兰州引黄灌区小麦田杂草群落及其生态位研究

通过田间调查,并结合生态位理论和方法对不同栽培条件下兰州引黄灌区小麦田主要杂草群落组成及生态位特征进行研究。结果表明:小麦田主要杂草种类有打碗花(Calystegia hederacea)、藜(Chenopodium album)、刺儿菜(Cephalanoplos segetum)、马齿苋(Portulaca oleracea)、反枝苋(Amaranthus retroflexus)、狗尾草(Setaria viridis)、苣荬菜(Sonchus brachyotus)和萹蓄(Polygonum aviculare)。藜时间、水平、垂直生态位宽度值最高,是群落中的优势杂草;其次是打碗花,为主要杂草;且藜与打碗花的时间、水平、垂直生态位重叠值比较大。研究表明小麦田杂草群落存在潜在的变化因素,随着农田环境的变化,会导致农田杂草群落发生变化。     

耕作方式对新垦沙地农田杂草群落结构的影响

通过田间调查的方式,研究了黑河中游边缘绿洲新垦沙地农田杂草分布状况,并对不同耕作方式下农田杂草群落结构特征进行了分析。调查中共记录杂草16种,隶属10科。新垦沙地农田杂草群落基本组成为藜(Chenopodium album)+牛筋草(Eleusineindica)+狗尾草(Setaria viridis)+反枝苋(Amaranthus retroflexus)。与当地传统的地膜覆盖、秋耕和玉米连作耕作方式相比,秸秆覆盖、减少秋耕和玉米-大豆轮作均可增加农田杂草物种丰富度、多样性指数和群落优势度(P0.05)。与当地传统耕作方式相比,秸秆覆盖可增加杂草群落中牛筋草优势度比,降低藜和反枝苋优势度比;减少秋耕可增加狗尾草、反枝苋、灰绿藜(C.glaucum)和米瓦罐(Silene conoidea)优势度比,降低牛筋草优势度比;玉米-大豆轮作可增加米瓦罐优势度比。不同耕作方式对偶见种杂草在田间的分布和组成影响不明显。可以看出,新垦沙地农田杂草物种较少,群落组成单一;不同耕作方式对新垦沙地农田杂草物种多样性和群落结构组成有明显影响,进一步深入研究对沙地农田杂草合理防除具有重要的指导意义。     

棉隆土壤消毒对党参育苗田杂草群落特征的影响

为了探寻党参育苗田杂草防控途径,在甘肃省宕昌县党参主产区采用含98%棉隆微粒剂对土壤消毒(F)后进行党参育苗,以未消毒处理为对照(CK),出苗后定期比较两育苗田杂草群落消长动态及其差异。结果表明:1)未消毒对照田发生杂草14种(10科14属),优势杂草有一年生鹅肠菜、狗尾草、多年生刺儿菜、田旋花和长裂苦苣菜。消毒田与未消毒对照田杂草群落相似度(WCs)为83.3%;与未消毒对照田相比较,消毒田出苗期杂草减少5种,生长期减少3种(萹蓄、灰绿藜和细果角茴香),平均减少39.8%;平均出苗期和生长期杂草群落WCs降低18.9%。2)土壤消毒使党参育苗前期杂草多样性降低,恶性杂草种群丰度降低,并显著抑制其再生力。3)土壤消毒可有效降低杂草发生密度,尤其一年生杂草鹅肠菜、狗尾草。消毒田较未消毒对照田6月上旬杂草减少477株·m~(-2), 6月下旬至10月减少143株·m~(-2),杂草平均密度和鲜生物量分别降低89.0%和77.5%;育苗前期可显著抑制鹅肠菜、心叶野荞麦等有性繁殖杂草的初生量,后期可显著抑制长裂苦苣菜、田旋花等多年生兼性繁殖杂草的再生力。研究结果表明,播前采用98%棉隆微粒剂土壤消毒可有效抑制并减轻党参育苗田一年生杂草危害程度,但对多年生深根系杂草需配合及早除草管理。     

