Seasonal variation in the emergence of annual weeds — an introductory investigation in Sweden

Seeds of thirteen annual weed species were collected in early autumn. Within a few weeks they were incorporated in soil. They were stored either in the field or in climate chambers where seasonal variations in field soil temperature were simulated. Seedling emergence under various conditions was determined at different times, within a period of 1 or 2 years after the incorporation of seeds in soil. Some material was transferred from the storage places at different times of year and placed in cabinets with standardized temperature regimes for 3-week emergence tests. These showed increased emergence during late autumn and winter and a maximum at some time in winter in both summer and winter annuals. Some winter annuals showed a second maximum in late summer. Counts of seedlings in the storage places, in unstirred soil, showed maximum emergence in spring for both winter and summer annuals — or in summer for Spergula arvensis and, possibly, Capsella bursa-pastoris. In certain treatments in the field, the soil was stirred once, on different dates, simulating tillage at different limes of year. The emergence following stirring of the soil was greatest in spring for the summer annuals, except for Spergula arvensis, which showed more emergence from early to mid summer. Several winter annuals showed an emergence peak after stirring in late summer or early autumn. Variations saisonnières dans la levèe des mauvaises herbes annuelles-étude préliminaire en Suède     

土层深度对三种麦田禾本科杂草出苗及生长的影响

为明确小麦田禾本科杂草在不同土层深度的出苗及生长情况,选取雀麦Bromus japonicas、节节麦Aegilops tauschii和野燕麦Avena fatua三种小麦田常见禾本科杂草,采用盆栽法系统研究不同土层深度对杂草出苗及生长的影响。结果表明,小麦田禾本科杂草雀麦、节节麦和野燕麦出苗和生长与不同土层深度密切相关,在浅土层中均有较好的出苗率,且后期生长也正常。从出苗时间来看,雀麦和野燕麦集中出苗时间在播种后5～11 d,节节麦略晚于这2种杂草;从最适出苗土层深度来看,雀麦最适出苗土层深度为0.5～3.5 cm,出苗率在76.0%～87.0%之间,节节麦的最适出苗深度为0.5～8.0 cm,出苗率在66.7%～79.3%之间,而野燕麦的最适土层深度为0.5～18.0 cm,出苗率达84.2%～94.4%;从出苗后生长影响来看,0～20 cm土层对野燕麦后期生长没有显著影响,土层深度大于10.0 cm对节节麦生长有显著抑制作用,大于6.0 cm即对雀麦有显著影响。研究表明通过深翻土地可以对雀麦和节节麦达到一定的控制作用,但对野燕麦控制效果相对略差。     

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.     

Potential of weed seedbanks for managing weeds: a review of recent New Zealand research

Weed seedbanks are the primary source of weeds in cultivated soils. Some knowledge of the weed seedbank may therefore be appropriate for integrated weed management programs. It would also be very useful in planning herbicide programs and reducing the total herbicide use. However, a number of problems are inherent in the estimation of the seedbank size for arable weeds that usually have annual life cycles. In a long-term research project we have investigated the dynamics of weed seedbanks in corn fields for the past 8 years. Specific studies have included (i) developing cheap and efficient methods for estimating the weed seedbank; (ii) developing guidelines for efficient soil sampling (including the number and size of samples); (iii) influence of cultivation methods on weed seed distribution; (iv) mapping the spatial variability of the seedbank; (v) estimating the rate of seedbank decline for certain weed species; and (vi) assessing the potential of using the weed seed content in the soil to predict future weed problems. This paper reviews and summarizes the results of our research on the above aspects. The strong correlation between seedlings emerged in the greenhouse and seeds extracted in the laboratory for the most abundant weed species has demonstrated the potential for using the weed seed content of the soil to predict future weed infestations. The next step is to establish correlations with field emergence under commercial conditions using the sampling guidelines developed in our studies. Subsequently, we aim to offer the weed seedbank estimation as a commercial service to farmers for planning the most appropriate weed management options.     

