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The establishment of plants in an ecosystem is limited by the availability of seeds and the availability of suitable sites for establishment. Describing plant population dynamics through the relative strength of seed and establishment limitation is an important concept in the study of natural ecosystems. To date, it is unclear whether this concept can be applied to describe populations of annual weeds in agricultural fields. Using a recruitment function, we show that limitation parameters prove valuable in describing seedling recruitment in weed populations. We conducted a seed addition experiment in three cornfields (Zea mays L.) and recorded seedling recruitment in populations of the economically important weed barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.]. Seed predation, competition with other weeds, and seed burial were prevented. We estimated the strength of seed and establishment limitation in the population with two parameters: n, which is the number of microsites, and b, which is the suitability of those sites to support a seedling. We further estimated the relative proportions of density-dependent and density-independent establishment limitation in the seedling population. Recruitment rates of E. crus-galli ranged from 31% to 36% across all evaluated seed densities and fields, which is high compared with results from other seed addition studies. Two of the three monitored populations were predominantly establishment limited at the highest evaluated seed density of 2,400 added seeds m−2. Further knowledge about the relative strength of limitations in other weed populations will provide important information on how effective different weed management strategies can be.

Elymus repens (L.) Gould), Cirsium arvense (L.) Scop. and Sonchus arvensis L. are important arable creeping perennial weeds in Europe. These are clonal plants with subterranean reproductive organs (E. repens, rhizomes, the two dicots, horizontal creeping roots) sprouting from ramets. We tested the sprouting ability and early growth of ramet sprouts at temperatures typical for Nordic autumn climate and with different preconditions of the mother plant (time in autumn, mother plant age, climate change experiences of the mother plants (two experiments)). The species reacted differently, with S. arvensis not sprouting at all, and C. arvense ramets sprouting at higher temperatures than those of E. repens, which sprouted at all tested temperatures. Plant age affected only the ramet sprout biomass of E. repens. Climate change during mother plant growth only affected C. arvense, with the highest above-ground biomass of the sprouted ramets at an elevated temperature and ambient CO2. Testing earlier in autumn showed more sprouting and biomass for C. arvense and E. repens than testing later in the season. The observed temperature responses confirmed more and bigger sprouts with higher autumn temperatures. Controlling the sprouted ramets in autumn is easier for E. repens than for C. arvensis. Due to their low/no sprouting ability in autumn, the ramets of S. arvensis cannot be controlled in autumn. Late-Autumn Ramet Sprouting of Three Arable Creeping Perennial Weed Species

The creeping perennial weed species Cirsium arvense (L.) Scop. occurs in patches. Expanding creeping roots allow these patches to increase their covered area. This characteristic has rarely been addressed when investigating the effects of control options in arable fields. We designed a three-year field experiment (2019–2021) in north-eastern Germany, accounting for existing patch patterns. The experimental setup included an untreated control, a competition treatment (cover crop, CC), two disturbance treatments by mouldboard ploughing (PL), root cutting (RC), and four combined applications (RC + CC, PL + CC, PL + RC, PL + RC + CC). Root cutting was performed by a prototype tillage machine produced by “Kverneland”. Plots were defined by the species growth pattern and mapped by GPS and UAV. The experiment investigates the thistle response variables: “Expansion”, “Density”, “Coverage”, and “Height”. Treatments including disturbance by ploughing (PL, PL + CC, PL + RC, PL + RC + CC) reduced “Density” by the factor 0.15 and “Expansion” by 0.25, while those without ploughing (CC, RC, RC + CC) only reduced “Density” by the factor 0.68 and “Expansion” by 0.71. Adding root cuttings or cover crops did not further increase the reduction effect of ploughing. Treatments with competition by cover crops impacted “Expansion” more clearly than “Density”. When cover crops were combined with root cutting (RC + CC), “Expansion” was almost additively reduced, resulting in a reduction comparable to that of ploughing. The “Height” of the shoots was significantly reduced in four treatments (PL, RC + CC, PL + RC, PL + RC + CC), while “Coverage” did not change significantly. UAV patch monitoring proved to be accurate enough for thistle “Expansion” but not for thistle “Density” within the patch. The results of this study demand innovative research when controlling patch-forming creeping perennial weeds. The need for patches will limit small-scale experimental set ups.

11 Pág., Over the last 30 years, many studies have surveyed weed vegetation on arable land. The 'Arable Weeds and Management in Europe' (AWME) database is a collection of 36 of these surveys and the associated management data. Here, we review the challenges associated with combining disparate datasets and explore some of the opportunities for future research that present themselves thanks to the AWME database. We present three case studies repeating previously published national scale analyses with data from a larger spatial extent. The case studies, originally done in France, Germany and the UK, explore various aspects of weed ecology (community composition, management and environmental effects and within-field distributions) and use a range of statistical techniques (canonical correspondence analysis, redundancy analysis and generalised linear mixed models) to demonstrate the utility and versatility of the AWME database. We demonstrate that (i) the standardisation of abundance data to a common measure, before the analysis of the combined dataset, has little impact on the outcome of the analyses, (ii) the increased extent of environmental or management gradients allows for greater confidence in conclusions and (iii) the main conclusions of analyses done at different spatial scales remain consistent. These case studies demonstrate the utility of a Europe-wide weed survey database, for clarifying or extending results obtained from studies at smaller scales. This Europe-wide data collection offers many more opportunities for analysis that could not be addressed in smaller datasets; including questions about the effects of climate change, macro-ecological and biogeographical issues related to weed diversity as well as the dominance or rarity of specific weeds in Europe., This work was made possible via the Weeds and Biodiversity working group of the European Weed Research Society. This project was funded under a Rothamsted Research and BBSRC grant number BB/W510543/1. Helen Metcalfe was partly supported by the Natural Environment Research Council (NERC) and the Biotechnology and Biological Sciences Research Council (BBSRC) research programme NE/N018125/1 LTS-M (ASSIST). Jana Bürger's work on this project was supported by Deutsche Forschungsgemeinschaft DFG (grant number BU 3097/1-1).

