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The nitrogen applied (N-input) to cropping systems supports a high yield but generates major environmental pollution in the form of greenhouse gas (GHG) emissions and losses to land and water (N-surplus). This paper examines the scope to meet both GHG emission targets and zero N-surplus in high-intensity, mainly cereal, cropping in a region of the Atlantic zone in Europe. A regional survey provides background to crops grown at an experimental farm platform over a run of 5 years. For three main cereal crops under standard management (mean N-input 154 kg ha−1), N-surplus remained well above zero (single year maximum 55% of N-input, five-year mean 27%), but was reduced to near zero by crop diversification (three cereals, one oilseed and one grain legume) and converted to a net nitrogen gain (+39 kg ha−1, 25 crop-years) by implementing low nitrification management in all fields. Up-scaling N-input to the agricultural region indicated the government GHG emissions target of 70% of the 1990 mean could only be met with a combination of low nitrification management and raising the proportion of grain legumes from the current 1–2% to at least 10% at the expense of high-input cereals. Major strategic change in the agri-food system of the region is therefore needed to meet GHG emissions targets.

Purpose (1) To assess the biological N fixation (BNF) potential of varieties of faba bean (Vicia faba L.) cropped with or without compost in an experimental field-scale rotation with no recent history of legumes, (2) to enumerate soil populations of Rhizobium leguminosarum sv. viciae (Rlv), and to genetically characterize the nodulating Rlv strains, (3) compare BNF with other sites in Britain. Methods BNF was evaluated from 2012 to 2015 using 15 N natural abundance. Treatments were either PK fertilizer or compost. Soil rhizobial populations were determined using qPCR, the symbiotic rhizobia genotyped (16 S rRNA, nodA and nodD genes), and their BNF capacity assessed ex situ. The reliance of legumes on BNF at other British sites was estimated in a single season, and their nodulating symbionts examined. Results Faba bean obtained most of its N through BNF (>80%) regardless of variety or year. N-accumulation by cvs Babylon and Boxer increased with compost treatment in 2014/2015. Rhizobial populations were c. 105-106Rlv cells g−1 soil regardless of field or treatment. 157 Rlv microsymbionts grouped into two large nodAD clades; one mainly from V. faba, and the other from various legumes. All isolates nodulated, and some performed better than commercial inoculant strains. Conclusions Faba bean can provide most of its nitrogen through BNF and leave economically valuable residual N for subsequent crops. Recent legume cropping in northern Europe is not essential for effective nodulation: rhizobia may persist in a range of farmland locations. Nevertheless, there is the potential to apply elite rhizobial strains as inoculants in some soils.

A systematic approach to quantifying the weed–crop balance through the flux of solar radiation was developed and tested on commercial fields in a long-established Atlantic zone cropland. Measuring and modelling solar energy flux in crop stands has become standard practice in analysis and comparison of crop growth and yield across regions, species and years. In a similar manner, the partitioning of incoming radiation between crops and the in-field plant community may provide ‘common currencies’ through which to quantify positive and negative effects of weeds in relation to global change. Here, possibilities were explored for converting simple ground-cover measures in commercial fields of winter and spring oilseed rape in eastern Scotland, UK to metrics of solar flux. Solar radiation intercepted by the crops ranged with season and sowing delay from 129 to 1975 MJ m−2 (15-fold). Radiation transmitted through the crop, together with local weed management, resulted in a 70-fold range of weed intercepted radiation (14.2 to 963 MJ m−2), which in turn explained 93% of the corresponding between-site variation in weed dry mass (6.36 to 459 g m−2). Transmitted radiation explained almost 90% of the variation in number of weed species per field (12 to 40). The conversion of intercepted radiation to weed dry matter was far less variable at a mean of 0.74 g MJ−1 at both winter and spring sites. The primary cause of variation was an interaction between the temperature at sowing and the annual wave of incoming solar radiation. The high degree of explanatory power in solar flux indicates its potential use as an initial predictor and subsequent monitoring tool in the face of future change in climate and cropping intensity.

