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Robotic weed control may reduce labor requirements, soil disturbance, and amount of herbicide applied relative to non-robotic methods. Tertill® is among the first weeding robots to become commercially available. This solar-powered robot moves in a random walk, avoiding obstacles using capacitive sensors, and cuts weeds with a string trimmer. We tested the effects of Tertill (two hours per week) with and without the string trimmer and hand weeding (from 3 to 5.6 min per week with a stirrup hoe) on weed communities at two field sites in Ithaca, NY. Tertill with trimmer and hand weeding provided similar levels of weed control (visual estimates averaging 2–9% ground cover at the end of the experiment, compared to 14–48% in the unweeded control). Without the string trimmer, Tertill was ineffective. Tertill did not significantly reduce monocot weed density but did reduce dicot weed density. At one site, Tertill reduced species richness and increased evenness based on density. Overall, these results suggest that Tertill can effectively remove newly emerged weed seedlings. Future research should investigate Tertill performance against more established weeds and the long-term effects of Tertill on weed community composition (e.g., possible selection for monocots and other species with low growing points).

Glyphosate applied POST can provide a high level of efficacy on many weed species in soybean, but delayed application beyond optimal weed growth stages might fail to fully protect yield potential. Further, we do not have a good understanding of the extent to which delayed glyphosate application and its associated yield loss is occurring on-farm. Our goal was to characterize on-farm weed communities in glyphosate-resistant soybean just prior to glyphosate application and estimate potential yield loss associated with early-season soybean-weed competition. In field surveys conducted across 64 site-yr in southern Wisconsin in 2008 and 2009, common lambsquarters, velvetleaf, dandelion, Polygonum spp., and Amaranthus spp. were the five most abundant broadleaf weed species across site-years, present in 92, 69, 64, 42, and 50% of all fields, respectively, at average densities of 14, 5, 5, 14, and 10 plants m−2, respectively. Average height of these species was 21 cm or less at or near the time of glyphosate application. Grass and sedge species occurred in 95% of fields at an average density of 41 plants m−2 and height of 21 cm. The mean and median values of total weed density across site-years were 101 and 41 plants m−2, with heights of 19 and 17 cm, respectively. Recommended height for treatment is 15 cm. Glyphosate application occurred on average at V3 to V4 soybean growth stage, which is later than V2 soybean typically targeted to protect yield. Average yield loss predicted by WeedSOFT® was 5% with a mean economic loss of $47 ha−1. Predicted yield loss was greater than 5% on one-fourth of the site-years, all of which were treated at V4 soybean or later. The maximum predicted yield loss was 27%. These results suggest that glyphosate was applied at weed height and soybean growth stages that were greater than optimal to protect yield in many fields across southern Wisconsin. A soil-residual herbicide applied PRE, or a more timely POST application of glyphosate would alleviate the majority of these losses. Nomenclature: Glyphosate; Amaranthus spp.; common lambsquarters, Chenopodium album L. CHEAL; dandelion, Taraxacum officinale G. H. Weber ex Wiggers TAROF; velvetleaf, Abutilon theophrasti Medik. ABUTH; Polygonum spp.; soybean, Glycine max (L.) Merr.

Characterizing the long-term effect of agricultural management systems on weed communities will aid in developing sustainable weed management practices. Weed seedbanks and aboveground biomass were measured within a corn-soybean-wheat crop sequence from 1990 through 2002 at Hickory Corners, MI. Four management systems were compared: conventional (CONV; full rates of N fertilizer and herbicides, moldboard tillage), no till (NT; same as CONV with no primary tillage), reduced input (RI; reduced rates of N fertilizer and herbicides, moldboard tillage, mechanical weed control, wheat underseeded with red clover), and organic (ORG; same as RI but no synthetic inputs). Multivariate ordinations of weed seedbanks showed a divergence of the CONV and NT systems from the RI and ORG systems. The CONV and NT seedbanks were dominated by grass species (mainly fall panicum and large crabgrass), whereas the RI and ORG systems were dominated by common lambsquarters and common chickweed. Within a single growing season, weed seedbanks in the RI and ORG systems were positively correlated with weed biomass whereas seedbanks in the CONV and NT system had little predictive value. Weed biomass from 1990 through 2002 showed a strong association of grass weed species with the corn phase of the CONV and NT system and common lambsquarters and redroot pigweed with the corn and soybean phases of the RI and ORG systems. Weed biomass diversity measures were negatively correlated with soybean yields in RI and ORG and wheat yields in NT, RI, and ORG. It is not clear whether crops were less competitive in the NT, RI, and ORG treatments, allowing new weed species to enter the plots, or whether less effective weed management in the NT, RI, and ORG treatments resulted in increased species richness, causing reduced crop yields. Mechanistic studies are needed to elucidate the relationship between weed community diversity and crop performance.

