Gap colonization by weeds in a wheat crop grown under different cultivation regimes

The effects of tillage systems (mouldboard plough, chisel, disk and non-tillage, over 3 years) and gap openings during August and October of 0, 0.30 m × 0.30 m and 0.45 m × 0.45 m on the weed community were investigated in a wheat (Triticumaestivum L.) crop. Weed flora composition and species abundance were recorded in August, September and November and the data analysed with MULVA programs and non-parametric tests. The tillage system was more important than the timing or gap size on the weed floristic composition, and the changes in weed communities were evident within a 3-year period in spite of herbicide use. Less disturbing tillage systems (non-tillage and chisel plough) allowed the build-up of a more diverse community, whereas the most disturbing one (mouldboard plough) prevented high diversity in the weed community.     

Modelling herbicide dose and weed density effects on crop:weed competition

The effects of a range of herbicide doses on crop:weed competition were investigated by measuring crop yield and weed seed production. Weed competitivity of wheat was greater in cv. Spark than in cv. Avalon, and decreased with increasing herbicide dose, being well described by the standard dose–response curve. A combined model was then developed by incorporating the standard dose–response curve into the rectangular hyperbola competition model to describe the effects of plant density of a model weed, Brassica napus L., and a herbicide, metsulfuron‐methyl, on crop yield and weed seed production. The model developed in this study was used to describe crop yield and weed seed production, and to estimate the herbicide dose required to restrict crop yield loss caused by weeds and weed seed production to an acceptable level. At the acceptable yield loss of 5% and the weed density of 200 B. napus plants m^–2, the model recommends 0.9 g a.i. metsulfuron‐methyl ha^–1 in Avalon and 2.0 g a.i. in Spark.     

世玛控制小麦田杂草的效果

小麦拔节期进行了不同除草剂防除田间杂草的药剂筛选试验。结果表明,30％世玛EC 450ml／hm^2对麦田单子叶杂草的防除效果最好,30％世玛300ml／hm^2＋世玛助剂EC 450ml／hm^2防效次之,对单子叶杂草的防效均优于对阔叶杂草的防效。     

Modelling the effects of weeds on crop production

In most quantitative studies on interplant competition, static regression models are used to describe experimental data. However, the generality of these models is limited. More mechanistic models for interplant competition, which simulate growth and production of species in mixtures on the basis of the underlying physiological processes, have been developed in the past decade. Recently, simulation models for competition between species for light and water were improved and a detailed version was developed for sugarbeet and fat hen (Chenopodium album L.). The model was validated with data sets of five field experiments, in which the effect of fat hen on sugarbeet production was analysed. About 98% of the variation in yield loss between the experiments (which ranged from –6 to 96%) could be explained with the model. Further analysis with the model showed that the period between crop and weed emergence was the main factor causing differences in yield loss between the experiments. Sensitivity analysis showed a strong interaction between the effect of the variables weed density and the period between crop and weed emergence on yield reduction. Different quantitative approaches to crop-weed competition are discussed in view of their practical applicability. Simulations of experiments, where both the weed density and the period between crop and weed emergence were varied over a wide range, showed a close relation between relative leaf cover of the weeds shortly after crop emergence and yield loss. This relation indicates that relative leaf cover of the weeds accounts for both the effect of weed density and the period between crop and weed emergence. This relation has the potential to be developed into a powerful tool for weed-control advisory systems.     

地乐胺等在小麦田作土壤处理的除草效果

小麦播前15d,用地乐胺、氟乐灵、乙草胺和百草枯进行土壤处理,药后20d、40d、60d除草效果分别达到93%、90%和80%以上,其中地乐胺、氟乐灵防效最好,乙草胺和百草枯次之。四种除草剂对小麦均有明显的增产作用,且无明显药害。     

Assessment of competition between crops and weeds

A two-species model was used to summarize results of four experiments with two component mixtures of barley (Hordeum vulgare L.), peas (Pisum sativum L.), Chenopodium album L. and Sinapis alba L. grown in pots in greenhouses. The results, covering a wide range of plant densities both in mixtures and pure stands, showed that the model was not always able to describe the relationship between the yield of a species and the densities of itself and its companion species. The deviations from the model were in all instances greatest for the least competitive species. The model that quantifies competition and niche differentiation appeared to be too general because competition between species was not independent of the wide plant density ranges used here. The results are discussed in relation to possible improvements of the model and an analogy between the principles of assessing crop weed competition and the assessment of the relative potency of herbicides in bioassay studies is put forward.     