Agriculture needs to reduce inputs of inorganic fertilizers and close the loop on nutrients that can otherwise become environmental pollutants. This can be achieved by promoting recycling of nutrients within the agricultural landscape. We investigated the extent to which plants found in riparian buffer zones have the potential to provide nutrients to crops as a green manure, through plant growth and decomposition studies. Under controlled conditions, species typical of Scottish riparian buffer strips were tested for their ability to accumulate biomass and nutrients in tissue under N- and P-replete conditions and whether this ability enhanced the utility of the resulting green manure in promoting crop growth. In this proof-of-concept study, we found that green manure derived from riparian buffer strips did not effectively replace inorganic fertilizer and only had a significant positive effect on growth, yield, and nutrient accumulation in barley (Hordeum vulgare L.) when it was integrated with the addition of inorganic fertilizers. The individual species tested varied in the amount of P they accumulated in their tissue (1.38–52.73 mg P plant−1), but individual species did not differ in their ability to promote yield when used as a green manure. Our results indicate that selecting certain species in the buffer strip on the basis of their nutrient accumulating abilities is not an effective way to increase the utility of buffer strip green manure as a nutrient source for crops.

Current food production systems are major contributors to the environmental degradation that leads to climate change and biodiversity loss. Levels of production required for future food security cannot be met by further increases in inputs of non-renewable resources. The world’s food crops must therefore be managed in a sustainable way that maintains long-term ecological functioning, including nutrient, carbon and water cycles, soil quality, primary productivity, microbe-plant associations, pest and pathogen regulation, pollination and arable food web resilience. All of these are determined by agronomic practices at local and regional scales, and all are sustained by the abundance, diversity and functional composition of plants, microbes and invertebrates in the farmed ecosystem. Presence of viable populations and communities of these organisms is therefore essential for system resilience. Long-term sustainability must rely more heavily on the internal generation of products and regulatory ecosystem services than on external inputs. Fully closed systems are impossible to achieve in agriculture as the product is removed for human consumption. There is ample evidence, however, that semi-closed, regenerative, systems can harness the ecosystem services provided by functional biodiversity to enhance crop production whilst simultaneously improving environmental quality. Here, agroecological alternatives to intensive farming practices are reviewed, focusing on key functional indicators and whole-system integration of practical management options designed to achieve multiple beneficial outcomes at field and farm scales.

Soil organic carbon (SOC) is declining globally due to intensification of agriculture. Reversing declines should reduce soil erosion, maintain yields, raise the soil&rsquo, s atmospheric carbon sink, and improve habitat for biodiversity. Commercial fields were sampled in a diverse European Atlantic zone cropland to relate SOC status to cropping intensity and to define a realistic target for restoration. SOC (%C by mass) decreased from 4% to 2% as the proportion of high-intensity crops increased from zero to 55% (linear regression, F pr. &lt, 0.001). In further sampling in and around high-intensity fields, mean SOC increased from 2.4% in cultivated soil to 3.3% in field margins and 4.8% in nearby uncultivated land (F pr. &lt, 0.001). Three broad zones of SOC in close spatial proximity were then defined: 1) high-intensity arable from 1% to 3%, 2) mid-intensity arable and arable-grass from 3% to 5% and 3) uncultivated and semi-natural land from 5% upwards. C:N ratio was constrained around 12, unaffected by cropping intensity, but slightly lower in fields than in margins and uncultivated land (F pr. &lt, 0.001). A feasible target SOC of just above 3% was defined for high-intensity sites. There should be no biophysical obstacle to raising SOC above 3% in the high-input sector. Results argue against treating cropland of this type as uniform: assessment and restoration should be implemented field by field.

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The long-term sustainability of crop production depends on the complex network of interactions and trade-offs between biotic, abiotic and economic components of agroecosystems. An integrated arable management system was designed to maintain yields, whilst enhancing biodiversity and minimising environmental impact. Management interventions included conservation tillage and organic matter incorporation for soil biophysical health, reduced crop protection inputs and integrated pest management strategies for enhanced biodiversity and ecosystem functions, and intercropping, cover cropping and under-sowing to achieve more sustainable nutrient management. This system was compared directly with standard commercial practice in a split-field experimental design over a six-year crop rotation. The effect of the cropping treatment was assessed according to the responses of a suite of indicators, which were used to parameterise a qualitative multi-attribute model. Scenarios were run to test whether the integrated cropping system achieved greater levels of overall sustainability relative to standard commercial practice. Overall sustainability was rated high for both integrated and conventional management of bean, barley and wheat crops. Winter oilseed crops scored medium for both cropping systems and potatoes scored very low under standard management but achieved a medium level of sustainability with integrated management. In general, high scores for environmental sustainability in integrated cropping systems were offset by low scores for economic sustainability relative to standard commercial practice. This case study demonstrates the value of a &lsquo, whole cropping systems&rsquo, approach using qualitative multi-attribute modelling for the assessment of existing cropping systems and for predicting the likely impact of new management interventions on arable sustainability.

