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While intensive control of weed populations plays a central role in current agriculture, numerous studies highlight the multifaceted contribution of weeds to the functionality and resilience of agroecosystems. Recent research indicates that increased evenness within weed communities may mitigate yield losses in contrast to communities characterized by lower diversity, since weed species that strongly affect crop yields, also dominate weed communities, with a concurrent reduction of evenness. If confirmed, this observation would suggest a paradigm shift in weed management towards promoting higher community diversity. To validate whether the evenness of weed communities is indeed linked to higher crop productivity, we conducted two field experiments: one analyzing the effects of a natural weed community in an intercrop of faba bean and oat, and the other analyzing the effects of artificially created weed communities, together with the individual sown weed species, in faba bean, oats and an intercrop of both crops. The evenness of the weed communities ranged from 0.2 to 0.9 in the natural weed community, from 0.2 to 0.7 in faba bean, from 0 to 0.8 in the intercrop and from 0.3 to 0.9 in oats. Neither the natural nor the artificial weed community showed significant effects of evenness on crop grain yield or crop biomass. The results of this study do not validate a positive relationship of crop productivity and weed evenness, possibly due to low weed pressure and the absence of competitive effects but suggest that also less diverse weed communities may be maintained without suffering yield losses. This is expected to have far reaching implications, since not only diverse weed communities, but also higher abundances of few weed species may contribute to ecosystem functions and may support faunal diversity associated with weeds. [ABSTRACT FROM AUTHOR]

Durum wheat (Triticum turgidum spp. durum) is one of the most important grain crops cultivated across the Mediterranean Basin, where a strong return to local landraces cultivation is occurring to meet the market demand for high-quality food and low-input cropping systems. A characterisation of the long-term effect (10 years) of durum wheat landraces and modern cultivars on the potential and real weed flora is still lacking. Hence, a multilocation trial over 10 farms in Central-Eastern Sicily was carried out to investigate the repeated cultivation of several old landraces (OLD) and modern cultivars (MOD) on the abundance and diversity of weed flora. Overall, OLD was associated with a 47% reduction of the soil seedbank size and to −64% of the aboveground weed biomass compared to MOD. In addition, diversity indices pointed out a high similarity between MOD and OLD farm groups for the soil seedbank, while a lower diversity was found in OLD for aboveground weed communities. From the principal component analysis emerged that the species compositions of MOD and OLD were quite separated for both soil seedbank and real flora, with the latter showing few specific associations with major weeds. These findings demonstrated the indirect effect of durum wheat landraces in sustainably reducing weed pressure without the adoption of chemical weed control. [ABSTRACT FROM AUTHOR]

The problems with herbicide‐ and tillage‐based weed management in agriculture are well documented and have precipitated research into finding alternatives. Integrating livestock grazing into organic agroecosystems has benefits and is a viable method for terminating cover crops, yet its impacts on weed communities are largely unknown. This lack of knowledge is particularly true in semi‐arid environments, including the Northern Great Plains, where we conducted our research. We compared weed community responses (biomass, species richness, Simpson's diversity, composition) of a sheep‐grazed organic cropping system with those of two contrasting cropping systems (high input conventional no‐till, tilled organic) across a five‐year crop rotation (safflower, sweet clover, winter wheat, lentils, winter wheat). We found that the conventional no‐till and tilled organic systems suppressed weed biomass and reduced species richness and diversity, while the grazed organic resulted in higher weed biomass, species richness, and diversity. During the first two years of the study, the composition of the two organic communities were distinct from the conventional no‐till communities but were indistinguishable from one another. Over the final three years of the study, grazed organic communities were tightly grouped and became distinct from both the tilled and conventional communities. We found that weed biomass and diversity were highest in the sweet clover and lowest in the winter wheat. The spring annual crops, safflower and lentil, demonstrated similar weed biomass, species richness, and composition. Our findings indicate that integrating livestock into cropping systems alters plant communities and increases the agroecosystem plant biodiversity of semi‐arid organic farming and that specific crops interact with cropping systems to alter agroecosystem plant communities. However, the increase in weed biomass associated with our grazing treatment makes this approach impractical as the sole weed management strategy and necessitates that integrating livestock into semi‐arid organic cropping systems must be part of a larger integrated weed management program. [ABSTRACT FROM AUTHOR]

