Timing of seedling emergence and reproduction in some tropical dicotyledonous weeds

The periodicities of seedling emergence of seventeen dicotyledonous weeds were determined and fourteen of these examined in detail. In addition, the periodicity of vegetative growth and reproductive development was recorded for all dicotyledonous species in the study area. Field emergence at monthly intervals during one year was compared with the emergence of seedlings from soil transferred to a shade house and kept moist. This comparison suggested that lack of water during the dry season was the dominant factor controlling germination, although several species failed to germinate when given adequate water under shade-house conditions indicating that innate or induced dormancy also occurred. Species were separated into two groups based on the liming and duration of their main phenological stages. The first group contained species which had individuals present throughout the year while plants in the second group died during the dry season and reappeared at the start of the wet season. Most species in the former had some individuals flowering or shedding seed all year round while the latter had a short period of vegetative growth followed by prolonged reproduction. The possibility of using emergence and phenological data for improving tropical weed control is discussed.     

Effects of tropical weeds on yield in white yam (Dioscorea rotundata Poir)

The effects of tropical weeds on the yield of while yam were studied outdoors in wooden boxes. When the foliage and roots of weeds were in physical contact with the crop until harvest (full interference), tuber yield of yam was reduced by 76–79% of that obtained under weed-free conditions over 3 years of study. When there was no physical contact between roots of crop and weeds, the leachate from the weed zone caused tuber yield reductions of 42, 40 and 38% in 1978, 1979 and 1980, respectively, when it was applied to the yam zone. This leachate also reduced leaf area index (LAI) in the yam crop but the adverse effects on yam root and shoot biomass were less pronounced. This technique made it possible to separate competitive interference from allelopathic interference of tropical weeds with the yam crop.     

Effect of soil solarization on weeds and nematodes under tropical Indian conditions

The control of weeds and nematodes by solar heating of the soil using transparent polyethylene (PE) sheets was studied in the field during the summer of 1990. PE mulching for 32 days decreased the emergence from seed of the dominant weeds Dactyloctenium aegyptium (L.) P. Beauv., Acrachne racemosa (Roem. & Schult.) Ohwi, Trianthema monogyna L. and Cyperus rotundus L. by over 90%. Emergence of C. rotundus from tubers was increased by the mulching treatments. Mulching for 16 days also decreased weed emergence but to a lesser extent than the 32-day treatment. The main solarization effect was restricted to the 0–5 cm layer of soil. Solarization reduced the population of plant-parasitic nematodes (Tylenchus, Heterodera, Xiphinema, Hoplolaimus, Pratylenchus and Ro-tylenchus spp.) by about 90% and of saprophytic nematodes by about 60% but, after 70 days, the nematode levels had largely recovered. The mean maximum soil temperatures recorded at 5 cm were higher when mulching followed irrigation. Data are given on the soil temperatures recorded over the 32-day period. The growth of soybean was improved and seed yield increased by up to 78% following solarization. Effet de la solarisation du sol sur les mauvaises herbes et les nematodes en conditions tropicales indiennes La lutte contre les mauvaises herbes et les nématodes par solarisation du sol à l'aide de films de polyéthylène transparent (PE) a étéétudiée au champ pendant l'été 1990. Trente deux jours de solarisation diminuaient de plus de 90% la levée à partir de graines des mauvaises herbes dominantes Dactyloctenium aegyptium (L.) P. Beauv., Acrachne racemosa (Roem. & Schult.) Ohwi, Trianthema monogyna L. et Cyperus rotundus L. La levée de C. rotundusà partir de tubercules était accrue par la solarisation. Seize jours de solarisation diminuaient aussi la levée des mauvaises herbes, mais dans un moindre mesure. L'effet de solarisation s'exerçait principalement dans les 5 centimètres superficiels du sol. La solarisation réduisait d'environ 90% la population de nématodes parasites des plantes (Tylenchus, Heterodera, Xiphinema, Hoplolaimus, Pratylenchus et Rotylenchus spp.) et d'environ 60% la population des nématodes saprophytes. Après 70 jours, les populations de nematodes étaient pratiquement reconstituées. Les moyennes des températures maximales du sol enregistrées à 5 cm de profondeur étaient plus élevées quand l'installation du film polyéthylène suivait une irrigation. Des données concernant la température du sol sur 32 jours sont communiques. La croissance du soja était accrue et le rendement en grains augmentait jusqu'à 78% après solarisation. Wirkung der Bodensolarisation auf Unkräuter und Nematoden unter tropischen Bedingungen Die Bekämpfung von Unkräutern und Nematoden durch Solarisation mittels farbloser Polyethylenfolia (PE) wurde im Sommer 1990 im Freiland untersucht. Nach 32tägiger Solarisation nahm die Keimung der vorherrschenden Unkräuter Dactyloctenium aegypticum (L.) P. Beauv., Acrachne racemosa (Roem. & Schult.) Ohwi, Trianthema monogyna L. und Cyperus rotundus L. um über 90% ab. Der Austrieb von Cyperus rotundus aus Knollen wurde gefördert. Eine l6tägige Solarisation war nicht so wirkungsvoll. Die Wirkung war auf die oberste Bodenschicht bis 5 cm Tiefe beschränkt. Gegen pflanzenparasitische Nematoden (Tylenchus, Heterodera, Xiphinema, Hoplolaimus, Pratylenchus und Rotylenchus spp.) betrug die Wirkung der Solarisation etwa 90%, gegen saprophytische Nematoden rund 60%, aber nach 70 Tagen hatten sich die Nematodenpopulationen wieder weitgehend erholt. Nach Bewässerung wurde in 5 cm Tiefe eine höhere Bodentemperatur erreicht. Für die 32-Tage-Periode werden die Temperaturdaten wiedergegeben. Nach der Solarisation war das Wachstum von Sojabohne verbessert, und die Erträge stiegen um bis zu 78%.     

