Weed Ecology Research Articles

Weed ecology is affected by succession in differently aged gardens of Citrus sinensis and C. reticulata

The concepts of destruction and rebuilding in the succession play an important role in agro-ecology. Agricultural ecosystems are always affected by tillage, soil preparation, harvest, burning, and arboriculture. A common practice in the northern province of Mazandaran (Iran) is to replace rice (Oryza sativa L.) cultivation with Citrus farming. It can be accordingly interesting to investigate the ecology of weed community specifically the dominance and characters during the different stages of succession, using constitutive and physiological aspects. In a 2-year research work, some functional (species composition and stability) and physiological characteristics (relative growth rate, biomass, and N and P uptake) of different weeds in the initial and final stages of secondary succession in Citrus gardens were compared. Three young (Citrus sinensis L.) and three old Citrus (Citrus reticulata Blanco) gardens (with the average age of 2 and 29 years, respectively), were selected in the suburb of Qaemshahr city (Iran), the centre of Citrus production. In each garden, three main fixed plots (30 m2), with five subplots (1 m2) and destructive quadrates in each one, were prepared and used for the experiment (January 2013–August 2014). Weed composition was monthly recorded. The concept of dominance diversity was used to estimate the community consistency. Thirty-three weed species were identified among which the Poaceae and Asteraceae families were the dominant ones. In the young gardens, the number of weed species was twice more than the old ones. Poa nemoralis as a perennial and sciophytes species were plentiful in the old gardens. Just in the young gardens, the weed species were moved by pappus. There was a linear and stable regression between weed frequency and dominance in the final sampling. Higher relative growth rate as well as higher N and P uptake was resulted in the young gardens. Seed size and growth rate were correlated in the young gardens, and the smaller seeds resulted in a higher rate of weed survival. Parameters including weed dominance, functional and physiological characteristics, seed size, and the environment may determine weed ecology and survival at different stages of succession in Citrus gardens.

Emerging Challenges and Opportunities for Education and Research in Weed Science.

In modern agriculture, with more emphasis on high input systems, weed problems are likely to increase and become more complex. With heightened awareness of adverse effects of herbicide residues on human health and environment and the evolution of herbicide-resistant weed biotypes, a significant focus within weed science has now shifted to the development of eco-friendly technologies with reduced reliance on herbicides. Further, with the large-scale adoption of herbicide-resistant crops, and uncertain climatic optima under climate change, the problems for weed science have become multi-faceted. To handle these complex weed problems, a holistic line of action with multi-disciplinary approaches is required, including adjustments to technology, management practices, and legislation. Improved knowledge of weed ecology, biology, genetics, and molecular biology is essential for developing sustainable weed control practices. Additionally, judicious use of advanced technologies, such as site-specific weed management systems and decision support modeling, will play a significant role in reducing costs associated with weed control. Further, effective linkages between farmers and weed researchers will be necessary to facilitate the adoption of technological developments. To meet these challenges, priorities in research need to be determined and the education system for weed science needs to be reoriented. In respect of the latter imperative, closer collaboration between weed scientists and other disciplines can help in defining and solving the complex weed management challenges of the 21st century. This consensus will provide more versatile and diverse approaches to innovative teaching and training practices, which will be needed to prepare future weed science graduates who are capable of handling the anticipated challenges of weed science facing in contemporary agriculture. To build this capacity, mobilizing additional funding for both weed research and weed management education is essential.

Centralisation and long-term change in farming regimes: Comparing agricultural practices in Neolithic and Iron Age south-west Germany

This study uses two novel archaeobotanical techniques – crop carbon and nitrogen isotope analysis and functional weed ecology – to determine directly how the intensity of agricultural practice changed from the Neolithic to the Early Iron Age in south-west Germany, with the emergence of fortified hilltop settlements (Fürstensitze or chiefly seats) regarded as the first urban centres in central Europe. The crop isotope and functional weed ecological evidence suggest that surplus cereal production in the Early Iron Age was achieved through sustained use of manure combined with expansion in arable cultivation, both developments that are connected with more widespread use of animal traction. The increased scale of cultivation is broadly apparent across rural as well as fortified hilltop centres in the Early Iron Age, and considerable variability in manuring intensity is consistent with agricultural decision-making at a local level rather than centralised control. Additionally, the more intensive manuring of hulled six-row barley, used in beer production, demonstrates that the political importance of drinking and feasting in Early Iron Age society was reflected in crop husbandry practices. In terms of animal husbandry, faunal isotope data reveal a radical decrease in forest cover, potentially reflecting an expansion in the scale of herding accompanying that of arable cultivation. Site-specific patterning points to a range of herding strategies, from specialised herding of cattle at the Heuneburg to generalised patterns of livestock management at rural sites.

