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1.
Physical, cultural and biological methods for weed control have developed largely independently and are often concerned with weed control in different systems: physical and cultural control in annual crops and biocontrol in extensive grasslands. We discuss the strengths and limitations of four physical and cultural methods for weed control: mechanical, thermal, cutting, and intercropping, and the advantages and disadvantages of combining biological control with them. These physical and cultural control methods may increase soil nitrogen levels and alter microclimate at soil level; this may be of benefit to biocontrol agents, although physical disturbance to the soil and plant damage may be detrimental. Some weeds escape control by these methods; we suggest that these weeds may be controlled by biocontrol agents. It will be easiest to combine biological control with fire and cutting in grasslands; within arable systems it would be most promising to combine biological control (especially using seed predators and foliar pathogens) with cover‐cropping, and mechanical weeding combined with foliar bacterial and possibly foliar fungal pathogens. We stress the need to consider the timing of application of combined control methods in order to cause least damage to the biocontrol agent, along with maximum damage to the weed and to consider the wider implications of these different weed control methods. 相似文献
2.
JAMAL R. QASEM 《Weed Biology and Management》2006,6(4):212-220
The competitive ability of onion with weeds and the effects of weeds on onion crop growth and yield were investigated in three field experiments carried out in the central Jordan Valley during the 1997–1998 growing season. Fertilizer application to the onion plants in the presence of weeds significantly lowered the onion yield and reduced the bulb diameter, compared to the unfertilized, weed-infested onion crop. Weed competition and onion yield reduction increased with an increase in the fertilizer rate. All weed-free treatments with or without fertilizer gave a significantly higher onion yield than any of the fertilized, weedy plots. The highest yield of onion was obtained from the weed-free plots with a moderate application of fertilizer. Weed competition reduced the growth, bulb yield, and size of onion in the plots established from bulbs, seedlings, and seeds when compared to the relevant weed-free controls. The effect increased with competition duration and was more pronounced in direct-seeded onion than in the other two types of planting material. However, onion grown from bulbs or seedlings gave better growth, bulb weight, and number and was more competitive than the direct-seeded onion. The results showed that the minimum number of days of weed competition needed for a significant reduction in onion growth was 42 days when propagated from bulbs or seedlings and 21 days after direct-seeding. Onion grown from bulbs tolerated weed competition better and produced a higher bulb yield than that obtained from direct-seeded or transplanted onion, irrespective of the planting dates. December was found to be the best planting time for onion that was grown from bulbs and seedlings, while November was the best planting time for direct-seeded onion, provided the plots were weed-free throughout the growing season. 相似文献
3.
E. S. MOHAMED A. H. NOURAI G. E. MOHAMED M. I. MOHAMED M. C. SAXENA 《Weed Research》1997,37(4):211-218
Weeds are a major constraint to increasing production of lentil (Lens culinaris Medik.) in Sudan, Field studies were conducted to determine the yield loss due to weeds, to identify the critical period of weed interference, to evaluate the activity of different herbicide mixtures in controlting weeds and their selectivity for lentil, and to evaluate different methods of weed control for developing an integrated weed management practice. At Rubatab. unrestricted weed growth accounted for up to 84% loss in yield. The critical period of weed control was between 2 and 4 weeks after sowing. However, a weeding regime experiment at Dongola, a cooler location with a longer growing season, indicated that the critical period was between 4 and 6 weeks after sowing. suggesting that the critical period might vary with the environmental conditions. The herbicides imazethapyr (0.05 kg a.i. ha-1), terbutryn (1.0 kg a.i. ha-1) and prometryn (1.0 kg a.i. ha-1), each in a tank mixture with pendimethalin (1.2 kg a.i. ha-1), were tolerated by lentil, controlled weeds effectively and significantly increased yields at Wad Hamid. Their efficacy in controlling weeds at Rubatab was low, however, because of the presence of Tephrosia apollinea (Del.) DC. and Melilotus indica (L.) All., which tolerated these herbicides. Efficacy was also reduced in heavier soils. One supplementary hand-weeding at 4 weeks after sowing enhanced the performance of these herbicides under such conditions. A tank mixture of oxyfluorfen (0.24 kg a.i. ha-1) with either terbutryn (1.0 kg a.i. ha-1) or prometryn (1.0 kg a.i. ha-1) also provided good weed control and increased yield of lentil at Wad Hamid. Application of a higher dose (1.5 kg a.i. ha-1) of terbutryn and prometryn caused phytotoxicity. Irrigation before seed-bed preparation reduced grass and broad-leaved weeds by 58% and 40% respectively, and gave a 30% increase in grain yield over no irrigation. Pre-emergence application of oxyfluorfen (0.24 kg a.i. ha-1) and a supplementary hand-weeding at 4 weeks after sowing gave excellent control of weeds and increased lentil yield by 57% over the weedy control. Thus, use of presowing irrigation, pre-emergence herbicide and one hand-weeding form an effective integrated package for controiling weeds in northern Sudan. 相似文献
4.
