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1.
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   

2.
K Rasmussen 《Weed Research》2002,42(4):287-298
Summary Injection of liquid manure (slurry) into the soil is an alternative to the traditional surface application. By the injection method, it is possible to place nutrients closer to the crop sown, thus offering the crop a competitive advantage over weeds. This study compares the response in crop yield, weed density and weed biomass to injection vs. surface application of liquid manure through three growing seasons in barley and oats. The manure applications were combined with treatments of weed harrowing or herbicide spraying or no treatment at all. The levels of weed control and crop yield obtained by harrowing and herbicides were larger when slurry was injected compared with surface application. Without any weed control treatments, the injection method decreased the final weed biomass in barley. The influence of nutrient injection on yield and weed control seemed to be modulated by the time of emergence and the early growth rate of the crop relative to weeds. Thus, because of its early root growth and development, barley responded more quickly to the injection treatment than oats. Consequently, barley became a more competitive crop.  相似文献   

3.
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   

4.
Rasmussen  Rasmussen 《Weed Research》2000,40(2):219-230
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   

5.
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   

6.
This study was conducted in the Mediterranean environment of Central Italy from 2011 to 2013 with the aim of evaluating the effects of winter cover crops and their residues on weed composition in a cover crop‐tomato sequence. Treatments consisted of five soil managements (three cover crop species ‐ hairy vetch, phacelia, white mustard, winter fallow mulched with barley straw before tomato transplanting and conventionally tilled soil), two nitrogen fertilisation levels (0 and 100 kg N ha?1) and two weed management levels (weed free and weedy) on tomato. Cover crop residues were arranged in strips on the soil surface and then used as beds for transplanting the tomato seedlings in paired rows. Rotary hoeing was performed in the bare strips between paired tomato rows. At tomato harvesting, the weed aboveground biomass and density was higher in nitrogen‐fertilised tomato than unfertilised tomato, except in hairy vetch and barley straw that showed similar values. Hairy vetch used as a cover crop and dead mulch was the most suppressive species with the highest production of residues, while phacelia and mustard were not suitable for controlling weeds. The tomato yield was high in nitrogen fertilised and weed‐free treatments, except in barley straw mulch, which showed similar values among the weed management treatments. The mulch strips caused variations in weed species composition that was mainly composed of perennial ruderal weeds, while in tilled soil, the weed flora was dominated by annual photoblastic weeds.  相似文献   

7.
Summary The effectiveness of crop competition for better weed control and reducing herbicide rates was determined for Avena ludoviciana and Phalaris paradoxa . Four experiments, previously broadcast with seeds of the two weeds in separate plots, were sown with three wheat densities, and emerged weeds were treated with four herbicide doses (0–100% of recommended rate). The measured crop and weed traits were first analysed across experiments for treatment effects. Grain yield and weed seed production data were then analysed using cubic smoothing splines to model the response surfaces. Although herbicide rate for both weeds and crop density for P. paradoxa had significant linear effects on yield, there was a significant non-linearity of the response surface. Similarly, herbicide rate and crop density had significant linear effects on weed seed production, and there was significant non-linearity of the response surface that differed for the weed species. Maximum crop yield and reduction in seed production of P. paradoxa was achieved with approximately 80 wheat plants m−2 and weeds treated with 100% herbicide rate. For A. ludoviciana , this was 130 wheat plants m−2 applied with 75% herbicide rate. Alternatively, these benefits were achieved by increasing crop density to 150 plants m−2 applied with 50% herbicide rate. At high crop density, application of the 100% herbicide rate tended to reduce yield, particularly with the A. ludoviciana herbicide, and this impacted adversely on the suppression of weed seed production. Thus, more competitive wheat crops have the potential for improving weed control and reducing herbicide rates.  相似文献   