Biological control of broad-leaved dock infestation in wheat using plant antagonistic bacteria under field conditions.

Conventional weed management systems have produced many harmful effects on weed ecology, human health and environment. Biological control of invasive weeds may be helpful to minimize these harmful effects and economic losses incurred to crops by weeds. In our earlier studies, plant antagonistic bacteria were obtained after screening a large number of rhizobacteria for production of phytotoxic substances and effects on wheat and its associated weeds under laboratory conditions. In this study, five efficient strains inhibitory to broad-leaved dock and non-inhibitory to wheat were selected and applied to broad-leaved dock co-seeded with wheat both in pot trial and chronically infested field trial. Effects of plant antagonistic bacteria on the weed and infested wheat were studied at tillering, booting and harvesting stage of wheat. The applied strains significantly inhibited the germination and growth of the weed to variable extent. Similarly, variable recovery in losses of grain and straw yield of infested wheat from 11.6 to 68 and 13 to 72.6% was obtained in pot trial while from 17.3 to 62.9 and 22.4 to 71.3% was obtained in field trial, respectively. Effects of plant antagonistic bacteria were also evident from the improvement in physiology and nutrient contents of infested wheat. This study suggests the use of these plant antagonistic bacteria to biologically control infestation of broad-leaved dock in wheat under field conditions.

Forest clearance and land use by early farmers in Europe: Insights from north Greek oral history

European prehistorians have long debated whether Neolithic farmers, especially in temperate central and northern Europe, exploited cleared woodland for short-term ‘slash-and-burn’ crop husbandry or for cultivation of ‘permanent’ gardens/fields. Because empirical evidence was scarce and rather indirect, circumstantial arguments based on the relative costs and benefits of the two rival regimes have hitherto dominated this debate, but more direct archaeobotanical proxies for Neolithic crop husbandry (based on weed ecology and crop isotopes) now favour the predominance of intensively cultivated permanent plots. At the same time, it is argued from ongoing experimental cultivation at Forchtenberg in southern Germany that short-term slash-and-burn husbandry offers much better returns on both land and labour, at least on poor soils marginal for Neolithic cereals. This paper presents oral historical evidence for mid-twentieth century clearance and subsequent long-term cultivation of mixed deciduous woodland in the Pieria region of northern Greece. These data extend the sparse European ethnographic and historical record of manual clearance for crop husbandry to deciduous woodland of the northern Mediterranean, while also providing comparative material against which to evaluate experimental results. Pierian farmers achieved good cereal yields for many years on cleared woodland, with very limited use of fire, demonstrating the viability of a permanent-cultivation regime for early farmers in the north Mediterranean, but suitable land was scarce in Pieria and informants had no experience of the alternative slash-and-burn regime. Conversely, the Forchtenberg experiments have effectively tested only the slash-and-burn regime under soil pH conditions hostile to successful long-term cultivation. Evaluation of these experiments in the light of the Pierian data suggests that long-term cultivation of cleared woodland would have offered Neolithic famers better returns than slash and burn under good or neutral soil conditions. Comparison of the likely returns of the two rival regimes thus offers no grounds for questioning archaeobotanical indications of Neolithic permanent cultivation. The Pierian and Forchtenberg data agree, however, in suggesting that the time elapsed between clearance and reliable grain harvests, under either regime, may have been long enough to pose a significant challenge to the survival of pioneer Neolithic farmers, especially if these were colonists settling beyond ‘commuting’ distance from their previous homes.

Herbicide resistance in weeds and its management

Repeated use of herbicides with similar modes of action for weed control in wheat has resulted in evolution of multiple herbicide resistance in Phalaris minor, which could threaten the sustainability of the rice-wheat cropping system in north-western India. Herbicide resistance could also become a problem in direct seeded rice and soybean crops, which rely heavily on acetolactate synthase (ALS) and acetyl coenzyme A carboxylase (ACCase) inhibiting herbicides. As discovery of new herbicide modes of action has slowed dramatically, all effort should be made to increase the effective life of existing herbicides and make weed management cost-effective and efficient. Early detection of resistance can facilitate timely adoption of alternative tactics and minimise the financial impact on farmers. Structured surveys of resistance affected areas can provide required information for site-specific recommendations as expression of herbicide resistance tends to be highly site-specific. Greater emphasis is needed on weed management systems based on sound knowledge of weed ecology. Refinement is needed in seeding machinery for high residues systems, improvements in equipment for inter-row cultivation and application technology of herbicides. Farmer-participatory research and adoption of improved agronomy could delay evolution of resistance in weeds and enhance the sustainability of Indian cropping systems. This paper has reviewed and discussed herbicide resistance in weeds in Indian context.