20%辛酸乳油对非耕地杂草的田间防效

采用茎叶喷雾法测定了20%辛酸EC 3.6、10.8、32.4、48.6、64.8和97.2 kg/hm 2(有效成分,下同)对非耕地杂草的防除效果。结果表明,20%辛酸EC 64.8~97.2 kg/hm 2处理药后7 d对总草株防效为86.98%~95.65%,药后15 d鲜重防效为85.40%~94.86%,显著高于对照药剂41.7%草甘膦AS 1.0 kg/hm 2处理,与对照药剂20%百草枯AS 0.6 kg/hm 2处理相近;20%辛酸EC 3.6~32.4 kg/hm 2处理药后7 d对总草株防效及药后15 d鲜重防效均低于或显著低于对照药剂41.7%草甘膦AS 1.0 kg/hm 2处理和20%百草枯AS 0.6 kg/hm 2处理。20%辛酸EC可有效地控制非耕地杂草,推荐使用剂量为64.8~97.2 kg/hm 2。     

杂草对耕层土壤的生态缓冲效应初探

在安徽省万罗山选择石砾林、茶园、水稻田3种植被类型，研究3个不同水平(密、疏、少)的杂草群落对耕层土壤的温度、湿度、pH值、有机质、质地等生态因子的影响，结果表明：杂草能调节土壤温度、湿度，提高土壤有机质含量，改善土壤质地和缓冲土壤pH值。稻田杂草对水稻田土壤中的上述生态因子影响相对较小。     

Seasonal variation in sprouting capacity from intact rhizome systems of three perennial weeds

The three rhizomatous perennials Elytrigia repens, Equisetum arvense and Tussilago farfara are all problematic in Scandinavian agriculture, due to their low susceptibility to soil cultivation. While repeated soil tillage is a fundamental part of the integrated control of these species, it is highly energy consuming and inefficient during periods when little sprout regrowth occurs. Substituting cultivation with mowing will reduce the environmental impact and labour costs, but its efficiency will still depend on the capacity of plants to sprout. Therefore, we studied the seasonal pattern in emergence and rhizome biomass allocation from July to April in six populations for each of the species. Plants were grown outdoors in pots buried in soil and exhumed at regular intervals in a two‐year experiment. In all three species, biomass allocation to rhizomes continued until late in the autumn. Emergence was severely impaired in E. arvense and T. farfara in September–October, while in E. repens, there was no such reduction in the number of emerged shoots. However, in the latter species, the shoot/rhizome ratio decreased and remained low until the plants had been exposed to a period of low temperatures. The increase in shoot/rhizome ratio for E. repens coincided with the resumed capacity to emerge for E. arvense and T. farfara. These results imply that there is no need to repeat a defoliation of E. arvense and T. farfara, if carried out in September–October. However, removal of the aerial plant parts early in the autumn is important to interrupt the upload of storage compounds to the rhizome systems of all species.     

A method to obtain fast and uniform emergence of weeds for field experiments

In studies on competition between crops and weeds it may be desirable to manipulate time of emergence, density and spatial arrangement of weeds. This requires a method to obtain a fast and uniform emergence of weeds. Two planting methods were compared that differed in the medium (agar or blotting paper) on which seeds were germinated, and in the method of transplanting the seeds (with or without the medium). In wet soil, emergence started earlier when seeds were germinated on agar and subsequently planted with agar. Root tips of seeds germinated on blotting paper may have been damaged to a greater extent during transplanting, because root tips tended to grow into the blotting paper. The duration, heterogeneity and final level of emergence were not affected by the planting method. In dry soil in a greenhouse experiment, the final level of emergence was much less when seeds were planted using the blotting paper method than when they were planted using the agar method. The agar may have provided a small source of water which reduced dehydration of emerging plants. The results were similar for the three species studies, namely, Chenopodium album L., Senecio vulgaris L. and Solanum nigrum L.     

Reducing tillage intensity affects the cumulative emergence dynamics of annual grass weeds in winter cereals

Annual grass weeds such as Apera spica‐venti and Vulpia myuros are promoted in non‐inversion tillage systems and winter cereal‐based crop rotations. Unsatisfactory weed control in these conditions is often associated with a poor understanding of the emergence pattern of these weed species. The aim of this study was to investigate, understand and model the cumulative emergence patterns of A. spica‐venti, V. myuros and Poa annua in winter cereals grown in three primary tillage regimes: (i) mouldboard ploughing, (ii) pre‐sowing tine cultivation to 8–10 cm soil depth and (iii) direct drilling. Direct drilling delayed the cumulative emergence of A. spica‐venti and V. myuros (counted together) in contrast with ploughing, while the emergence pattern of P. annua was unaffected by the type of tillage system. The total density of emerged weed seedlings varied between the tillage systems and years with a higher total emergence seen under direct drilling, followed by pre‐sowing tine cultivation and ploughing. The emergence patterns of all species were differently influenced by the tillage systems, suggesting that under direct drilling, in which these species occur simultaneously, management interventions should first and foremost consider that A. spica‐venti and V. myuros emerge over a longer period to avoid control failures.     