Early vigour and allelopathy – two useful traits for enhanced barley and wheat competitiveness against weeds

The objectives of this study were to identify traits in spring barley (Hordeum vulgare) and spring wheat (Triticum aestivum) related to the competitive ability of the crop and to determine their importance. Weed biomass 1–2 weeks prior to ear emergence was used as a measure of genotypic differences in competitiveness against weeds. Crop trait measurements comprised early crop biomass, early shoot height, straw length, heading and maturity. Early crop biomass 1–2 weeks prior to ear emergence was used as an overall trait for the various characters related to early vigour. In addition to these morphological traits, the potential allelopathic activity of the tested cultivars was determined using an agar-based bioassay with Lolium perenne (ryegrass). In both barley and wheat, multiple regression analysis revealed that early crop biomass and potential allelopathic activity were the only parameters that significantly contributed to competitiveness. In barley, early crop biomass explained 24–57% of the observed genotypic variance across 4 years, allelopathic activity explained 7–58% and combined they explained 44–69% of the observed genotypic variance. In wheat, the corresponding figures were lower: 14–21% for early biomass, 0–21% for allelopathic activity and 27–37% when combined. Model predictions suggested that new cultivars with increased early vigour and allelopathic activity offer a potential to further reduce weed interference.     

Selective regulation of germination and growth of annual weeds by crop residues

Residues from mature, harvested crops of sorghum (Sorghum bicolor Moench.), sunflower (Helianthus annuus L.), oilseed rape (Brassica napus L.), wheat (Triticum aestivum L.) and field pea (Pisum sativum L.), exhibited selective effects on weed germination and growth under field conditions. Weed species in the study included Avena fatua L., Avena sterilis ssp. ludoviciana (Durieu) Nyman, Echinochloa crus-galli (L.) Beauv., Phalaris aquatica L., Phalaris paradoxa L., Lolium perenne L., Vulpia myuros (L.) Gmel., Hibiscus trionum L., Polygonum aviculare L., Bilderdykia convolvulus (L.) Dumort. and Lamium amplexicaule L. All crop residues tested, and in particular wheat and pea residues, promoted the germination and growth of A. fatua and A sterilis ssp. ludoviciana. Other grass weeds, however, were inhibited by the presence of crop residue, the extent of inhibition being dependent on residue type. Germination response of dicotyledonous weed species was also a function of residue type, H. trionum numbers were significantly higher in plots where oilseed rape, sorghum or sunflower residue had been incorporated, while L. amplexicaule was inhibited by these residue types and stimulated by pea and wheat residues.     

Wild oat (Avena sterilis L.) competition with winter barley: plant density effects

The competitive interactions between Avena sterilis ssp. ludoviciana (Dur.) Nyman and winter barley have been studied, taking into consideration the densities of both species. As the density of A. sterilis increased, barley yield decreased exponentially. A 10% reduction in yield was found with wild oat densities ranging from 20–80 panicles m^–2, and yield losses reached 50%, with densities of >300 panicles m^–2, Barley grain yield was reduced by wild oats through a reduction in the number of fertile tillers. Climatic conditions during the growing seasons affected the response of barley to wild oat competition. In general, barley yields were relatively unaffected by seeding rates, with similar responses observed in the presence and in the absence of wild oat infestations. However, the highest yield losses were obtained with the lowest seeding rate (100 kg ha^–1). Furthermore, low barley densities allowed the wild oat plants to produce more seeds, increasing the potential infestation during the following season.     

10%单嘧磺酯WP防除冬小麦田杂草试验

通过田间小区试验证实，10％单嘧磺酯WP可有效防除冬小麦田的藜和播娘蒿等一年生及越年生阔叶杂草，防效与10％苯磺隆WP相当或优于该对照药剂，且对冬小麦安全，无任何药害症状。     

Effect of fungicide treatment on yield of winter wheat and spring barley cultivars

Analyses of the results of 21 winter wheat and 32 spring barley trials showed that cultivars differed significantly in their yield response to a standard fungicide treatment. Responses were also strongly influenced by differences between sites and between years. Regression analyses showed that responses were significantly related to reductions in foliar disease, particularly that of mildew, although the proportion of variance accounted for was small. Measurements made on seven winter wheat trials indicated that the percentage of leaf area remaining green after anthesis was increased by the fungicide treatment to a greater extent than could be attributed to reduction in foliar disease alone. In one of these trials, yield response was more closely correlated with the increase in leaf area remaining green than with reduction in foliar disease.     

