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1.
The development of integrated weed management strategies requires knowledge of mechanisms that influence compositional changes in weed flora. A 9-year study was initiated in 1988 at Delhi, Canada, on a loamy sand soil to evaluate the effect of tillage systems [conventional (CT) and no-till (NT)] and cover crops (only in NT) on weed density, species composition and associations, and crop yield in a winter wheat ( Triticum aestivum L.)/bean/winter wheat rotation. Three bean types: soyabean ( Glycine max L. Merr.), white bean ( Phaseolus vulgaris L.) and kidney bean ( P . vulgaris L.) were included. The NT system included variations: rye ( Secale cereale L.) or maize ( Zea mays L.) cover crop, volunteer wheat disked after harvest and wheat stubble. Data were collected in 1994, 1995 and 1996. Tillage systems, cover crops and crop type had differential effects on weed densities, species composition and associations. Weed densities were not affected by tillage or cover crops in wheat but, in the beans, densities were greater in the CT than in the NT systems. Various associations of weed species with tillage system, cover crop and crop type were observed. Crop yields were not affected by tillage type or cover crop, except that soyabean yields were highest in plots with cover crops.  相似文献   

2.
Crop residue retention could affect the emergence and biomass of weeds in different ways. A summer and winter pot study was conducted to evaluate the effect of different amounts of sorghum and wheat residue on the emergence and biomass of 12 summer and winter Australian weeds. The equivalent amount of sorghum residue to 0, 1, 2, 4 and 6 t/ha was used in the summer study and winter weed seeds were covered with wheat residue equivalent to the amount of 0, 1, 2, 4 and 8 t/ha in the winter study. The emergence and biomass of Amaranthus retroflexus and Echinochloa colona was not affected by sorghum residue treatment. For other summer weeds, the use of the 6 t/ha sorghum residue treatment resulted in 59–94% reductions in biomass compared to no‐sorghum residue retention. Similarly, the application of 8 t/ha wheat residue in the winter study resulted in a reduced biomass of 15–100% compared to no‐crop residue treatment. The results demonstrated the high potential of using crop residues in eco‐friendly weed management strategies, such as harvest weed seed control tactics.  相似文献   

3.
Summary There is a lack of information on the combined effects of preceding crop, reduced tillage (especially no-tillage) and the time of herbicide application on the development of weed populations and the efficiency of weed control in winter wheat in humid temperate climates. An experiment was conducted with a crop rotation (winter wheat – oilseed rape – winter wheat – maize) on a sandy loam and a loamy silt soil in the Swiss midlands to investigate the impact of different preceding crops and pre- and post-emergence control of weeds in conventional tillage (CT; mouldboard plough), minimum tillage (MT; chisel plough) and no-tillage (NT; no soil disturbance systems). When winter wheat was grown after maize and winter wheat was grown after oilseed rape, the ranking order of weed density in treatments without herbicide application was NT < MT < CT and CT < MT < NT respectively. Analysis of variance and canonical discriminant analysis showed that Epilobium spp., Sonchus arvensis , Myosotis arvensis and volunteer crops were more abundant in NT than in MT and CT. The efficiency of post-emergence weed control was generally better than that of pre-emergence weed control, regardless of tillage intensity.  相似文献   

4.
Reduced tillage provides ecological and economic benefits to arable land on the Loess Plateau of China, where soil erosion has long been a serious problem and soil water availability is largely restricted. However, high abundances of weeds in reduced tillage systems cause significant yield losses. In this study, we explored the effects of no-tillage and stubble retention on the number and density of weeds and weed seeds in a 12-year maize-winter wheat-common vetch rotation on the Loess Plateau. Four treatments including conventional tillage, no-tillage, conventional tillage+stubble retention and no-tillage+stubble retention were designed and applied. We found that no-tillage increased the number of weed species and weed density in most of the crops, while stubble retention decreased weed density in maize and tended to suppress weeds in both no-tillage treatments(no-tillage and no-tillage+stubble retention). No-tillage led to an increase in the number of weed species in the weed seedbank and tended to increase seed density during the spring growth of winter wheat, but it decreased seed density during post-vetch fallow. Stubble retention tended to reduce seed density during the spring growth of winter wheat and post-vetch fallow. We concluded that no-tillage can promote weeds in the experimental crop rotation, while stubble retention suppresses weeds in untilled fields. The combined effects of stubble retention and no-tillage on weed suppression varied among the three crops. Based on these results, we recommend stubble retention in untilled legume-crop rotations on the Loess Plateau to improve the control of weeds.  相似文献   