The intensification of arable production since the 1950s has resulted in increases in yield but only at significant cost to the environment, raising serious concerns about long-term consequences for the sustainability of food production systems. While a range of policies and practices have been put in place to mitigate negative effects in terms of pollution, soil degradation and loss of biodiversity, their efficacy has not been properly quantified. Whole-system effects of management change are rarely studied and so trade-offs and conflicts between different components of the agricultural system are poorly understood. A long-term field platform was therefore established in which conventional arable management was compared with a low-input, integrated cropping system designed with the goal to maintain yields whilst enhancing biodiversity and minimizing environmental impact. Over the first rotation, only winter wheat yielded less under integrated management, yield was maintained for the remaining five crops (spring and winter barley, winter oilseed rape, potato and field beans), suggesting a negligible impact on economic returns. Beneficial broad-leaved weeds were significantly more abundant in the integrated management system across all crops whereas grass weeds showed no overall response to treatment. Soil carbon, pH and soil concentrations of the main plant growth-limiting macronutrients were enhanced under the integrated management system. The integrated system was therefore successful in meeting the goals to enhance biodiversity and reduce environmental impact without jeopardizing crop yields.

Efforts to maintain or increase food production in developed agriculture would be compromised if current high-intensity production was degrading supporting ecosystem services, such as the ability of soil to function. The link between cropping intensity, defined by pesticide and fertiliser applications, and soil biophysical status was examined at 70 sites in a high-yielding region of the UK, in which cropping sequences covering a wide range of intensity had diverged from a common low-intensity origin in the 1970s. Two sequences of still low or moderate intensity based on spring cereals or a low frequency of winter cereals formed comparators for three high intensity sequences based on winter wheat and potato which together were associated with adverse effects of −30% on soil carbon content in the upper soil layer (P

Myxospermous seeds become bound by mucilage upon hydration and this trait is ecologically important. Major impacts could be enhancing seed-soil contact and improving water retention, which we quantify in this study. Myxospermous or demucilaged seeds of Capsella bursa-pastoris L. Medik. (shepherd’s purse) were added to a test sandy clay loam at seed : soil densities of 5 and 10 % [w/w]. The soil water retention and hydraulic conductivity were assessed. Soil rheology was also assessed using extracted mucilage only amendment at 0.5 and 1 % [w/w]. Shepherd’s purse seeds increased soil water retention and reduced soil hydraulic conductivity for myxospermous and demucilaged seeds. Soil rheological properties (complex shear modulus, viscosity and yield stress) increased in response to seed mucilage addition, and became more pronounced as soil dried. The mucilage had greatest impact on the yield stress compared to the other rheology parameters. The densities of myxospermous and non-myxospermous seeds, and mucilage tested here reflect that may be found naturally in soil seedbanks. The findings provide the first evidence that the soil seedbank provided from a wild arable species may regulate the soil water retention and enhance soil stability, and that this capacity is greater for myxospermous seeds.

The outer surface of myxospermous seed coats contains mucilage which absorbs large amounts of water relative to its dry weight. Ecologically, the seed mucilage can affect seed germination and dormancy. Upon hydration, a large proportion of the seed mucilage is lost to the soil and the physics of soil-seed mucilage interactions has not been assessed. Towards that end, the dynamic rheological properties of mucilage extracted from Capsella bursa-pastoris L. Medik. (shepherd's purse) seeds were assessed as a function of mucilage concentration (1-10% (w/w)), temperature (0-80 ◦ C) and shear frequency (0.1- 100 rad s −1 ). The seed mucilage was shear thinning and was classified as a highly viscous "weak gel". The relationship between the viscoelastic parameters (viscosity, η ∗ , storage and loss modulus, Gand G �� , yield and flow stresses, τy and τf ) and mucilage concentration were well fitted by power law models. The values of η ∗ , Gand G �� increased as temperature increased above 40 ◦ C and were also slightly frequency dependent. The shepherd's purse seed mucilage is more viscous than that from other plant parts, such as fruits and roots. These properties highlight the possibility that seed mucilage may affect soil conditions and therefore present an additional facilitative ecological role (beyond that already reported, which directly affect seed biology); and this is discussed.

