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1.
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   

2.
Diversity and weed community composition of mid-season plant stands and autumn seedbanks were examined in spring barley–red clover cropping systems that varied according to crop rotation, tillage and weed management. Weed plant and seed density data collected over 4 years were used in the calculation of species richness (number of species), evenness (Shannon's E) and diversity (Shannon's H′), and in multivariate analysis (canonical discriminant analysis) of weed communities. Weed diversity indices were low (H′ < 2.0) but sensitive to management practices. Evenness had intermediate values (E = 0.4–0.8), suggesting little evidence of truly dominant species, particularly in the seedbanks. The difference in the number of species between treatments was never large (approximately two to four species). Overall, diversity indices were highest in the low disturbance treatments, particularly those with minimum weed management. Factors affecting ordination were somewhat different from those affecting diversity. Tillage had little effect on weed diversity indices but had a more major role in determining weed community composition. Seedbanks in no-till and monoculture-chisel plough treatments appeared to have more distinctive species composition compared with other treatments. Weed species assembly in seedbanks showed little discrimination across treatments and over time, confirming the ability of seedbanks to buffer disturbances across a variety of cropping systems. The use of diversity indices revealed part of the complexity of weed communities associated with disturbance in cropping systems, whereas ordination singled out species–cropping systems associations, which may be more meaningful to weed management.  相似文献   

3.
The aim of this study was to assess the effects of crop management practices on the diversity, structure, and composition of weed communities. A total of 30 fields (15 fields each) in low‐input and conventional farming systems were surveyed in north‐eastern Iran. In the conventional cropping system, both mineral fertilizers and herbicides were applied, while in the low‐input cropping system, the fertilizer was mainly manure and herbicides were avoided. The results showed that the pool of species, species richness, number of unique species, and Shannon's diversity index were greater in the low‐input system than in the conventional system. Both cropping systems had more broad‐leaved species than grasses and more annual species than perennial species. All the multivariate methods of analysis that were applied revealed that the weed community composition was significantly different between the two management types. The low‐input cropping favored herbicide‐susceptible broad‐leaved weeds, legumes, and weeds with biodiversity value, whereas a high proportion of herbicide‐tolerant grasses was found in the conventional fields. The results suggest that low‐input cropping can sustain high weed diversity and abundance.  相似文献   

4.
Weeds have negative impacts on crop production but also play a role in sustaining biodiversity in agricultural landscapes. This trade‐off raises the question of whether it is possible to promote weed communities with low competitive potential but high value to biodiversity. Here, we explored how weed communities respond to different vineyard management practices in South Africa's Western Cape, aiming to identify whether any specific practices are associated with more beneficial weed communities. Eight weed community characteristics representative of abundance, diversity and functional composition were used as indicators of competitive potential and biodiversity value. We explored how these responded to farm management strategy (organic, low input or conventional) and weed management practices (herbicides, tillage, mowing or combinations of these) using ordination and mixed models. Mown sites were associated with weed communities of high biodiversity value, with higher weed cover in both winter and summer, higher diversity and more native weeds. Mowing also promoted shorter weeds than either tillage or herbicides, considered to be less competitive with grapevines. However, high summer weed cover may be problematic where competition for water is critical, in which case tillage offers a method to limit summer weed cover that did not adversely affect diversity or native weeds. In contrast, herbicide‐treated sites had characteristics indicative of a lower biodiversity value and higher potential for competitiveness with few native weeds, lower diversity and relatively tall, small‐seeded weeds. Mowing in winter combined with tillage in spring may thus optimise the biodiversity benefits and production costs of Western Cape vineyard weeds.  相似文献   