5.
The objective of this study was to obtain detailed information on the long‐term weed suppression potential of four winter soil cover types included in an arable crop system managed at various input levels. We used weed seedbank size and composition to assess weed suppression potential. A field experiment was established in 1993 as a split‐split‐plot design with four replications, including two tillage systems [a conventional system (CS) including ploughing in the cover crops and a low‐input system (LIS) including no tillage with surface mulching of the cover crops] in the main plots, three mineral nitrogen fertilization rates for the main crop in the sub‐plots and four soil cover types (main crop residue, rye, crimson clover and subterranean clover) in the sub‐sub‐plots. Seedbank sampling took place in winter 2000/01. The weed seedbank was analysed with the seedling emergence method. Data were analysed using anova and multivariate techniques. Results indicated that the seedbank density in the LIS was about five times higher than in the conventional input system. In the CS, use of a rye cover crop resulted in a lower seedbank density with respect to the crop residue treatment (?25%), whereas in the LIS the subterranean clover cover crop decreased weed seedbank density as compared with the other cover crops and the crop residue treatment (?22% on average). Differences in species composition were mainly related to tillage system. Implications for cover crop management and the development of sustainable cropping systems are discussed.  相似文献   

6.
Cover crops are increasingly being used for weed suppression and to enhance the sustainability of agro‐ecosystems. However, the suitability of cover crops for weed suppression in integrated and organic conservation tillage systems is still poorly investigated. Therefore, a 2‐year field study at eight sites was conducted to test the weed suppressive potential of six legume‐based cover crops, with the aim to reduce herbicide input or mechanical weed management interventions. In all experiments, cover crops were directly sown after cereals before next year's main crop (grain maize or sunflower). The presence of cover crops caused a 96% to 100% reduction of weed dry matter at the four sites managed under integrated production, while effects were lower at the four sited managed under organic production, ranging from 19% to 87%. Cover crops that covered soil quickly and which produced much dry matter had the best weed suppressive potential. However, their weed suppressing effect was difficult to predict, as it depended on the year of the investigation, experimental site, cover crop species, the speed of soil cover in autumn and the density of the resulting mulch layer in spring. The study demonstrated that cover crops are a useful tool to suppress weeds under integrated and organic conservation tillage practices. Our recommendation for supporting weed management in conservation tillage systems is to use locally adapted cover crops that have rapid establishment, good soil coverage and high dry matter production. However, additional weed management measures are required for reliable weed control under on‐farm conditions.  相似文献   

7.
Soil weed seed bank is an important factor determining above-ground floristic composition and weed density in agricultural systems. The quantitative and qualitative measures of weed seed bank can help growers to predict the extent to which they are facing weed problems. Along with tillage, crop residues can affect the fate of weeds in the upcoming crops. To investigate such effects, we compared the effects of tillage systems [conventional tillage (CT), reduced tillage (RT), and no tillage (NT)], wheat residue retention, and nitrogen (N) rates (0, 69, 138, and 207 kg N ha−1) on depth-related characteristics of the weed seed bank under a sweet corn-wheat sequence during 2014–2015 growing seasons in Shiraz, Iran. Soil bank was not affected by tillage systems but tended to be slightly higher under RT. The highest (898 seeds m−2) and lowest (322 seeds m−2) weed population at 0–10 cm depth were found when 138 kg N ha−1 in 2015 and 207 kg N ha−1 in 2014 were applied. Species richness and diversity were higher under NT and RT practices at the top layer, but CT system was more diversified at deeper depths. They were higher when crop residues were retained as well. Barnyard grass (Echinochloa crus-galli [L.] Beauv), common lambsquarter (Chenopodium album L.), common purslane (Portulaca oleracea L.), field bindweed (Convolvulus arvensis L.), flixweed (Descoreinia sofia [L.] Webb. & Berth.), henbit (Lamium amplexicaule L.), pigweeds (Amaranthus spp.), and stinking goosefoot (Chenopodium vulvaria L.) were the most common weeds found in all tillage systems and soil depths. Grasses were relatively lower than broadleaves regardless of treatments. Weed seed bank was mostly affected by weather conditions than treatments in this short-term experiment.  相似文献   