From Traditional Farming in Morocco to Early Urban Agroecology in Northern Mesopotamia: Combining Present-day Arable Weed Surveys and Crop Isotope Analysis to Reconstruct Past Agrosystems in (Semi-)arid Regions

ABSTRACTWe integrate functional weed ecology with crop stable carbon and nitrogen isotope analysis to assess their combined potential for inferring arable land management practices in (semi-)arid regions from archaeobotanical assemblages. Weed and GIS survey of 60 cereal and pulse fields in Morocco are combined with crop sampling for stable isotope analysis to frame assessment of agricultural labour intensity in terms of manuring, irrigation, tillage and hand-weeding. Under low management intensity weed variation primarily reflects geographical differences, whereas under high management intensity fields in disparate regions have similar weed flora. Manured and irrigated oasis barley fields are clearly discriminated from less intensively manured rain-fed barley terraces in southern Morocco; when fields in northern and southern Morocco are considered together, climatic differences are superimposed on the agronomic intensity gradient. Barley δ13C and δ15N values clearly distinguish among the Moroccan regimes. An integrated approach combines crop isotope values with weed ecological discrimination of low- and high-intensity regimes across multiple studies (in southern Morocco and southern Europe). Analysis of archaeobotanical samples from EBA Tell Brak, Syria suggests that this early city was sustained through extensive (low-intensity, large-scale) cereal farming.

세계 잡초연구 동향 및 전망

This paper provides the current status of weed science and prospects for the development of weed science based on the research trends presented at the 7th International Weed Science Conference in 2016. Approximately 520 researchers from 59 countries, including Korea, participated in the conference and presented 625 papers in nine research areas. Major research topics were herbicide resistance, weed ecology, weed management in agricultural and non-agricultural lands, herbicide spray technology, and non-chemical weed control. Studies on herbicide resistance presented more than 30% of all papers presented. Particularly, resistance to non-selective herbicides, such as glyphosate and glufosinate-ammonium, and non-target sites of resistance mechanisms were the main subjects of the herbicide resistance research area. Moreover, the conference focused on research concerning herbicide resistant weeds of staple crops of the world (corn, wheat, and rice). Arylex was introduced as a new compound which has a mode of herbicidal action similar to synthetic auxin. Three compounds being developed as HPPD inhibitors were studied for ways to reduce their toxicity and tested as mixed with safeners. Additionally, parasitic weeds, which are not native to Korea, are an expanding research subject in the world. Although 45 years have passed since the first report of herbicide resistance in 1970, herbicide resistance remains a serious problem in most intensive cropping systems of the world and will continue to be a major area of study in the future.

Role of crop competition in managing weeds in rice, wheat, and maize in India: A review

In India, the three staple food crops viz., rice, wheat, and maize, contribute more than four-fifths of the total food grain production. Among the several factors limiting their productivity, weeds account for about 40%. In order to meet the requirements of growing population, it is essential to improve productivity by reducing such unwarranted losses. Managing weeds with crop competition is an eco-friendly approach. Once the mechanisms of competition are understood, further improvements in weed control could be gained by manipulating other agronomic practices. The choice of cultivars, crop density, seeding rate, direction of planting, and intercropping could be exploited to enhance crop competitiveness against weeds. The variation in competitiveness and weed suppression among cultivars has been documented in rice, and to a lesser extent in wheat and maize. Research has demonstrated that the integration of crop competitiveness with other methods, such as the use of herbicides and manual weeding, is successful in managing weeds. However, in India, greater efforts are needed to exploit crop competitiveness for managing weeds in rice, wheat and maize. The success of these approaches relies on proper understanding of the biology and ecology of weeds, to identify weak points in their life cycle.

Brassicaceous Weed Seed Predation by Ground Beetles (Coleoptera: Carabidae)

We used laboratory and field feeding trials to investigate adult carabid beetle preferences for three brassicaceous weed species (rapeseed, wild mustard, and field pennycress) that are pests in canola. All carabid species preferred seeds of rapeseed most and those of field pennycress least and showed intermediate preference for wild mustard seeds. Beetles highly preferred imbibed seeds of all three weed species. Activity–density of carabids and mean weed seed removal were highly correlated in field plots of canola, with activity–density accounting for 67% of the observed variation in seed removal. Our study indicates that seed consumption among carabids is influenced by several factors, including weed species, physiological state of seeds, and carabid activity–density. Carabid seed predation is significant in canola agroecosystems; therefore, understanding these influences has implications for ecological weed management.

