气相色谱串联质谱法测定土壤中除草剂残留含量

以气相色谱串联质谱法（GC-MS/MS）多反应监测（MRM）方式进行定量和定性分析建立了土壤中除草剂莠去津、塞克津、2,4-D丁酯残留含量的联合测定方法。结果表明,本方法有效地降低了样品复杂基质带来的干扰,简化了分析步骤。采用外标法定量测得回收率为73%～104%,标准偏差为5.9%～11.5%,方法的回收率和线性关系结果令人满意,实验证明,该方法快速、准确、灵敏度高,适用于土壤中除草剂莠去津、塞克津、2,4-D丁酯残留含量的联合检测。     

降解菌N1对嗪草酮的降解效果研究

【目的】研究降解菌N1对土壤中嗪草酮的降解效果,为嗪草酮土壤残留的修复处理提供支持。【方法】以嗪草酮高效降解菌N1为供试菌种,通过土壤接种,分析N1菌株对土壤嗪草酮的降解能力,并研究嗪草酮初始含量、N1菌株接种量、土壤pH、反应温度对降解效果的影响。【结果】当土壤中的嗪草酮含量为20mg/kg时,在灭菌土壤中添加N1菌株1011 CFU/g后,嗪草酮的降解率可由10.69%提高到54.07%,而在未灭菌土壤中添加N1菌株后,嗪草酮的降解率由19.04%提高到66.42%。当嗪草酮的初始含量为20mg/kg、N1菌株接种量为1011 CFU/g、土壤pH=7~8、反应温度为30℃时,N1降解嗪草酮的效果较好。【结论】降解菌N1可明显提高土壤嗪草酮的降解率。     

嗪草酮对大豆叶片叶绿素荧光特性的影响

利用盆栽法研究了嗪草酮对大豆叶片叶绿素荧光特性的影响。结果表明,在嗪草酮较低用量(有效用量630和945g/hm2)时,荧光参数NPQ增大,而Fv/Fm、Fv/Fo、qP、ETR等参数及光能分配与空白对照差异不显著;嗪草酮较高有效用量(大于1 155g/hm2)时,会使NPQ变化趋势由上升变为下降,Fv/Fm、Fv/Fo、qP、ETR、Y(Ⅱ)等较空白对照显著下降、Y(NO)、β/α-1迅速增加。说明较低用量嗪草酮对大豆叶片PSⅡ有一定的影响,但大豆通过自身的调节机制使叶片的光合能力下降不明显,而较高用量的嗪草酮会使大豆PSⅡ反应中心发生不可逆破坏,能量分配不平衡,光合能力下降,甚至丧失。随施药后时间的推移,嗪草酮对大豆主要功能叶片PSⅡ的影响逐渐减弱,至施药后50d,嗪草酮不同使用量之间大豆叶片的荧光参数无显著差异。     

Effectiveness of selective herbicides for the control of annual weed species in lathyrus (Lathyrus sativus L.)

Field research was conducted over a four-year period, 1987–1990, to evaluate the efficacy and selectivity of trifluralin, metribuzin, cyanazine, bentazone, imazethapyr and several formulations of MCPA in lathyrus (Lathyrus sativus L.). Lathyrus exhibited satisfactory tolerance to trifluralin applied pre-planting soil incorporated and to postemergence applications of bentazone and imazethapyr. Lathyrus tolerated both pre-planting soil-incorporated and postemergence applications of metribuzin in dry years, but was injured by this herbicide in years with adequate precipitation. Tank mixtures of metribuzin or cyanazine with sethoxydim plus surfactant markedly increased the phytotoxicity of these herbicides to lathyrus. Lathyrus was sensitive to all formulations of MCPA and phytotoxicity increased with the addition of sethoxydim plus surfactant to the spray mixture.     

Evaluation of herbicides against Phalaris minor in wheat in north-western Indian plains

