夏大豆田稗草的生态经济防治阈期研究

本文提出了杂草生态经济防治阈期的概念。并在北京地区１９８４和１９８５年田间试验的基础上,建立了苗后放任的免除夏大豆田稗草生长的相对天数与大豆相对产量的函数关系及其生态经济防治阈期的计算模型。利用此模型计算的结果表明,夏大豆田稗草的生态经济防治阈期处在大豆苗后生育期总天数的１６．８％－２６．０％之间,即按绝对天数计算,北京地区夏大豆田该杂草的生态经济防治阈期约处在大豆苗后１５－２３ｄ之间,此期保持无     

北京地区夏大豆田间杂草的生态经济杀除阈期研究

本文提出了杂草生态经济杀除阈期的概念，并在北京地区田间试验的基础上，建立了苗后放任和免除夏大豆田间杂草生长的相对时间与大豆相对产量间的函数关系，并在此基础上确立了夏大豆田间杂草群落的生态经济杀除阈期的计算模型。结果表明，夏大豆田间杂草的相对生态经济杀除阈期约处在大豆出苗至成熟期总天数的１２．４％－３１．０％的天数之前。在此期间进行除草，即能确保大豆不会因杂草生长而显著减产，又可节约阈期之前和之后盲     

北京地区夏大豆田间杂草的生态经济杀除阈期研究

本文提出了杂草生态经济杀除阈期的概念,并在北京地区田间试验的基础上,建立了苗后放任和免除夏大豆田间杂草生长的相对时间与大豆相对产量间的函数关系,并在此基础上确立了夏大豆田间杂草群落的生态经济杀除阈期的计算模型。结果表明,夏大豆田间杂草的相对生态经济杀除阈期约处在大豆出苗至成熟期总天数的12.4%—31.0%的天数之前。在此期间进行除草,既能确保大豆不会因杂草生长而显著减产,又可节约阈期之前和之后盲目除草所消耗的费用,并在一定程度上可利用杂草的固土保肥、增加土壤有机质等作用。     

棉区夏玉米田节肢动物群落的研究

系统研究了夏玉米田节肢动物群落的相对多度,丰富度、生态优势度,多样性指散和均匀度的变动。分析提出了以保护利用天敌为主的综合防治对策。     

高粱舟蛾发生规律与防治研究

高粱舟蛾Dinaracombusta (Walker)以幼虫取食玉米、高粱、甘蔗叶片。近年来 ,河北省正定、磁县、滦城等地危害夏玉米成灾。该虫在河北中南部每年发生 1代 ,以蛹在土中越冬 ,6月底至 7月上旬夏玉米田开始见卵 ,7月中下至 8月上旬为幼虫发生危害盛期。虫口密度与气象、天敌及食物因素有关。幼虫抗药性低 ,在夏玉米田采用高效氯氰菊酯乳油等低龄期防治 ,效果均在 90 %以上     