8.
A glasshouse experiment was carried out to investigate the influence of increasing levels of nitrogen and phosphorus on the growth of six common weed species growing alone or in competition with spring barley (Hordeum vulgare). Capsella bursa‐pastoris, Chenopodium album, Papaver rhoeas, Sinapis arvensis, Spergula arvensis, Viola arvensis and spring barley were grown in pots with different levels of nitrogen (0, 30, 60, 90, 120 and 150 kg N ha?1) or phosphorus (0, 10, 20, 30, 40 and 60 kg P ha?1). The aboveground parts of the plants were harvested after 7 weeks and the dry weight of shoots, percentage N and P content of the shoot and uptake of N and P were determined. A linear or a polynomial model was used to describe the data. Growing alone, Spergula arvensis was the only weed species that increased its dry weight at the same rate as barley. Weed species with low dry weight increase had larger increases in percentage N or P content than barley, indicating a luxury accumulation of nutrients. The uptake of N and P per pot did not differ much between weeds and barley. V. arvensis and P. rhoeas accumulated least nutrients (per cent of dry matter) and Spergula arvensis accumulated most. Weeds grew poorly in competition with barley. The percentage N and P content in barley did not change when they grew in competition with weeds.  相似文献   

9.
Information on temporal and spatial variation in weed seedling populations within agricultural fields is very important for weed population assessment and management. Primarily, spatial information allows a potential reduction in herbicide use, when post‐emergent herbicides are only applied to field sections with high weed infestation levels. This paper presents a system for site‐specific weed control in sugar beet, maize, winter wheat, winter barley, winter rape and spring barley. The system includes on‐line weed detection using digital image analysis, computer‐based decision making and Global Positioning System‐controlled patch spraying. In a 2‐year study, herbicide use with this map‐based approach was reduced in winter cereals by 6–81% for herbicides against broad leaved weeds and 20–79% for grass weed herbicides. Highest savings were achieved in cereals followed by sugar beet, maize and winter rape. The efficacy of weed control varied from 85% to 98%, indicating that site‐specific weed management will not result in higher infestation levels in the following crops.  相似文献   

10.
Summary This paper tests the hypothesis that increased soil nitrogen supply reduces the growth of late-emerging weeds in wheat and potato by enhancing canopy leaf area development and thereby reducing the availability of light for weed growth. Two series of experiments were conducted: one in spring wheat (1997, 1999) with sown Stellaria media and one in potato (1998, 1999) with naturally emerged weeds, including S. media . For each crop, two cultivars were grown at three levels of nitrogen supply. In wheat, as in a monoculture of S. media , total dry weight and seed number of the weed increased with soil nitrogen supply, whereas in potato the opposite was found. Increased soil nitrogen supply increased the nitrogen uptake of S. media in wheat, despite the reduced light availability, indicating that S. media in wheat was limited by nitrogen. In potato, on the other hand, growth of S. media was limited by light availability, which decreased with increased soil nitrogen supply . We conclude that the differences in response of S. media in wheat and potato to additional nitrogen supply are attributable to the dual influence of soil nitrogen supply on light and nitrogen availability, which are mediated by the crops.  相似文献   

11.
Melander  Rasmussen 《Weed Research》2000,40(2):205-218
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   

12.
Weed competition and nutrient scarcity often restrict organic cereal production, especially where the availability of livestock manure is limited. While harrowing of annual weeds and legume cover crops can be used, these methods are both executed in early spring and may hinder each other. Two cycles of a 2‐year crop rotation were carried out in south‐east Norway (60°42′N, 10°51′E, altitude 250 m) with weed harrowing and undersown cover crops (WHCC) at two fertiliser rates (40 and 100 kg nitrogen ha?1). The effect of the WHCC treatments was measured by weed density and species, weed biomass, changes in weed seedbank and grain yield. The weed density depended on the interaction between WHCC, fertiliser and year. On average, pre‐emergence weed harrowing reduced weed density by 32% and weed biomass by 49%, while pre‐ and post‐emergence weed harrowing reduced weed density by 59% and weed biomass by 67% compared with the untreated control. Spergula arvensis became more abundant at low rather than at high fertiliser rates. On average, white clover cover crop sown after pre‐emergence weed harrowing resulted in the highest yields for both oat (+12.1%) and wheat (+16.4%) compared with the untreated control. Despite differences in weed population density and biomass among WHCC treatments within years, the weed biomass, weed density and seedbank increased for all WHCC treatments over the 4‐year period. More research is required into improving the efficacy of mechanical and cultural weed suppression methods that organic systems rely on.  相似文献   

