A method of investigating the effect of droplet size on pesticide collection by vegetation

A new technique is described which allows an estimation of the relative collection of insecticide on a crop, for three discrete droplet sizes simultaneously. Three droplet clouds, each consisting of a different chemical, were released along a line perpendicular to the wind. Subsequent chemical analysis of vegetation samples showed the relative efficiency of capture by any part of the plant as a function of the droplet size. The target vegetation and the micrometeorological conditions were the same for all three droplet clouds and thus did not mask the effects of droplet size. Initial results for a young crop of irrigated cotton are presented. The downwind distributions of chemical residues were in good agreement with a theoretical model published by Bache and Sayer.     

沉降剂控制热雾机热雾滴扩散范围及防效的研究

热雾机一般以柴油为热雾剂承载农药,形成的热雾喷出后随着喷口产生的动力和热雾的自身密度压差向前方自行推进,该施药技术由于效率高而广泛用于林业病虫害的防治。但由于热雾易飘移、难控制,造成农药污染的缺陷,在农作物生产中难以推广应用。本试验通过加入热雾沉降剂的方法,加大了热雾机热雾滴的比重和沉降速度,在此基础上,选择难以进入田间施药的玉米、油菜,进行了中、后期病害的防治试验,结果表明：加入热雾沉降剂后热雾滴的主体分布于田间水平距离(0~25 m)和垂直高度(0~2 m)范围内,分布密度为148.5~265.4粒/cm2,同柴油对照相比,加入热雾沉降剂后,同等直径的热雾滴飘移的距离和高度明显降低。田间防治试验结果也表明,热雾机施药对油菜菌核病和玉米南方锈病的防治效果普遍高于机动弥雾机喷雾的防治效果,加入热雾沉降剂后可提高有效防治范围内的防效。     

A simple model of crop loss by weed competition from early observations on relative leaf area of the weeds

A new simple empirical model for early prediction of crop losses by weed competition was introduced. This model relates yield loss to relative leaf area of the weeds shortly after crop emergence using the relative damage coefficient q as the single model parameter. The model is derived from the hyperbolic yield density relationship and therefore accounts for the effects of weed density. It is shown that the model also accounts for the effect of different relative times of weed emergence. A strong advantage of the approach is that it can be used when weeds emerge in separate flushes. The regression model described experimental data on sugar-beet – lambsquarters (Beta vulgaris L. –Chenopodium album L.) and maize-barnyard grass (Zea mays L. –Echinochloa crus-galli L.) competition precisely. The model describes a single relationship between crop yield loss and relative leaf area of the weeds over a wide range of weed densities and relative times of weed emergence. Possibilities for scientific and practical application of the model are discussed.     

Effect of the foliar application of diquat herbicide on selected natural area and field crop species

Field experiments were conducted to determine the non-target impact of foliar-applied diquat on selected plant species. Diquat was applied to emerged bracken fern, chain fern, slash pine, soybean, sunflower, cotton, corn, and onion at rates varying from 0.02–4.5 kg ai ha⁻¹ of diquat cation, which allowed for the determination of the no-effect rate and the rate that caused 25, 50, and 100% injury, as measured by visual injury ratings, plant heights, and dry weights. Bracken fern, chain fern, and slash pine were more tolerant to diquat and exhibited regrowth potential at the higher rates. The other six species were not only more susceptible to diquat, but they did not exhibit regrowth potential at high rates. However, these species were able to recover from slight injury caused by the lower rates of diquat.     

三种叶面肥在新疆两种葡萄上应用效果的比较研究

研究了3种叶面肥对红地球葡萄和木纳格葡萄产量和品质的影响。结果表明,在葡萄不同生育时期喷施螯合氨基酸钙液肥、腐植酸液肥和平衡营养肥,均明显增加了2个葡萄品种叶片叶绿素SPAD值、产量、可溶性固形物含量和还原型Vc含量,显著降低可滴定酸含量。其中红地球葡萄和木纳格葡萄,以连续喷施4次螯合氨基酸钙液肥效果最好:每公顷产量增幅分别为8.50%和17.15%,明显高于其它两喷肥处理,品质也好于其它两喷肥处理。     

The influence of spray droplet characteristics on the efficacy of permethrin against the diamondback moth Plutella xylostella: The effect of drop size and concentration on the potency of ulv- and ec-based residual deposits