A better understanding of weed seed production is a key element for any long-term management allowing some weeds to shed seeds. The challenge with measuring seed production in weeds is the large effort required in terms of time and labour. For the weed species Echinochloa crus-galli, it was tested whether the number of seeds per panicle dry weight or per panicle length can be used to estimate seed production. Experiments were conducted in three maize fields in north-eastern Germany. The effect of factors that could influence this relationship, such as the time of seedling emergence, the density of E. crus-galli, the control intensity of other weeds, seed predation and field, was included. A few days before maize harvest, all panicles were removed and weighed, panicle length was measured, and for a subsample of 178 panicles, the number of seeds was counted manually. Panicle dry weight predicted the number of seeds per panicle better (R2 = 0.92) than did panicle length (R2 = 0.69). The other factors except for ‘field’ and ‘seed predation’ had no effect on these relationships. The relationships between seed number and panicle dry weight found in this study closely resembled those reported in an earlier study. Based on our results, we conclude that both plant traits are appropriate for the estimatation of seed production, depending on required level of precision and availablilty of resources for the evaluation of sustainable weed management strategies.

Glyphosate herbicides play a prominent role internationally in weed management due to their broad spectrum effectiveness. There are concerns that a high reliance on glyphosate herbicides will negatively affect biodiversity over time. In Europe, where cropping systems are carried out without glyphosate resistant crops (GMO), glyphosate herbicides are applied between cropping seasons either in combination with or in place of plowing. We explored the effects of mouldboard plowing, chisel plowing, and glyphosate herbicide application (in a dose reflecting 100% of the manufacturer’s recommendation and a dose reflecting 50%) on weed species number, density, true diversity and community composition. The field experiment was conducted for three consecutive years in a randomized plot design on a naturally occuring weed community without a crop. A total of 83 species and 4 genus were identified over the three years of surveying. By applying a Multinomial Species Classification to the dataset, it was determined that root and rhizome propagating species as well as annual agricultural weeds with no pronounced seasonality in their germination were rarer on glyphosate treated plots than on tillaged plots. Promoted by glyphosate application were in particular grassland legumes and hemicryptophytes. Partial Redundancy Analyses (pRDA) showed that the species communities evolved over the years with dependency on the type of treatment and timing of the treatments. The overall average number of species was 19.7/m2 and the true diversity was 8.3/m2. The average density was 295 plants/m2. In all of the treatments, a factorial ANOVA demonstrated that species numbers and true diversity sank in all three of the years of the experiment over the course of the vegetation period whereas the density tended to rise. The reality of weed management is that any method employed will influence the weed composition in some way. Our experiment demonstrated that some species will be favored over others depending on the weed management method, but the overall biodiversity of the weed community was not more negatively affected by one method compared to another.

Renewable energy produced at biogas plants has tremendously increased the demand for digestible biomass in central Europe over the last twenty years. As a consequence, new crop rotations combining conventional and recently introduced bioenergy crops are tested in long-term field trials. The aim of this work was to determine risks for soilborne wheat stem base diseases in new bioenergy crop rotations. Crop rotations tested consisted of maize, sorghum, cereals, grasslegume mixtures, and phacelia. Field trials with five rotations were established at four different sites in Germany, whereby winter wheat was grown at the end of each rotation. Field trials were set up in a block or strip plot design in 2005 and 2006. After eight years, stem base diseases of winter wheat were visually assessed during milk ripeness. ‘Random forests’, a non-parametric statistical method, was used to select the most important variables describing weather, soil productivity and rotation. Subsequently, disease incidences were modeled with generalized linear models. Disease incidence was high for Fusarium foot rot (47%), moderately high for eyespot (30%), and low for sharp eyespot (4%). An increasing number of days with high precipitation during six weeks after sowing, and less growing degree days from February through June led to higher eyespot incidence (R2 = 60%). Fusarium foot rot incidence was correlated to high mean precipitation during six weeks after sowing, and low number of growing degree days from February through June (R2 = 78%). In contrast to the eyespot model, year and region had additional explanatory power to the Fusarium foot rot model. Based on the results of this study we could show that annual weather patterns had a high impact on eyespot and Fusarium foot rot incidences, while the effect of rotation was low. Although unexplained site and year-specific effects require further investigations, weather patterns identified by applying an innovative variable selection method provide a valuable starting point for developing and improving forecasting models for Fusarium foot rot.

Within organic crop production, weed interference remains one of the main constraints on productivity, yet diverse weed vegetation supports the ecosystem services of arable fields. The use of crop diversification could alter weed communities and increase diversity, preventing the dominance of single detrimental weed species. This study investigated the type of crop diversification implemented in organic cropping systems in northern Europe and whether this affects the arable weed vegetation. A weed survey was conducted in 207 organic spring-sown cereal fields in five northern European regions (Denmark, Finland, Germany, Latvia and Sweden). Weed density data were combined with management and crop diversification data collected on the farms. The data set was analysed using linear mixed models and multivariate ordinations. The 197 weed species recorded were representative for the type of organic arable farming conducted in the regions. The management and crop diversification variables studied differed considerably among the regions. Management, such as the type of spring-sown cereal and crop mixture during monitoring, the preceding crop and weed harrowing, primarily influenced weed densities, while weed diversity increased with the duration of organic management and use of winter cover crops. The weed species communities were altered by the crop diversification applied. This study reflects the impact of regionally varied crop diversity and reinforces the importance of regionally adapted crop and weed management.

We present a detailed analysis of glyphosate-based herbicide (GBH) use patterns with a dataset of herbicide use on arable farms in five districts of Northern Germany. Two aspects are focused: (1) The relationship between GBH and selective herbicides used on a specific field in the same cropping period and (2) the interplay of tillage, GBH and selective herbicide use in weed management. The most interesting result of our analysis is that the intensity of selective herbicide use for in-crop weed management was not related to GBH treatment prior to the crop (except maize). GBH treatments increased the total herbicide intensity on a field. Hence, using GBH pre-crop does not necessarily save herbicides in the following crop. GBH were additional treatments, not replacing selective herbicides. Our data was collected from different districts in Northern Germany extending from West to East. In the Eastern districts, a larger proportion of fields were treated with GBH. When a field was treated with GBH, it was applied with a similar intensity, regardless of the district. Hence, differences in GBH use patterns were caused only by the decision to treat pre-crop, while the intensity of these GBH treatments is hardly varied. In the Eastern districts, the higher proportion of fields treated with GBH is associated with larger proportion of fields with non-plough tillage. Non-plough fields were also treated more intensively with selective herbicides. Nevertheless, the use of both GBH and selective herbicides on the same field was more frequent and intensive in the Western districts of Northern Germany. We attribute the differences in pre-crop GBH use and in-crop selective herbicide use to regional production differences. Small to medium proportions of fields with both ploughing for primary tillage and pre-crop GBH use in all districts and most prominent in winter barley, winter wheat and maize indicate a luxurious, easy reducible use of GBH. We propose to promote farms with non- and low-use of GBH as an example of good practice.