燕山北部板栗林下杂草群落动态及生态位研究

为准确掌握燕山北部板栗园杂草的发生现状及群落组成,分别于2017年、2018年、2020年对燕山北部板栗林下杂草的种类、数量等进行调查,并运用Levins生态位指数和Pianka生态位重叠指数分析板栗林下优势杂草的生态位动态及群落对资源的利用情况和种间竞争情况。结果表明:(1)2017年、2018年、2020年燕山北部板栗林下杂草群落中分别有53种(27科48属)、47种(24科43属)和44种(24科41属)植物。其中优势杂草15种。(2)15种优势杂草中,葎草和灰绿藜占据较宽的生态位,它们对环境资源利用的多样性程度比较高。鸭跖草、艾蒿、狗尾草、茜草、苦荬菜、白屈菜、紫花地丁、灰绿藜、毛地黄和野大豆等物种对资源的利用能力在逐步增强。(3)杂草群落中生态位重叠值＜0.2的优势物种种对数明显减少,优势杂草物种在逐渐增加对周边资源环境充分利用的能力,灰绿藜逐渐取代葎草的优势地位,进而导致种间竞争关系更加复杂,群落向更高级更合理利用环境资源的群落方向演替,逐步形成更加复杂的种群结构。因此,准确掌握板栗园杂草的发生现状、优势种群及群落组成,可为燕山北部板栗林下杂草的针对性防治提供理论依据。     

秀山县稻田杂草种类及危害情况调查

2019年,秀山县开展了稻田杂草种类及危害程度调查。结果表明,秀山县稻田杂草种类有25科57种,其中莎草科杂草15种,禾本科杂草6种,眼子菜科4种,鸭跖草科3种,千屈菜科3种,其他种类均为1～2种。密度较大的杂草有青萍、水绵、满江红、牛毛毡、黑藻、金鱼藻、轮藻等;频度较大的杂草有青萍、空心莲子草、稗草、双穗雀稗、鸭舌草、野慈菇、野荸荠、水绵、眼子菜、千金子等;多度较大的杂草有青萍、水绵、轮藻、满江红、牛毛毡、金鱼藻、黑藻等。按照"三层三级目测调查法"调查杂草的危害等级,发现秀山县稻田杂草优势种为稗草、青萍、满江红、金鱼藻、矮慈菇、牛毛毡、水绵等。     

永宁县春麦田杂草发生特点调查初报

分别于2015、2018年4月中下旬,采用随机5点取样法对宁夏回族自治区永宁县春麦田杂草种类及发生情况开展了2次调查。结果表明,当地春麦田杂草群落组成大体无变化,常见杂草分属藜科、蓼科、旋花科、菊科、十字花科及禾本科,约20种,其中藜科藜属的藜、灰绿藜、小藜为优势种杂草,藜为极优势种,2次调查显示藜科杂草发生的相对密度为50%左右。建议当地春麦田除草应选择对阔叶类杂草防效好的除草剂,实现农药减量控害的目的。     

草坪杂草发生规律及春季阔叶杂草的防除

本研究采取倒置"W"9点取样法并结合踏查的方法,对廊坊地区草坪杂草进行了为期1年的调查,鉴定出草坪杂草20科53种,其中优势杂草有地锦(Euphorbia humifusa Willd.)、山苦荬(Ixeris chinensis Nakai.)、马唐(Digitaria sanguinalis Scop.)、马齿苋(Portulaca oleracea L.)、独行菜(Lepidium apetalum Wild.)、灰菜(Chenopodium album L.)、朝天萎陵菜(Potentilla supina L.)、附地菜(Trigonotis peduncularis Benth.)。针对调查结果,选用选择性、触杀型除草剂克草特(10%乙羧酸草醚),对在春季危害草坪草比较严重的阔叶杂草马齿苋和灰菜进行防除试验,结果表明,用药量为100mL/m2的500～4500倍液克草特对马齿苋杂草具有特效而对灰菜防效一般。对新建高羊茅草坪草和已经成坪的碱茅草坪草进行了安全性试验,结果表明,除草剂的最佳防除浓度在1500～3500倍;在防除新建植的高羊茅草坪上的杂草时应注意喷药时期最好是在高羊茅的分蘖前期或分蘖期,对于灰菜的防除时期最好选在其出苗期。     