玉米田养鹅措施对杂草群落生态特征的影响

探索如何在利用和控制农田杂草的同时又能维持较高的杂草群落多样性的生产方式, 是当前农业发展的重要方向。作者以“农牧一体化”生产方式下的“玉米(Zea mays)田养鹅”处理和常规玉米种植处理为研究对象, 探讨了玉米田养鹅处理放牧前后及同期常规玉米种植处理下杂草生态位、功能群结构和杂草群落生物多样性的变化。结果表明: (1)在玉米田养鹅模式下, 黑麦草(Lolium multiflorum)、紫花苜蓿(Medicago sativa)和灰绿藜(Chenopodium glaucum)在放牧前的生态位宽度较大, 但放牧后黑麦草、紫花苜蓿的生态位宽度减小, 而灰绿藜、尼泊尔蓼(Polygonum nepalense)、西南草莓(Fragaria moupinensis)和老鹳草(Geranium sibiricum)等物种的生态位宽度则有不同程度的增大, 放牧后群落内新增加了7种杂草; 对照中, 前期丝叶球柱草(Bulbostylis densa)的生态位宽度最大, 而后期鼠麹草(Gnaphalium affine)的生态位宽度变为最大, 新增2种杂草。(2)放牧前玉米田养鹅处理下的黑麦草和紫花苜蓿的重叠度最大, 而放牧后黑麦草和西南草莓的重叠度变为最大; 在常规玉米种植模式下, 前期丝叶球柱草和马唐(Digitaria sanguinalis)的重叠度最高, 而后期丝叶球柱草和鼠麹草的重叠度最高。(3)两种模式下放牧前后均是一年生双子叶(DA)杂草功能群占据最大优势, 但玉米田养鹅处理模式下放牧后多年生功能类群所占的比例较放牧前增加, 且分配更均匀。(4)放牧前, 玉米田养鹅处理的Shannon-Wiener多样性指数、Margalef物种丰富度指数和Simpson多样性指数均高于对照, 其中Shannon-Wiener多样性指数和Margalef物种丰富度指数差异显著(P<0.05, n=3), 而Pielou均匀度指数低于对照, 但差异并不显著(P>0.05, n=3); 放牧后玉米田养鹅处理的Shannon-Wiener多样性指数和Margalef物种丰富度指数仍显著高于对照(P<0.05, n=3), 而Pielou均匀度指数和Simpson多样性指数则分别显著低于对照 (P<0.05, n=3)。放牧前后, 玉米田养鹅处理杂草群落的地上总生物量均高于对照, 但差异不显著(P>0.05, n=3)。(5)玉米田养鹅处理的玉米产量与对照相比减产4.0%, 但并未达到显著差异(P>0.05, n=12)。总的来看, 玉米田养鹅生产方式维持了较高的农田生态系统生物多样性, 虽然造成了一定的减产, 但可通过鹅的产出获得更高的经济效益。     

小麦秸秆水浸提液对五种植物化感作用的研究

该文研究了不同浓度的小麦秸秆水浸提液对徐州地区2种玉米(郑单958和农大108)和3种常见玉米田间杂草(马唐、稗草和反枝苋)种子萌发和幼苗生长的影响。结果表明:当小麦秸秆浸提液浓度分别大于75、50和25 g·L~-1时,马唐、稗草和反枝苋种子的萌发受到显著的抑制;当小麦秸秆浸提液浓度分别大于50和37.5 g·L~-1时,玉米郑单958和农大108种子的萌发受到显著的抑制;但当小麦秸秆浸提液浓度大于37.5 g·L~-1时,马唐、稗草和反枝苋幼苗根和芽的生长均受到明显的抑制;当小麦秸秆浸提液浓度小于75 g·L~-1时,玉米郑单958和农大108幼苗根与芽的生长受到明显的促进,且郑单958幼苗叶片中叶绿素的含量以及郑单958的POD酶活性均得到提高。该研究结果表明较高浓度的小麦秸秆浸提液(50 g·L~-1)会抑制杂草的生长,有利于玉米郑单958的生长,为小麦秸秆还田和玉米田杂草的生态防治提供了理论基础。     

