigation for 1 week to create and maintain a water seal. The magnitude of MITC concentrations was similar between nurseries for metam-sodium in both tarp and water seal treatments and for dazomet in the tarp treatment. Consistently greater MITC and CP concentrations were found in the upper 30 cm of soil in the tarped plots compared with the water-sealed plots. Despite potential environmental and economic benefits with the water seal method, tarp covers were more reliable for achieving and maintaining higher MITC and CP concentrations and less prone to variations due to irrigation/rain, soil bulk density and other environmental conditions. 相似文献
15.
Metam sodium (metam) is a widely used soil fumigant. Combined application of metam and other available fumigants is intended to produce synergic pesticidal effects for a broad spectrum of pest control in soil fumigation. This study aimed to test the compatibility of metam with the halogenated fumigants 1,3-dichloropropene (1,3-D), chloropicrin, methyl bromide, methyl iodide and propargyl bromide. Halogenated fumigants and metam were spiked simultaneously into organic solvents, water and moist soils, and metam-induced degradation of these halogenated chemicals was evaluated. In all three media, the halogenated fumigants were incompatible with metam and degraded via rapid chemical reactions. The degradation rate varied with halogenated fumigant species and increased as the amount of metam present was increased. In moist soil, 15-95% of the halogenated fumigants were decomposed within 72 h by metam at a 1:1 molar ratio. Combined application of Telone C-35 (62.5% 1,3-D + 35% chloropicrin) at 265 mg kg(-1) and Vapam (42% metam) at 567 mg kg(-1) in soil resulted in complete disappearance of the applied chloropicrin and 20-38% of the 1,3-D within 8 h. The results suggest that simultaneous application of halogenated fumigants and metam at the same soil depth will not maximize pest control. In practice, sequential treatment of soil or application at different soil depths is recommended when these two types of fumigants are used in combination. 相似文献
16.
Ajwa HA Trout T Mueller J Wilhelm S Nelson SD Soppe R Shatley D 《Phytopathology》2002,92(12):1349-1355
ABSTRACT Strawberry fields in California (9,500 ha annually) are pre-plant fumigated with methyl bromide and chloropicrin to prevent serious soil pest and disease problems. Although soil fumigation with methyl bromide has ensured stability of strawberry production, its use is being discontinued because of its effect on stratospheric ozone. The likely short-term alternatives such as 1,3-dichloropropene, chloropicrin, and metham sodium, although not ozone depleters, are potentially hazardous to the environment and humans if applied improperly. Water-soluble formulations of alternative fumigants can be applied through drip irrigation systems established to irrigate crops. In comparison to conventional shank methods of injection, application of soluble formulations through drip irrigation systems would be economical and environmentally friendly, reduce worker exposure, and allow for simultaneous or sequential application of a combination of fumigants. This paper discusses techniques developed to apply alternative fumigants through drip irrigation systems, and reviews ongoing studies to determine optimum application rates, soil conditions, plastic mulches, and amount of irrigation water used to apply these alternative fumigants. 相似文献
17.
Duniway JM 《Phytopathology》2002,92(12):1337-1343
ABSTRACT None of the chemical alternatives currently registered and available has the full spectrum of activity and versatility of methyl bromide as a pre-plant soil fumigant. Chloropicrin and 1,3-dichloropropene (Telone) can provide significant control of many plant pathogens in soil and growth stimulation in annual crops. These compounds, however, provide limited control of weeds or other residual plant materials in soil of concern in nursery production systems, and some perennial replant diseases. Methyl isothiocyanate generators such as metam sodium have broad biocidal activity in soil, but are more difficult to apply effectively. In most soil applications, the available alternatives are likely to be used in combinations, either as mixtures (e.g., 1,3-dichloropropene and chloropicrin) or sequentially (e.g., chloropicrin followed by metam sodium). They may also be supplemented with other more specific pesticides and cultural controls. Among the alternatives currently under active development but not yet available, methyl iodide and propargyl bromide probably have activity that most closely parallels that of methyl bromide in soil. However, all of the chemical alternatives to methyl bromide will be subject to continuing review and more regulation. Furthermore, we do not know the actual prospects for registration of the new fumigants currently under development and there is a risk that registered fumigants will not be available for large-scale use in soil indefinitely. 相似文献
18.
BACKGROUND: Producers of several high‐value crops in California have traditionally used preplant soil fumigation with methyl bromide/chloropicrin combinations. Although methyl bromide has been phased out since 2005, several crop industries, including cut flower producers, have continued methyl bromide use under Critical Use Exemptions, a provision of the Montreal Protocol. This research was conducted to evaluate newer, emerging methyl bromide alternative chemicals. RESULTS: Two field trials were conducted to test several emerging chemicals in combination with metam sodium as replacements for methyl bromide. Emerging chemicals included 2‐bromoethanol, dimethyl disulfide, furfural, propylene oxide and sodium azide. Weed and pathogen populations were measured after chemical application, and seed viability was assessed from weed seed previously buried in the plots. In the first trial, the emerging chemicals did not improve pest control compared with metam sodium alone. However, in the second trial, several of these chemicals did improve the pest control performance of metam sodium. CONCLUSIONS: The emerging alternative chemicals have the potential to provide better control of soilborne pathogens and weeds when used with metam sodium than metam sodium alone. Registration of these materials could provide California growers with a broader choice of tools compared with the limited methyl bromide alternatives now available. Published 2011 by John Wiley & Sons, Ltd. 相似文献
19.
Developing effective irrigation and drainage strategies to improve the quality of saline-alkali soil is vital for enhancing agricultural production and increasing economic returns. In this study, we explored how irrigation and drainage modes (flood irrigation, drip irrigation, and sub-surface pipe drainage under drip irrigation) improve the saline-alkali soil in Xinjiang, China. We aimed to study the transport characteristics of soil water and salt under different irrigation and drainage modes, and analyze the effects of the combination of irrigation and drainage on soil salt leaching, as well as its impacts on the growth of oil sunflower. Our results show that sub-surface pipe drainage under drip irrigation significantly reduced the soil salt content and soil water content at the 0-200 cm soil depth. Under sub-surface pipe drainage combined with drip irrigation, the mean soil salt content was reduced to below 10 g/kg after the second irrigation, and the soil salt content decreased as sub-surface pipe distance decreased. The mean soil salt content of flood irrigation exceeded 25 g/kg, and the mean soil desalination efficiency was 3.28%, which was lower than that of drip irrigation. The mean soil desalination rate under drip irrigation and sub-surface pipe drainage under drip irrigation was 19.30% and 58.12%, respectively. After sub-surface drainage regulation under drip irrigation, the germination percentage of oil sunflower seedlings was increased to more than 50%, which further confirmed that combined drip irrigation and sub-surface pipe drainage is very effective in improving the quality of saline-alkali soil and increasing the productivity of agricultural crops. 相似文献