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1.
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   

2.
Abstract

Field research was conducted near Hyderabad, India, during 1981 and 1982 to investigate zero‐tillage and reduced‐tillage systems for production of sorghum (Sorghum bicolor (L.) Moench.) under semi‐arid tropical conditions. Part of the investigation compared post‐seeding hand weeding and herbicide treatments for weed control efficacy. The results showed that shallow pre‐seeding tillage was just as effective as deep cultivations in producing high sorghum fodder and grain yields provided weeds were controlled after crop emergence. Both tillage regimes were more effective than a no tillage regime which received only a mixture of glyphosate and 2,4‐D prior to seeding. Post‐seeding weed control practices were essential to maintain high fodder and grain yields of sorghum. Hand weeding and inter‐row blade harrowing were more effective than atrazine applied pre‐emergence or 2,4‐D applied post‐emergence.  相似文献   

3.
Four field experiments were conducted at The International Rice Research Institute during the 1975 and 1976 crop seasons to develop minimum and zero tillage techniques for transplanted rice (Oryza sativa L.). High rates of glyphosate followed by a lower rate of paraquat effectively controlled Paspalum distichum L., but not Fimbristylis littoralis L. The tenminimum tillage treatments based on different combinations and sequences of pre-plant herbicide application, tillage and flooding, gave a similar grain yield to conventional tillage, and significantly higher grain yield than zero tillage treatments. Conventional, minimum and zero tillage were compared over four successive crops. After two crops with zero tillage, the plots were dominated by the perennials, P. distichum and Scirpus maritimus L., but with minimum or conventional tillage, weed control and grain yield were satisfactory. Efficiency of nitrogen fertilizer usage by the crop was the same with minimum as with conventional tillage but higher than with zero tillage and was increased by placement at 10 cm depth. The studies indicate that minimum tillage systems are a dependable alternative to conventional tillage for lowland rice production.  相似文献   

4.
The influence of no-tillage and conventional tillage on the outcome of early weed interference in maize (Zea mays L., cv. TZB), cowpea [Vigna unguiculata (L.) Walp, cv. VITA-5] and their intercrop at populations of 40000, 50 000 and 30 000 + 40 000 plants ha?1 was investigated on a loamy sand Oxic Ustropept in a subhumid tropical environment between April and July 1980. Both tillage treatments received 60 kg N, 30 kg P2O5 and 30 kg K2O ha?1. Although the weed spectrum was wider under no-tillage, weed weight was only 52% of the weight recorded under conventional tillage 6 weeks after sowing and the average food energy yield reductions caused were 28 and 65%, respectively. Cropping pattern had no effect on plot weediness. With minimum or no weed interference, maize performance was better in conventional than no-tillage but worse with prolonged weed interference. Cowpea responded more to weed interference than to tillage practice. Regardless of tillage practice and weed interference duration (up to 6 weeks) after sowing, maize monoculture produced the highest food energy yield, followed by maize/cowpea intercrop and cowpea monoculture in that order.  相似文献   

5.
Interactions between the weeds Bromussterilis L., Galium aparine L. and Papaver rhoeas L. were investigated over 3 years of continuous winter wheat (Triticum aestivum L.) across a factorial combination of organic and conventional fertilizer, and ploughing and hand-roguing contrasted with minimum tillage and herbicide. The species were sown separately and together at 50 seeds m?2 per species at the start of the experiment in October 1989. In addition, there were weed-free and background-weed controls. Weed densities were monitored at roughly monthly intervals and crop yield recorded for three seasons. B. sterilis populations increased 10-fold under minimum tillage, but declined under ploughing. Densities of P. rhoeas remained largely low. G. aparine increased on the organically fertilized minimum-tillage plots, except where B. sterilis was present; the high densities of B. sterilis reduced the population size of G. aparine. Crop yield was influenced most strongly by the fertilizer treatment in the first season, but later the density of B. sterilis was by far the most important factor; the evidence of interactive effects of the different weed species on crop yield was weak at best. Interactive effects of arable weed species can be observed, but only at very high densities, and so are unlikely to be of widespread economic importance.  相似文献   