5.
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   

6.
FELDMAN  ALZUGARAY  TORRES  LEWIS 《Weed Research》1998,38(1):35-45
The effects of tillage systems (mouldboard plough, chisel, disk and non-tillage, over 3 years) and gap openings during August and October of 0, 0.30 m × 0.30 m and 0.45 m × 0.45 m on the weed community were investigated in a wheat (Triticumaestivum L.) crop. Weed flora composition and species abundance were recorded in August, September and November and the data analysed with MULVA programs and non-parametric tests. The tillage system was more important than the timing or gap size on the weed floristic composition, and the changes in weed communities were evident within a 3-year period in spite of herbicide use. Less disturbing tillage systems (non-tillage and chisel plough) allowed the build-up of a more diverse community, whereas the most disturbing one (mouldboard plough) prevented high diversity in the weed community.  相似文献   

7.
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   

8.
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   

9.
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   

10.
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   

11.
BACKGROUND: The widespread acceptance of reduced‐tillage farming in cereal cropping systems in the Pacific Northwest of the United States has resulted in increased use of herbicides for weed control. However, soil residual concentrations of widely used imidazalone herbicides limit the cultivation of barley, which is more sensitive than wheat. In addition, increased severity of the root rot disease caused by Rhizoctonia solani is associated with reduction in tillage. Many crops exhibit altered disease responses after application of registered herbicides. In this study, the injury symptoms in barley caused by sublethal rates of two acetolactate synthase (ALS)‐inhibiting herbicides, imazamox and propoxycarbazone‐sodium, were assessed in factorial combinations with a range of inoculum concentrations of the root rot pathogen Rhizoctonia solani AG‐8. RESULTS: Both herbicides and pathogen had negative impacts on plant growth parameters such as root and shoot dry weight, shoot height and first leaf length, and interactions between pathogen and herbicide were detected. CONCLUSIONS: The results suggested that sublethal rates of herbicides and R. solani could alter severity of injury symptoms, possibly owing to the herbicide predisposing the plant to the pathogen. Copyright © 2012 Society of Chemical Industry  相似文献   

12.
Understanding how weed communities assemble as a function of biotic and abiotic filters and transform through time has important implications for the sustainable management of agronomic systems. In a three‐year study, we evaluated weed community responses to lucerne (Medicago sativa, perennial) vs. continuous spring wheat (Triticum aestivum, annual, CSW) and weed management practices where weeds in the CSW system were managed with three contrasting approaches (herbicide, tillage or sheep grazing). Our results indicated no differences in weed diversity between the perennial and annual crops or across the different management practices in CSW. However, there were differences in weed community composition. Lucerne, with the exception of the establishing year, impeded the growth and reproduction of several annual weeds, including Amaranthus retroflexus, Thlaspi arvense, Lamium amplexicaule and Chenopodium album, but favoured perennial broad‐leaved weeds such as Taraxacum officinale and Cirsium arvense. The replacement of herbicide treatments in pre‐plant and post‐harvest in CSW with soil tillage or sheep grazing selected for different weed communities beyond the second year of establishment. The weed species driving the differences in CSW systems were Androsace occidentalis, more common in CSW managed chemically; Asperugo procumbens, more common in CSW managed with tillage; and T. officinale and Lactuca serriola, more common in CSW managed with sheep grazing. Understanding how cropping systems modify weed communities is a necessary step to shift from reactive weed control programmes to predictive management strategies.  相似文献   

13.
In order to better understand the effects of urbanization on weed communities, the distribution of weed communities in Shanghai, China, was systematically investigated. The diversity of weed communities and four environmental factors, including the relative light intensity, soil moisture, soil compaction and soil pH, were measured in 1375 plots along an urban–rural gradient. The species diversity indices in each area along the urban–rural gradient were compared by using a one‐way ANOVA. The weed communities were identified by using clustering methods that were based on relative dominance information. A canonical correspondence analysis was used to reveal the relationships between the species composition and the environmental factors at the community level and the Spearman's rank correlation test was used to test the relationship between the number of weed communities and each environmental factor. A total of 183 species, belonging to 41 families and 123 genera, was recorded. It was found that the species richness, Shannon–Wiener diversity index and Pielou evenness index followed a unimodal curve along the urban–rural gradient. The 1375 plots were divided into 133 weed community types. All four environmental factors significantly affected the species composition of the weed communities, but only soil compaction had significant effects on the number of weed communities. It was concluded that the diversification of habitat type and environmental change along the urban–rural gradient led to more weed communities in rural areas and fewer weed communities in urban areas. Based on the species' habitats and distribution patterns, the weeds were divided into “widespread”, “urban” and “rural”.  相似文献   