广西农田杂草探讨

从1977年初至1978年底,1982年12月至1984年12月,先后4年调查了广西4个市,16个县的农田杂草;采用点面结合,按不同季节,定点观察记载,共收集农田杂草91科,346属,604种。通过含种数较多的科,与广西、全国植物区系同科种数比较,初步看出广西农田杂草的特点,是以亚热带杂草为主,并有少量热带科及温带科的杂草;主要集中在11个科,其中禾亚科、菊科、蓼科、伞形科和玄参科为优势科。本文对广西农田杂草的生态分布、危害性、防除及其利用,作了简要的阐述。     

秀山县稻田杂草发生态势及控制技术探讨

通过对秀山县稻田杂草发生危害状况及萌发、生长趋势的调查研究,结果表明:秀山县稻田杂草有20科32种,各地种群组合差异较大,群落结构复杂,发生频度较高的有8科9种杂草,优势草种为:牛毛毡、草茨藻、节节菜、鸭舌草等;杂草发生量大,密度高,危害重;杂草发生危害时间长,出草高峰在插秧后10～25天。根据田间草害发生态势,提出了“前期药除,中期水控、药补,后期人工拔除”的综合治理对策。     

都匀市草坪杂草种类调查与分析

通过实地调查和查阅有关文献,对都匀市草坪杂草种类进行调查和统计分析。结果表明:都匀市草坪杂草有39科112种,其中菊科最多,有23种占杂草总数的20.54%,禾本科有15种,占杂草总数的13.39%,蓼科有7种,占杂草总数的6.25%;其他占杂草总数的59.82%。一年生和二年生杂草68种,占杂草总数的60.71%。同时分析草坪中杂草的主要危害种类及各时期的发生状况,并提出了相应的防除措施。     

Type and time of autumn tillage with and without herbicides at reduced rates in southern Sweden: 2. Weed flora and diversity

The design of integrated weed management (IWM) systems is essential in order to reduce the use of herbicides for crop production. By combining different weed management practices, herbicides may be used at lower doses than normally recommended, while still maintaining acceptable weed population levels. The purpose of this study was to develop tillage strategies, with and without herbicides at reduced rates, appropriate for different weed populations. The influences of type and time of stubble cultivation, harrowing and mouldboard ploughing on the weed flora were followed during 1988–1994 in eight long-term field trials situated in southern Sweden. Spring-sown barley (Hordeum distichon L.) and oats (Avena sativa L.) dominated the crop rotations. Herbicides were either omitted or used at ca. 50% of a full dose. The perennial species Sonchus arvensis L. was favoured by omittance of ploughing but was better controlled by late ploughing not preceded by stubble cultivation; the reduction in the latter treatment being 74%. Stubble cultivation succeeded by ploughing reduced biomass of Elymus repens (L.) Gould. by 90% compared with ploughing solely. Early ploughing reduced the biomass of the species by 50% compared with late ploughing. The species Cirsium arvense (L.) Scop. was highly favoured by early ploughing followed by late autumn harrowing, the biomass of the species being six-fold higher than in other treatments. Compared with other treatments, stubble cultivation favoured four annuals but efficiently controlled three others, while omittance of ploughing favoured six annual and two perennial weed species. Late ploughing not preceded by stubble cultivation favoured four annual and one perennial species, while early ploughing was more efficient than late ploughing in controlling two of the annual species. Influences of treatments on weed species were frequently moderated by interspecific competition resulting in inconsistent response at different sites. Herbicides reduced the number of species by three, from 11 to eight species, averaged across sites and tillage systems. Influences of treatments on diversity were not consistent, since weed floras differed between sites and since some of the species responded inconsistently to tillage and herbicides. This study shows that by utilizing appropriate tillage strategies it is possible at many sites to maintain acceptable weed population levels, although herbicides are used at 50% lower doses than is normally recommended. The timing and type of tillage have to be chosen for being as efficient as possible to the most troublesome weed species at a site.     