ZE PU ZHANG 《Weed Biology and Management》2003,3(4):197-203
More than 200 species of weeds are infesting main crop fields in China, among which approximately 30 species are major weeds causing great crop yield losses. About 35.8 million hectares of crop fields are heavily infested by weeds and the annual reduction of crop yields is 12.3–16.5% (weighted average). Along with rural economic development, approximately 50% of the main crop fields undergo herbicide application. Chemical weed control has changed cultural practices to save weeding labor in rice, wheat, maize, soybeans and cotton. At the same time, continuous use of the same herbicides has caused weed shift problems and weed resistance to herbicides. Consequently, integrated weed management in main crops is being developed. 相似文献
5.
J Rasmussen 《Weed Research》2003,43(6):393-403
Punch planting is introduced as a new method to reduce weeds within rows in organically grown crops. In this method a hole is punched in the soil, and a seed is dropped into it, without seedbed preparation and soil disturbance outside the hole. In 2 years, punch planting with flame weeding, normal planting with flame weeding and normal planting without flame weeding were compared in fodder beet for five planting dates. Each planting date represented a lag‐period since establishment of the stale seedbed. Over all planting times and years, punch planting with flame weeding reduced intra‐row weed densities by 30% at the two to four leaf stage of fodder beet compared with normal drilling with flame weeding. Punch planting with flame weeding also reduced intra‐row weed densities by 50% compared with normal drilling without flame weeding. In general, there was no improved performance of punch planting with flame weeding over years by later planting, but delayed planting reduced intra‐row weed densities significantly. Over 2 years, 240 day degrees Celsius (4 weeks) planting delay reduced intra‐row weed densities in the range of 68–86% depending on plant establishment procedure. Punch planting with flame weeding offers a promising method of weed control in organic farming. 相似文献
6.
Intrarow weed emergence in row crops can be reduced by means of a biennial cultivation system that is based on an exhaustion of the weed seedbank in the upper soil layer of crop‐free bands established in a preceding cereal crop, year I, before the row crop, year II. In this study, a series of field experiments is presented focusing more specifically on the influence of prevention of weed seed shedding and of different cultivation tactics in the system on intrarow weed emergence in the bands in year II. As the system excludes inverting soil tillage between years I and II, the prevention of weed seed shedding in year I turned out to be a key factor in achieving the desired effect of the system. This was seen with spring barley grown in year I, but not with winter wheat, where the system actually resulted in an increase in intrarow weed numbers in spite of the measures taken in year I. Cultivating the crop‐free bands in spring barley in year I with conventional goose‐foot shares in order to enhance seed germination and mortality further had no significant effects regardless of time and intensity. Results from two other experiments, in which freshly shed weed seeds were incorporated into the soil, supported the finding that cultivating the bands was of no advantage. 相似文献
7.
8.