Environmental risk assessment of GM crops in Europe proceeds by step-wise estimation of effect, first in the plant, then the field plot (e.g. 10–100 m−2), field (1000–10,000 m−2) and lastly in the environment in which the crop would be grown (100–10,000 km2). Processes that operate at large scales, such as cycling of carbon (C) and nitrogen (N), are difficult to predict from plot scales. Here, a procedure is illustrated in which plot scale data on yield (offtake) and N inputs for blight resistant (both GM and non-GM) and blight-susceptible potato are upscaled by a model of crop resource use to give a set of indicators and metrics defining N uptake and release in realistic crop sequences. The greatest potential damage to environment is due to loss of N from the field after potato harvest, mainly because of the large quantity of mineral and plant matter, high in N, that may die or be left in the field. Blight infection intensifies this loss, since less fertiliser N is taken up by plants and more (as a proportion of plant mass) is returned to the soil. In a simulation based on actual crop sequences, N returns at harvest of potato were raised from 100 kg ha−1 in resistant to 150 kg ha−1 in susceptible varieties subject to a 40% yield loss. Based on estimates that blight-resistant types would require ~20% of the fungicide applied to susceptible types, introduction of resistant types into a realistic 6-year cropping sequence would reduce overall fungicide use to between 72 and 54% depending on the inputs to other crops in the sequence.

There is increasing pressure on the agricultural industry to maintain or increase production of high‐quality food while maintaining long‐term environmental sustainability. and policies and practices have been developed and implemented in an attempt to improve the sustainability and efficiency of arable farming and satisfy these potentially conflicting requirements. However, to the authors' knowledge, there has been no attempt to quantify whether new interventions have the desired effect on improving sustainability at a whole‐systems level. Most studies focus on one, or a few, elements of a specific system and therefore fail to account for trade‐offs and conflicts between the many different interacting components. Here, we propose a whole‐systems approach based on a suite of indicators for a complete and holistic assessment of the efficacy of policies to improve economic, environmental, and ecological sustainability.

BACKGROUND AND AIMS Simple indicators of crop and cultivar performance across a range of soil types and management are needed for designing and testing sustainable cropping practices. This paper determined the extent to which soil chemical and physical properties, particularly soil strength and pore-size distribution influences root elongation in a wide range of agricultural top soils, using a seedling-based indicator. METHODS Intact soil cores were sampled from the topsoil of 59 agricultural fields in Scotland, representing a wide geographic spread, range of textures and management practices. Water release characteristics, dry bulk density and needle penetrometer resistance were measured on three cores from each field. Soil samples from the same locations were sieved, analysed for chemical characteristics, and packed to dry bulk density of 1.0 g cm(-3) to minimize physical constraints. Root elongation rates were determined for barley seedlings planted in both intact field and packed soil cores at a water content close to field capacity (-20 kPa matric potential). KEY RESULTS Root elongation in field soil was typically less than half of that in packed soils. Penetrometer resistance was typically between 1 and 3 MPa for field soils, indicating the soils were relatively hard, despite their moderately wet condition (compared with

†Background and Aims Myxospermy is a term which describes the ability of a seed to produce mucilage upon hydration. The mucilage is mainly comprised of plant cell-wall polysaccharides which are deposited during development of those cells that comprise the seed coat (testa). Myxospermy is more prevalent among those plant species adapted to surviving on arid sandy soils, though its significance in determining the ecological fitness of plants is unclear. In this study, the first mathematical model of myxospermous seed mucilage expansion is presented based on seeds of the model plant species Capsella bursa-pastoris (shepherd’s purse). †Methods The structures underpinning the expansion process were described using light, electron and time-lapse confocal micrographs. The data and experimental observations were used to create a mathematical model of myxospermous seed mucilage expansion based on diffusion equations. †Key Results The mucilage expansion was rapid, taking 5 s, during which the cell mucilage volume increased 75-fold. At the level of the seed, this represented a 6-fold increase in seed volume and a 2.5-fold increase in seed surface area. These increases were shown to be a function of water uptake (16 g water g 21 mucilage dry weight), and relaxation of the polymers which comprised the mucilage. In addition, the osmotic pressure of the seed mucilage, estimated by assessing the mucilage expansion of seeds hydrated in solutions of varying osmotic pressure, was ‐0.54 MPa (equivalent to 0.11 M or 6. 6g L 21 NaCl). †Conclusions The results showed that the mucilage may be characterized as hydrogel and seed-mucilage expansion may be modelled using the diffusion equation described. The potential of myxospermous seeds to affect the ecological services provided by soil is discussed briefly.