13.
发展化学除草重视综合治理   总被引：4，自引：0，他引：4  
我国农田杂草有２５０多种，全国农田受草害面积４３００多万ｈｍ２，平均受草害减产１３．４％，每年减产粮食１７５０万ｔ，皮棉２５．５万ｔ和大豆５０万ｔ。传统农业生产采用机械作业及人力等除草。随着农村经济的发展，化学除草面积迅速扩大，全国农田化学除草面积从１９７５年的１７０万ｈｍ２增加到１９９５年的４１３３万ｈｍ２。但是，长期化学除草也带来了除草剂土壤残留对后茬作物药害、农田杂草种群更替和产生抗药性等新问题。必须重视农田杂草综合治理，通过采用各种有效的农业技术措施，为农作物保持良好的生态条件，结合化学除草才是最有效的防除杂草方法  相似文献   

14.
To better understand the potential for improving weed management in cereal crops with increased crop density and spatial uniformity, we conducted field experiments over two years with spring wheat ( Triticum aestivum ) and four weed species: lambsquarters ( Chenopodium album ) , Italian ryegrass ( Lolium multiflorum ), white mustard ( Sinapis alba ), and chickweed ( Stellaria media ). The crops were sown at three densities (204, 449, and 721 seeds m−2) and in two spatial patterns (normal rows and a highly uniform pattern), and the weeds were sown in a random pattern at a high density. In most cases, the sown weeds dominated the weed community but, in other cases, naturally occurring weeds were also important. There were strong and significant effects regarding the weed species sown, the crop density, and the spatial distribution on the weed biomass in both years. The weed biomass decreased with increased crop density in 29 out of 30 cases. On average, the weed biomass was lower and the grain yield was higher in the uniform compared to the row pattern in both 2001 and 2002. Despite the differences in weed biomass, the responses of L. multiflorum , S. media , and C. album populations to crop density and spatial uniformity were very similar, as were their effects on the grain yield. Sinapis alba was by far the strongest competitor and it responded somewhat differently. Our results suggest that a combination of increased crop density and a more uniform spatial pattern can contribute to a reduction in weed biomass and yield loss, but the effects are smaller if the weeds are taller than the crop when crop–weed competition becomes intense.  相似文献   

15.
The effects of cover crops on weeds and the underlying mechanisms of competition, physical control and allelopathy are not fully understood. Current knowledge reveals great potential for using cover crops as a preventive method in integrated weed management. Cover crops are able to suppress 70–95% of weeds and volunteer crops in the fall‐to‐spring period between two main crops. In addition, cover crop residues can reduce weed emergence during early development of the following cash crop by presenting a physical barrier and releasing allelopathic compounds into the soil solution. Therefore, cover crops can partly replace the weed suppressive function of stubble‐tillage operations and non‐selective chemical weed control in the fall‐to‐spring season. This review describes methods to quantify the competitive and allelopathic effects of cover crops. Insight obtained through such analysis is useful for mixing competitive and allelopathic cover crop species with maximal total weed suppression ability. It seems that cover crops produce and release more allelochemicals when plants are exposed to stress or physical damage. Avena strigose, for example, showed stronger weed suppression under dry conditions than during a moist autumn. These findings raise the question of whether allelopathy can be induced artificially. © 2019 Society of Chemical Industry  相似文献   

16.
Weeds and weed control are major production costs in global agriculture, with increasing challenges associated with herbicide‐based management because of concerns with chemical residue and herbicide resistance. Non‐chemical weed management may address these challenges but requires the ability to differentiate weeds from crops. Harvest is an ideal opportunity for the differentiation of weeds that grow taller than the crop, however, the ability to differentiate late‐season weeds from the crop is unknown. Weed mapping enables farmers to locate weed patches, evaluate the success of previous weed management strategies, and assist with planning for future herbicide applications. The aim of this study was to determine whether weed patches could be differentiated from the crop plants, based on height differences. Field surveys were carried out before crop harvest in 2018 and 2019, where a total of 86 and 105 weedy patches were manually assessed respectively. The results of this study demonstrated that across the 191 assessed weedy patches, in 97% of patches with Avena fatua (wild oat) plants, 86% with Raphanus raphanistrum (wild radish) plants and 92% with Sonchus oleraceus L. (sow thistles) plants it was possible to distinguish the weeds taller than the 95% of the crop plants. Future work should be dedicated to the assessment of the ability of remote sensing methods such as Light Detection and Ranging to detect and map late‐season weed species based on the results from this study on crop and weed height differences.  相似文献   