Chemical-dependent weed control has led to the evolution of herbicide-resistant weeds and pollution of arable land and water systems, posing a great threat to food security and environmental safety. For the first time, we developed a simple weed management regime to ecologically deplete the weed seed bank under a wheat-rice cropping system, which in turn allowed a reduction in the frequency of conventional herbicide applications while sustainably reducing weed infestation levels. The key ecological methods adopted here involve cleaning irrigation water by intercepting seeds at the water entrance and exit and removing floating weed seeds with a net during irrigation before rice planting, which significantly reduced the input of weed seeds into the seed bank. Quantitative analysis of the weed seed bank and population dynamics showed that implementation of this management regime consecutively for 6 years reduced the density of the total weed seed bank by 51% and the dominant grassy weed population density by 53% compared to those at the beginning. The effect of this ecologically sound weed control regime was comparable to that of conventional dual- or triple-application herbicide chemical control in each crop growing season. The results indicated that, compared with the conventional control method, the integrated weed management method could reduce the number of herbicide applications by half and reduce costs and labor by 30%. Furthermore, quantitative modeling analysis of the seed bank and population dynamics of the dominant weed species, Alopecurus japonicus, showed that continuous adoption of this ecological strategy could deplete the seed bank by more than 90%, thereby freeing the fields of the presence of this noxious weed. [ABSTRACT FROM AUTHOR]

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While weeds generally are considered as the most important overarching production constraints in inland-valley cropping systems in West Africa, little is known about species' associations with environmental and crop management factors. Weed species' associations with seasonal and environmental factors, such as their position on the catena, soils and cropping systems, were studied during two seasons (dry and wet) in 45 arable fields of three inland valleys in south-western Benin, Africa. The three most dominant weed species were Dactyloctenium aegyptium, Commelina benghalensis and Digitaria horizontalis on the inland-valley crests (uplands), Ludwigia hyssopifolia, Corchorus aestuans and Ludwigia octovalvis on the sloping hydromorphic fringes and Leersia hexandra, Ipomoea aquatica and Fimbristylis ferruginea in the valley bottoms (lowlands). Echinochloa colona, Cleome viscosa and Talinum triangulare were the three most dominant species in the dry-season crops (maize or vegetables) and Leer. hexandra, I. aquatica and Sphenoclea zeylanica were the three most dominant species in the wet-season crop (rice). Ageratum conyzoides, Synedrella nodiflora and D. horizontalis were observed throughout the catena. Problem weeds in inland-valley agro-ecosystems are those that combine a high frequency with a high submergence tolerance and ecological plasticity, C4 grasses, perennial C3 species with persistent root structures and broad-leaved species with high propagation rates. Weed management strategies that are aimed at increasing the resilience of rice-based cropping systems in the inland valleys of the southern Guinea Savanna of Africa should address the categories of problem species that were identified in this study. This can be done best by following an integrated approach, including the use of more weed-competitive cultivars and rotation crops. [ABSTRACT FROM AUTHOR]