Weeds typically occur in patches of different sizes and densities. Post-dispersal seed predators contribute to biological weed control by removing newly produced weed seeds before they can enter the seedbank. Seed predation can limit weed population growth if seed predators respond to seed densities so that seed predation is highest within weed patches. To determine whether this relationship holds for Echinochloa crus-galli seeds in corn fields, we observed the levels and responses of seed predators to different densities of E. crus-galli seeds during autumn in 2014 and 2015 (August until corn harvest in September–October) and during the winter of 2014 (August 2014 until March 2015) in three corn fields. We tested whether seed predation in autumn is a good estimate of seed predation from seed shed until the following spring (autumn plus winter), because seed predators were assumed to be less active during winter. In autumn 2014, the levels of seed predation and the response to seed density differed between fields because the main type of seed predator varied between fields. In autumn 2015, almost all seeds were lost due to seed predation in all fields, probably because of a high abundance of rodents. A response to seed density could not be detected. Seed predation during winter resulted partially in an increased level and a density independent response to seed density in all fields. Seed predation in autumn does not reflect seed predation from seed shed until the following spring. Furthermore, the effect of seed predation on weed population dynamics will differ between years and fields.

The reduction of pesticide use intensity is a societal and political ambition. Crop rotation is one important method to control pests and diseases in arable farming. We investigated the contribution of crop rotation to the variability of herbicide and fungicide use of 60 farms in four regions of Northern Germany. Our study aimed at answering the question: do diverse crop sequences lead to reduced herbicide and fungicide use in arable farming? Ten-year data on chemical plant protection measures and field management were examined for six field crops. We classified crop sequences (triplets of three succeeding crops) according to their susceptibility for weeds and diseases (= ’riskiness’). The Treatment Frequency Index (TFI) of the last crop in the triplet was set in relation to the crop triplet riskiness, additionally also in combination with tillage. In general, herbicide and fungicide use intensities were smaller in more diverse crop sequences. Diversified cereal sequences, involving roots and tubers, maize or spring cereals were less dependent on herbicides. Cultivation of maize in three subsequent years increased herbicide use. Crop sequences including high proportion of winter cereals increased fungicide use in cereals, while roots and tubers, winter oilseed rape and set-aside in the crop sequence decreased it. In winter oilseed rape, sequences with roots and tubers also increased fungicide use. In sugar beets, sequences with maize or a high concentration of sugar beets led to increasing fungicide use. If farmers chose riskier crop sequences tillage by plough decreased the need for herbicide and fungicide use. To reduce herbicide and fungicide use intensities we recommend increasing the diversity of crop rotations, including a higher number of crops per rotation together with ploughing. Simplifying both crop sequence diversity and tillage intensity implies higher use of herbicides and fungicides. Results will be useful for convincing farmers to diversify crop sequences.

Herbicide use simplified cropping systems, which lead to short rotations and sowing dates rather focusing on yield than on weed management. Re-diversifying these cropping systems should reduce the vast use of herbicides. We hypothesize that herbicide use decreases with more diverse cropping systems even with few common crops. Cropping system experiments raise methodological questions connected with herbicide use. So far, herbicide use in field experiments is a-priori fixed and not adapted to changing situations. To overcome this, we developed a heuristic decision rule to employ herbicide intensities as response variable in statistical models. Field trials were set up at two locations in Germany as split plot design with cropping systems as main factor and weed control targets as sub-factor. The cropping systems contained maize, winter wheat and winter oilseed rape, and differed in length and sowing date of winter wheat. Weed control targeted a high, medium and low multi-year level. The outcome ‘herbicide intensity’ was described as treatment frequency index (TFI) and as number of active ingredients (NAI). Finally, crops were harvested and yields measured. The heuristic decision rule enabled reproducible, objective herbicide decisions to adapt herbicide intensities to various weed infestations. Herbicide intensities sorted themselves according to the multi-year control target. All crops required a lower herbicide intensity when grown in longer rotations: on average TFI decreased by 19% and 11% resp. depending on the location, and NAI decreased by 0.3 on average per year. Highest yields were harvested with a medium to high weed control target. The heuristic approach opens up new opportunities to collect data on herbicide use as a dependent variable. More diversity in cropping systems reduced herbicide intensity, nevertheless, could not completely compensate the use of herbicides. Thus, we consider them as a useful tool in integrated weed management.

In scientific and public communities pesticide use in arable cropping is a strongly discussed management measure. Nevertheless, information about on-farm pesticide use intensities is scarce. We studied the contribution of regional and farm effects to average pesticide use and its variability and major influencing factors. Data on chemical plant protection measures of 60 farms in four regions of Northern Germany were examined for twelve field crops between 2005 and 2014. The regions correspond to administrative districts of similar size located on gradients of climatic, soil, and structural production conditions. First, we analysed pesticide use intensity described as Standardised Treatment Index (STI) per district and crop. Second, we estimated the variance components on STIs (‘District’, ‘Farm’, ‘Field’, ‘Year’) for total and groups of pesticides. We found a decreasing gradient in pesticide use intensity from the west to the east in Northern Germany. STIs were lower in districts with less favourable conditions for arable land use. However, analysis of variance components showed that the influence of the natural gradient is smaller than the influence of the farm. Hence, differences in farm management and socio-economic characteristics superimpose the production conditions. Finally, we checked the meaningfulness of our results by comparing them with previous and on-going large scale surveys. We determined differences (lower STIs) to the statistical means of the German reference farm network Plant Protection. We assume that this is caused by the higher aggregation level of regions of the German reference farm network Plant Protection.