8.
J PETERSEN 《Weed Research》2005,45(2):103-113
The changes in weed:crop competition as affected by the interaction of slurry distribution pattern with crop sowing pattern was examined, using the parameters dry matter (DM) production, nitrogen (N) uptake and recovery of applied N in spring wheat and weeds. Pig slurry enriched with isotopic nitrogen (15N) was applied either fully incorporated or in concentrated bands. The two slurry distribution patterns were combined with either crop density or distance between the slurry band and seed row. Spring wheat and weeds were sampled separately seven times during the season. A high and fast crop recovery of applied N coincident with a low recovery in weeds may be obtained by at least three management elements: sowing the crop with a high seed density, sowing the crop row close to the band-applied slurry N, and early sowing. The effects on crop DM, N-uptake and 15N recovery of a high crop density and a narrow distance between the slurry band and crop row appear clearly at the beginning of the spring wheat elongation phase. For weeds the effects were most pronounced for 15N recovery, and using DM as the only response variable may cause insignificant results. However, methods for N application may be part of a strategy controlling weeds, but to obtain satisfactory weed control the N management needs to be supplemented with chemical or mechanical weed management.  相似文献   

9.
Knowledge of the effects of agricultural practices on weed seedbank dynamics is essential for predicting future problems in weed management. This article reports data relative to weed seedbank structure after 18 years of continuous application of conventional tillage (CT, based on mouldboard ploughing) or no tillage (NT) within three crop sequences (continuous wheat, WW; wheat–faba bean, WF; and wheat–berseem clover, WB). Tillage system did not affect the size of the total weed seedbank, but altered both its composition and the distribution of seeds within the soil profile. In particular, the adoption of CT favoured some species (mainly Polygonum aviculare), whereas the continuous use of NT favoured other species (Papaver rhoeas, Phalaris spp. and Lactuca serriola). The effects of tillage system on weed seedbank size and composition were less pronounced in the WB cropping system than in either the WW or WF. Compared with WF and WB, WW resulted in an increase in total weed seedbank density (about 16 000 seedlings m?2 in WW, compared with 10 000 and 6000 seedlings m?2 in WF and WB, respectively) and a reduction in weed diversity, with a strong increase in some species (e.g. Polygonum aviculare). Our results for the effect of NT application on weed seedbank size and composition suggest that farmers should only apply such a conservative technique within an appropriate crop sequence.  相似文献   

10.
Size and composition of the weed seedbank was assessed after 12 years of application of four tillage systems in two crop rotations. Mouldboard and chisel ploughing at 45 cm, minimum tillage at 15 cm and no tillage were compared in continuous winter wheat and a pigeon bean/winter wheat 2-year rotation. Weed control was based upon post-emergence herbicide application. Weed seedling emergence from soil samples taken at 0–15, 15–30 and 30–45 cm depths was assessed in a non-heated glasshouse for 12 months. The tillage system influenced weed seedbank size and composition to a much greater extent than crop rotation. Total weed seedling density was higher in no tillage, minimum tillage and chisel ploughing plots in the 0–15, 15–30 and 30–45 cm layers respectively. Density in the whole (0–45 cm) layer did not differ significantly among tillage systems. With no tillage, more than 60% of the total seedlings emerged from the surface layer, compared with an average 43% in the other tillage systems. Crop rotation did not influence either weed seedbank size or seedling distribution among soil layers, and only had a small influence on major species abundance. The weed seedbank was dominated (>66%) by Conyza canadensis (L.) Cronq. and Amaranthus retroflexus (L.), which thrived in chisel ploughing and no tillage respectively. Results suggested that crop rotation and substitution of mouldboard ploughing by non-inversion tillage (especially by minimum tillage) would not result in increased weed problems, whereas use of no tillage might increase weed infestations because of higher seedling recruitment from the topsoil.  相似文献   