6.
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   

7.
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   

8.
Over the last two decades, the demand for organic products has grown rapidly in the world due to increased concern about side effects of pesticides on the environment and human health. Studies were conducted in organic lettuce (Lactuca sativa L.) from 2004 to 2005 at the Black Sea Agricultural Research Institute in Samsun, Turkey, to determine the suppressive effects of summer cover crops on weeds. The experiment was arranged in a randomized complete block design with four replications. Treatments consisted of grain sorghum [Sorghum bicolor (L.) Moench.], sudangrass [Sorghum vulgare Pers. var. sudanense (Piper) Hitchc.], hairy vetch (Vicia villosa Roth.), grain amaranth (Amaranthus cruentus L.), pea (Pisum sativum L.) and bare ground with no cover crop. Weed density and total weed dry biomass were assessed before and at 14, 28, and 56 days after incorporation (DAI) of the cover crops. The cover crops produced between 1.2 and 3 t ha−1 biomass and grain sorghum produced more dry matter than any other species in both years. After incorporation of the cover crops, hairy vetch and sorghum treatments showed fewer weed species, and lower weed density than the other cover crops in both years. Hairy vetch, grain sorghum, and sudangrass were the most effective cover crops and reduced total weed dry biomass by 90.3%, 87.4%, and 86.9% in 2004, and by 88%, 86.3%, and 85.2% in 2005, respectively. Cover crop residue suppressed many broadleaved weed species but failed to control grass weeds. Hairy vetch treatments produced the highest yield, followed by sudangrass and grain sorghum. Yields with grain amaranth and pea were similar to that of the control. These results indicate that hairy vetch, grain sorghum, and sudangrass can be used to suppress weeds in early season of organic lettuce production.  相似文献   

9.
The vegetation cover during the non‐cropping season could have important implications for the maintenance and recovery of soil fertility, as well as for biodiversity conservation in croplands. In this study, five fertilization regimes (control: non‐fertilization; N: inorganic N fertilization; P: inorganic P fertilization; NPK: balanced fertilization with inorganic N, P and K; NPKM: balanced NPK plus farmyard manure) were conducted from 1981 in a double‐rice (Oryza sativa L.)‐cropping system in subtropical China. The effects of long‐term fertilization were investigated on the weed growth, diversity and community structure during the fallow period. The results showed that, relative to the control, both inorganic fertilization alone (N, P and NPK) and NPKM in the rice‐growing season significantly increased the weed density and biomass during the fallow period in the paddy field. There was no significant difference in the weed species richness (the number of species) among the treatments. Compared with the control, fertilization tended to reduce the weed diversity (Shannon's H′) and evenness (Shannon's E), especially in the N treatment. Long‐term fertilization resulted in a significant shift in weed community's composition during the fallow period. The weed community's structure was affected by soil nutrients in the order P > N > K.  相似文献   

10.
A long-term study of weed flora shifts in different tillage systems   总被引：1，自引：0，他引：1  
Knowledge of the long-term effects of tillage on weed flora will provide useful information to improve weed management in agroecosystems. Field studies were conducted from 1991 to 1997 to evaluate the effects of tillage systems on weed density and species composition before control methods in rotations including wheat ( Triticum aestivum L.), soyabean [ Glycine max (L.) Merr.] and maize ( Zea mays L.). In wheat, annual broad-leaved species showed higher populations in conventional tillage in 4 out of 6 years, and grassy annuals and perennial species showed an erratic response with tillage systems. In summer crops, broad-leaved populations were higher under conventional tillage than non-tillage for the last 5 years in the wheat/soyabean rotation and for the last 4 years in the maize/soyabean rotation. The weed spectrum changed rapidly in non-tillage plots. With time, in the absence of tillage, grassy annual populations increased in the maize/soyabean rotation, and wind-dispersed weed populations increased in the wheat/soyabean rotation. Perennial weeds showed an inconsistent behaviour in relation to tillage systems in the maize/soyabean rotation.  相似文献   

11.
Abstract

Grain sorghum (Sorghum bicolor (L.) Moench) is the dominant crop in North Yemen agriculture, covering about 70–80% of the arable land. Weed control is still carried out mainly by hand. Many of the weeds are used as fodder for animals. A total of 137 weeds was collected in sorghum. Most frequent were Cynodon dactylon (L.) Pers. and Cyperus mtundus (L): their importance decreased, however, under a well‐established sorghum crop providing good shade cover and under conditions of increased crop fertilization with mineral nitrogen. Under these conditions, for example, Commelina spp. and Flaveria trinerva (Spreng.) Mohr became commoner. Thus increased use of nitrogen altered the nature and hierarchy of the weed flora. Relationships between the indicator figures of the weeds and the habitat, as defined by Ellenberg, were confirmed. Traditional methods of weed control have so far worked well, as witness an average cover of 60% sorghum and 20% weeds. In future, however, rising costs and labour shortages will increase the demand for less time‐consuming weed control strategies.  相似文献   