The effect of droplet diameter (36-274 μm) and concentration (10-400 g litre^?1) of permethrin on the knockdown and mortality of 2nd-instar Plutella xylostella larvae was investigated. Larvae were placed on brussels sprout leaf discs treated with residual deposits of permethrin applied as ULV or emulsion formulations. The LD₅₀ of permethrin decreased with droplet size at all concentrations tested. This effect could not be accounted for solely by increased drop numbers per unit area of leaf, suggesting that for both formulations transfer of permethrin to larvae is more efficient for deposits composed of small drops. The concentration of permethrin in the ULV formulation could be reduced to approach a minimum quantity of toxicant per unit area to maintain 50 per cent mortality. The approach to the minimum dose varied with drop size and drop number per unit leaf area. The ULV formulation was approximately 2.7 times more effective at killing larvae than the emulsion, presumably as a result of greater availability of toxicant and transfer to larvae.     

Visualisation of the uptake of two model xenobiotics into bean leaves by confocal laser scanning microscopy: diffusion pathways and implication in phloem translocation

The diffusion of two fluorescent dyes, Oregon Green 488 (Oregon Green) and Rhodamine B into the leaves of broad bean (Vicia faba L) plants was studied to simulate the foliar uptake process of pesticides. The uptake rate of these model xenobiotics into bean foliage was measured using a standard leaf surface wash-off method. Diffusion into leaf tissues was visualised in vivo by confocal laser scanning microscopy (CLSM). The moderately lipophilic dye (Rhodamine B) showed faster uptake than the hydrophilic one (Oregon Green), despite the former being a larger molecule. While no distinct channels or domains for preferential entry of any of the dyes could be detected in the cuticle layer by CLSM, two different diffusion patterns were identified for the movement of these two dyes after traversing the cuticle. Upon desorption from the cuticle, Rhodamine B diffused extensively into the vacuole of the epidermal cells. Further transport of this dye from the epidermal cells to the mesophyll cells was not observed. In contrast, Oregon Green was found in the epidermal cell walls and cytoplasm, and was also present in the mesophyll cells. Examination of the petioles of the treated leaves revealed that, once absorbed, Oregon Green moved readily out of the treated leaf, whereas Rhodamine B did not show any phloem translocation. It is proposed that these two different diffusion characters may be responsible for the contrasting phloem mobility of the two xenobiotics. The results are discussed in relation to the current knowledge on the uptake, translocation and efficacy of pesticides as influenced by their properties.     

Mechanisms of cuticular uptake of xenobiotics into living plants: 1. Influence of xenobiotic dose on the uptake of three model compounds applied in the absence and presence of surfactants into Chenopodium album, Hedera helix and Stephanotis floribunda leaves

This study determined the uptake of three model compounds, applied in the presence and absence of surfactants, into the leaves of three plant species (Chenopodium album L, Hedera helix L and Stephanotis floribunda Brongn). The results with 2-deoxy-D-glucose, 2,4-dichlorophenoxyacetic acid and epoxiconazole in the presence ofsurfactants (the polyethylene glycol monododecyl ethers C12EO3, C12EO6, C12EO10 and a trisiloxane ethoxylate with mean EO of 7.5, all used at one equimolar concentration and therefore different percentage concentrations) illustrate that the initial dose (nmol mm(-2)) of xenobiotic applied to plant foliage is a strong positive determinant of uptake. This held true for all the xenobiotics studied over a wide concentration range in the presence of these surfactants. Uptake on a unit area basis (nmol mm(-2)) could be related to the initial dose of xenobiotic applied per unit area (ID) by an equation of the form: Uptake = a [ID]b at time t = 24h. ID is given by the mass of xenobiotic applied, M divided by the droplet spread area, A. Total mass uptake is then calculated from an equation of the form: Total Uptake = a [ID]b x A.     

A review of the effects of humidity, humectants, and surfactant composition on the absorption and efficacy of highly water-soluble herbicides

It is well known that environmental conditions have an important influence on herbicide efficacy. In particular, the effect of humidity on herbicide uptake has been attributed to changes in cuticle hydration and droplet drying. As early as the 1950s, it was hypothesized that humectants such as glycerol would enhance herbicide uptake by not letting droplets dry, thus maintaining the herbicide in solution, and hence making it available for uptake. Shortly thereafter, evidence was found to support this hypothesis and humectants were used successfully in warm, dry areas to increase herbicide efficacy. However, by the mid-1980s, there was little use of humectants as research on humectants gave way to investigations on the effect of ethylene oxide (EO) content on surfactant performance to improve herbicide uptake and efficacy. While ethoxylated surfactants effectively increase the uptake of both lipophilic and hydrophilic herbicides, the suggestion that long EO chains have humectant properties is misleading, since the studies that led to this suggestion were performed at high humidity, which would prevent rapid droplet drying. Furthermore, current evidence suggests that highly water-soluble, ionic herbicides may be more sensitive to low humidity and rapid drop drying than lipophilic herbicides. Therefore, an overview is presented on the interaction of water-soluble herbicides with surfactants, the cuticle, and humidity, with particular emphasis on the impact of low humidity and humectants on herbicide uptake. It was found that when one focuses on research performed at low humidity the importance of humectants emerges, which is not in keeping with what is now commonly accepted.     