11.
Sustainable cropping systems based on low inputs have received much attention, even if they may lead to the establishment of a competitive weed flora. This study, conducted from 2011 to 2014 in a Mediterranean environment, evaluated the changes in weed community composition in two cropping systems [conventional (CONV ) and organic (ORG )] with different soil tillage [inversion tillage (IT ) and non‐inversion tillage (NoIT )] in a wheat–tomato–chickpea rotation that began in 2000. The treatments were replicated three times according to a randomised complete block design. The organic system was managed according to EU regulations. Inversion tillage consisted of mouldboard ploughing to a depth of 30 cm, while NoIT consisted of subsoiling to a depth of 20 cm. Weed control was based on herbicide application in CONV and mechanical weeding in ORG . The organic non‐inversion system showed the highest weed biomass (134, 128 and 195 g dry matter (DM ) m?2 in wheat, tomato and chickpea, respectively) and weed density (66, 77 and 76 plants m?2 in wheat, tomato and chickpea, respectively), as well as community richness. However, ORG always increased weed diversity, even if annual dicotyledon species were abundant in ORG ‐IT and perennial dicotyledon species in ORG ‐NoIT . The conventional system enhanced the relative frequency of both annual (CONV ‐IT ) and perennial (CONV ‐NoIT ) grasses. There was a negative correlation between density of perennial weeds and crop yield (r 2 = 0.24, P  <  0.001). Therefore, in the Mediterranean environment, combining organic practices with non‐inversion tillage could lead to the establishment of perennial weeds that are difficult to control, thus requiring specific weed management practices.  相似文献   

12.
In India, wheat is prone to being heavily infested with weeds, which cause considerable yield losses. Agronomic practices, including sowing method, influence weed interference in wheat growth. A herbicide mixture is usually more effective than a single herbicide for controlling a broad-spectrum of weeds. It may prevent weed species shift and delay resistance development in weeds. This study attempted to develop an integrated approach, combining a modified sowing method with applying a herbicide mixture for efficient weed management in wheat. We found that flat bed missing-row sowing resulted in significant reductions in: (i) the three-year mean population densities of grassy, broad-leaved and total weeds at 40 days after sowing (d.a.s), (ii) total weed population density and biomass (dry weight) at 60 d.a.s., compared to a mainly, furrow-irrigated raised bed system. Applying a tank-mix of fenoxaprop-p-ethyl at 0.08 kg/ha and isoproturon at 0.4 kg/ha applied 30 d.a.s. resulted in significant reductions in total weed population density and biomass, leading to a significant improvement in wheat growth and yield compared to either a weedy check or a regime of fenoxaprop-p-ethyl applied at 0.10 kg/ha. However, a combination of the flat bed missing-row sowing and tank-mix application of fenoxaprop-p-ethyl 0.08 kg/ha and isoproturon 0.4 kg/ha 30 d.a.s. resulted in higher wheat yield through better management of weeds compared with other sowing/ weed control combinations.  相似文献   

13.
渭北旱塬保护性耕作春玉米田杂草发生及防除   总被引：1，自引：0，他引：1  
通过田间调查和药效试验,对渭北旱塬一年一熟区春玉米田保护性耕作条件下杂草发生规律及化学除草效果进行了初步研究.结果表明:倒秆免耕秸秆全程覆盖春玉米田杂草种类与传统翻耕田差别不明显,优势种均为田旋花、反枝苋和灰绿藜,主要差别在于保护性耕作农田杂草生物量大.96%金都尔乳油900 mL/hm2和70%乙草胺乳油900 mL/hm2土壤封闭处理对保护性耕作春玉米田杂草均具有一定的防效,且对玉米出苗无影响,而96%金都尔乳油播后封闭处理明显优于70%乙草胺乳油,其50d的鲜重防效仍高达87.4%;20%克无踪水剂1 500 mL/ hm2和40%莠去津悬浮剂2 250mL/hm2定向喷雾处理也可有效控制春玉米田杂草,但20%克无踪水剂明显优于40%莠去津悬浮剂,其23 d的株防效仍高达88.4%;4种药剂的3种防治方法均具有保产作用,其中20%克无踪水剂处理后保产效果最好.可见,在黄土高原保护性耕作玉米田杂草防治中,可优先考虑以96%金都尔乳油进行播后土壤封闭处理,其次可选用20%克无踪水剂于苗期进行定向喷雾处理.  相似文献   