双斑长跗萤叶甲在玉米田的种群消长规律

【目的】明确双斑长跗萤叶甲Monolepta hieroglyphica(Motschulsky)的发生规律,为双斑长跗萤叶甲的预测预报和综合治理提供科学依据。【方法】2011年通过田间系统调查对山西省忻州市和晋中市玉米田的双斑长跗萤叶甲的种群消长动态进行了系统研究。【结果】在山西省忻州市的玉米田,越冬卵在5月下旬开始孵化,幼虫以玉米根系为食,6月中旬为幼虫的发生高峰期,部分老熟幼虫开始化蛹,6月下旬成虫开始羽化出土,为害玉米叶片,8月初成虫种群数量达到最高峰,8月中旬以后随着玉米花丝大部分萎蔫,叶片开始衰老,玉米田间的成虫种群数量也急剧下降。10月中旬玉米田成虫基本消失,但是在杂草上还能发现少量的成虫。在山西省晋中市,玉米的生育期比忻州市晚10 d左右,双斑长跗萤叶甲的发生期也相对晚一些,但是种群数量的发生发展趋势基本是一样的。双斑长跗萤叶甲成虫在靠近杂草的玉米田边比在玉米田中部的发生更重,而在成虫的发生高峰期,田边和田中间的种群密度无显著性差异。【结论】双斑长跗萤叶甲在山西省1年发生1代,在山西省忻州市的发生期比晋中市的要早10 d左右,这与两地玉米田的不同的土壤性质、灌溉方式、玉米生育期等因素有关。     

桃蛀螟为害玉米部位的观察

<正> 随着玉米面积的扩大,桃蛀螟Dichocrocispunctiferalis Guenee已上升为玉米的主要害虫,其发生量超过玉米螟和高粱条螟。为制订测报方法和防治对策,笔者于1989年固定3块春玉米田和7块夏玉米田,从抽雄开始,5天一次,每次每块田顺序调查50株,逐株检查玉米各个部位桃蛀螟的虫量,直到玉米成熟为止。对     

转植酸酶基因玉米种植对土壤线虫群落的影响

土壤是生态系统中物质循环和能量转化的重要场所,转基因作物外源基因对土壤非靶标生物的影响已经引起人们的广泛关注.我国转植酸酶基因玉米(即自交系BVLA430101)于2009年9月27日获得了生物安全证书,该转植酸酶基因玉米可提高饲料利用效率,减少动物粪便造成的环境污染.本文以转植酸酶基因玉米(简称转基因玉米)和常规对照亲本玉米(简称对照玉米)为试验材料,通过大田试验研究了转基因玉米和对照玉米种植对土壤线虫群落组成与生态指标的影响.结果表明： 转基因玉米和对照玉米大田土壤分别分离出29个属和26个属的线虫.与对照玉米相比,转基因玉米种植田食细菌线虫相对多度与数量、捕/杂食线虫数量和土壤线虫总数,以及群落多样性指数等都有升高的趋势,而植食线虫相对多度与线虫总成熟度指数呈降低趋势.重复测量方差分析表明,整个生长季节内转基因玉米与对照玉米田间不同营养类群土壤线虫相对多度与数量及生态指标均无显著差异;而T检验分析表明,玉米乳熟期转基因玉米田食细菌线虫、捕/杂食线虫数量和土壤线虫总数显著高于对照玉米田,这可能与乳熟期转基因玉米田土壤总氮含量显著升高有关.     

Interference of horse purslane (Trianthema portulacastrum L.) and other weeds affect yield of autumn planted maize (Zea mays L.)

To assess comparative losses of Trianthema portulacastrum (HP) relative to other weeds, the experiment was set during consecutive summer seasons 2018 and 2019 at the Research Farm MNS-University of Agriculture, Multan, Pakistan. Experiment consisted three replications which were laid out under randomized complete block design. Experiment consisted of ten treatments viz: weeds free (whole season), HP free till 20 Days after emergence (DAE), HP free till 40 DAE, HP free till 60 DAE, all weeds free 20 DAE, all weeds free 40 DAE, all weeds free 60 DAE, weedy check (all weeds), weedy check except HP and weedy check containing only HP. During 2018 in all weeds weedy check, maximum HP relative density (33.33%) was observed while in 2019, plot where weeds were controlled from growing till 20 DAE showed (80%) relative density at 30 DAE. HP maximum frequency (66.67%, 77.78%) and relative frequency (66%, 100%) was recorded at 45 DAE in plots where HP was kept controlled till 20 DAE and all weeds kept controlled till 20 DAE, respectively. Maximum number of grains per cob (738, 700.68), 1000 grain weight (306.66, 271.51 g) and grain yield (6150, 8015 kg hec^-1) were recorded in plots which were kept all weed free till 60 DAE. As the competition period of weeds increased over 40 DAE, it substantially reduced yield of maize. Keeping the plots HP free till 40 DAE in the maize fields with HP as the major dominating weed, likely increase in maize grain yield is up to 30% compared to the fields where HP left un attended throughout the growing season. However, if maize field is infested with a mix of weeds with more than one dominating weeds including HP, compared to weedy situation the whole season, 30% higher grain yield can be obtained if all weeds are kept controlled till 40 DAE. Hence it can be concluded that whether the farmers face heavy HP infestation only or the mix of weeds as dominating weeds, in either case farmer should control weeds within first 40 days in maize field for better grain yield.     