Design and syntheses of novel phthalazin-1(2H)-one derivatives as acetohydroxyacid synthase inhibitors

A series of 2-substituted-8-(4,6-dimethoxypyrimidin-2-yloxy)-4-methylphthalazin-1-one derivatives, 7a-7w, were designed via an ortho-substituent cyclization strategy to discover a new herbicidal lead structure. These compounds were synthesized by a seven-step route using 3-hydroxy-acetophenone as a starting material. Determination of the Ki values against wild-type A. thaliana acetohydroxyacid synthase (AHAS) (EC 4.1.3.18) indicated that some of the compounds displayed good enzyme inhibition activity comparable to that of KIH-6127. The further preliminary bioassay data on weeds showed that the synthesized compounds exhibited typical injury symptoms of AHAS-inhibiting herbicides, and some of them showed broad-spectrum and high herbicidal activities in postemergence treatments against Echinochloa crusgalli, Digitaria sanguinalis, Setaria viridis, Brassica juncea, Amaranthus retroflexus, and Chenopodium album at an application rate of 150 g ai/ha. To our knowledge, this is the first report of methylphthalazin-1-one derivatives as AHAS inhibitors.     

Use of resistant ACCase mutants to screen for novel inhibitors against resistant and susceptible forms of ACCase from grass weeds

The aryloxyphenoxypropionic acid (AOPP) and cyclohexanedione (CHD) herbicides inhibit the first committed enzyme in fatty acid biosynthesis, acetyl CoA carboxylase (ACCase). The frequent use of AOPP and CHD herbicides has resulted in the development of resistance to these herbicides in many grass weed species. New herbicides that inhibit both the susceptible and resistant forms of ACCase in grass weeds would have obvious commercial appeal. In the present study, an attempt was made to identify molecules that target both the herbicide-sensitive and -resistant forms of ACCase. Seven experimental compounds, either CHD-like or AOPP-CHD hybrids, were synthesized and assayed against previously characterized susceptible and resistant forms of ACCase. All seven compounds inhibited ACCase from sensitive biotypes of Setaria viridis and Eleusine indica (I50 values from 6.4 to >100 microM) but were not particularly potent compared to some commercialized herbicides (I50 values of 0.08-5.6 microM). In almost all cases, the I50 values for each compound assayed against the resistant ACCases were higher than those against the corresponding sensitive ACCase, indicating reduced binding to the resistant ACCases. One compound, a CHD analogue, was almost equally effective against the resistant and susceptible ACCases, although it was not a very potent ACCase inhibitor per se (I50 of 51 and 76 microM against susceptible ACCase from S. viridis and E. indica, respectively). The AOPP-CHD hybrid molecules also inhibited some of the resistant ACCases, with I50 values ranging from 6.4 to 50 microM. These compounds may be good leads for developing ACCase inhibitors that target a wider range of ACCase isoforms, including those found in AOPP- and CHD-resistant weed biotypes.     

Foliar applied harpin effects on fruit quality of peppers

Abstract

During the past century, changes in cropping systems have led to selective pressure on weed flora. The number of competitive species with decreased susceptibility to herbicides has increased, at the cost of more susceptible species. For a long period, the economically important perennial weed species Cirsium arvense (L.) Scop. and Sonchus arvensis L. have mainly been controlled by the herbicide MCPA (phenoxy-acetic acid), which stimulates the weed plant to abnormal growth. However, it has been reported from Sweden, Great Britain, Hungary and North America that C. arvense has become less susceptible to MCPA since the 1950s. Therefore, two greenhouse experiments were performed at Uppsala, Sweden with clones of C. arvense and S. arvensis. The purpose was to study whether ecotypes (clones) from high input farmland, where herbicides had been used intensively and regularly for a long time, were less susceptible to herbicide (MCPA) treatment than ecotypes from low input farmland. Sixty clones of C. arvense and 36 clones of S. arvensis were treated with nine different doses of MCPA. The results supported the suggestion that a shift towards less MCPA-susceptible ecotypes of C. arvense had occurred on high input farmland. Clone material from such farmland had, on average, significantly higher dry matter content after herbicide treatment than ecotypes from low input farmland. Similar decrease in susceptibility was not detected for S. arvensis. This was probably due to S. arvensis generally being less susceptible to MCPA than C. arvense. Sonchus arvensis has therefore being exposed to a lower selection pressure than C. arvense.     