14.
Glyphosate is a key component of weed control strategies in Australia and worldwide. Despite widespread and frequent use, evolved resistance to glyphosate is rare. A herbicide resistance model, parameterized for Lolium rigidum has been used to perform a number of simulations to compare predicted rates of evolution of glyphosate resistance under past, present and projected future use strategies. In a 30‐year wheat, lupin, wheat, oilseed rape crop rotation with minimum tillage (100% shallow depth soil disturbance at sowing) and annual use of glyphosate pre‐sowing, L. rigidum control was sustainable with no predicted glyphosate resistance. When the crop establishment system was changed to annual no‐tillage (15% soil disturbance at sowing), glyphosate resistance was predicted in 90% of populations, with resistance becoming apparent after between 10 and 18 years when sowing was delayed. Resistance was predicted in 20% of populations after 25–30 years with early sowing. Risks of glyphosate resistance could be reduced by rotating between no‐tillage and minimum‐tillage establishment systems, or by rotating between glyphosate and paraquat for pre‐sowing weed control. The double knockdown strategy (sequential full rate applications of glyphosate and paraquat) reduced risks of glyphosate and paraquat resistance to <2%. Introduction of glyphosate‐resistant oilseed rape significantly increased predicted risks of glyphosate resistance in no‐tillage systems even when the double knockdown was practised. These increased risks could be offset by high crop sowing rates and weed seed collection at harvest. When no selective herbicides were available in wheat crops, the introduction of glyphosate‐resistant oilseed rape necessitated a return to a minimum‐tillage crop establishment system.  相似文献   

15.
The management of crop fertilization may be an important component of integrated weed management systems. A field study was conducted to determine the effect of various application methods of nitrogen (N) fertilizer on weed growth and winter wheat yield in a zero-tillage production system. Nitrogen fertilizer was applied at 50 kg ha−1 at the time of planting winter wheat over four consecutive years to determine the annual and cumulative effects. The nitrogen treatments consisted of granular ammonium nitrate applied broadcast on the soil surface, banded 10 cm deep between every crop row, banded 10 cm deep between every second crop row, and point-injected liquid ammonium nitrate placed between every second crop row at 20 cm intervals and 10 cm depth. An unfertilized control was also included. Density, shoot N concentration and the biomass of weeds was often lower with subsurface banded or point-injected N than with broadcast N. The winter wheat density was similar with all N fertilizer application methods but wheat shoot N concentration and yield were consistently higher with banded or point-injected N compared with broadcast N. In several instances, the surface broadcast N did not increase the weed-infested wheat yield above that of the unfertilized control, indicating that it was the least preferred N application method. Depending on the weed species, the weed seedbank at the conclusion of the 4 year study was reduced by 29–62% with point-injected N compared with broadcast N. Information gained from this study will be used to develop more integrated weed management programs for winter wheat.  相似文献   