12.
Weed populations were monitored for 4 years on two experiments designed to compare the effect of different primary tillage treatments on winter wheat (Triticum aestivum L.) cropping. Ploughing was compared with deep and shallow tine cultivation and with no tillage on both a clay loam and a silt loam over chalk. Soil-acting residual herbicides were used to control weeds, especially Alopecurus myosuroides Huds. and Avena fatua L. Dicotyledonous weeds were uncommon on the clay loam but on the silt loam, in a year when no residual herbicide was used, they were most numerous where the soil was disturbed most. In other years there was little difference in the number emerging. Six species were reduced in number by reduced cultivation or no tillage, whilst four species, including two grasses, were increased. At both sites, A. myosuroides was more numerous on direct drilled and tine cultivated plots than on ploughed. Herbicides gave good control on the silt loam but failed to control the weed on the clay loam. On the clay loam, A. fatua was most numerous on tine cultivated plots and a combination of herbicides and roguing produced a decline in the population.  相似文献   

13.
The effects of crop genotype and sowing time on competition between safflower (Carthamus tinctorius L.) and weeds were investigated in a 2-year field study. Each year, safflower was grown as a pure stand and in mixture with a natural weed infestation, mostly represented by Polygonum aviculare L., Fallopia convolvulus (L.) A. Löve and Chenopodium album L., in an additive design including weed stands grown without the crop. Grain yield reduction ranged from about 50% to 80% depending on crop genotype, and was higher under spring sowing (mid-March) than under winter sowing (mid-February). In general, those genotypes incurring the least yield reduction gave the greatest suppression of weed biomass. More competitive genotypes also tended to reduce the proportion of C. album in the weed biomass at harvest, particularly in 1994 (the wetter growing season). The competitive ability of the crop was mainly correlated with its biomass at early growth stages, but was not related to its grain-yielding ability in the absence of weeds. Results showed that more competitive crops may be obtained by sowing the most competitive genotypes early. Selecting for higher competitive ability in safflower does not seem to imply a reduction in grain-yielding ability.  相似文献   

14.
A. BERTI  M. SATTIN 《Weed Research》1996,36(3):249-258
The importance of the position of weeds with respect to crop rows in the determination of crop yield-weed density relationships and the usefulness of relative cover (RC) of the weeds as an explanatory variable were studied in soyabean [Glycine max (L.) Merrill] competing with two summer weeds with contrasting canopy structure (Xanthium strumarium L. ssp. italicum and Echinochloa crus-galli L.). The position of the weeds was of little importance in the relationship between yield loss and weed density. This information is important because published experiments have used different types of weed distribution (e.g. evenly distributed or sown in rows). For both weed species it was possible to obtain a single relationship between yield loss and RC for measurements made from 30 days after crop emergence to soyabean canopy closure. The competitive effect of the weeds appeared to be strictly related to RC, indicating that for weeds growing taller than the crop the main competitive factor may be the shading caused by the leaves of the weeds situated above the crop canopy.  相似文献   

15.
Abstract

Yield and weed growth in dry-seeded rice (Oryza sativa L.) were unaffected by method of seeding. Weeds depressed rice yields by 95%. Fourteen weed species were found growing in association with dry-seeded rice at maximum flowering of the weeds. Echinochloa colona (L.) Link and Leptochloa chinensis (L.) Nees were the major weeds. A dramatic change in the weed flora was observed in transplanted rice planted immediately after the harvest of the dry-seeded crop. Only five species grew in association with the transplanted crop. Monochoria vaginalis (Burm.) Presl. dominated. E. colona and L. chinensis were present in transplanted rice but were only minor weeds. The number of weeds in the transplanted crop was less than 50%, and weighed only 5% as much as those in the dry-seeded crop. There was no carryover of the weed control treatments from the dry-seeded crop to the transplanted crop.  相似文献   