What do we really know about alien plant invasion? A review of the invasion mechanism of one of the world's worst weeds.

This review provides an insight into alien plant invasion taking into account the invasion mechanism of parthenium weed ( Parthenium hysterophorus L.). A multi-lateral understanding of the invasion biology of this weed has pragmatic implications for weed ecology and management. Biological invasions are one of the major drivers of restructuring and malfunctioning of ecosystems. Invasive plant species not only change the dynamics of species composition and biodiversity but also hinder the system productivity and efficiency in invaded regions. Parthenium weed, a well-known noxious invasive species, has invaded diverse climatic and biogeographic regions in more than 40 countries across five continents. Efforts are under way to minimize the parthenium weed-induced environmental, agricultural, social, and economic impacts. However, insufficient information regarding its invasion mechanism and interference with ecosystem stability is available. It is hard to devise effective management strategies without understanding the invasion process. Here, we reviewed the mechanism of parthenium weed invasion. Our main conclusions are: (1) morphological advantages, unique reproductive biology, competitive ability, escape from natural enemies in non-native regions, and a C3/C4 photosynthesis are all likely to be involvedin parthenium weed invasiveness. (2) Tolerance to abiotic stresses and ability to grow in wide range of edaphic conditions are thought to be additional invasion tools on a physiological front. (3) An allelopathic potential of parthenium weed against crop, weed and pasture species, with multiple modes of allelochemical expression, may also be responsible for its invasion success. Moreover, the release of novel allelochemicals in non-native environments might have a pivotal role in parthenium weed invasion. (4) Genetic diversity found among different populations and biotypes of parthenium weed, based on geographic, edaphic, climatic, and ecological ranges, might also be a strong contributor towards its invasion success. (5) Rising temperatures and atmospheric carbon dioxide (CO2) concentrations and changing rainfall patterns, all within the present day climate change prediction range are favorable for parthenium weed growth, its reproductive output, and therefore its future spread and infestation. (6) Parthenium weed invasion in South Asia depicts the relative and overlapping contribution of all the above-mentioned mechanisms. Such an understanding of the core phenomena regulating the invasion biology has pragmatic implications for its management. A better understanding of the interaction of physiological processes, ecological functions, and genetic makeup within a range of environments may help to devise appropriate management strategies for parthenium weed.

Facilitating ecological weed management decisions by assessing risk-benefit tradeoffs

ABSTRACTWe used the mental models research method to generate a conceptual map of how Midwest farmers use knowledge, experience, and individual perceptions of weed-related risk to make weed management decisions. We discovered that Midwest farmer knowledge of ecological weed management practices is robust, and that the difficult tradeoffs farmers make regarding cultivation, cover crops, and soil health determine what weed management practices they use. Midwest farmers balance the risks of cultivation and implementation of cover crops with their valuable benefits to soil health and weed suppression. Developing a decision support tool that provides a baseline of scientific evidence and that offers flexibility based on farmers’ experiences and values will clarify these tradeoffs and guide effective decision making.

Possibilities for converting conventional cattle production to the organic model in the Grijalva River Basin, Mexico

AbstractThe possibilities for converting conventional cattle production to the organic model were evaluated in the Grijalva River Basin, Mexico, and possible interventions were identified. A multi-criteria organic livestock conversion index (OLCI) with 10 indicators comprising 35 variables was used. Information was obtained through participatory workshops, direct observation, and interviews to 91 farmers of 11 different communities in the municipalities of Mazapa de Madero (n = 17), Huitiupan (n = 30), and Tacotalpa (n = 44). Results show higher OLCI values in Mazapa (56.8%) and Tacotalpa (56.7%) than in Huitiupan (49.0%). The production units evaluated show: (i) limitations with respect to indicators ecological weed control in pastures and crops, veterinary prevention and treatment, food safety, and ecological management, and (ii) strengths to reach the organic standards are: feed management, sustainable pasture management, soil fertilization, ecological pest and disease control in pastures and crops, br...

Use of herbarium data to evaluate weediness in five congeners.