采矿业对环境影响效应研究

定西市水土保持监测工作由综合典型监测站、国家重点工程项目临时监测点和区域内水文站点3部分组成。综合典型监测站设在安定区安家沟流域,由21个径流小区、1个卡口站和1个气象站组成;水文站点由安定区的东河、西河水文站、通渭县景屏水文站、渭源县清源水文站、临洮县红旗水文站和李家村水文站及岷县水文站组成,观测任务由定西水文水资源局负责实施;临时监测点由安定区的道回沟、渭源县的唐家河、陇西县的揭皮沟3条坝系和安定区、通渭县的生态修复项目两大部分5个点组成。     

Biodiversity and Biomass Production of Weeds in a Long-Term Fertilization Experiment

A field experiment was carried out to study the influence of nitrogen (N), phosphorus (P), and potassium (K) nutrient supply on weed flora in maize. The investigations were conducted in a long-term fertilization experiment launched in 2003 on a loamy chernozem soil with lime deposits, in Fejér County, Hungary. The composition, biomass weight, and density of weeds were determined in relation to different nutrient supplies. Seventy-five percent of weeds consisted of three species: Ambrosia artemisiifolia L., Datura stramonium L., and Helianthus annuus L. Density of weeds varied relative to the different nutrient treatments, with a range of 82–131 plants m^?2. The total weed density was significantly lower by 19.9–37.8 percent in the N-containing treatments (NP, NPK) than in non-N treatments. The density of the nitrophil D. stramonium L., Chenopodium album L., Chenopodium hybridum L., and Amaranthus blitoides S. Watson was higher when N supply was greater.     

荒漠化草原人工封育区植物生态位研究--以宁夏盐池为例

运用L ev ins生态宽度指数及P ianka生态位重叠指数对宁夏盐池荒漠草原人工封育区2002年及2003年生态位宽度及生态位重叠进行计量。结果表明:2002年封育区茵陈蒿、狗尾草生态位宽度值最大,分别为0.758、0.505,是2002年封育区的优势种;2003年封育区的优势种是茵陈蒿、狗尾草、老瓜头、苦豆子,其生态位宽度值分别为0.868,0.567,0.563,0.552。最大生态位重叠值2002年与2003年均未出现在优势种之间,2002年出现在赖草与叉枝鸦葱、新疆猪毛菜与志远之间;2003年出现在沙珍棘豆与中亚虫实、沙珍棘豆与狭叶米口袋、中亚虫实与狭叶米口袋之间。     

Weed management in canola (Brassica napus L): a review of current constraints and future strategies for Australia

ABSTRACT

Weeds are a major constraint to canola (Brassica napus L.) production, reducing grain yield and quality. The repeated use of pre- and post- emergent herbicides to control several grasses and broadleaf weeds has escalated the problem of herbicide resistance in weeds. The development of herbicide-tolerant canola cultivars has increased the flexibility of weed management but has also increased the risks of outcrossing with wild relatives and weed shifts to resistance. Herbicide-resistant weed species, and the related biological repercussions, pose a major threat to sustainable weed management. These developing risks have led researchers to examine integrated weed management (IWM) techniques for sustainable weed control. Weed control strategies using non-chemical tactics have valid roles for managing weeds. However, in broad-acre commercial fields, the effectiveness of several non-chemical selections are less proven than commercial chemical herbicides. Canola competition and allelopathy for weed suppression are potential components for integrated weed management in canola. This review examines current chemical and non-chemical options available for developing IWM strategies for profitable canola production, as well as future research directions.