Abstract Plots 17 × 5 m were laid out in farmers' fields in three villages. Treatments (replicated thrice) included atrazine (0.5 or 1.0 kg a.i./ha) on sorghum and nitrofen (0.75 and 1.5 kg a.i./ha) on groundnuts with or without hand-weeding or farmers normal weed control. Groundnuts were unfertilized, sorghum received 20 or 80 kg N/ha. Cooperating farmers were allocated plots for traditional weed control, other operations were carried out by research staff. Some plots were discounted because farmers withdrew cooperation or did not participate correctly or because of flooding. In groundnuts nitrofen alone was inferior to nitrofen + one hand-weeding. In sorghum there were no differences between high and low fertilizer regimes. Atrazine gave superior yields to farmers' weed control. All treatments were better than the unweeded control. Generally farmers fields had low weed populations due to good, timely control and low soil fertility. Herbicides are not economic at present. Problems associated with research in farmers fields included: selection of farmers who would participate correctly, variability between different farmers' weeding practices and between different fields due to previous crops and cultural practices; lack of control of farmers weeding operations and the distance of experimental plots from the research station. The authors suggest that small experiments with only 4-6 treatments are easier for participating farmers to comprehend, selecting suitable size and shape of plots is important and that if many farmers are involved the number of replicates can be reduced. 相似文献
9.
Effects of winter wheat cultivars and seed rate on the biological characteristics of naturally occurring weed flora 总被引：3，自引：0，他引：3
Summary Differential competitive ability of six winter wheat cultivars and traits that confer such attributes were investigated for a range of seed rates in the presence or absence of weeds for a naturally occurring weed flora in two successive years in split-plot field experiments. Crop height and tillering capacity were considered suitable attributes for weed suppression, although competitiveness is a relative rather than an absolute characteristic. Maris Huntsman and Maris Widgeon were the most competitive cultivars whereas Fresco was the least competitive. Manipulation of seed rate was a more reliable factor than cultivar selection for enhancement of weed suppression, although competitiveness of cultivars Buster, Riband and Maris Widgeon was not enhanced by increased seed rate. Crop densities ranging between 125 and 270 plants m−2 were found to offer adequate weed suppression. Linear relationships were observed between individual and total weed species dry weight and reproductive structures per unit area. 相似文献
10.
Abstract: Field investigations were carried out during 1999 and 2000 to identify effective chemical/ cultural methods of weed control in rose-scented geranium (Pelargonium spp). The treatments comprised pre-emergence applications of oxyfluorfen (0.15, 0.20 and 0.25 kg AI ha(-1)) and pendimethalin (0.50, 0.75 and 1.00kg AI ha(-1)), successive hand weeding, hoeing and mulching using spent of lemon grass (at 5 tonnes ha(-1)) 45 days after planting (DAP), three hand-weedings 30, 60 and 90 DAP, weed-free (frequent manual weeding) and weedy control. Broad-leaf weeds were more predominant than grass and sedge weeds, accounting for 85.8% weed density and 93.0% weed dry weight in 1999 and 77.2% weed density and 93.9% weed dry weight in 2000. Unrestricted weed growth significantly reduced geranium oil yield, by 61.6% and 70.6% in 1999 and 2000, respectively. Pre-emergence application of pendimethalin (0.75-1.00 kgAI ha(-1)) or oxyfluorfen (0.25 kg AI ha(-1)), successive hand-weeding, hoeing and mulching and three hand-weedings were highly effective in reducing weed density and dry weight and gave oil yield comparable to the weed-free check. Application of oxyfluorfen (0.15 or 0.20 kg AI ha(-1)) and pendimethalin (0.50 kg AI ha(-1)) were less effective in controlling the weed species in geranium. None of the herbicides impaired the quality of rose-scented geranium oil measured in terms of citronellol and geraniol content. 相似文献
11.