Summary During the last decade, maize has become the crop with the second largest acreage in Germany. Therefore, agricultural advisors and the plant protection sector are interested in an overview of the weed species composition in maize fields, their determining factors and trends. From 2001 to 2009, a weed survey was conducted in 1460 maize fields throughout Germany. Data on crop management and soil characteristics were collected via farmer questionnaires. Principal component analysis and redundancy analysis were used to analyse patterns in weed species composition. The late spring and summer germinating species Chenopodium spp., Echinochloa crus-galli and Solanum nigrum occurred with high densities and frequencies, but their occurrence was determined by different factors. Other frequent weed species were those that typically accompany autumn-sown crops. The variation in species composition was significantly related to environmental factors (9.1% explained variance), particularly geographical latitude and precipitation, and management factors (4.7% explained variance), particularly crop sequence. The relative importance of these factors seems universal, when compared with surveys in other crops and regions. The factor ‘year’ was of minor importance (0.9% explained variance). Over the 9-year period, no changes in weed species composition could be determined. The results suggest that despite the limited impact of crop management on weed species composition, farmers can use crop sequence to suppress individual species. The survey furthermore sets a baseline against which future changes can be measured in a landscape of rapidly changing agricultural land use.

The question on intraregional versus inter-regional variability in herbicide sensitivity for weed populations is of major importance, both in extrapolation of model parameters and in herbicide zonal approval procedures. We hypothesised that inter-regional variability in herbicide sensitivity for field populations would be the same as intraregional variability for regions with similar climatic conditions. Seeds of field weed populations were collected in a Danish, German and Polish region. Herbicide sensitivity was tested in dose–response experiments in the glasshouse with flufenacet and iodosulfuron (Apera spica-venti), florasulam and tribenuron (Tripleurospermum inodorum), diflufenican, diflufenican + flurtamone and pendimethalin (Viola arvensis). ED50 values and variance components of the ED50 values were estimated to describe the influence of region, year and population. The regions accounted for a maximum of 26% of the variance and always less than the variance accounted for by individual populations. Sensitivity indices (SI50) were calculated as the ratio between ED50 of the test population and a reference population. There was considerable intraregional variability in SI50 values and SI50 values from a single region did not consistently differ from other regions. The large intraregional variability in herbicide sensitivity between populations, with no evidence of resistance, is of interest both for zonal evaluation of herbicides and resistance research. For practical weed management, we conclude that dose–response functions can be transferred between the study regions, for example for the common use in decision support systems with proper insurance for the control of less sensitive populations. The question on intraregional versus inter-regional variability in herbicide sensitivity for weed populations is of major importance, both in extrapolation of model parameters and in herbicide zonal approval procedures. We hypothesised that inter-regional variability in herbicide sensitivity for field populations would be the same as intraregional variability for regions with similar climatic conditions. Seeds of field weed populations were collected in a Danish, German and Polish region. Herbicide sensitivity was tested in dose–response experiments in the glasshouse with flufenacet and iodosulfuron (Apera spica-venti), florasulam and tribenuron (Tripleurospermum inodorum), diflufenican, diflufenican + flurtamone and pendimethalin (Viola arvensis). ED50 values and variance components of the ED50 values were estimated to describe the influence of region, year and population. The regions accounted for a maximum of 26% of the variance and always less than the variance accounted for by individual populations. Sensitivity indices (SI50) were calculated as the ratio between ED50 of the test population and a reference population. There was considerable intraregional variability in SI50 values and SI50 values from a single region did not consistently differ from other regions. The large intraregional variability in herbicide sensitivity between populations, with no evidence of resistance, is of interest both for zonal evaluation of herbicides and resistance research. For practical weed management, we conclude that dose–response functions can be transferred between the study regions, for example for the common use in decision support systems with proper insurance for the control of less sensitive populations.

Climate change is predicted to result in rising temperatures which directly influence weed growth. Moreover, alterations in farming practice and variations in the timing of maize sowing affect weeds also indirectly. The main objective of this study was to establish the methodological concept of time-for-climate substitution for use in applied research. For this purpose, a semi-field experiment was conducted with the three important maize weeds Amaranthus retroflexus, Echinochloa crus-galli and Setaria viridis, which were cropped together with maize. In four treatments sowing of weeds was delayed in order to use naturally raising temperatures. This study focusses on late weed growth properties such as tillers, panicles, seeds and biomass as they allow important demographic conclusions for long-term weed population development. Over the season, temperature was continuously monitored with data loggers and growing degree days were calculated in order to relate the late growth properties to the climatic conditions the weeds experienced during early growth in the four treatments. The results from this study suggest that the tested weeds may benefit in two ways: (1) From warmer conditions during seedling emergence and early growth with enhanced vegetative growth and seed set; (2) from more growing degree days available as a result of earlier maize sowing and related extended cropping seasons. We conclude that our methodology is suitable to investigate climate change effects on weeds for applied questions. In order to limit weed growth and weed seed set under future conditions, management measures such as herbicide treatments at later growth stages and earlier harvest of maize should be explored. Furthermore, we suggest that functional relationships between late weed growth properties such as fecundity and different climatic conditions can be used to improve the accuracy of demographic and bioclimatic models.

Data on agricultural pesticide use are of increasing interest since understanding farmers’ pesticide use patterns is crucial for farm business, farm advisory, and agricultural and environmental policy. Member states of the European Union established different systems to estimate applied amounts of active ingredients per crop and hectare. However, the aggregation of use data at crop level lacks information of farm-specific use patterns. Former studies showed that pesticide use varies strongly between farms. Consequently, approaches are needed to obtain more farm or field-specific data of pesticide use. Glyphosate is the most applied active ingredient worldwide and widely used in Germany. Studies have been carried out in recent years to analyze glyphosate use patterns in German arable farming. For this study, data of a glyphosate-related survey conducted among German farmers were compared with field record data from on-farm studies. Using data originating from the two different sources will help to judge the comparability and adequacy of the methods. This comparison has not been done before for the case of glyphosate or any other pesticide. Questionnaire-based surveys among farmers correspond predominantly with field records, even in the highly political case of glyphosate. In view of glyphosate use patterns, the study indicates that many farmers are not fully aware of the difference between two uses currently registered: stubble and pre-sowing applications. In the on-going public debate, consistent definitions of glyphosate uses are needed to ensure clear communication between stakeholders.