It is often desirable to quantify a plant's relative weediness or synanthropy, that is, the degree to which a species associates with human-caused disturbance, in order to study and understand the biology, ecology and evolution of weeds and invasive plants. Herbarium specimens are among the most accessible and verifiable sources of data on distribution and habitat. However, the habitat distribution of species may not be reflected accurately by herbarium specimen data, due to well-known biases in plant collection. Here, we assess how well herbarium specimens reflect species' weediness, when compared with direct field surveys. We used five species of Melampodium (Asteraceae) and classified their degree of weediness with a modification of Nuorteva's synanthropy index, based on herbarium specimens. We then modelled the distribution of our focal species in Mexico using MaxEnt and identified a polygon of ∼3000 km(2) in the state of Nayarit, Mexico, where there was a high probability of finding all five species. Systematic field searches in the target area documented all visible populations of four species along major and minor roads. Then we, again, classified their degree of weediness with the synanthropy index, based now on field data, and compared. We found that herbarium data were an accurate predictor of a species' weediness relative to its congeners despite the well-documented skew of herbarium data towards natural areas, which our data reflected as well. So, herbarium data can be used to classify species' weediness relative to each other, but not in absolute terms, if the specimens were correctly identified and none of the species were subject to particular collection bias. This study is the first attempt to compare herbarium and field data on this subject and may be relevant for other types of investigations based on herbarium data. Our work also highlights the usefulness of distribution models based on herbarium specimens.

Competitive Ability, Critical Period of Competition, and Density Level of Hydrolea zeylanica (L.) Vahl against Transplanted-Irrigated Lowland Rice

Determining the competitive ability of a certain weed is a valuable guide as to what, where, and when best weed management techniques must be implemented. Likewise, identifying the critical period of weed-crop competition will help crop growers as to when weeds must be controlled or maybe allowed to compete with crops without having significant yield loss and unacceptable economic returns. Pot experiments were conducted to determine the competitive ability, critical period of competition, and density level of Hydrolea zeylanica (L.) Vahl under transplanted-irrigated lowland rice conditions. Treatments for the duration of weed-free period involved keeping rice plants free from H. zeylanica within periods of 10, 20, 30, 40, and 50 DAT; while the duration of tolerable period of competition involved allowing of the weed to compete with rice from 0 DAT, then simultaneously uprooted at 10, 20, 30, 40, and 50 DAT. In the critical density level experiment, H. zeylanica was allowed to compete with rice plants from 0 DAT until harvest at a ratio of 1:1, 1:3, 1:5, 1:7, 1:10, and 1:20 (rice: Hydrolea). Unweeded (control) and weed-free (check) treatments until harvest were included for comparison. Results showed that H. zeylanica was a very competitive weed against transplanted-irrigated lowland rice. When allowed to grow and compete, the weed signifi cantly reduced rice grain yield and its vital agronomic parts. Th e critical period of competition based on classical method suggested that H. zeylanica can be allowed to compete only within 5 to 40 DAT and 10 to 30 DAT to control yield reduction at 5 and 10%, respectively. Th e estimations of Gompertz and logistic models suggested that H. zeylanica should not be allowed to compete within 0 to 700 GDD to achieve 100% relative grain yield. Under unavoidable circumstances in the fi eld, however, the models suggested that the weed can be allowed to compete with transplanted rice within 0 to 670 GDD and 5 to 580 GDD to minimize yield reductions at 5 and 10%. Furthermore, the negative eff ects of the weed on grain yield and yield components intensified when it was allowed to compete in dense population. Yields of rice that competed with H. zeylanica at 1:1, 1:3, 1:5, 1:7, 1:10, and 1:20 rice:weed ratios were reduced by 18.99, 24.68, 23.80, 35.46, 51.72, and 55.90%, in the same order. Keywords - Hydrolea zeylanica, Oryza sativa, weed ecology, weed control, logistic model, Gompertz model, Philippines

Cover crops as a means of ecological weed management in agroecosystems

Weeds cause an estimated crop yield loss of about 43% world-wide. The heavy use of herbicides in weed management has several environmental and health risks. Therefore, systems-oriented approaches to weed management that make better use of alternative weed management tactics need to be developed. One of these approaches is the use of plants with strong weed-suppressing abilities as a component of integrated crop management. Cover crops are well-suited in such a holistic approach as they provide many other agroecosystem services besides suppressing weeds. However, compared to the use of herbicides, the use of cover crops as a weed management tool needs careful follow-up throughout the intended period to maximize the agroecosystem services they provide, minimize the disservices they exert, and optimize their selectivity between weed and crop suppression. Although there are many review papers that address the contribution of cover crops for managing weed problems in agroecosystems, few systematically address the difficulties that are encountered in fitting in the cover crops in the different cropping systems and the methods how to overcome these difficulties. Therefore, this paper is to examine how to maximize weed suppressive effects of cover crops and minimize the negative side effects of introducing cover crops into annual and perennial cropping systems and how to optimize selectivity between weeds and crops. We suggest further research regarding the selection of cover crops that are compatible with annual and perennial cropping systems under different climatic conditions and identify the traits responsible for adaptation in various cropping systems and environments.