Winegrowers have diversified their weed management practices over the last two decades changing the structure and the composition of weed communities. Complementary to taxonomic studies, trait-based approaches are promising ways for a better understanding of weed community responses to environmental and agronomic filters. In the present study, the impacts of climate, soil characteristics, seasons and weed management practices (chemical weeding, tillage and mowing) were assessed on weed communities from 46 plots in three French wine-growing regions (Champagne, Languedoc and Rhône valley). These agro-environmental gradients structuring weed communities according to their combinations of traits were highlighted using multivariate analysis (RLQ). The impacts of these filters on Community Weighted Means (CWM) and Community Weighted Variance (CWV) of weed communities were analysed using mixed and null modelling. Our results showed that spatio-temporal and weed management practice variables explained from 13% to 48% of the total variance of CWM (specific leaf area, maximum height, seed mass, flowering onset and duration and lateral spread). Region, seasonality and management practices explained 53%, 28% and 19% of CWM marginal variance, respectively. Weed management impacted CWM and CWV through two main gradients: (i) a soil disturbance gradient with high mechanical disturbance of soil in tilled plots and low mechanical disturbance in chemically weeded plots and (ii) a vegetation cover gradient with high vegetation abundance in mowed plots compared to barer soils in tilled and chemically weeded plots. In Languedoc, chemical weeding filtered weed communities with ruderal strategy trait values (low seed mass, small-stature) while mowed communities were more competitive (higher seed mass, higher stature and lower SLA). In Languedoc and Champagne, tillage favoured communities with high seed mass that increases the viability of buried seeds and high lateral spread values associated to the ability to resprout after tillage. This study demonstrated that trait-based approaches can be successfully applied to perennial cropping systems such as vineyards, in order to understand community assembly to better guide weed management practices. Region and seasonality were the main drivers of functional structure of weed communities while weed management explained lower proportion of average traits variance. In Languedoc, our study highlighted a vegetation cover gradient from mown communities (high vegetation cover) to tilled and chemically weeded communities (low vegetation cover). Mown communities had more competitive strategies while tilled and chemically weeded community showed trait values associated to ruderal strategy. [Display omitted] • Region (53%) and season (28%) explained most of Community Weighted Means variance. • Weed management practices explained 19% of Community Weighted Means variance. • Chemically weeded communities showed trait values of ruderal strategies. • Mowed plots were associated with more competitive communities. • Tillage favoured weed communities with higher lateral spread ability. [ABSTRACT FROM AUTHOR]

Question How do different weed management systems based on glyphosate-resistant ( GR) crops affect weed community structure and composition? Location A total of 156 agricultural fields across six US states. Methods Fields were selected and categorized into three weed management systems based on a 3-yr history: (1) a single continuous GR crop; (2) a rotation of two GR crops; and (3) a GR crop rotated with a non- GR crop. Weed species population density was surveyed in 20 0.5-m2 plots per field four times each season from 2006 to 2010. Weed population density, species richness and diversity were analysed using repeated measures mixed models to test the effect of year, geographic location (based on plant hardiness zone) and weed management system (as described above). Weed community composition was analysed using NMDS ordination. The importance of geographic location, planted crop and weed management system were analysed using analysis of similarity and permutational ANOVA based on the Bray- Curtis similarity among sites calculated from the maximum weed species population density per site per year. Results A total of 329 weed species were identified across the six states and all time periods. Weed communities were most strongly correlated with geographic location and secondarily to the crop planted. Weed management system affected similarity among weed communities through an interaction with site location but not every year. The weed management systems of crop rotation and GR trait rotation generally reduced weed population density and species diversity, but the effect of crop rotation varied by geographic location. Conclusions The overall effects of weed management systems in fields including the GR trait on arable weed communities reinforce the need for locally adapted weed management programmes to steward the GR crop trait to manage for high weed diversity while reducing crop-weed competition and maximizing yield. [ABSTRACT FROM AUTHOR]

A field experiment was carried out in the years 2008-2010 on rendzina soil. The aim of the study was to evaluate weed infestation of winter spelt cultivars ('Schwabenkorn' and 'Spelt I.N.Z.') grown under different conditions of mineral fertilization and chemical plant protection. In the experiment, two levels of mineral fertilization were compared (kg x ha-1): I. N 60; P 26.2; K 83; and II. N 80; P 34.9; K 99.6. The chemical protection levels were as follows: A. Control treatment; B. Mustang 306 SE, Stabilan 750 SL; C. Mustang 306 SE, Attribut 70 WG, Stabilan 750 SL; D. Mustang 306 SE, Attribut 70 WG, Alert 375 SC, Stabilan 750 SL. Apera spica-venti, Setaria pumila, and Galium aparine occurred in greatest numbers in the spelt wheat crop. The cultivar 'Schwabenkorn' was more competitive against weeds. The number of dicotyledonous and monocotyledonous weeds, their total number, and air-dry weight of weeds in the crop of this cultivar were significantly lower compared to cv. 'Spelt I.N.Z.'. Chemical protection of spelt wheat decreased weed dry weight compared to the control treatment without chemical protection. The application of higher rates of mineral fertilizers slightly increased the number of weeds but did not influence their dry weight and number of weed species. [ABSTRACT FROM AUTHOR]