16.
Weed flora in a crop rotation of soybean, sugar beet, and spring wheat were studied under combinations of conventional and reduced tillage, biocide application, and chemical fertilization to investigate whether any combination of conservational practices offers the potential to increase weed community diversity while maintaining weed biomass at an acceptable level. Weed density increased under reduced biocide application. Weed density and size increased under manure compost application (with reduced chemical fertilization) because of weed seed introduction. Weed emergence from seeds dispersed in the previous year was greater under reduced tillage. Two-year individuals increased under a combination of reduced tillage, reduced biocide application and manure compost application. These increases in weed population density and size under conservational practices were yet not consistent; rather, they showed an annually fluctuating trend. In terms of weed diversity, species richness and Shannon's diversity index were higher under manure application because of the introduction of new species and probably as a result of suppression of weed growth and reproduction, which can reduce the chance of dominance by certain species. When combined with manure application, reduced tillage may offer the potential for increasing diversity by reducing the competitiveness of dominant species and facilitating establishment of new or minor species.  相似文献   

17.
A national survey was conducted in Finland from 1982 to 1984 to determine the main weed species in spring cereals and the efficacy of herbicides on Finnish farms. The most common dicotyledonous weeds producing the highest biomass in spring cereals were Chenopodium album L., Galeopsis spp. L., Stellaria media (L.) Vill. and Lapsana communis L. The main grass weed was Elymus repens (L.) Gould. The average reduction of weed biomass by herbicide treatment was 75%. More reliable efficacy was obtained with herbicide mixtures than with MCPA alone.  相似文献   

18.
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   

19.
Imran  Amanullah 《Gesunde Pflanzen》2022,74(1):167-176

Effective weed management in maize-wheat (M-W) cropping systems are accountable for higher yield and plant biomass. The objective of this study was to evaluate the effectiveness of manual weeding and chemicals (pre- and post-emergence herbicide) for actual weed control to enhance maize yield and M?W system productivity. Herbicides were treated as pre-emergence (sole), post-emergence (sole) and its combined application (pre- and post-emergence) for weed eradication and suppression. Sole pre-emergence herbicide (acetyclour?+?atrazine) and sole post-emergence herbicides (nicosulfuron), and its mixed application were used in the experiments. The experiment was comprised on 6 treatments with one weedy check or control plot: W1?=?weedy check, W2?=?acetyclour?+?atrazine, W3?=?atrazine, W4?=?nicosulfuron, W5?=?nicosulfuron?+?atrazine, W6?=?acetyclour?+?atrazine?+?nicosulfuron and W7?=?manual weeding. Main weeds were Cyperus rotundus, Tribulus terrestris, Dactyloctenium aegyptium and Cynodon dactylon. Experiential findings revealed that manual weeding was found most effective in terms of controlling weed and suppression. Among the herbicides application, promising results in terms of weed destruction and suppression were shown by combined application of acetyclour?+?atrazine?+?nicosulfuron which effectively controlled weeds as compared to other treatments. It was concluded that manual weeding drastically reduced weeds frequency and biomass while among the herbicides application acetyclour?+?atrazine and nicosulfuron could be promising for weeds suppression and clamp downing as compared to all other treatments under M?W cropping system.

  相似文献   

20.
Field experiments were conducted in northern Greece in 2003 and 2004 to evaluate effects of tillage regimes (moldboard plowing, chisel plowing, and rotary tilling), cropping sequences (continuous cotton, cotton‐sugar beet rotation, and continuous tobacco) and herbicide treatments with inter‐row hand hoeing on weed population densities. Total weed densities were not affected by tillage treatment except that of barnyardgrass (Echinochloa crus‐galli), which increased only in moldboard plowing treated plots during 2003. Redroot pigweed (Amaranthus retroflexus) and black nightshade (Solanum nigrum) densities were reduced in continuous cotton, while purple nutsedge (Cyperus rotundus), E. crus‐galli, S. nigrum, and johnsongrass (Sorghum halepense) densities were reduced in tobacco. A. retroflexus and S. nigrum were effectively controlled by all herbicide treatments with inter‐row hand hoeing, whereas E. crus‐galli was effectively reduced by herbicides applied to cotton and tobacco. S. halepense density reduction was a result of herbicide applied to tobacco with inter‐row hand hoeing. Yield of all crops was higher under moldboard plowing and herbicide treatments. Pre‐sowing and pre‐emergence herbicide treatments in cotton and pre‐transplant in tobacco integrated with inter‐row cultivation resulted in efficient control of annual weed species and good crop yields. These observations are of practical relevance to crop selection by farmers in order to maintain weed populations at economically acceptable densities through the integration of various planting dates, sustainable herbicide use and inter‐row cultivation; tools of great importance in integrated weed management systems.  相似文献   

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