We present an approach to modelling interdependent types of vegetation that support different functions in a managed ecosystem. For optimal management, plants that provide economic output (e.g., crops) and those that support ecological functions (e.g., wild plants or ‘weeds’) should coexist in an agroecosystem. To make progress with understanding how such plant communities interact over time, we analyse paired time series data about the cover of crop and weed vegetation in oilseed rape fields. The percentage crop and weed cover were measured every 7–14 days at 128 sites in the UK, covering a wide range of localities and management regimes. To analyze the data, we first cluster the time course profiles of crop cover (using the k -medoids clustering algorithm and the dynamic time warping distance between time series). The clustering revealed five typical clusters of crop cover profiles that differed in terms of rate of increase, lag phase and maximum value, but were largely independent of the type of crop (winter/spring oil seed rape) and the weed management regime. Cluster membership for each crop cover profile was used as an additional independent variable (attribute) in the predictive modelling analysis that followed. We then constructed predictive clustering trees (a generalized form of decision trees) that predict the weed cover profile (time series) from independent (input) variables that include the crop cover cluster, other crops descriptors and environmental variables. The crop cover cluster was more informative in predicting the weed cover profile than any other input variable, including the type of crop and the crop transgenic status (conventional or genetically modified / herbicide tolerant). The approach was successful in identifying the interdependencies between the two types of vegetation. We envisage that it will have plentiful further practical use in relating and interpreting ecological or environmental time series.

Drivers behind food security and crop protection issues are discussed in relation to food losses caused by pests. Pests globally consume food estimated to feed an additional one billion people. Key drivers include rapid human population increase, climate change, loss of beneficial on-farm biodiversity, reduction in per capita cropped land, water shortages, and EU pesticide withdrawals under policies relating to 91/414 EEC. IPM (Integrated Pest Management) will be compulsory for all EU agriculture by 2014 and is also being widely adopted globally. IPM offers a 'toolbox' of complementary crop- and region-specific crop protection solutions to address these rising pressures. IPM aims for more sustainable solutions by using complementary technologies. The applied research challenge now is to reduce selection pressure on single solution strategies, by creating additive/synergistic interactions between IPM components. IPM is compatible with organic, conventional, and GM cropping systems and is flexible, allowing regional fine-tuning. It reduces pests below economic thresholds utilizing key 'ecological services', particularly biocontrol. A recent global review demonstrates that IPM can reduce pesticide use and increase yields of most of the major crops studied. Landscape scale 'ecological engineering', together with genetic improvement of new crop varieties, will enhance the durability of pest-resistant cultivars (conventional and GM). IPM will also promote compatibility with semiochemicals, biopesticides, precision pest monitoring tools, and rapid diagnostics. These combined strategies are urgently needed and are best achieved via multi-disciplinary research, including complex spatio-temporal modelling at farm and landscape scales. Integrative and synergistic use of existing and new IPM technologies will help meet future food production needs more sustainably in developed and developing countries, in an era of reduced pesticide availability. Current IPM research gaps are identified and discussed.