16.
In Northern Europe, inter-row hoeing has become a popular tactic for controlling weeds in organic cereals. Hoeing is highly effective and can be implemented from crop emergence until stem elongation to maintain a nearly weed-free inter-row zone. However, hoeing has a lesser effect on weeds growing in the intra-row zone, where crop–weed proximity results in heightened competition. In the hoed cereal system, it is investigated whether tall-growing, competitive, cruciferous weeds in the intra-row zone affect crop biomass, yield and thousand kernel weight (TKW). An additive experimental design is employed to enable the fitting of rectangular hyperbolas, describing and quantifying the effects of increasing intra-row surrogate weed density on crop growth parameters. Regressions were studied under the influence of crop (spring barley and spring wheat), row spacing (narrow [12.5 or 15.0 cm] and wide [25.0 cm]) and nitrogen rate (50 and 100 kg NH4-N/ha). Cruciferous surrogate weeds were found to impact crop yield and quality severely. For example, ten intra-row plants/m2 of surrogate weed Sinapis alba reduced grains yields by 7%–14% in spring barley and by 7%–32% in spring wheat with yield losses becoming markedly greater in wheat compared to barley as weed density increases. Compared to wheat, barley limited yield and quality losses and suppressed intra-row weed growth more. Row spacing did not have a consistent effect on crop or weed parameters; in one of six experiments, the 25 cm row spacing reduced yields and increased intra-row weed biomass in wheat. Nitrogen rate did not affect crop or weed parameters. Results warrant the implementation of additional tactics to control intra-row weeds and limit crop losses.  相似文献   

17.
我国农田杂草治理技术的发展   总被引：36，自引：0，他引：36  
张泽溥 《植物保护》2004,30(2):28-33
我国稻、麦、玉米、大豆及棉花等主要农作物农田杂草有580种,属于危害重而又难于防除的有17种,受杂草危害较重的农田有3 580万hm2,年平均受草害减产12.3％～16.5％(加权平均)。自1980年以来,全国化学除草面积以年增200万hm2的速度扩大,农田化学除草面积从20世纪70年代早期不到100万hm2扩大到近年来6 000万hm2。本文概述了我国农田主要作物杂草的发生危害、化学除草剂应用现状及其综合防治进展,并提出今后杂草防除的设想与建议。  相似文献   

18.
Heterogeneous field conditions are ubiquitous throughout agricultural systems and have given rise to the practice of site‐specific management, in an effort to increase sustainability and/or homogenise growing conditions and thereby increase crop yields. The spatial pattern of weeds in conventional systems is widely accepted to be aggregated, but there have been no scientific studies regarding the spatial pattern of weed distribution in organic systems. Using a combination of aggregation measures and quadrat variance techniques, this study compared the spatial pattern of weed distribution in conventionally managed no‐tillage spring wheat fields to those of organically managed spring wheat fields. Per cent weed cover data (by species) were collected in the summers of 2005 and 2006 from transects located in conventional no‐tillage and organic spring wheat fields. Weed cover was aggregated in both the conventional and the organic systems, but the patterns of aggregation were different for the two systems. Conventional no‐tillage systems showed a patch/gap pattern, while organic systems showed multiple scales of patchiness with few gaps. These results suggest that processes causing aggregation in the two systems may be different and that site‐specific management may be applicable to organic systems as well as conventional spring wheat systems.  相似文献   

19.
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   

20.
Field experiments were conducted to study weed population shifts in long‐term conservation tillage systems. The objectives of this study were to determine weed community abundance, diversity and composition on conventional tillage (CT), minimum tillage (MT), no‐tillage with paraplow (ZT) and no‐tillage (NT) systems, and to identify species that are associated with specific tillage systems. The paraplow is a subsoiling technique that results in a deep loosening of the soil, in order to alleviate compaction in certain soils where NT is practiced. The results showed significant differences in both the composition and the abundance of weeds, depending on the tillage systems. Weed diversity, species richness and Shannon's diversity and evenness indices were higher under the conservation tillage systems than in the CT system. In addition, various weed species were associated with reduced tillage systems. For instance, Anthemis arvensis, Hirschfeldia incana and Lolium rigidum became more prevalent in the NT system, whereas Chenopodium album and Filago pyramidata dominated in the ZT system. Therefore, the application of a paraplow treatment changed the weed community in the NT system. Other weed species, such as Capsella bursa‐pastoris and Torilis nodosa, dominated in all three conservation tillage systems, whereas soil disturbance by mouldboard ploughing favoured species such as Polygonum aviculare and Phalaris paradoxa.  相似文献   

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