Weed Management in Rice: Wheat Rotation by Allelopathy

Rice is major crop in India and its cultivation in northwest India started 25 to 30 years ago in assured irrigation areas during the summer rainy season. In this region, rice-wheat rotation became most popular owing to its high yields; however, these crops are highly infested by the weeds, thus farmers use herbicides for their control. Hence, this rotation consumes a maximum quantity of herbicides in this region, which has resulted in several problems (environmental pollution, human health hazards, development of herbicide resistance in weeds). Thus, serious ecological questions about the reliance on herbicides for weed control in this rotation have been raised. One of the alternatives to overcome these problems is with the use of allelopathic strategies, including the use of weed-smothering crops for weed management and for the sustainability of agriculture. The field, pot culture, and laboratory studies have shown that inclusion of weed-smothering crops in rotation considerably reduced the weed population in the current and succeeding crops. Early summer (April-June) fodder crops of sorghum, pearlmillet and maize drastically smothered the weed population and biomass. The residual suppression effect of peralmillet also persisted in the next crop up to 45 days. Thus, it is conceptualized that the inclusion of such summer fodder crops before the rice crop in the rice-wheat rotation may provide satisfactory weed control in the succeeding rice crop and may minimize the use of herbicides. Likewise, the replacement of wheat by winter fodder crops of oat and berseem (Trifolium alexandrinum) may also help in the control of winter weeds. Hence, further studies in this direction may provide satisfactory weed management in rice-wheat rotation and may minimize the use of herbicides and thereby help indeveloping sustainable agricultural practices.     

An ecological approach to study the physical and chemical effects of rye cover crop residues on Amaranthus retroflexus, Echinochloa crus-galli and maize

Weeds can be suppressed in the field by cover crop residues, extracts of which have been demonstrated to exert chemical inhibition of crop and weed germination and early growth in bioassays. In this study, two complementary bioassays were developed with soil and mulch material originating from a long‐term maize–cover crop experiment to determine the relative physical and chemical effect of rye cover crop residues on weed and maize germination and early growth. This was compared with the effect exerted by residue material from the natural vegetation that developed in the crop stubble during the winter before maize sowing. Germination percentage and early growth of maize and two maize weeds, Amaranthus retroflexus and Echinochloa crus‐galli, were assessed in a seed incubator in tilled (green manured) and nontilled (surface mulched) soil, with and without N fertilisation, at various dates after cover crop destruction. Responses were compared to those of the same species in a standard soil without mulch or with an inert poplar mulch. A second bioassay was set up in a glasshouse to determine the effect of different quantities of fresh residue material and additional N fertilisation on emergence speed and percentage and on plant vigour during the first 22 days after cover crop destruction. These results were compared with no‐mulch controls and poplar mulch controls. Results of these trials were compared with weed density and biomass that developed in the maize crop sown after cover crop destruction. Soil and mulch chemical and biological properties were determined for material collected in the field at different times after cover crop destruction. Chemical properties of the mulch differed only occasionally between the treatments, but variation in cover crop biomass production led to significantly different soil chemical properties. Although soil total phenolic acid content did not always correlate to weed and maize germination and early growth inhibition, soil microbial activity did. In suboptimal conditions, as is often the case in the field, plant residue material exerted both a physical and a chemical effect on maize and weed emergence and early growth. Nitrogen fertilisation and application timing can give the maize crop a competitive advantage with respect to the weeds, but the final response and the practical consequences depended largely on the weed species involved.     