QUESTION: The intensification of crop cultivation in much of Europe since the mid‐20th century has greatly increased crop yields but caused dramatic biodiversity losses in arable fields. We investigated the extent of these losses at the level of plant community types. LOCATION: Ten areas in central Germany with different soil/climate conditions and various arable plant communities. METHODS: We compiled historical surveys of arable fields in the 1950s/early 1960s before the onset of pervasive agricultural industrialization, and in 2009 revisited 392 arable fields. Historical and recent data were compared with supervised manual classification, detrended correspondence analysis (DCA) and ANOVA. RESULTS: Ten out of 16 plant communities at association rank observed in fields in the 1950s/1960s were not recorded again. The proportion of relevés assignable at association level decreased from 75% to 5%, while the proportion of relevés assignable only at higher syntaxon level or not assignable at all had increased from 2% to 75%. The impoverishment of vegetation was slightly less pronounced at field margins, where around one quarter of the recent relevés could be assigned to associations. Present arable plant communities in the region are species‐poor and consist chiefly of common, often herbicide‐tolerant, generalist species, with no clear preference for cereal vs root crops, autumn‐ vs spring‐sown crops or base‐rich vs base‐poor soils. CONCLUSION: Our new approach using phytosociological syntaxa and a semi‐permanent plot design enabled us to quantify biodiversity losses at the community type level. The currently used set of phytosociological associations is inadequate to represent present‐day arable plant assemblages. The concept of residual plant communities provides a useful methodological supplement.

Sustainable strategies for managing weeds are critical to meeting agriculture’s potential to feed the world’s population while conserving the ecosystems and biodiversity on which we depend. The dominant paradigm of weed management in developed countries is currently founded on the two principal tools of herbicides and tillage to remove weeds. However, evidence of negative environmental impacts from both tools is growing, and herbicide resistance is increasingly prevalent. These challenges emerge from a lack of attention to how weeds interact with and are regulated by the agroecosystem as a whole. Novel technological tools proposed for weed control, such as new herbicides, gene editing, and seed destructors, do not address these systemic challenges and thus are unlikely to provide truly sustainable solutions. Combining multiple tools and techniques in an Integrated Weed Management strategy is a step forward, but many integrated strategies still remain overly reliant on too few tools. In contrast, advances in weed ecology are revealing a wealth of options to manage weeds at the agroecosystem level that, rather than aiming to eradicate weeds, act to regulate populations to limit their negative impacts while conserving diversity. Here, we review the current state of knowledge in weed ecology and identify how this can be translated into practical weed management. The major points are the following: (1) the diversity and type of crops, management actions and limiting resources can be manipulated to limit weed competitiveness while promoting weed diversity; (2) in contrast to technological tools, ecological approaches to weed management tend to be synergistic with other agroecosystem functions; and (3) there are many existing practices compatible with this approach that could be integrated into current systems, alongside new options to explore. Overall, this review demonstrates that integrating systems-level ecological thinking into agronomic decision-making offers the best route to achieving sustainable weed management.

Weeds are a fundamental component of agroecosystems and, if not appropriately managed, can cause severe crop yield losses. New perspectives on weed management are required, because current approaches, such as herbicide application or soil tillage, have significant environmental and agronomic drawbacks. We propose the concept of “neutral weed communities,” which are weed communities that coexist with crops and do not negatively affect crop yield and quality compared with weed-free conditions. Management practices that promote neutral weed communities can enable reduced use of herbicides and soil tillage while enhancing ecosystem services and biodiversity. We report scientific evidence of neutral weed communities and survey ecological explanations for why different weed communities have different effects on crop production. We also propose two weed management approaches for attaining neutral weed communities. The first approach aims to maximize weed biodiversity using traditional approaches such as cropping system diversification and integrated weed management. Higher weed biodiversity is associated with lower dominance of competitive weed species that reduce crop yield. The second approach relies on modern tools such as robots and biotechnology to manipulate the density of specific weed species. This approach can remove highly problematic species and minimize niche overlap between the weeds and crops. Given the complexity of interactions among crops, weeds, and other components of the agroecosystem, we highlight the need for multidisciplinary research to illuminate mechanisms that determine the neutrality of weed communities.