Combining functional weed ecology and crop stable isotope ratios to identify cultivation intensity: a comparison of cereal production regimes in Haute Provence, France and Asturias, Spain.

This investigation combines two independent methods of identifying crop growing conditions and husbandry practices—functional weed ecology and crop stable carbon and nitrogen isotope analysis—in order to assess their potential for inferring the intensity of past cereal production systems using archaeobotanical assemblages. Present-day organic cereal farming in Haute Provence, France features crop varieties adapted to low-nutrient soils managed through crop rotation, with little to no manuring. Weed quadrat survey of 60 crop field transects in this region revealed that floristic variation primarily reflects geographical differences. Functional ecological weed data clearly distinguish the Provence fields from those surveyed in a previous study of intensively managed spelt wheat in Asturias, north-western Spain: as expected, weed ecological data reflect higher soil fertility and disturbance in Asturias. Similarly, crop stable nitrogen isotope values distinguish between intensive manuring in Asturias and long-term cultivation with minimal manuring in Haute Provence. The new model of cereal cultivation intensity based on weed ecology and crop isotope values in Haute Provence and Asturias was tested through application to two other present-day regimes, successfully identifying a high-intensity regime in the Sighisoara region, Romania, and low-intensity production in Kastamonu, Turkey. Application of this new model to Neolithic archaeobotanical assemblages in central Europe suggests that early farming tended to be intensive, and likely incorporated manuring, but also exhibited considerable variation, providing a finer grained understanding of cultivation intensity than previously available.Electronic supplementary materialThe online version of this article (doi:10.1007/s00334-015-0524-0) contains supplementary material, which is available to authorized users.

Derivation of a Cropping System Transfer Function for Weed Management: Part 1 – Herbicide Weed Management

System behaviour is described by the transfer functions, which relate the system’s output to one or more input variables. No-till cropping systems depend on herbicide inputs for weed management and crop yield optimisation. This paper derives the transfer function for crop yield potential as a function of herbicide input, in the presence of herbicide resistance in the weed population, using several mathematical components for crop and weed ecology from published literature. The resulting transfer function reveals the herbicide application rate for optimal crop yield potential and highlights the growing herbicide resistance problem in no-till cropping systems.

Mechanisms of Ecological Weed Management by Cover Cropping: A Review

Mechanisms of Ecological Weed Management by Cover Cropping: A Review

Organic Farmer Knowledge and Perceptions are Associated with On-Farm Weed Seedbank Densities in Northern New England

Weed management remains a high priority for organic farmers, whose fields generally have higher weed density and species diversity than those of their conventional counterparts. We explored whether variability in farmer knowledge and perceptions of weeds and weed management practices were predictive of variability in on-farm weed seedbanks on 23 organic farms in northern New England. We interviewed farmers and transcribed and coded interviews to quantify their emphasis on concepts regarding knowledge of ecological weed management, the perceived risks and benefits of weeds, and the perceived risks and benefits of weed management practices. To characterize on-farm weed seedbanks, we collected soil samples from five fields at each farm (115 fields total) and measured germinable weed seed density. Mean weed seed density per farm ranged from 2,775 seeds m−2to 24,678 seeds m−2to a soil depth of 10 cm. Farmers most often reported hairy galinsoga and crabgrass species (Digitariaspp.) as their most problematic weeds. The proportion of the sum of these two most problematic weeds in each farm's seedbank ranged from 1 to 73% of total weed seed density. Farmer knowledge and perceptions were predictive of total seed density, species richness, and proportion of hairy galinsoga and crabgrass species. Low seed densities were associated with farmers who most often discussed risks of weeds, benefits of critical weed-free management practices, and learning from their own experience. These farmers also exhibited greater knowledge of managing the weed seedbank and greater understanding of the importance of a long-term strategy. Targeted education focusing on this set of knowledge and beliefs could potentially lead to improved application and success of ecological weed management in the future, thus decreasing labor costs and time necessary for farmers to manage weeds.