马蹄金草坪杂草发生特点及防除技术研究

马蹄金草坪危害严重的杂草有稗草、凹头苋、香附子、粟米草、马唐、铁苋菜等.精禾草克对禾本科杂草的株防效达100%,且对马蹄金无明显药害.草除灵对香附子的株防效可达90%以上,并能部分杀死地下根茎,对其他阔叶类杂草株防效也达90%以上.胺苯磺隆用量少,价格低廉,也是马蹄金草坪的适宜除草剂.精禾草克、胺苯磺隆、草除灵三者复配后喷施,可以保证对马蹄金草坪杂草的防除效果,又能降低成本.     

河南农田杂草植物区系特征及生态分布

通过野外调查和资料分析,对河南不同类型农田杂草区系及生态分布特点进行研究.结果表明河南有农田杂草701种,隶属于343属、83科;属的分布区可划分为15个类型和14个变型,其中温带成分占除世界分布属以外的65.30%(下同),热带成分占33.58%,反映出北亚热带与南暖温带过渡的性质;种的区系成分复杂,可归为15种分布类型,以泛热带分布、北温带分布、旧世界温带分布、东亚分布和中国特有分布占优势;杂草的生态分布具有广泛性、南北交错、南北分布差异等特点,其对农田的危害表现出麦田、秋田、水田、果园、荒地等时空生态位的多重变化.根据杂草时空生态分布特点,在农业生产中应加强秋田和果园杂草的防治力度.     

浅水藕田杂草发生特点及控制技术

1浅水藕田杂草的发生特点 1．1杂草发生时间长,具有明显的萌发高峰期 两年观察结果表明,浅水藕田杂草萌发有一个高峰期,高峰期出现的时间为栽种后10—20d,高峰期间的出草量占总草量的60．3％～69．5％。从各类杂草的萌发数量看,禾本科杂草和莎草科杂草主要集中在栽种后10～15d,其出草量分别占总草量的80．3％和76．8％,呈单峰型发生。阔叶草萌发表现为明显的双峰型,第一峰为浅水藕栽种后15～20d,出草量占总草量的51．9％,第二峰在栽种后30—35d,出草量占总草量的36．5％。     

Ecophysiological characteristics of five weeds and a wheat crop in the Indo‐Gangetic Plains,India

The objective of this research was to compare selected ecophysiological parameters for a wheat crop found in the Indo‐Gangetic Plains of India and its five dominant weeds. The dominant and regionally ubiquitous weeds in the wheat field that was selected for the study were Anagallis arvensis, Chenopodium album, Melilotus albus, Phalaris minor and Rumex dentatus. Taller weeds, such as C. album and P. minor, constituted one group along with the crop, with a low photosynthetic rate, specific leaf area, leaf nitrogen mass basis, chlorophyll content, photosynthetic nitrogen‐use efficiency and leaf area ratio, in comparison to shorter weeds, such as A. arvensis, M. albus and R. dentatus, which formed another group with a high photosynthetic rate, specific leaf area, leaf nitrogen mass basis, chlorophyll content, photosynthetic nitrogen‐use efficiency and leaf area ratio. Interspecific variations in the photosynthetic rate were driven mainly by variability in the specific leaf area and leaf nitrogen content. The taller weeds and the crop had a low specific leaf area later in the season, whereas the smaller weeds had a relatively high specific leaf area, which might be an adaptation to the shaded environment below the canopy. The result indicates that any weed management in the wheat fields of the Indo‐Gangetic Plains will need two different approaches because of the different strategies followed by the two weed groups that were identified in the present study.     