A simulation of herbicide use based on weed spatial distribution 总被引：3，自引：0，他引：3
Intensive field surveys were conducted to deter mine the spatial distribution of composite broad leaf and grass weed seedlings in seven maize and five soybean fields in eastern Nebraska in 1992. Farmer fields where herbicides were applied in a 38-cm band over 76-cm spaced rows were chosen for this study. Weed populations were measured in the interrow and in the band-treated intrarow. Spatial maps constructed for grass or broadleaf weeds revealed that individual species as well as species assemblages are highly aggregated. On average, 30% of the sample area in the 12 fields surveyed was free of broadleaf weeds and 70% free of grass weeds in the interrow area (no her bicide). Where a pre-emergence herbicide was applied (intrarow), 71% of the sample area was free of broadleaf weeds and 94% free of grass weeds. Increasing the threshold to some value other than zero resulted in a larger field area not requiring a herbicide application. The results of these distribution studies indicate that herbicide use could be substantially reduced if weed dis tribution maps or real-time plant sensing were available to provide information for intermittent herbicide application systems or refinement of economic thresholds. 相似文献
12.
Akihiko Kamoshita Hiroyuki Ikeda Junko Yamagishi Bunna Lor Makara Ouk 《Weed Biology and Management》2016,16(3):93-107
The effects of the planting method (transplanting vs. direct seeding), rice cultivar (Sen Pidao vs. Phka Rumduol), and herbicide application (admixture of bentazone and cyhalofop‐butyl) on weeds and weed seed banks were quantified in unflooded, shallowly flooded, and deeply flooded paddy fields in Cambodia in 2005 and 2006. Broad‐leaved weeds infested more toward maturity in 2006 than in 2005, particularly in directly seeded plots. Weed dry weights at pre‐heading and/or maturity were consistently reduced by herbicide application and Phka Rumduol cultivar, while weed numbers increased under unflooded condition. The proportion of sedges was consistently larger in directly seeded and non‐herbicide plots at pre‐heading. Larger numbers and dry weights of sedges and total weeds in 2005 caused larger seed bank sizes of sedges and total weeds in 2006, which further caused their infestation in 2006. A greater weed dry weight at 62 days after sowing in 2005 resulted in larger seed banks of Cyperus iria and Fimbristylis miliacea, which were most severe under non‐herbicide, direct‐seeded treatment, while that at rice maturity resulted in larger seed banks of Cyperus difformis, Scirpus juncoides, and Lindernia antipoda. Overall, sedges shared the majority of the total weed seed bank, followed by broad‐leaved weeds and then grasses. A lower yield in 2005 led to significantly larger seed bank sizes of sedges, but not of grasses or broad‐leaved weeds. Rice yield reduction was consistently related to larger numbers of sedges by heading and those of grasses at maturity. 相似文献
13.
Two field experiments investigated the influences of crop seed vigour on the effect of weed harrowing and crop:weed interactions in spring barley. Artificially reduced seed vigour, which was similar to the variation within commercial seed lots, caused a reduction in germination rate, delayed time of emergence and, consequently, caused reduced competitive ability against weeds. During both years, the reduced seed vigour increased the average weed biomass by 169% and 210%, and reduced the average crop yield by 16% and 21%. Without the influence of weeds, the yield reduction was estimated to be 8% and 10%. A three‐times harrowing strategy reduced the weed biomass by 75% and 72% on average. However, it also caused damage to the crop and reduced yield. There was no clear interaction between barley seed vigour and weed harrowing in the experiments but, in one year, reduced seed vigour tended to decrease the effect of weed harrowing and also increased crop damage. Results in both years, however, indicate potential possibilities for successful integrated weed control by adding the use of high seed quality to a weed harrowing strategy. 相似文献
14.