Summary Weed seed predation is an ecosystem service, influencing weed population dynamics. The impact of weed seed predation on weed population dynamics depends on how predators respond to seed patches at the field scale. Seed predation will be most effective if the proportion of seeds predated increases with increasing size and seed density of patches. Density-dependent rodent seed predation was measured by varying seed density and patch size in four irrigated conventionally managed cereal fields in north eastern Spain. Artificial weed seed patches were created by applying a range of Lolium multiflorum seed densities from 0 to 7500 seeds m−2 in 225 m2 patches (2008) or in patches that varied in size from 1 to 9 m2 (2009). Seed predation was estimated using seed cards and seed frames. The granivorous rodents Mus spretus and Apodemus sylvaticus caused high seed predation rates (92%) in three fields, whereas in a fourth field, it was lower (47%). Rodents responded in an inversely density-dependent manner, but this had little biological meaning as even in patches seeded with the highest density, the input to the soil seedbank was reduced by 88%. For the period of time this experiment lasted, hardly any new seeds would have entered the seedbank.

International audience; AbstractArable weeds always accompany arable farming; however, species and abundances vary in space and change in time. Surveys assess weeds on a large spatial scale. The regional and national importance, the abundances in which weeds occur, is derived from surveys. Environmental and management background data assist to explain the weed vegetation. Arable weed surveys can have an agronomic, a botanical or an ecological purpose—we approach the agronomic viewpoint. Scientific value results from spatial data about the arable weed vegetation for modelling the dependencies and predicting future changes on a large scale. Researchers, botanists, farmers, advisors, herbicide manufacturers and other industry players engaged in weed control can get rationale spatial impressions of trends in the weed vegetation. This review focuses on methodical aspects of weed surveys. Forty-three surveys on farmed fields, mainly but not exclusively undertaken in Europe, done in up to nine crops per survey covering periods of 1 to 67 years and including 59 to 4423 fields were excerpted for suitable methods to conduct and analyse surveys. The methods reflect agronomic and other targets, e.g. from vegetation science. When accessing existing data, the interdependencies of the layout and all targets should be handled with care. When setting up surveys for agronomic purpose, it is worthwhile to include 3 years and apply stratified sampling. We recommend assessing abundances rather than presence only. Weed survey data is most suitable for applying multivariate statistics. We recommend using proven methods, without discouraging to explore others. To collect sound explanatory data demands for robust contacts with land managers. Explanatory variables are important in survey analyses to extract knowledge about the drivers of the weed vegetation. We conclude that extra value can be obtained from existing weed survey data. We propose to setup public–private partnerships as a way to carry on with arable weed surveys.

We present an approach of Linear Mixed Effects Modelling to analyse the influence of crop management factors like rotation, tillage, seeding time and cultivar on pesticide use intensity from on-farm data. We use data from 761 winter wheat crops in eight commercial farms and six different regions of Eastern Germany. By defining cropping year, farm and region as random effects, the variability caused by these external factors can be accounted for before estimating effects of crop management factors. The objective of the research we present was to develop and test a method to analyse pesticide use monitoring data appropriately in order to (1) gain insight into the relationship between crop management and pesticide use, (2) integrate external sources of variability into the analysis and quantify their effect, and thereby (3) make a large data pool accessible for further interpretation which will develop further because this kind of monitoring has recently been made mandatory throughout Europe. The benefit of such an analysis is to utilise the practical experience generated by farmers with their daily work that is mirrored in these data for research purposes. This could be valuable in, for example, assessing the effect of Integrated Pest Management (IPM) measures on the pesticide use intensity in arable agriculture, for which evidence is still scarce. We quantified pesticide use intensity using the Standardised Treatment Index (STI). For fungicides, herbicides and growth regulators, we modelled the STI as response of 11 management variables using Linear Mixed Effects Modelling. Insecticide use intensity was not modelled since most fields were not treated with insecticides. Our results confirmed that pesticide use variability is mainly caused by external sources, but pesticide use intensity is significantly connected to crop management, mainly to preceding crop, seeding time and cultivar characteristics. Pesticide use was smaller when preventive measures typical for IPM were applied. We show that the Linear Mixed Effects Modelling approach with multiple predictor variables is well suited for analysing the connection between crop management and pesticide use. We discuss how the random variables influence pesticide use and treatment decisions. Our findings imply that future pesticide use analysis must take regional and farm specific factors into account more strongly, especially when deriving statistical means from on-farm samples. We conclude that the pesticide use monitoring could serve as a valuable data base for scientific research on IPM when data acquisition and analysis are well exploited. Results may be useful for convincing farmers to adopt cropping systems which are less dependent on pesticide use.

We analysed pesticide use data of 539 winter wheat fields grown on seven commercial farms in North East Germany in the seasons 2001–2007. The data were originally collected as part of economic analysis. The aim of our study was to show the impact of agronomic measures typical for integrated pest management (IPM) on pesticide use intensity. We used multivariate methods including hierarchical clustering and unconstrained ordination to describe variability of pesticide use and to identify pesticide use patterns. 166 fields had a complete record of eight crop management variables characterising rotation, tillage, cultivar, seeding time and N fertilisation. We subjected pesticide data of these fields to an ordination constrained by crop management data and considered weather and farm characteristics as co-variables influencing the pesticide use intensity. Crop management had a measurable effect even beyond the single farm and changing weather conditions: it accounted for approx. 10% of the explained variability of pesticide use. Pesticide intensity is adjusted by farmers to overall cropping intensity. Fields which were managed with typical IPM characteristics like late seeding and resistant cultivars were treated with a lower pesticide intensity. The downside of our findings is that these lower input CM systems are typically used only on less productive sites. Variability of pesticide use was mainly influenced by the farm, this factor accounted for 37% of explainable variance. We discuss two components of this high explanatory power: (I) farm characteristics which determine overall cropping intensity and (II) the routine of treatment decisions on the farm. We discuss the implications of our results regarding robust study design and sampling for pesticide use monitoring. To enhance IPM adoption in the context of recent European pesticide regulations, we identify the need for: (I) studies on the economy of reducing pesticide use by integrating agronomic measures, and (II) identification of innovative farmers for possible farmer to farmer exchange on successful IPM adoption.