阔世玛春后防除麦田杂草的效果及对小麦的安全性

2007年3月5日～3月10日用3.6%阔世玛WG 25 g/667m2+伴宝80 ml/667m2防治麦田杂草有良好的效果,药后40 d对禾本科杂草株防效达90.8%～94.9%,鲜重防效达92.4%～96.9%,对阔叶类杂草的株防效为69.8%～75.0%,鲜重防效为75.6%～78.6%,对小麦生长安全,小麦增产24.4%～29.9%.     

Effects of herbicide and timing of removal on interference between barley and weeds

Field experiments were done during the rainy season of 1984–85 and 1985–86 at Harma, Qatar. A weed survey of barley fields was conducted with the primary purpose of identifying the weed vegetation present. The effects of time of hand-weeding and of application of the herbicide metoxuron on the yield and yield components of barley were studied. Removing weeds at 15,30,45 and 60 days after sowing gave yields similar to that of the clean-weeded check. Neither a critical period nor a threshold density below which no yield loss occurred were observed. Metoxuron (1,2 and 3 kg ha^?1) gave good to excellent broad-leaved and grass-weed control. The use of this herbicide at the rate of 1 kg ha^?1 showed considerable promise.     

大能防除小麦田硬草的效果

50g／L大能（唑啉草酯·炔草酸）EC是先正达（中国）投资有限公司最新开发的小麦田苗后茎叶处理除草剂。冬前用50g／L大能1200—1350ml／hm^2,早春用50g／L大能1350～1500ml／hm^2,兑水600-750kg/hm^2喷细雾,对硬草均有理想的防除效果,对扬麦15号等小麦无明显药害。     

大能防除小麦田杂草技术研究

5％大能EC1200ml／hm^2,在冬前禾本科杂草4叶期和春后禾本科杂草6～7叶期施用,对小麦田看麦娘、日本看麦娘、蔺草和硬草等禾本科杂草具有理想的防除效果,优于目前应用的6．9％骠马。施药器械、兑水量对禾本科杂草防效无明显影响,但低用水量（225kg／hm^2）喷雾时要注意行进速度,确保喷到、喷匀。大能可与苯磺隆、异丙隆、麦喜、普瑞麦、使它隆混用,以扩大对麦田单双子叶杂草的控制效果。按推荐剂量（1200ml／hm^2）使用对扬麦13号、扬麦15号等小麦安全。     

Annual weed competition in wheat crops: the effect of weed density and applied nitrogen

Experiments investigating the effect of weed density on the yjeld of a wheat crop at three levels of applied nitrogen were conducted in north-western Victoria. Australia, during 1970. There were five sites, each infested with a pure stand of one of the following annual broad-leaved weed species: Lithospermum arvense, Brassica tournifortii. Lamium amplt'xicaule, Amsinckia hispida and Fumaria parviflora. At the three-leaf stage of crop growth, the weed populations were systematically thinned with a specially developed spray boon) (which is described) to give a range of weed densities in competition) with the crop. The relalionship between dry matter production and population density for all but one weed species was curvilinear, but the degree of curvature was small and competition in the wheat crop was linear for four of the five weed species. There were large differences in the competitive ability of individual weed species and these have been described by regression equations. Applied nitrogen increased wheat yields at all sites but weed competition was not affected. The use of these grain yield-weed density relationships in predicting crop losses from weed competition is discussed.     

金马防除小麦田禾本科杂草的效果

冬季用7.5%金马EW 60~100 m l/667m2,对看麦娘的株防效达96%以上,鲜重防效达98%以上,对野燕麦的株防效、鲜重防效均在98%以上。春季用7.5%金马60~80 m l/667m2,对看麦娘的株防效在93%以上,药后25 d的鲜重防效在80%左右。金马对小麦无不良影响,安全性较好。     

50%速除(异·丁·苄)WP对麦套稻田杂草的防治效果及安全性

麦套稻是在前茬 (麦子 )收获前 10～ 15d ,先灌“跑马水” ,然后将用营养土包衣好的露白稻谷直接撒播于麦田的一种种植方式。因该种植方式不打破原土层结构 ,与旋耕稻田相比 ,杂草种类更多 ,出草时间更早 ,密度更高。麦套稻能否夺取高产 ,关键是草害 ,为此 ,笔者进行了 5 0 %速除WP防除麦套稻田杂草的试验。1　材料与方法1 1　供试药剂5 0 %速除WP、4 2 %新野EC ,均由江苏省苏科实验农药厂生产。1 2　试验设计试验设 5个处理 :5 0 %速除WP 6 5g 6 6 7m2 、80g 6 6 7m2 、10 0g 6 6 7m2 、110g 6 6 7m2 及 4 2 %新野EC12 0ml 6 6 7m2 ,分…