14.
Understanding drivers of weed density and diversity is essential for the development of weed management strategies. Here, we compared temporal changes in weed density and diversity under no-till (NT) and conventional (CONV) tillage systems in cotton–maize rotations on loam, clay loam and sandy loam soils immediately after transition to NT in Kadoma, Zimbabwe. The effect of tillage system on weed density varied through the growth season and was dependent upon soil type and species composition of the weed community. Although weed responses to tillage system varied amongst species, we identified general trend effects on weed density on specific soils. At 3 weeks after crop emergence (WACE), weed density on loam soils was 76% and 96% higher in NT than in CONV during the 2009/2010 and 2010/2011 seasons, respectively, and on clay loam soils it was 37% and 33% higher in NT than CONV, respectively. Weed densities in NT and CONV were similar across all soil types at 6 WACE during the 2009/2010 and 2010/2011 seasons and at 9 WACE in 2009/2010. Tillage system did not affect weed density during the growth season on sandy loam soils. Weed diversity (Shannon index) was at least 75% higher in NT than CONV on loam and clay loam soils at 3 WACE during both seasons. It is likely these increases in weed densities following conversion to NT will exacerbate already prevalent weed management problems in the smallholder sector. Earlier weeding is recommended to suppress weed emergence and reduce likely associated crop yield losses.  相似文献   

15.
施肥对农田杂草生理生态及群落形成的影响综述   总被引：1，自引：0，他引：1  
本文综述了施肥对农田杂草群落及土壤杂草种子库的影响,并探讨施肥可显著改变农田杂草发生的原因,论证合理的施肥能改善作物与杂草之间的关系,有效控制一些恶性杂草的发生,保持生物多样性。梳理了农田杂草研究的一些新的发展方向,并认为农业生态系统中施肥对杂草群落的演替、优势杂草种群的确定及其生理生态和遗传进化规律的影响是今后研究的重点和难点。  相似文献   

16.
BACKGROUND: Weed management in glyphosate‐resistant (GR) maize, cotton and soybean in the United States relies almost exclusively on glyphosate, which raises criticism for facilitating shifts in weed populations. In 2006, the benchmark study, a field‐scale investigation, was initiated in three different GR cropping systems to characterize academic recommendations for weed management and to determine the level to which these recommendations would reduce weed population shifts. RESULTS: A majority of growers used glyphosate as the only herbicide for weed management, as opposed to 98% of the academic recommendations implementing at least two herbicide active ingredients and modes of action. The additional herbicides were applied with glyphosate and as soil residual treatments. The greater herbicide diversity with academic recommendations reduced weed population densities before and after post‐emergence herbicide applications in 2006 and 2007, particularly in continuous GR crops. CONCLUSION: Diversifying herbicides reduces weed population densities and lowers the risk of weed population shifts and the associated potential for the evolution of glyphosate‐resistant weeds in continuous GR crops. Altered weed management practices (e.g. herbicides or tillage) enabled by rotating crops, whether GR or non‐GR, improves weed management and thus minimizes the effectiveness of only using chemical tactics to mitigate weed population shifts. Copyright © 2011 Society of Chemical Industry  相似文献   

17.
Weed management in conservation crop production systems   总被引：1，自引：0，他引：1  
Information on weed management in conservation crop production systems is needed as adoption of practices such as reduced tillage and cover crops becomes more widespread. This review summarizes recent research on weed management aspects in these systems. Changes in patterns of tillage, planting systems, and other management strategies can alter the soil environment and lead to shifts in weed populations. Weed patterns and populations are not always consistent and vary with locale, crop, and herbicide use. However, in many long-term conservation management studies, a general increase in perennial weeds and grass species has been observed. The development of low-dose herbicides, selective postemergence herbicides, and transgenic crops has greatly improved the flexibility of producers who use conservation systems where opportunities for tillage are limited. With a higher level of management inputs, producers can successfully implement conservation management practices.  相似文献   