R Y VAN DER WEIDE P O BLEEKER V T J M ACHTEN† L A P LOTZ† F FOGELBERG‡ & B MELANDER§ 《Weed Research》2008,48(3):215-224
Weed control within crop rows is one of the main problems in organic farming. For centuries, different weed removal tools have been used to reduce weeds in the crop rows. Stimulated by the demand from organic farmers, research in several European countries over the last decade has focused on mechanisation using harrowing, torsion finger weeding and weeding with compressed air (Pneumat). Intelligent weeders are now being developed which offer more advanced ways to control weeds, including larger ones and to leave the crop plants unharmed. One of the first commercially available intelligent weeders, the Sarl Radis from France, has a simple crop detection system based on light interception, which guides a hoe in and out of the crop row, around the crop plants. The inclusion of innovative technologies, including advanced sensing and robotics, in combination with new cropping systems, might lead to a breakthrough in physical weed control in row crops leading to significant reductions, or even elimination, of the need for hand weeding. 相似文献
15.
Seed predation by natural predators can contribute to the regulation of the weed seedbank, hence has been acknowledged as a promising way to significantly reduce the use of chemicals and mechanical weeding to manage arable weeds. However, the complex aspects that determine seed species preference are not yet fully understood, especially, the relationship between weed seed traits and the feeding behaviour of seed predator species. In this study, we examine predation on 42 weed species by four ground beetle species as a function of two major seed traits: seed mass and seed lipid content. We used an _original experimental design to create a statistically independent trait value distribution for evaluating the separate and interactive effects of these two traits. Our results show that all the ground beetles species consumed weed seeds, but at different rates. The smallest weed seeds with high lipid content were among the most consumed. While seed mass might be limiting for ground beetles, due to ease of handling or the thickness of the seed coat, they may preferentially consume seeds rich in lipids to increase energy uptake. To our knowledge, this study is the first to reveal that two major seed traits drive seed predation by ground beetles. 相似文献
16.
Field experiments were carried out in order to assess the selectivity of in-row brush weeding in carrots with a natural flora of annual weeds, represented by Urtica urens L., Stellaria media (L.) Vill., Chenopodium album L., Senecio vulgaris L., Capsella bursa-pastoris (L.) Med., Chamomilla suaveolens (L.) Pursh Buch. and Matricaria inodora L. The mechanisms by which the weeds and carrots were controlled (uprooting vs. soil covering) were studied using a portable vacuum-cleaner. Weeds at the two- to four-true-leaf stage proved to be more sensitive to brushing than carrots with two to four true leaves but, for later development stages of the weeds, there were no differences. Weeds at the six- to eight-leaf stage were only killed to an extent of 20–50%. Uprooting generally accounted for 45–90% of the weed mortality at the two- to four-leaf stage, whereas most of the mortality in carrots was the result of soil covering. The vacuum-cleaning method proved to be a simple and rapid way of determining whether plants had been killed by uprooting or soil covering. It was concluded that the major mechanism of weed control obtained by brush weeding is uprooting. 相似文献
17.
Abstract Field experiments were conducted at Jobner (Rajasthan) during the winter seasons of 1982 and 1983 to evaluate certain physical and chemical weed control systems in fenugreek at two levels of applied phosphorus. The experiments comprised four herbicides (fluchloralin, pendimethalin, thiobencarb, and chloramben) at two levels each, manual weeding at three levels; and an unweeded check. The second factor, namely, application of phosphorus was evaluated at 0 and 40 kg P2O5/ha. The soil of the experiment site was loamy sand, containing 0.16% organic carbon. The results showed that amongst the herbicides, preemergent pendimethalin at 0.75 kg/ha controlled the weeds most effectively and gave 8.91 q/ha fenugreek seed yield, which was more than twice the seed yield obtained from the unweeded check plots. The twice hoed plots were found to give 1.32 q/ha higher seed yield than the pendimethalin herbicide treatment, but the benefit‐cost ratio was found higher for the herbicidal treatment. Application of phosphorus at 40 kg P2O5/ha was found to bring about significant increase in the seed yield of fenugreek by 59 kg/ha over control, without any interaction with the weed control treatments. 相似文献
18.