Initiatives to reduce the reliance of agriculture on pesticides, including the European Union (EU) Directive 2009/128/EC on the sustainable use of pesticides (SUD), have yet to lead to widespread implementation of Integrated Pest Management (IPM) principles. Developments in weed management have strongly focused on increasing the efficiency of herbicides or substituting herbicides with other single tactics such as mechanical control. To increase sustainability of agricultural systems in practice, a paradigm shift in weed management is needed: from a single tactic and single growing season approach towards holistic integrated weed management (IWM) considering more than a single cropping season and focusing on management of weed communities, rather than on control of single species. To support this transition, an IWM framework for implementing a system level approach is presented. The framework consists of five pillars: diverse cropping systems, cultivar choice and establishment, field and soil management, direct control and the cross-cutting pillar monitoring and evaluation. IWM is an integral part of integrated pest management (IPM) and adopting IWM will serve as a driver for the development of sustainable agricultural systems of the future. • Integrated weed management (IWM) is an integral part of integrated pest management (IPM) and adopting IWM will serve as an important driver for sustainable IPM. • A paradigm shift in weed management is needed from single tactic and single growing season approaches towards a holistic IWM approach. • A generic framework for holistic IWM is proposed to support agronomists and weed scientist to design novel weed management strategies. • The IWM framework is based on five pillars: diverse cropping systems, cultivar choice and establishment, field and soil management, direct control and the cross-cutting pillar monitoring and evaluation. [ABSTRACT FROM AUTHOR]

Parietaria debilis is a dominant annual weed in many non-tillage fallow and undisturbed areas in Argentina. Herbicides control P. debilis inconsistently. A study on the growth of P. debilis, in a fallow in a soyabean–maize rotation including glyphosate-resistant cultivars and in an undisturbed area without crops or weed control, was conducted in the central soyabean area of Argentina. The biomass dynamics of all species in the community, as well as biomass, density and growth traits of P. debilis were assessed. Biomass of several species including P. debilis and total biomass were greater in undisturbed than in fallow plots in both years of the study. Diversity was greater in undisturbed plots in 2000, but no differences in diversity were observed in 2001. In both treatments, P. debilis emergence began in March and finished in October and density increased from March to May. High mortality occurred in June and July, particularly in undisturbed plots. In the fallow plots, no other tall weed species were present and light interception was higher in spring when fruit production was at its peak. Conversely, in the undisturbed plots, P. debilis was substantially taller and had greater leaf area due to lower light interception by the high canopy of the rest of the community. In fallow, P. debilis is favoured by single applications of glyphosate, because the herbicide eliminates competitors. Control, if applied, should be directed to both fallow and undisturbed environments, as the weed produces considerable numbers of seeds and can invade extensively managed areas. [ABSTRACT FROM AUTHOR]

Summary Total weed control with machete and herbicides was compared in a field experiment from 1994 to 1999, with four selective ground cover management tactics (± herbicides and ± planted ground cover legume) in the inter-rows of coffee plants. The aim of the selective management was to control weeds in patches, leaving uncontrolled species considered suitable to protect the soil from erosion and compaction, and to suppress more aggressive weed growth. Fresh biomass was sampled early and late in the rainy seasons. Weed data from the different years, treatments and blocks were analysed with a multivariate technique, partial redundancy analysis (pRDA), using different combinations of independent variables and covariables and resulting in a multivariate anova. Weed biomass and number of species drastically decreased over time as coffee and shade trees aged. The five treatments also significantly affected the composition of the weed vegetation. The combination of partial slashing and application of herbicides in patches was more effective in reducing unwanted weed biomass and also enhanced the spread of the ground cover legume, whereas the use of only partial slashing enhanced the spread of the ‘weed’Oplismenus burmannii . This species was considered a suitable ground cover species to protect the soil, as it emerges at the onset of the rainy season, is more persistent late in the rainy season and sustains growth under the shade of coffee in production. [ABSTRACT FROM AUTHOR]