18.
In the conservation agricultural systems practised in Australia, cultivation is not commonly utilised for the purpose of weed control. However, occasional use of tillage (strategic tillage) is implemented every few years for soil amelioration, to address constraints such as acidity, water repellence or soil compaction. Depending on the tillage method, the soil amelioration process buries or disturbs the topsoil. The act of amelioration also changes the soil physical and chemical properties and affects crop growth. While these strategic tillage practices are not usually applied for weed control, they are likely to have an impact on weed seedbank burial, which will in turn affect seed dormancy and seedbank depletion. Strategic tillage impacts on seed burial and soil characteristics will also affect weed emergence, plant survival, competitive ability of weeds against the crop and efficiency of soil applied pre-emergent herbicides. If growers understand the impacts of soil amelioration on weed demography, they can more effectively plan management strategies to apply following the strategic tillage practice. Weed seed burial resulting from a full soil inversion is understood, but for many soil tillage implements, more data is needed on the extent of soil mixing, burial of topsoil and the weed seedbank, physical control of existing weeds and stimulation of emergence following the tillage event. Within the agronomic system, there is no research on optimal timing for a tillage event within the year. There are multiple studies to indicate that strategic tillage can reduce weed density, but in most studies, the weed density increases in subsequent years. This indicates that more research is required on the interaction of amelioration and weed ecology, and optimal weed management strategies following a strategic tillage event to maintain weeds at low densities. However, this review also highlights that, where the impacts of soil amelioration are understood, existing data on weed ecology can be applied to potentially determine impacts of amelioration on weed growth.  相似文献   

19.
Summary Weeds cause yield losses and reductions in crop quality. Prior to the introduction of selective herbicides, the drudgery of manual weeding forced farmers to adhere to a suit of weed management tactics by carefully combining crop rotation, appropriate tillage and fallow systems. The introduction of selective herbicides in the late 1940s and the constant flow of new herbicides in the succeeding decades provided farmers with a new tool, ‘the chemical hoe’, putting them in a position to consider weed control more independently of the crop production system than hitherto. The reliance on herbicides for weed control, however, resulted in shifts in the weed flora and the selection of herbicide‐resistant biotypes. In the 1980s, the public concern about side‐effects of herbicides on the environment and human health resulted in increasingly strict registration requirements and, in some countries, political initiatives to reduce the use of pesticides were launched. Today, the number of new herbicides being introduced has decreased significantly and integrated weed management has become the guiding concept. Farmers also have the option of growing herbicide‐resistant crops where the biology of the crop has been adapted to tolerate herbicides considered safe to humans and environmentally benign. This paper discusses some of the recent developments in herbicide discovery, technology and fate, and sketches important future developments.  相似文献   

20.
This study assessed the cultural and weed management factors influencing the weed communities of Hungarian rice fields. Hungary is situated at the northern limit of rice production with a history of about 300 years of rice culture. We surveyed the weed flora and 25 background variables in 100 active rice fields. Using a minimal adequate model containing 11 terms, 48.5% of the total variation in weed species data could be explained. The net effects of nine variables on species composition were significant. Crop cover was found to be the most important explanatory variable, which was followed by the herbicides penoxsulam and azimsulfuron, tillage depth, phosphorous and potassium fertilisers, years after last rotation, water depth in May, sowing type, pendimethalin and water conductivity. Filamentous algae, as the most abundant group of weeds, were positively associated with deep tillage, deep water and surface sowing. Echinochloa crus‐galli, one of the most troublesome grass weeds, was associated with low rice cover, shallow water and later years after crop rotation, while weedy rice favoured high crop cover, deep water and soil sowing. These findings can be used to design improved weed management strategies. The occurrence of red list species and charophytes in diverse micro‐mosaic patterns deserves attention from a conservation perspective, as well. The maintenance of these unique charophyte communities can be facilitated by shallow tillage without soil inversion.  相似文献   

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