基于TCM-CVM综合模型的古城旅游景区经济价值评估-以阆中古城为例

古城旅游景区作为我国旅游产业的重要组成部分,其经济价值综合评估的重要性日益显著.本研究选取阆中古城旅游景区为案例地,根据问卷调查及统计年鉴数据,运用TCM-CVM综合模型进行景区经济价值综合评估研究.结果 表明:(1)2018年阆中古城旅游景区的经济价值为1.610×1010,其中使用价值＞非使用价值,反映出阆中古城旅...     

洞庭湖区防鼠墙对东方田鼠防治效果调查

东方田鼠（Microtus fortis Buechner）是洞庭湖区重要的害鼠种类,在数量暴发年份,在由湖滩被迫迁入农田过程中会对农作物造成毁灭性的危害,因此修筑防鼠墙以阻断迁移通路是最为有效的防治手段。为了解防鼠墙的防治效果,在2012年4月和7月分别在湖滩和对应的堤内农田进行调查。结果有防鼠墙的堤垸内农田的东方田鼠密度为0.52%,明显低于经过人工捕杀和药物灭鼠后无防鼠墙的农田1.76%（χ2=3.900,P=0.048）;迁入农田后的密度下降幅度为98.53%,明显高于无防鼠墙堤垸的86.61%（χ2=11.060,P=0.01）。充分显示了防鼠墙防治效果,因此建议大力推广。     

A model to study the effect of certification of planting material on the occurrence of leek rust

Based on a simple model, the possible effects of certification of planting material on the occurrence of leek rust in a region can be derived from information on the proportion of infected fields (v) and the proportion of newly planted fields with infected planting material (i) in that region. Ifv i, certification of planting material will be highly effective.     

黄土高原丘陵区红富士苹果水肥耦合效应研究

针对黄土高原丘陵区的水资源状况和施肥现状,以农民能够承受的施肥、灌水标准为基础,进行了水肥耦合试验。以肥料配比(A)、施肥纯量基准(B)、灌水量(C)、灌水时间(D)作为试验因子,利用4因素3水平进行正交试验设计,经过2a试验,分析不同水肥组合对产量、水分利用效率、净效益的影响。结果表明,四个因素对产量和水分利用效率的重要性顺序是：施肥量(B)-灌水时间(D)-肥料配比(A)-灌水量(C);对净增值率的重要性顺序是：肥料配比(A)-施肥量(B)-灌水时间(D)-灌水量(C)。最优的处理组合均为：A1B3C2D1。即N：P：K=1：1：2,施肥量基准0．6kg,灌水时间为冬灌 花前期 幼果期 膨大期,灌水定额为82．5m^3／hm^2。同时说明果树对肥的需求比对水的需求更为迫切,且果园土壤中钾肥最为缺乏。     

具铁载体活性病原细菌的筛选及铁摄取干预对其生长影响

绝大多数病原菌可分泌铁载体,利用螯合性铁载体及病原菌对Fe~(3+)的竞争可实现病害的有效防控。从植物病原菌中筛选高产铁载体的优势菌株,并基于EDTA对铁离子的强螯合性,可为病害防控提供新的方法。本研究采用CAS检测法和光吸收法对42株供试植物病原菌株进行定性、定量筛选及铁载体类型的初步鉴定,依据菌株形态电镜观察和分子生物学技术对优势菌株进行分类鉴定,并基于微量稀释法测定EDTA对优势菌株的最低抑菌浓度。经定性、定量筛选,确定7株供试细菌为高产铁载体优势菌株,分泌铁载体类型为儿茶酚型和异羟肟酸型;根据形态特征观察和分子生物学鉴定,菌株TZT-057和TZT-058与恶臭假单胞菌Pseudomonas putida的一致性最高,TZT-059、TZT-063和TZT-064与肺炎克雷伯氏菌Klebsiella pneumoniae的一致性最高,TZT-062、TZT-073分别与鲁氏不动杆菌Acinetobacter lwoffii、迪克氏菌Dickeya zeae的一致性最高。根据微量稀释法抑菌活性测定结果可知,EDTA对菌株TZT-058、TZT-073的抑菌效果较好,抑菌率分别为85.16%、80.08%,表明强螯合剂EDTA能有效干预病原细菌对铁元素的摄取过程,进而影响其生长繁殖。     