A functional group approach to the management of UK arable weeds to support biological diversity

Weeds have an important role in maintaining farmland biodiversity. This needs to be balanced with their potential negative impact on crop yield and quality. Mechanistic models of crop–weed competition are an important tool in striking this balance. A range of common UK annual weeds were screened for the eco‐physiological traits required by the models. Using multivariate techniques, a number of functional groups with a similar pattern of productivity and competition were identified, based on trade‐offs between traits. A scheme was developed to assign species outside of the data set to one of the groups, based on life cycle, seed mass, maximum height and time of first flowering. As well as having a similar competitive ability, species within a group also appeared to have a similar ecosystem function, in terms of supporting higher trophic groups. Two beneficial groups of species were identified that combined a relatively low competitive ability with a high importance for invertebrates and birds. The identification of functional groups in the UK arable flora is a useful tool for assessing a weed community in the context of reconciling biodiversity provision with crop production. Preserving beneficial plant functional types within the crop would complement non‐cropped wildlife refuges, such as field margins.     

水稻小苗(抛秧)田杂草的生态特点及控制技术

近年来.随着水稻轻型栽培技术的大面积推广,应用工厂秧、抛秧和肥床旱育秧的面积不断扩大.由于栽培措施改革,田间草相发生明显变化.为了有效地控制各类轻型栽培稻田的杂草危害,本文作者根据近几年宜兴地区水稻小苗(抛秧)田杂草生态特点及控制技术进行探讨,以期对苏南地区水稻小苗(抛秧)田杂草控制提供参考.     

通州市油菜田杂草发生特点与分布规律初步研究

通州市水旱轮作区以禾本科杂草为主,杂草种类主要是早熟禾、硬草、牛繁缕等;旱作物区以阔叶杂草为主,杂草种类主要是猪殃殃、卷耳、波斯婆婆纳等。通州市油菜田平均杂草密度为520株/m2,其中水旱轮作区的平均密度约为旱作物区的2.5倍。不同杂草中,早熟禾的出现频率和发生密度最高,不同农业区都有分布,但水旱轮作区显著多于旱作物区,在半数以上乡镇已取代硬草成为油菜田优势种杂草。     

新疆核桃-小麦间作麦田杂草组成及群落特征

为明确新疆核桃与小麦间作对麦田杂草种类及群落结构的影响,于2012—2017年对新疆南疆核桃-小麦间作、单作麦田杂草发生情况进行了调查。结果表明,南疆麦区杂草有39种,隶属14科33属,其中以菊科、禾本科、藜科为主;优势杂草有9种,分别是灰绿藜Chenopodium glaucum L.、稗草Echinochloa crusgalli(L.)Beauv.、播娘蒿Descurainia sophia(L.)Schur.、扁蓄Polygonum aviculare L.、硬草Sclerochloa kengiana L.、田旋花Convolvulus arvensis L.、离蕊芥Malcolmia africana(L.)R. Br.、小蓟Cephalanoplos segetum(Bunge.)Kitam.、苣荬菜Sonchus brachyotus DC.;与小麦单作田相比,核桃-小麦间作麦田杂草物种丰富度及Shannon-Wiener指数较高,2017年物种丰富度最高达27种,代表杂草优势集中性的Simpson指数则是小麦单作田高于核桃-小麦间作麦田,2013年高达0.32;核桃-小麦间作有利于麦田播娘蒿、苣荬菜和离蕊芥发生,但不利于萹蓄发生,其它5种优势杂草在间作和单作麦田的发生密度无显著差异。     

旱直播稻田杂草发生特点及化除技术

2005-2006年进行了旱直播水稻田杂草发生及防除技术研究,42%新野、50%速除、30%扫特 10%苄磺隆于水稻播后封杀,药后45 d防效达90%以上。     

超高茬麦套稻田杂草发生特点、成因及化除策略

1998～2001年对江苏省5个不同生态区125个麦套稻田示范点的田间杂草发生情况进行了调查分析,初步掌握了麦套稻田杂草的发生特点,主要表现为种类多、发生早、群体大、危害重。免耕方式、前茬余草和前期田间管理粗放是造成杂草发生严重的原因。通过试验提出了"前封后杀"的化除策略,并研究出多项配套化学除草技术,促进了超高茬麦套稻田技术的大面积推广应用。     