Phalaris minor, the most serious weed in wheat in north‐western India, has developed extensive isoproturon resistance due to continuous isoproturon use. For its control, alternative herbicides (flufenacet, metribuzin and sulfosulfuron) at different application rates and timing were evaluated in wheat. In addition, herbicide carryover risk onto rotational crops (sorghum; maize and green gram, Vigina radiata) was also assessed. Isoproturon at 1 and 2 kg a.i. ha^?1 provided only 10.5% and 51.8%P. minor control respectively. Of the other herbicides, early post‐emergent [15–21 days after sowing (DAS)] flufenacet at 180–480 g a.i. ha^?1 provided acceptable control of P. minor, but failed to control broad‐leaved weeds and was phytotoxic to the wheat crop. Metribuzin at 210 g a.i. ha^?1 was effective in controlling both Phalaris and dicotyledonous weeds. Mixtures of both flufenacet and metribuzin at reduced rates were better than flufenacet for weed control and grain yield. The efficacy of flufenacet and metribuzin was drastically reduced with later growth stages of P. minor (four to five leaf). Whereas sulfosulfuron at 25–30 g a.i. ha^?1, applied either early post‐emergence (19 DAS) or post‐emergence (30–42 DAS), was quite effective. Overall, sulfosulfuron was the most effective treatment with regard to weed control and crop yield. However, maize and sorghum grown in rotation after harvest of sulfosulfuron‐treated wheat plots showed 65–73% crop biomass inhibition. The residual effect of sulfosulfuron was also noticed on Trianthema portulacastrum (Horse purslane), causing 73.5% dry matter reduction. By contrast, no carryover damage with flufenacet was observed on maize, sorghum and green gram. Glasshouse pot experiments and field trials investigating crop sensitivity to pre‐plant applications of sulfosulfuron found the decreasing order: sorghum > maize > green gram. The risk of carryover onto rotational crops should be considered when choosing alternative herbicides for P. minor control in wheat.     

Weed management challenges in small-holder potato systems in Bhutan

Over the past four decades potato has emerged as the most important cash crop for Bhutanese mountain farmers. Farmers' feedback and field observations were used to describe weed populations, weed management and weed-production environment-yield interactions in small-holder potato production systems. Weed species across a range of locations in order of declining importance are: Persicaria runcinata , Galium aparine , Fagopyrum dibotrys , Digitaria ciliaris , Commelina maculata , Galinsoga parviflora and Persicaria nepalensis. The same species were common in the traditional buckwheat and maize production systems as well as the more recently established potato production systems. Limited associations between soil properties, management practices, weed species abundance and potato yield were observed. Species emerging as potential problem weeds, especially P. runcinata and F. dibotrys , are little known outside the Himalayan region. The increase in P. runcinata , reported by 42% of the respondents, was attributed to the use of metribuzin, cutting of rhizomes by plough or spade, high inputs of fertiliser and continuous cultivation of potato by 61%, 17%, 9%, 9% and 4% of respondents respectively. Metribuzin application reduced growth of P. runcinata but could not fully control it. Metribuzin is an effective and affordable weed management tool for small-holder potato farmers, but perennial weed species need further research, combining mechanical and chemical methods with cropping strategies.     

Availability and biodegradation of metribuzin in alluvial soils as affected by temperature and soil properties

Herbicide degradation in soils is highly temperature‐dependent. Laboratory incubations and field experiments are usually conducted with soils from the temperate climatic zone. Few data are available for cold conditions and the validation of approaches to correct the degradation rate at low temperatures representative of Nordic environments is scarce. Laboratory incubation studies were conducted at 5, 15 and 28°C to compare the influence of temperature on the dissipation of metribuzin in silt/sandy loam soils in southern and northern Norway and in a sandy loam soil under temperate climate in France. Using ¹⁴C‐labelled metribuzin, sorption and biodegradation were studied over an incubation period of 49 days. Metribuzin mineralisation and total soil organic carbon mineralisation rates showed a positive temperature response in all soils. Metribuzin mineralisation was low, but metabolites were formed and their abundance depended on temperature conditions. The rate of dissipation of ¹⁴C‐metribuzin from soil pore water was strongly dependent on temperature. In Nordic soils with low organic content, metribuzin sorption is rather weak and biodegradation is the most important process controlling its mobility and persistence.     

Retention and degradation of metribuzin in sandy loam and clay soils of Lebanon

The retention and degradation of metribuzin herbicide were studied under two environmental conditions. Field studies were carried out on two soils, a sandy loam soil (soil A) and a clay soil (soil B). Metribuzin was applied with a jet sprayer at 1060 g a.i. ha^?1 and 1960 g a.i. ha^?1 on soils A and B respectively. Reconstituted soil columns were used to study the herbicide movement and metabolism in the two soils. Analyses of metribuzin and its metabolites were carried out using standardized methods. The results indicated a very weak capacity of adsorption of metribuzin in the two soils, and the weak adsorbed fraction is easily desorbed. Degradation and mobility of metribuzin in the field and laboratory soil columns were very intense and rapid. Soil A favoured reductive deamination whereas soil B favoured oxidative desulphuration and the respective metabolites deaminometribuzin and diketometribuzin yield the same product deaminodiketometribuzin. Both leaching by rainfall and degradation were important in the disappearance of metribuzin from the soils.