One of the concerns surrounding the import (for food and feed uses or processing) of genetically modified herbicide tolerant (GMHT) oilseed rape is that, through seed spillage, the herbicide tolerance (HT) trait will escape into agricultural or semi-natural habitats, causing environmental or economic problems. Based on these concerns, three EU countries have invoked national safeguard clauses to ban the marketing of specific GMHT oilseed rape events on their territory. However, the scientific basis for the environmental and economic concerns posed by feral GMHT oilseed rape resulting from seed import spills is debatable. While oilseed rape has characteristics such as secondary dormancy and small seed size that enable it to persist and be redistributed in the landscape, the presence of ferals is not in itself an environmental or economic problem. Crucially, feral oilseed rape has not become invasive outside cultivated and ruderal habitats, and HT traits are not likely to result in increased invasiveness. Feral GMHT oilseed rape has the potential to introduce HT traits to volunteer weeds in agricultural fields, but would only be amplified if the herbicides to which HT volunteers are tolerant were used routinely in the field. However, this worst-case scenario is most unlikely, as seed import spills are mostly confined to port areas. Economic concerns revolve around the potential for feral GMHT oilseed rape to contribute to GM admixtures in non-GM crops. Since feral plants derived from cultivation (as distinct from import) occur at too low a frequency to affect the coexistence threshold of 0.9% in the EU, it can be concluded that feral GMHT plants resulting from seed import spills will have little relevance as a potential source of pollen or seed for GM admixture. This paper concludes that feral oilseed rape in Europe should not be routinely managed, and certainly not in semi-natural habitats, as the benefits of such action would not outweigh the negative effects of management.

We investigated the effects of crop sequences on monocotyledon, dicotyledon and total weed seedbank abundance. Using seedbank data sampled from the conventionally cropped part of the GB farm-scale evaluations of genetically modified, herbicide-tolerant (GMHT) crops, we asked whether it is possible to identify crop sequence effects, to identify their duration and to simplify crop sequences into crop management classes with similar effects on weed seedbanks. This work showed that it is possible to detect historical effects of past crops, sown in sequence, on weed seedbanks for up to 3 years and that crop sequences may be simplified to crop management classes describing the season of sowing, crop type and weed target for herbicide application. Model estimates for the seedbanks were validated against an independent, follow-up seedbank data set. The analysis provided abundance estimates that ranged over 3 and 1.7 orders of magnitude for the monocotyledon and dicotyledon weed seedbanks for different crop sequences. This work yields a methodology for estimating seedbank abundance in current crop sequences, potentially allowing sequences to be identified that better reconcile the competing needs for weed control to maintain crop productivity and the demand for increased farmland biodiversity.

Sustainable food production depends critically on the development of crop genotypes that exhibit high yield under reduced nutrient inputs. Rooting traits have been widely advocated as being able to influence optimal plant performance, while breeding-based improvements in yield of spring barley suggest that this species is a good model crop. To date, however, molecular genetics knowledge has not delivered realistic plant ideotypes, while agronomic trials have been unable to identify superior traits. This study explores an intermediate experimental system in which root traits and their effect on plant performance can be quantified. As a test case, four modern semi-dwarf barley varieties, which possess either the ari-e.GP or the sdw1 dwarf allele, were compared with the long-stemmed old variety Kenia under two levels of nutrient supply. The two semi-dwarf types differed from Kenia, exhibiting smaller stem mass and total plant nitrogen (N), and improved partitioning of mass and N to grain. Amongst the semi-dwarfs, the two ari-e.GP genotypes performed better than the two sdw1 genotypes under standard and reduced nutrient supply, particularly in root mass, root investment efficiency, N acquisition, and remobilization of N and mass to grain. However, lack of between-genotype variation in yield and N use efficiency indicated limited potential for exploiting genetic variation in existing varieties to improve barley performance under reduced nutrient inputs. Experimental approaches to test the expression of desirable root and shoot traits are scrutinized, and the potential evaluated for developing a spring barley ideotype for low nutrient conditions.

Dynamics of population density and soil seed bank of weed beet was studied in a 5 year crop rotation consisting of spring barley, and sugar beet. Beside the crop rotation experiment, the seeds of weed beet were studied for their dormancy and viability in soil seed bank over the period of four years. The obtained data indicates that weed beet was able to produce seeds only in sugar beet, but not in barley. In sugar beet, its reproductive potential allows weed beet to restore and increase the soil seed bank of glomerules rapidly. Common infestation of sugar beet is able to persist over more than the 2-year period between repeated introductions of sugar beet in crop rotation. The experiment has also proven the negative effect of weed beet presence on sugar beet yield. The sugar beet root yield decreased of 0.4 t/ha with every 1000 weed beet plants per hectare. The yearly loss of viable seeds was about 75%. The number of surviving seeds decreased exponentially in time. Less than 2% of seeds remained viable after three years in the soil. Seasonal fluctuations of seed dormancy were observed. Seeds were dormant in autumn, lost dormancy in winter and recovered it in late summer.