Westerman PR, Heiermann M, Pottberg U, Rodemann B & Gerowitt B (2012). Weed seed survival during mesophilic anaerobic digestion in biogas plants. Weed Research52, 307–316. Summary Digestate, the semi-solid leftover after anaerobic digestion in biogas reactors, is frequently used as a crop fertiliser. The ability of seeds from five plant species (four weed species and one vegetable crop) to survive commercial biogas plants was tested, to assess the likelihood that these could be spread via digestate and to compare with results obtained from laboratory-scale reactors. Seeds were selected from among the best surviving species in experimental batch reactors in an earlier study. They were exposed for 1–9 days in two large-scale, commercial mesophilic biogas plants. The resulting exponential decay functions were estimated. The decimal reduction time, D, was estimated at 1.5 days for Abutilon theophrasti population D2003, 2 days for A. theophrasti population ES2008, 5.8 days for Malva neglecta, 4.7 and 19.7 days for Chenopodium album, and 1.2–9.1 days for Fallopia convolvulus. Given the differences in ranking of plant species, laboratory reactors are not necessarily a good model system for commercial reactors. Seeds could survive passage through biogas plants, although at (extremely) low numbers. If the objective is to eliminate all risks and dispose of all weed seeds, it will be necessary to either add extra sanitation steps, or to identify and manipulate the factors that are responsible for high seed mortality. However, it is currently unknown what these factors are.

Data on weed species currently found in winter oilseed rape, the extent of their occurrence and regional distinctions were collected in autumn 2005, 2006 and 2007 from a total of 1463 oilseed rape (OSR) fields throughout Germany. Investigations took place in untreated parts of OSR fields at the four to six leaf stage of rape. Weed frequencies and densities were determined by randomly placing a 0.1 m2 square frame ten times in each plot, identifying and counting all plants within the frame. Results presented here mainly focus the distribution of important weed species and differences in their frequencies and densities between German Federal states. The majority of weed species occurring in winter oilseed rape is not evenly spread over Germany. There are weed species with a limited distribution which can be frequently found in some regions but are absent in others. Sisymbrium officinale, Descurainia sophia, Centaurea cyanus, Anchusa spp., Sonchus spp., Rumex spp. or Euphorbia spp. are some weed species with mainly regional importance. Several ubiquitous weed species show regional differences in their densities. Capsella bursa-pastoris, Chenopodium album, Galium aparine, Lamium spp., Matricaria spp., Stellaria media, Thlaspi arvense, Veronica spp. and Viola arvensis were among the most frequent weed species in OSR in all German federal states though sometimes differing significantly in regional densities. Recent field observations reporting an increased spreading of Geranium spp., Sisymbrium spp. or Anchusa arvensis in intense OSR cropping areas are verified by these results.

Westerman PR, Hildebrandt F & Gerowitt B (2012). Weed seed survival following ensiling and mesophilic anaerobic digestion in batch reactors. Weed Research52, 286–295. Summary Digestate, the semi-solid leftover after anaerobic digestion in biogas reactors, is frequently used as a crop fertiliser. The ability of seeds from various weed species to survive anaerobic digestion was tested, because surviving seeds could be spread via the digestate. Experiments were conducted in experimental mesophilic batch reactors, either with or without ensiling as a pre-treatment to simulate biomass storage in silage prior to use in reactors. The emphasis was on weed species whose seeds have a water-impermeable layer, because these may be more thermoresistant. Species with hard seeds were more likely to survive ensiling (up to 98%) and mesophilic anaerobic digestion (up to 58%) compared with species whose seeds lack a water-impermeable layer (≤1%). There was considerable variation in survival probability between and within species, and between silages and reactors. For hard-seeded species, survival depended on the proportion of hard seeds and on the ability to remain hard-seeded during treatment. Freshly harvested seeds lost their water impermeability and survived poorly. The survival of tomato seeds, an indicator species used in the sanitation of composts, was comparable with that of the best surviving species without physical dormancy, but was not comparable with that of hard-seeded species. Tomato could therefore only represent species that are not hard-seeded.

Anaerobic digestion in biogas reactors generates a semi-solid leftover, the digestate, which is frequently used as a crop fertiliser. If weed seeds in the maize biomass that is used for feedstock survive the process of anaerobic digestion, the use of digestate could contribute to the spread of weeds. We investigated here the probability that weeds enter the biogas production chain via maize biomass. Five organic and four conventional maize fields were sampled to determine the identity, density and biomass of the weeds present, and the number and viability of seeds produced. This was done separately for plant parts below and above the anticipated cutting height of the maize crop, close to the anticipated harvest date. Weed density varied from 56 to 568 weeds m−2 and weed seed production from 886 to 229 256 seeds m−2. Conventional fields tended to have lower weed biomass, lower seed production, and lower proportion of the seeds above the cutting height of maize, with lower seed viability. The main weeds were Chenopodium album and Echinochloa crus-galli. In general, either weed plants were small and produced few seeds that were largely found below the cutting height of maize, or they were tall and produced numerous seeds that were largely found well above the cutting height. Given the numbers of weed seeds produced per hectare in this study, it is likely that some will survive anaerobic digestion in biogas plants, although in low numbers, as seed survival during anaerobic digestion tends to be low.

Baraibar B, Daedlow D, De Mol F & Gerowitt B (2011). Density dependence of weed seed predation by invertebrates and vertebrates in winter wheat. Weed Research 52, 79–87. Summary Weed seed predation has the potential to limit weed population growth within agricultural fields. Its success depends in part on the ability of predators to detect weed patches and respond in a direct density-dependent way to increasing weed seed densities. To test for density-dependent responses, an experiment was conducted in north-eastern Germany in four winter wheat fields during October 2008 and 2009. Zero, 1000, 2500 and 5000 seeds m−2 of Lolium multiflorum were applied to four adjacent 15 m × 15 m plots in each field. Seed predation was measured in 20 randomly located trays per plot that were accessible to all predators (eight per plot) or excluded vertebrates (12 per plot). Seeds were exposed in the field for 18 days. Remaining seeds were recovered from the soil and counted. In addition, 20 seed cards were randomly placed in each plot, half of them with vertebrate exclosure cages. Seeds on cards were counted every other day. Seed predators were identified. Predation rates measured by trays were low (32.7% per 18 days) and may have been caused by low densities of predators. Vertebrates responded in a direct density-dependent way to increasing seed densities, whereas the response of invertebrates was density independent. Seed predation from seed cards confirmed the density-dependent responses obtained using trays. Seed predators only needed a few days to detect and preferably exploit the high density plots. Weed seed patches are likely to persist in fields where invertebrates are the main predators, while they could be better controlled where granivorous rodents predominate.