糜子对铁矿复垦生土施肥的生物学响应

以襄汾溃坝区复垦生土为栽培基质,采用盆栽试验的方法,研究了施肥对糜子生长及生理生态效应的影响。结果表明：在施钾的基础上施用N、P、NP及有机肥均有利于糜子的生长,表现为株高分别增加了6.1%、42.0%、52.7%、45.1%,叶面积分别增加了197.6%、207.7%、261.6%、232.5%,地上部干重分别增加了46.3%、159.1%、186.6%、148.2%,根重分别增加了13.8%、65.9%、75.7%、67.1%,总根长分别增加了5.0%、68.4%、99.8%、91.6%,根系总吸收面积分别增加了24.9%、50.8%、68.3%、62.2%,活性吸收面积分别增加了46.9%、57.7%、96.9%、58.9%。糜子的旗叶净光合速率、叶绿素含量、可溶性糖含量、根系超氧化物岐化酶（SOD）活性、过氧化物酶（POD）活性、丙二醛（MDA）含量等各项生理指标与糜子的生长状况表现出高度的一致性。并最终表现为施用各种肥料均有利于糜子产量的提高,施用N、P、NP及有机肥分别比对照增产80.6%、200.1%、266.8%、230.6%。比较不同处理的增产效果可以发现,在本试验条件下,施磷的效果好于氮,磷是所用生土肥力形成的首要因素,也是糜子产量形成的限制因子。磷、氮、钾三要素之间表现出明显的正交互效应。单施有机肥,在糜子生长前期（拔节期）,对糜子的生长有明显的促进作用,但在后期（抽穗期）因缺氮而表现出效果不及其他处理。糜子根际土壤磷酸酶以及脲酶的活性与根系的生长状况表现为显著的正相关关系,表明发达的根系可以促使根际微生物群落的迅速生长和繁殖,并进而提高了根际土壤酶的活性,使得根际原来的生土不断向着熟化的方向发展。在施用一定肥料的前提条件下,矿区复垦生土地上种植糜子,当年便可获得较为正常的产量,并获得较好的经济效益,是当地可选的先锋杂粮作物之一。     

渭北旱塬花椒灌溉效应研究

利用试验资料分析了不同水文年份、灌水时间、耗水量对花椒产量、水分利用效率(WUE)、品质及新生枝条生长量的影响,结果表明:在无灌溉条件下,降水量较多的年份花椒产量较高;干旱年份,在水量缺乏的情况下,应把有限的水量灌到果实膨大期,保证果实膨大期的花椒需水,不仅可以获得较高的产量及WUE,而且可以获得较好的花椒品质;枝条生长量与生长期水分供应有关,充足的水分供应,可保树势健旺。同时为便于花椒需水量计算,确定出花椒的作物系数为0.91。     

Evaluation of the bioavailability of the herbicide prosulfocarb through adsorption on soils and model soil colloids, and through a simple bioassay

Adsorption isotherms of prosulfocarb were determined on soils with different physicochemical properties. The extent of adsorption increased with the organic carbon content, but the results also suggested the involvement of some inorganic soil surfaces. In order better to understand the role of each soil surface, adsorption-desorption isotherms were determined on model soil colloids consisting of a soil humic acid, a montmorillonite, a synthetic aluminium hydroxide and their associations. The highest adsorption was observed on the humic acid, but it was also confirmed that the montmorillonite interacted with prosulfocarb. In contrast, the aluminium hydroxide was not active and its association with montmorillonite provoked a decrease in adsorption compared with montmorillonite alone. Except for humic acid, the highest adsorption took place on the ternary association montmorillonite-aluminium hydroxide-humic acid. On each surface tested, the adsorption was largely reversible and decreased at increasing pH. The herbicidal activity of prosulfocarb was tested by the determination of the germination and growth of a typical weed, Lolium multiflorum Lam, in contact with prosulfocarb solutions at different concentrations. The herbicide did not prevent the germination of the seeds but inhibited the growth of the roots and leaves. The same test was performed in the presence of the ternary system to evaluate the influence of adsorption on the plant bioavailability. It was concluded that the presence of an adsorptive surface reduced the herbicidal activity and that the simple bioassay proposed could be useful in predicting the extent of adsorption in a given soil.