长期水旱轮作条件下不同复种方式对稻田杂草群落的影响

通过长期田间定位试验,研究了水旱轮作条件下不同复种方式对稻田杂草群落组成及物种多样性的影响.结果表明: 复种轮作可显著降低稻田杂草密度,抑制杂草生长.不同复种轮作方式下,紫云英-早稻-晚玉米→紫云英-早玉米间作早大豆-晚稻(CCSR)处理物种优势度最低,能降低优势种杂草地位,减轻危害.不同复种轮作方式下基本杂草群落组成均为鸭舌草+稗草+矮慈姑,杂草群落的相似性均较高,其中紫云英-早稻-晚玉米间作晚大豆→紫云英-早玉米-晚稻(CRCS)处理与CCSR处理的相似度最高.稻田复种轮作可在一定程度上提高对杂草的抑制效果,但需要注意某些次要杂草的危害.     

保护性耕作对陇东黄土高原轮作田杂草的影响

以陇东黄土高原旱地连续12年保护性耕作为基础,通过田间取样调查,研究了4种耕作措施下冬小麦-箭筈豌豆-玉米轮作田中杂草的组成和群落特征.结果表明： 不同作物生长期的杂草种类、密度和群落特征各异.免耕使冬小麦生长期杂草密度显著增大,轮作箭筈豌豆后免耕处理的杂草密度变小;秸秆覆盖显著降低了玉米生长期的杂草密度,玉米生长期免耕+秸秆覆盖处理的杂草密度最低.冬小麦和箭筈豌豆轮作前后杂草的群落多样性特征完全相反,从冬小麦生长期到箭筈豌豆生长期,免耕处理杂草群落的多样性指数先高于常规耕作处理,后期低于常规耕作处理;玉米生长期免耕处理的多样性指数均大于其他3种处理.因此,免耕和秸秆覆盖在一些作物生长期能抑制杂草的发生和分布,3种作物轮作对杂草防治具有明显作用.     

Narrow rows reduce biomass and seed production of weeds and increase maize yield

Smallholder farmers in southern African countries rely primarily on cultural control and hoe weeding to combat weeds, but often times, they are unable to keep up with the weeding requirements of the crop because of its laboriousness, causing them to incur major yield losses. Optimisation of crop planting pattern could help to increase yield and suppress weeds and to reduce the critical period of weed control and the weeding requirements to attain maximum yield. Experiments were carried out in Zimbabwe during two growing seasons to assess the effect of maize density and spatial arrangement on crop yield, growth and seed production of weeds and to determine the critical period for weeding. Planting maize at 60 cm row distance achieved higher yields and better weed suppression than planting at 75 or 90 cm row distance. Increasing crop densities beyond the customary three to four plants m⁻² gave modest reductions in weed biomass but also diminished crop yields, probably because of increased competition for water and nutrient resources. Maize planted in narrow rows (60 cm) intercepted more radiation and suffered less yield reduction from delaying hoe weeding than those planted in wider rows (75 or 90 cm), and the duration of the weed-free period required to attain maximum grain yield was 3 weeks shorter in the narrow spacing than that in the 75- and 90-cm row spacings. Weeding was more effective in curtailing weed seed production in the narrow row spatial arrangements than in the wide row planting. The results of these studies show that narrow row spacings may reduce weeding requirements and increase yields.     