Data on the occurrence of weed species in 1463 German oilseed rape (OSR) fields were used to multivariately investigate the interactions of management practices and ecological processes with weed species composition. Partial canonical correspondence analysis (pCCA) served to quantify the relative contribution of 25 characteristics of climate, site and crop to weed species composition. According to pCCA the considerable differences in weed species composition of OSR fields were mainly associated with the crop preceding OSR, the tillage intensity and soil quality. Longitude and precipitation were the most important environmental parameters. Factors driving the occurrence of weed species differed for the categories ‘common’, ‘frequent’ and ‘rare’ weed species. Common weed species showed the strongest response to factors acting at the field scale such as crop sowing date or soil quality, while only frequent species were affected by local environment, and the occurrence of rare weeds more than the other groups depended on large-scale geographical position variables as well as cropping intensity. Cluster analyses of thematically grouped explanatory variables resulted in the identification of four farming systems with different soil properties and management, two farming systems differing in the occurrence of OSR cropping, and five ecoregions, each with characteristic and statistically verified OSR weed communities.

The influence of potato cultivar (Solanum tuberosum L. cvs. Albatros, Borwina, Fasan, Kormoran, Pirol, Salome, Romanze and Terrana) and leaf zone on the reproduction rate of green peach aphid, Myzus persicae (Sulzer) and potato aphid, Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae), was assessed in glasshouse experiments. Aphids were caged in five leaf zones of each cultivar. M. persicae prefers senescent leaves. Fecundity and reproductive rate of M. persicae were greater on the lower leaves than on upper leaves (P< 0.001). The total fecundity and reproduction rate of M. euphorbiae were greater on the upper leaves than on lower leaves (P< 0.001). The results showed that the reproduction rate of M. persicae and M. euphorbiae differed significantly (P< 0.05) among cultivars.

German plant protection law demands farmers to limit the use of pesticides to a necessary extent. In this article, we have developed a theoretical framework on deciding on pesticide use. We look at three different ways of interpreting how much pesticide is “necessary” to control a pest on a crop: (1) using a product at the recommended dose when a pest is found or a precautionary treatment thought necessary, (2) optimising pesticide use for economic savings through adjusted doses, thresholds, etc. and (3) minimising pesticide need by altering the cultivation system to lower the risk of pests. The smallest pesticide use intensity can be reached by combining approaches 2 and 3. In practice, information on optimising pesticide use needs further research to reduce the uncertainty about the effects of agronomical control measures, both with respect to economics and risk.

Low-input measures is used as a generic term for all measures involving a reduced intensity of agricultural management to enhance the quality of biotic or abiotic goods. Intensive agricultural regions have the lowest share of implemented low-input measures, though they have to resolve the most serious nature conservation and environmental problems. To understand the conditions for a better implementation of these measures in intensive agricultural areas, we carried out a written survey among 865 farmers in intensively-used arable regions. The adoption patterns of arable and grassland measures were compared. The determining factors were analysed by logistic regression. Arable measures, such as mulch seeding, that claim a high share of the arable area often have comparatively slight restrictions and cause windfall gains. However, our results show that their adoption increases the ratio of probability of a subsequent implementation of low-input measures on grasslands by 0.05. This means that these arable measures can act as starting measures for probably more valuable low-input measures on grasslands. Furthermore, the relation of the farmers with their subsidising institution proved to have an influence in our analysis. With every next best rating the farmers give for their relation with their subsidising institution, the ratio of probability for the adoption of low-input measures on arable land rises by 0.3. We also detected a strong positive influence of defined contact persons within the subsidising institution on the probability of adopting grassland measures, with a ratio of probability of 4.802. These findings show that the subsidising institution has in many respects a central influence on the decision process of the farmer to adopt low-input measures. The described determinants reveal new insights usable for improving the off-farm conditions of an increased implementation of low-input measures in intensively-used arable regions.

DSSHerbicide Germany and DSSHerbicide Poland are two decision support systems (DSS) developed for weed control in winter wheat in Northern regions of Germany and Poland. DSSHerbicide is based upon an existing Danish DSS, Crop Protection Online (CPO). Herbicide recommendations from DSSHerbicide are based on efficacy estimates from a dose–response model and required weed control levels defined by expert evaluations and practical experience. DSSHerbicide was parameterised for 22 commonly occurring weed species and 48 herbicides in Poland and for 23 weed species and 32 herbicides in Germany. Validation trials were conducted in Poland, Germany and Denmark primarily in private farmer's winter wheat fields. This enabled a comparison between the herbicide use with standard recommendations and with the existing Danish CPO and the German and Polish DSSHerbicide. Differences among herbicide applications were analysed based on the treatment frequency index (TFI, relation of actually applied dose to label rate) and the costs of herbicide treatments.Recommendations from DSSHerbicide resulted in lower herbicide use than standard recommendations from advisory services in Germany and Poland. TFI of autumn applications from DSSHerbicide recommendations were lower than standard recommendations. The spring application, however, did not differ among herbicide treatments. Yield and weed coverage, estimated by visual observations, were measured at harvest. The TFI of recommendations from DSSHerbicide, measured over the whole growing season, were approximately 20 and 40% lower than standard recommendations in Germany and Poland, respectively. Yields or weed coverage did not differ among sprayed treatments at harvest. All herbicide treatments improved yield and lowered weed coverage compared to controls of no herbicide application. The cost for the chosen herbicides did not differ among treatments, but this is considered a consequence of the limited herbicide choices in these new DSS prototypes.DSSHerbicide provided equally robust recommendations as the existing Danish CPO, and indicated a potential for herbicide reductions in Germany and Poland compared to the reference standard recommendations. As the present DSSHerbicide versions for Germany and Poland are prototypes, fields trials providing data for parameterisation of more weed – herbicide relationships are required to implement additional herbicides in the systems.