The effects of three weeding systems with and without top-dressed nitrogen were examined in 40 experiments on bread wheat and durum wheat planted by farmers in the Chaouia (semi-arid area of Morocco) in 1984–1985 and 1985–1986 growing seasons. In both years, hand-weeding to simulate collection of forage reduced weed numbers by 30% and removed 63% of the weed dry weight. Treatment with 2, 4-D removed 66% of the weeds and reduced weed dry weight by 82%, in 1985–1986. Hand-weeding for forage produced 427 kg ha?1 weed dry matter in both years, but wheat grain yields were 179 kg ha?1 lower than with 2.4-D treatments. Over both years, the cost of each kg weed forage was 0·43 kg grain yield loss. Without weeding grain yields were 130 kg ha?1 lower than 2, 4-D treatments. Weed control with 2,4-D increased wheat grain yields over both non-weeded and hand-weeded treatments by an average of 154 kg ha?1. Overall, there were no significant effects of nitrogen on wheat or weed yields nor interactions between top-dressed nitrogen and weeding systems. A total of 157 weed species belonging to 29 botanical families were identified on the 40 experimental sites over both years; 89% were dicotyledons. Papaver rhoeas L. (common poppy), 2, 4-D susceptible plant, was the most annual weed in wheat fields in Chaouia. 相似文献
19.
To be proactive in minimizing pesticide use, the public authorities in Denmark agreed in 1998 to phase out the use of pesticides on publicly owned areas by the end of 2002. A part of the agreement was an increasing focus on research into and development of new methods and implements for non-chemical weed control on paved areas. Due to a large increase in the costs of non-chemical weed control, the park authorities have to put the different types and locations of paved areas in order of priority to optimize the weed control effort. The present authors divided the paved areas into five weed control levels, dependent on placement, quality and use. For the 3 years 1999-2001, experiments with different non-chemical weed control methods were conducted on pavements at six locations in Denmark. The aim was to test the reaction of the weeds to different treatments and strategies. The efficacies of the methods were evaluated by analysis of digital images to estimate the fraction of the paved area covered with green vegetation (weed coverage). The weed coverage was used as the dependent variable in the subsequent statistical analysis. The independent variables in the model were incoming radiation, wear, area of joints in the pavement, the dying process of the weeds and the number of runs/applied energy of the mechanical or thermal weed control methods, respectively. The estimated parameters from the statistical model were used to build a simulation model, which was used to optimise five weed control strategies to fulfil the suggested weed control levels. In the suggested strategy for maximum weed control, 12 thermal weeding applications at 2-week intervals are suggested. The 'clean-up' strategy is based on one weed-brushing in late spring or early autumn. 相似文献
20.
Inter‐row hoeing is known to control tap‐rooted and erect weed species more effectively in winter wheat than weed harrowing. However, little is known about its effectiveness for use in the spring in winter wheat grown at wide row spacing (240 mm) under the influence of different placement of fertilizer. Two field experiments, one in 1999 and one in 2000, were conducted to study the influence of fertilizer placement, timing of inter‐row hoeing, and driving speed on the weeding effect on different weed species and crop growth. Placement of fertilizer below the soil surface improved crop growth and grain yield in both years compared with placement on the surface, but the more vigorous crop did not give any better suppression of the weeds surviving hoeing. Timing was not important in one experiment, whereas hoeing twice beginning in early April was more effective in the other experiment where weed growth over the winter had been vigorous. Driving speed had no influence on either the weeding effect or the yield, except for one case where increasing speed reduced the control of well‐developed weeds. Compared with unweeded reference treatments, inter‐row hoeing reduced total weed biomass by 60–70% and tap‐rooted and erect weed species in particular by 50–90%. Sowing at 240 mm row spacing yielded less than 120 mm (Danish standard), and inter‐row hoeing for winter wheat needs to be adapted to narrower row spacing to avoid such yield decreases. 相似文献