Estimating the maximum interval between repeat surveys

Abstract Surveying species that are present in low numbers is difficult because often the survey fails to locate any individuals. One strategy to improve the sample design is to survey the site repeatedly. With repeat surveys the abundance of the target species, and hence likelihood of detection, may change between visits. We present a model for deciding on the maximum surveillance interval between repeat surveys so that there is a high probability of detecting the species. We use as an example surveys for new weed infestations and model the chance of detecting the weed before control costs reach a threshold. The maximum surveillance interval depends on the rate of weed growth, the ability to detect the weed, and the cost of controlling the weed. Typically weed growth rates are high. Fast growing plants need to be detected early before they spread, but often weeds are difficult to detect when young and still comparatively cheap to control. Results from the model to determine maximum surveillance intervals are given for five broad habitat types and seven weed types. Surveillance intervals ranged from 1 to 10 years. Longer intervals are appropriate when searching for weeds with slower growth rates, that are easier to detect, and those that can be controlled cheaply.     

Early establishment of planted Retama sphaerocarpa seedlings under different levels of light,water and weed competition

Large amounts of former cropland are being abandoned in developedregions. To formulate guidelines for land reclamation programmes, we exploredthe effects of artificial shading, irrigation, and removal of weed competitionon the performance of Retama sphaerocarpa (L.) Boiss.seedlings in a factorial experiment located in an abandoned cropland in CentralSpain. R. sphaerocarpa is of interest for revegetationbecause it is a drought tolerant leguminous shrub that is a major structuralcomponent of the native plant community. Seedling performance was evaluated inthree ways: seedling survivorship, growth, and photochemical efficiency. Wealsomeasured soil moisture and weed biomass production and found that bothincreasedunder artificial shading conditions. Soil moisture increased very slightlywhereweeds were removed. Thus, increased transpiration from weeds outweighed reducedevaporation from soils due to shading by weeds. Artificial shading was the mosteffective treatment for seedling survivorship, followed by removal ofcompetition by weeds. After summer, 34 % of the seedlings survived in the mostfavourable conditions (artificially shaded plots where weeds were removed),compared to ca. 1 % in full-light plots with no removal of weed competition. Apositive effect of irrigation was found for growth of seedling cover and heightin shaded plots. The analysis of photochemical efficiency pointed out therelevance of weed competition removal, and confirmed the usefulness of fastfluorescence transient techniques for the quantification of seedlingperformance. The data suggest that competition between seedlings and weeds wasprimarily for water rather than for light. We conclude that i) artificialshading improved seedling performance, but this is a little practical techniquebecause of its cost; ii) as weeds compete with, rather than facilitate, plantedseedlings, weed clipping around the seedlings is a feasible technique thatwouldimprove seedling survival; and iii) seedling performance could alsoconsiderablyimprove with a higher irrigation than was used in this experiment(75lm^–2 per growth period), provided that weedsare removed.     

Vector and Host-Plant Relationships of the Leafhopper-Borne Maize Yellow Stripe Virus

Maize yellow stripe virus (MYSV), associated with tenuivirus-like filaments, is transmitted in a persistent manner by the leafhopper Cicadulina chinai. In this vector, MYSV acquisition and inoculation threshold times were 30 min each, latent period ranged from 4.5 to 8 days depending on temperature (14-25 °C), and retention periods were as long as 27 days. Up to 26 % of C, chinai collected from maize fields in Giza, Egypt, during September and October 1985 were naturally infective with MYSV. Two symptom-types (fine and coarse stripe) appeared on experimentally infected plants, usually on separate leaves of the same plant. However, these two symptom-types could not be isolated on separate plants through transmission by single C. chinai leafhoppers. MYSV was transmitted by nymphs and adults of C. chinai from maize to maize, wheat and barley, and from wheat to maize plants. Up to 6 % of the wheat plants examined in Naga Hamadi (Southern Egypt) in February 1986, were naturally infected. It is suggested that wheat, barley and possibly graminaceous weeds may serve as winter hosts or reservoirs for MYSV and its leafhopper vector in Egypt.