直播稻田杂草化除技术的应用效果

对江苏省淮安市旱直播稻田杂革进行化除技术示范试验。结果表明,对直播稻田杂草防除应坚持化除为主、人工防除为辅的“一封二杀三补”策略,其中土壤封闭处理尤为重要。目前主体除草剂品种有丁草胺、二氯喹林酸、苄嘧磺隆、灭草松、2甲4氯等,恶草酮、氯氟毗氧乙酸对莎草科杂草防效较差。     

Seedling emergence and seed longevity of the tree weeds Celtis sinensis and Cinnamomum camphora

Factors influencing germination and seed survival of Celtis sinensis Pers. and Cinnamomum camphora (L.) Presl. were investigated in a series of experiments conducted under natural rainfall regimes in the field and under irrigation in a growth tunnel. Germination from surface-sown seeds of C. camphora was virtually nil under natural rainfall, in contrast to almost 100% germination under irrigation. This suggests that surface-lying seeds of this species will germinate only in highly protected microsites in the field. For C. sinensis , however, in one of the two field experiments germination from surface-sown seeds was similar (≈40%) to that achieved under irrigation. Germination from intact fruits of both species was generally considerably less than from seeds. Seeds of both species were relatively short-lived under field conditions. A maximum of 1% of seeds of C. camphora remained viable at 12 months post-sowing under field conditions, whereas a maximum of 8% viable seeds of C. sinensis was detected at 24 months post-sowing in one of the field experiments.     

杂草对重金属污染土壤修复能力的研究

用电感耦合等离子体分析了市郊排污河岸土壤重金属含量及“种杂草中重金属Cd、Cr、Cu、Mn、Pb和Zn的含量。结果表明,河岸土壤存在一定程度重金属污染,Cd含量较高,为3级,Cr为1级,Cu为2级,Pb为2级,Zn为2级。杂草对重金属的吸收、积累和运输能力因杂草种类、部位及重金属种类而不同。杂草对重金属的积累能力为：Cd〉Zn〉Cu〉Pb〉Mn〉Cr。杂草转移重金属系数为：Cr〉Pb〉Mn〉Cu〉Zn〉Cd。提出了适用于不同重金属Cd、Cr、Cu、Mn、Pb和Zn污染土壤的修复植物。     

黑龙江省耕地土壤养分贫瘠化研究

在Arcgis空间分析功能和SPSS数理统计功能支持下,利用隶属度模型、层次分析法、综合指数模型、障碍度诊断模型、叠加法等方法,分析黑龙江省耕地土壤养分贫瘠化状况与区域生态问题,诊断识别耕地土壤养分障碍因子与最佳量化表征性指标,空间表达土壤养分障碍类型区。结果表明:(1)全省70.58%耕地处于轻度及以上土壤养分贫瘠程度,从西南到东北逐渐减弱,其中重度贫瘠区主要分布在松嫩平原西部,占耕地面积的2.95%,农田生态问题是土壤沙化严重,中度贫瘠区主要分布在松嫩平原中部构造上属于断陷的中央凹陷区、三江平原西北部处于山前平原向平原的过渡带,占耕地面积的41.09%,农田生态共性问题为易积水,其中松嫩平原还存在土壤盐渍化问题,轻度贫瘠区主要分布在松嫩平原东部、东北和东南地区,少量分布在三江平原西部、西北和西南部,占耕地面积的26.54%,农田生态问题是水土流失;(2)有机质和全氮是区域土壤养分贫瘠化的主要障碍因素,累积占比达88.37%;(3)有机质是耕地土壤养分贫瘠化指数及养分因子含量最佳量化表征性指标;(4)区域47.92%的耕地存在中度及以上障碍因子,障碍类型区共计14类,以双因素MC-MN,三因素MC-MN-MP、MC-MN-MK占比最大,累积占比率为39.84%。     