Summary The genetic structure of typical Cirsium arvense patch populations in two arable fields was examined. Patches were mapped and plant samples were taken in these patches. Plants of a central patch and four surrounding patches were sampled in 1 year to investigate the influence of root fragment dispersal. Plants of another patch were sampled in three subsequent years to investigate the patch development. The genotypes of the plants were examined using repetitive enterogenic primer (REP) and inter simple sequence repeat (ISSR) analysis. The mean proportion of distinguishable genotypes ranged from 0.13 to 0.67 and the evenness index ranged from 0.58 to 1.00. Differences in genotypes between neighbouring patches indicated that root fragment dispersal via soil cultivation was of minor importance. Three years sampling within a patch showed that the patch mainly ‘grew’ via the establishment of new clones rather than by clonal growth of one genotype. The influence of various factors caused by population demography or arable practice on patch development in an arable field is discussed. Although various factors can help to maintain genetic diversity, there is strong evidence for regular seedling establishment in arable fields.

It is investigated, whether the arable weed vegetation can perform as a characteristic to stimulate sustainable development of agriculture in Central Europe. The concept of sustainable development represents a dynamic process, influenced by ecological, economic and social aspects. Characteristics are required to integrate desired ecological aspects into farming concepts, in order to stimulate production systems which add to a sustainable development of the sector. The investigations rely on data of an arable farming system experiment (INTEX). Three farming systems called good-farming-practice (GFP), integrated-flexible and integrated-non-inversion were established from 1994 to 1998 on two sites. The systems differed in crop rotation, soil tillage, fertilisation and pesticide use. Thus, weed management comprised cultural or indirect control by plant husbandry and direct mechanical and chemical control. A residual weed vegetation after terminating all direct control in the arable crops was ex-ante intended in the integrated systems. The spring weed densities were observed in winter wheat previous to any direct control treatments. The residual weed vegetation was investigated in all crops by monitoring species numbers and total ground cover after terminating all direct control. The direct chemical control intensity was considerably lower in the integrated farming system, in which the crop rotation was extended and the soil was ploughed annually. Spring densities of problematic weeds like annual grass weeds and Galium aparine in the winter wheat crop were not higher in these systems. Higher covers of the residual weed vegetation occurred more often in the productive arable crops of the two integrated farming systems, which additionally hosted higher number of species after terminating direct control. The different system strategies, including a higher input of herbicides in the system integrated-non-inversion, averted severe problems, including those arising from the dominating species being generally problematic in arable land use.

This paper focuses on the possibilities to reward ecological goods and services of agriculture. Ecological goods in agriculture are achieved by various types of agricultural land use either creating resources or buffering resource consumption. From an economic point of view, positive consequences will result from rewarding the agricultural sector for the production of ecological goods according to market principles. A rewarding system can be developed according to market principles when results instead of actions are rewarded, producer and consumer surpluses are created, demand can be expressed and supply can be provided. Ecological goods are public goods, therefore the expression of demand is up to the community. However, the purchasing of such ecological goods is up to the authority administrating public finances. Establishing regional markets is necessary, since regional differences are evident. Principally, the price of an ecological good should be determined by its value to the public, not by the cost of production. With respect to the various ecological goods achieved by the agricultural sector, the contribution of agricultural land use to biodiversity, and more specifically to plant biodiversity seems to be the most appropriate for a market-orientated rewarding system. A framework for establishing such a market is outlined in this paper. Deviation from standard economic principles regarding prices for ecological goods are considered to be necessary during an introductory period. Finally based on both, ecological and economical considerations, and regarding the intrinsic and extrinsic characteristics of “plant biodiversity connected with agricultural land use”, it seems worth the effort to further examine and develop this concept.

Summary Agricultural land use has production, ecological, aesthetic and social functions. Certainly, in Europe, the concept of agricultural land use as being multifunctional seems to be increasingly accepted. Ecological goods and services can be rewarded as results or as actions – the differences between these ways are described and an outcome-based rewarding system is elucidated for the creation of incentives for innovation and taking responsibility. The principle requirements for ecological goods are summarized. The contribution of agricultural land use to plant biodiversity is the most appropriated factor for an outcome-based rewarding system. The various types of vegetation connected with agricultural land use can be used as recognizable ecological goods. The reasoning behind defining specific arable goods is shown. Information about creating the supply is available from the research performed on weed control in different arable systems. As the majority of ecological goods are public goods, mechanisms adapted from market situations for private goods must be stimulated and organized. The decision as to which ecological goods should be stimulated could be transferred to a decentralized and region-specific public committee in which the relevant stakeholders are represented. Implementation exercises undertaken in a region of the German Federal State of Lower Saxony are introduced.

Over the past decades, climate change has induced transformations in the weed flora of arable ecosystems in Europe. For instance, thermophile weeds, late-emerging weeds, and some opportunistic weeds have become more abundant in some cropping systems. The composition of arable weed species is indeed ruled by environmental conditions such as temperature and precipitation. Climate change also influences weeds indirectly by enforcing adaptations of agronomic practice. We therefore need more accurate estimations of the damage potential of arable weeds to develop effective weed control strategies while maintaining crop yield. Here we review the mechanisms of responses of arable weeds to the direct and indirect effects of climate change. Climate change effects are categorized into three distinct types of shifts occurring at different scales: (1) range shifts at the landscape scale, (2) niche shifts at the community scale, and (3) trait shifts of individual species at the population scale. Our main conclusions are changes in the species composition and new species introductions are favored, which facilitate major ecological and agronomical implications. Current research mainly considers processes at the landscape scale. Processes at the population and community scales have prevalent importance to devise sustainable management strategies. Trait-climate and niche-climate relationships warrant closer consideration when modeling the possible future distribution and damage potential of weeds with climate change.

The determination of fixed guide values for weed economic threshold in cereals is briefly reviewed. A 2-year experimental series in winter cereals to validate these threshold values in the Federal Republic of Germany is described. It was found that the use of fixed threshold values to decide when to control annual weeds was more profitable than prophylactic herbicide application. The fixed threshold values are 20–30 plants m −2 for grass weeds, broad-leaved weeds 40–50 plants m −2 , Galium aparine 0.1–0.5 plants m −2 and Fallopia convolvulus 2.0 plants m −2 . Alternatively, broad-leaved weeds have to be assessed as percentage ground cover, 5–10% being the threshold. In order to improve further the predictions from the economic thresholds a more flexible computer-based decision model has been developed. This includes updated biological data and simple economic calculations. Further experiments have been done to validate the model. Assessments based on the calculated net return indicate that weed control decisions were slightly improved by model recommendations compared with the fixed threshold concept. The basic assumptions in the decision model are discussed and possibilities for future applications under practical conditions are described.