The development of integrated weed management programs requires a clear understanding of the factors and mechanisms conditioning weed community dynamics in agroecosystems. This study evaluated the effect of different agricultural management systems on the aboveground and seedbank weed communities in annual row crops at the Long Term Ecological Research project in agricultural ecology at the W. K. Kellogg Biological Station, Michigan, USA. Weed biomass and species composition were sampled for six years over two corn-soybean-wheat sequence cycles in four agricultural management systems: (1) conventional (high external chemical input, moldboard plowed); (2) no-till (high external chemical input, no tillage); (3) low-input (low external chemical input, moldboard plowed); and (4) organic (no external chemical input, moldboard plowed). A greenhouse germination study assessed variation in the abundance and composition of the weed seedbank across the studied systems in the first and sixth year of this study. Aboveground weed biomass, species density, and diversity were lowest in the conventional system, intermediate in the no-till system, and highest in the low-input and organic systems, but there were significant year-by-system interactions. Monocot and dicot species were equally common in the conventional system, whereas annual grasses, such as Digitaria sanguinalis (large crabgrass) and Panicum dichotomiflorum (fall panicum), dominated the no-till system. Two perennial weed species (Trifolium pratense [red clover] and Elytrigia repens [quackgrass]) and one annual dicot (Chenopodium album [common lambsquarters]) dominated the low-input and organic systems. A multivariate ordination of all four systems revealed close associations between the conventional and no-till systems and between the low-input and organic systems. Separate ordinations of the four management systems revealed a crop effect in the low-input and organic systems, but no differentiation in the conventional and no-till ones. The seedbank study revealed a significant increase in the number of weed seeds and species, mainly of annual grasses such as D. sanguinalis and P. dichotomiflorum, in the conventional and no-till systems over the six years of study. During the same period, the number of weed seeds declined in low-input and organic systems. Three annual dicots (Stellaria media [common chickweed], Veronica peregrina [purslane speedwell], and C. album) dominated the seedbank of the low-input and organic systems. Weed aboveground and seedbank community composition were more constant over time in the low-input and organic systems than in the conventional and no-till systems over the study period. These results demonstrate that agricultural management systems can have both immediate and long-term effects on weed species density, abundance, and diversity. The differences observed among management systems in weed biomass, species composition, diversity, and community constancy indicate challenges that exist for the development of ecologically based weed management systems in row crop agriculture.

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.

Integrated weed management tactics are necessary to develop cropping systems that enhance soil quality using conservation tillage and reduced herbicide or organic weed management. In this study, we varied planting and termination date of two cereal rye cultivars (‘Aroostook’ and ‘Wheeler’) and a rye/hairy vetch mixture to evaluate cover-crop biomass production and subsequent weed suppression in no-till planted soybean. Cover crops were killed with a burn-down herbicide and roller-crimper and the weed-suppressive effects of the remaining mulch were studied. Cover-crop biomass increased approximately 2,000 kg ha−1 from latest to earliest fall planting dates (August 25–October 15) and for each 10-d incremental delay in spring termination date (May 1–June 1). Biomass accumulation for cereal rye was best estimated using a thermal-based model that separated the effects of fall and spring heat units. Cultivars differed in their total biomass accumulation; however, once established, their growth rates were similar, suggesting the difference was mainly due to the earlier emergence of Aroostook rye. The earlier emergence of Aroostook rye may have explained its greater weed suppression than Wheeler, whereas the rye/hairy vetch mixture was intermediate between the two rye cultivars. Delaying cover-crop termination reduced weed density, especially for early- and late-emerging summer annual weeds in 2006. Yellow nutsedge was not influenced by cover-crop type or the timing of cover-crop management. We found that the degree of synchrony between weed species emergence and accumulated cover-crop biomass played an important role in defining the extent of weed suppression.

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.