17.
春麦田除草剂的应用与杂草群落演替   总被引：10，自引：1，他引：10  
作者采用定点定位试验,对春麦田除草剂应用与杂草群落演替趋势进行研究。结果表明:在杂草群落多样性麦田,小麦连作并分别连续5年施用同一种除草剂,原杂草群落中占优势的靶标杂草得以控制,而非靶标杂草和抗、耐药性杂草因失去竞争和制约对象而猖獗发展,发生量较原来增加几倍至几十倍,并形成优势种群,对小麦造成新的更严重的危害。一种除草剂在同田块连续施用4年,由于杂草群落演替,抗、耐药杂草兴起,除草效果显著下降而失去其使用意义。作者提出除草剂配套使用、轮用、混用等措施,并配合以合理的轮作制度,以减轻杂草群落长期受到单一的定向选择性压力。  相似文献   

18.
A screening programme for crop variety competitiveness would ideally be based on only a few, non-destructive measurements of key growth traits. In this study we measured the weed suppressive ability of 79 varieties of spring barley in two ways: (i) directly, by weed coverage assessments under weedy conditions at three Danish locations in 2002–2004 and (ii) indirectly, by non-destructive measurements of varietal growth traits under weed-free conditions in 17 other experiments in Denmark in 2001–2003. Based on just four varietal growth traits (reflectance, leaf area index, leaf angle and culm length), we successfully developed a method for indexing the weed suppressive ability of spring barley varieties. The suppressive index ranged from 12% in Lux and 55% in Modena in proportion to the 90% quantile coverage of all varieties. The index was validated against independent data from two locations in 2005 with 14 and 24 varieties and was found valuable for future use in regular screening programmes.  相似文献   

19.
Two of the many benefits of including legume cover crops in a fallow cropping system are weed suppression and increased soil organic N. This study was conducted in order to examine the effect of hairy vetch (Vicia villosa) on weed growth and soil N through a fallow period in subtropical Okinawa, Japan. Together with an untreated control plot, hairy vetch was grown from November 2007 to April 2008 and subsequently incorporated into the soil. The weeds were allowed to develop uncontrolled for 2 months until the time when a cash crop would be planted. In the period after the incorporation of hairy vetch, the weed biomass in the hairy vetch (HV)+ plot was more than threefold greater than that in the HV? plot. Hairy vetch had a high tendency to uptake N in April before the incorporation of hairy vetch; the N uptake by the weeds was lower in the HV+ plot than in the HV? plot. After the incorporation of hairy vetch, the N uptake by the weeds in the HV+ plot was two‐to‐six times higher than that by the weeds in the HV? plot. The C/N ratios of hairy vetch and the weeds in the HV+ plot were lower than those of the weeds in the HV? plot. More than half of the hairy vetch residue and N in the residue had decomposed by 28 days after incorporation. The content of both the NH4‐N and NO3‐N in the HV+ soil was higher than that in the HV? soil. Moreover, the amount of NO3‐N increased during the growing period of hairy vetch and decreased after the incorporation of hairy vetch. The fallow soil into which hairy vetch had been incorporated displayed a greater weed biomass and resulted in a higher inorganic N content than the soil that had not supported hairy vetch.  相似文献   

20.
Small unmanned aerial systems (UAS) with cameras have not been adopted in weed research, but offer low‐cost sensing with high flexibility in terms of spatial resolution. A small rotary‐wing UAS was tested as part of a search for an inexpensive, user‐friendly and reliable aircraft for practical applications in UAS imagery weed research. In two experiments with post‐emergence weed harrowing in barley, the crop resistance parameter, which reflects the crop response to harrowing, was unaffected by image capture altitude in the range from 1 to 50 m. This corresponded to image spatial resolution in the range from 0.3 to 17.1 mm per pixel. This finding is important because spatial resolution is inversely related to sensing capacity. We captured 20 plots comprising a total of about 0.2 ha in one image at 50 m altitude without losing information about the cultivation impacts on vegetation compared with ground truth data. UAS imagery also gave excellent results in logarithmic sprayer experiments in oilseed rape, where we captured 37 m long plots in each image from an altitude of 35 m. Furthermore, perennial weeds could be mapped from UAS images. These first experiences with a small rotary‐wing UAS show that it is relatively easy to integrate as a tool in weed research and offers great potential for site‐specific weed management.  相似文献   

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