甘肃省河西走廊中部新垦荒地土壤养分空间变异特征

结合传统统计学、地统计学方法对新垦荒地土壤养分的空间变异性进行了分析研究.结果表明,土壤OM含量极低,土壤有效P极缺乏, NH4 -N缺乏,有效K局部缺乏,有效Ca、Mg、S含量丰富,尤其有效Ca含量较高.土壤OM、NH4 -N、有效P、K、Ca、Mg和S的变异系数在36.0%～164.6%之间.土壤OM及有效P含量的变异较大, 变异系数分别为87.8%及164.6%;土壤K和NH4 -N次之, 变异系数分别为52.7%及53.4%,有效Ca、Mg、S的变异相对较小,变异系数分别为36.0%、37.6%和46.5%.地统计学半方差分析结果显示,土壤各养分的空间变异结构有较大区别.有效P、K、Mg、S的基底效应介于25%～75%之间,具有中等程度空间相关性.OM、有效Ca及NH4 -N的基底效应均＞75%,空间相关性较弱.根据半方差分析结果,利用GS For Windows的Kriging最优内插法制作等值线分布图,从图中看出土壤OM、有效P、K的空间分布变异较小,分布均匀,NH4 -N的空间分布变异较大,有效Ca、Mg、S的空间分布具有中等程度的变异.     

“黑土型”退化草地人工植被杂草防除试验报告

选用5种除草剂以不同剂量和喷药时间,在青海玛沁县5龄禾草类人工草地进行了有毒杂草防除试验。结果表明,剂量对群落盖度的影响最大。除草剂品种对禾草类盖度的影响最大,剂量次之,喷药时间最小。除草剂品种对禾草盖度的影响依次为甲磺隆〉麦阔净〉使它隆〉龙拳〉麦客隆,2倍剂量下禾草盖度最低,随喷药时间推迟,禾草类盖度降低。6月25日左右喷药杂草盖度最低,此时大多数杂草处于现蕾盛期,喷药对其伤害较大。2.5倍剂量下杂草盖度最低,其次为1.5倍剂量,0.8倍剂量对杂草影响不大。本区进行人工草地杂草防除,最佳防除组合为6月25日左右喷1.5倍剂量的龙拳雾剂。     

Degradation of the dicarboximide fungicides iprodione,vinclozolin and procymidone in Patumahoe clay loam soil,New Zealand

An enhanced rate of degradation of the dicarboximide fungicides iprodione and vinclozolin was induced in the laboratory in Patumahoe clay loam soil by adding three successive applications of fungicide. Enhanced degradation of the dicarboximide fungicide procymidone could not be induced. Following the first fungicide treatment, the time to 50% loss of iprodione was greater than 35 days; for vinclozolin the time to 50% loss was 22 days. The rate of degradation accelerated with successive applications until, after a third successive application of fungicide, the time to 50% loss of iprodione was only two days and none was detectable at seven days. For vinclozolin, after the third successive application of fungicide, 50% loss occurred after 35 days. By comparison, minimal loss of procymidone was detected after 35 days following each of two successive soil treatments. The induction of enhanced degradation of iprodione and vinclozolin in this soil in the laboratory may explain the observed loss of field control of onion white rot disease. Degradation of iprodione occurred in non-sterile soil but not in sterile soil, indicating that microbial involvement may be responsible for the degradation of iprodione and vinclozolin in soil.     

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%.     

内蒙古草原土壤斥水性的季节变化

土壤斥水性是指水分不能或很难湿润土壤颗粒表面的物理现象,具有斥水性的土壤称为斥水土壤。本文以内蒙古锡林浩特市白音锡勒牧场中国科学院内蒙古草原生态系统定位站的羊草样地为例,运用滴水穿透时间法分析了1979年禁牧1、999年禁牧、冬季放牧和连续放牧等条件下内蒙草原土壤斥水性的季节变化。结果表明:草原土壤总体上表现为轻度斥水性或无斥水性,且斥水性具有显著的季节变化特点,一般在雨季或多雨年土壤具有较强的斥水性;不同的利用方式对草原土壤斥水性的季节变化规律具有一定的影响,存在时间上的滞后性,持续放牧处理在雨季较多的样点最先表现斥水性,其次为冬季放牧处理,然后为1999年禁牧处理,最后为1979年禁牧处理。