几种南方主要草坪杂草生物学特性及抗逆性

对在南方危害严重的5种草坪杂草的营养体繁殖能力、不同植株密度对草坪的侵蚀程度、植株对不同土层厚度的穿透力及其营养体抗逆性等作了试验观察。结果表明,空心莲子草的营养体繁殖力及抗逆性最强;地锦有性繁殖速度快和繁殖量大,但营养体抗逆性差。除地锦外,其余4种杂草对不同厚度的土层均有不同的穿透力。白茅和空心莲子草穿透力最强。提出了防控措施及颓废草坪的重建措施。     

Weed interference in maize, cowpea and maize/cowpea intercrop in a subhumid tropical environment. II. Early growth and nutrient content of crops and weeds

Early growth and nutrient content of crops and weeds from weed-free and weedy no-tillage maize (Zea mays L, cv. TZB), cowpea (Vigna unguiculata (L) Walp. cv. VITA-5) and maize/cowpea intercrop at populations of 40000, 50000 and 30000 + 40000 plants ha^?1 grown on a loamysand Oxic Ustropept in a subhumid tropical location were monitored in the early and late 1979 cropping seasons. In the first 6 weeks of growth in the early season, cropping pattern had no effect on weed growth; weeds did not suppress crop growth significantly until 5–6 weeks after sowing and total crop dry weights were not affected by cropping pattern. Three weeks after sowing, weeds from weedy crop plots had taken up two to four times as much nutrient (N, P, K, Ca + Mg) as was taken up by corresponding weed-free crops. In the late season, weed dry weight 6 weeks after sowing was depressed in the intercrop compared to monocultures and dry-matter production of the intercrop was higher than those of monocultures. The resource use index (RUI), defined as the amount of an environmental resource used by a weed-free crop divided by the combined amount of the same resource used by the corresponding weedy crop and the associated weeds, increased with age of crop and was higher for the intercrop than the monocultures only in the late season.     

Growth characteristics of spring barley and selected weeds. I. Effect of irradiance in growth chambers

A study in growth chambers with three irradiance levels was carried out over a four-week period on individual seedlings of spring barley (Hordeum vulgare L.) and five weed species (Brassica rapa L. ssp. oleifera (DC.) Metzger, Chenopodium album L., Galeopsis tetrahit L., Stellaria media (L.) Vill., and Viola arvensis Murray). Increased irradiance resulted in larger dry weight, net photosynthetic rate, relative growth rate (RGR), net assimilation rate (NAR), and lower leaf area ratio (LAR). The number of leaves per plant, plant length, leaf area, and shoot/root ratio were unaffected by irradiance levels, During the experimental period the net photosynthetic rate increased, while NAR remained the same, and RGR, LAR, and shoot/ root ratio decreased. On the basis of leaf area and dry weight, especially at the high irradiance level during the last part of the experimental period, barley, B. rapa, and C. tetrahit had the largest values, followed by C. album and S. media with medium values, and V. arvensis with the smallest values. As for leaf area and dry weight, S. media took more advantage of the low than the high irradiance level compared with C. album. Species differences are discussed with regard to competitive ability.     

北部高寒区大豆田恶性杂草生长特点及化学防控技术

北部高寒区是大豆主产区,因长残留除草剂的禁用,用于大豆田防除杂草的除草剂品种减少.防控大豆田恶性杂草,需了解大豆田恶性杂草发生的原因、恶性杂草的种类及生物学特性,方能有效地控制杂草危害.     

草甘膦抗性杂草的田间监测

北京的大兴区北藏村镇巴园子村的苦菜、节节草对草甘膦不敏感,防效仅为40%~60%;顺义区木林镇魏家店村的马唐对草甘膦不敏感,防效仅70%;通州区潞城镇小营村的藜对草甘膦不敏感,防效仅50%;延庆县井庄镇二司村的黄花蒿、刺儿菜、狗尾草、苦荬菜对草甘膦不敏感,防效仅40%~60%;延庆县农场的黄花蒿、刺儿菜、紫花地丁、苦荬菜对草甘膦不敏感,防效仅30%~50%;山东省淄博的铁苋菜对草甘膦不敏感,防效为70%;滕州的小飞蓬、苘麻、葎草对草甘膦不敏感,防效为40%~60%;广西的杂草对草甘膦都比较敏感,防效都在88%以上;其他杂草对草甘膦较敏感。