The diversity and abundance of the within-field seedbank and emerged weed flora, were measured in over 100 fields from conventional, integrated and organic farms across the arable east of Scotland. Both seedbank and emerged flora showed significant responses to a management intensity gradient from farms with high agrochemical inputs and winter cropping to those with no inorganic inputs, spring cropping and mixed farming practices. The emerged weed flora was more affected by recent agrochemical inputs than was the seedbank, which is buffered by the persistence of weed seeds in the soil. The seedbank was more strongly influenced by soil characteristics, such as % organic carbon and % total nitrogen, than by management. Overall farming approach (categorised here as organic, integrated and conventional) appeared to exert a selection pressure on the species composition of the seedbank, building up different communities under the three farming approaches over time. These effects were scale dependent. At a within-field scale, species richness was greatest in organic farms where there was a greater abundance of weeds. At a regional and landscape scale, species richness was greater in integrated and conventional farms. This was particularly evident in integrated farms which represented a greater range of crop types and cropping practices between fields than either conventional of organic farms alone. Increasing the diversity of cropping practices between fields may offer a complementary approach to reducing agrochemical inputs for enhancing arable biodiversity across landscapes.

A functional group approach was developed for plant and invertebrate assemblages from UK arable fields to assess the variation in functional composition of these highly disturbed, managed systems. Data were taken from the Farm-Scale Evaluations (FSE) of genetically modified herbicide-tolerant (GMHT) crops where the impact of management of the GMHT crop has been assessed for winter and spring sown oilseed rape, beet and maize. Twenty plant and 36 invertebrate functional groups were defined according to trophic behaviour and traits that affect resource capture, quality and availability. The functional composition of the plant community was significantly affected by season of sowing, the type of crop sown and, to a lesser extent, herbicide management. The invertebrate community composition was also affected by crop type and sowing season, but not by management. Resource and consumer groups were positively related, and data provide strong evidence for top-down control of herbivore populations. Two main interaction groups were identified within the arable food web: one between omnivores, generalist predators and detritivores, which are positively associated with monocots, and one between omnivores, parasitoids, sap feeders and leaf chewers, which have a stronger association with dicots. Although management has an impact on within-field arable biodiversity, crop type and sowing season have an overriding effect on the functional composition of plant and invertebrate assemblages in arable systems.

Summary The arable plant Capsella bursa-pastoris is phenotypically variable in many life history traits, particularly time from germination to flowering. The hypothesis was investigated that, associated with this variation, there are differences in traits that influence plant quality for insect herbivores. Significant within-species variation was found in plant growth, leaf surface characteristics and tissue nutrient composition among 21 accessions of Capsella. Short flowering time plants exhibited slow vegetative growth, relatively large shoot nitrogen content, high leaf hair densities and differences in phloem composition, compared with long flowering time plants. Insect herbivore response to distinctive trait combinations was assessed on a subset of seven accessions using the phloem-feeding aphids Aphis fabae and Myzus persicae. Variation in aphid performance was small but significant, with 15–25% fewer nymphs produced on plant variants that exhibited greater tissue water content and low tissue C:N ratio (A. fabae) or on variants with less phloem nitrogen (M. persicae). The differential responses exhibited by the two aphid species to the test accessions confirmed that quantifying intraspecific plant variation is a necessary first step in understanding plant functional diversity and its impact on consumers in arable systems.

Weeds are major constraints on crop production, yet as part of the primary producers within farming systems, they may be important components of the agroecosystem. Using published literature, the role of weeds in arable systems for other above-ground trophic levels are examined. In the UK, there is evidence that weed flora have changed over the past century, with some species declining in abundance, whereas others have increased. There is also some evidence for a decline in the size of arable weed seedbanks. Some of these changes reflect improved agricultural efficiency, changes to more winter-sown crops in arable rotations and the use of more broad-spectrum herbicide combinations. Interrogation of a database of records of phytophagous insects associated with plant species in the UK reveals that many arable weed species support a high diversity of insect species. Reductions in abundances of host plants may affect associated insects and other taxa. A number of insect groups and farmland birds have shown marked population declines over the past 30 years. Correlational studies indicate that many of these declines are associated with changes in agricultural practices. Certainly reductions in food availability in winter and for nestling birds in spring are implicated in the declines of several bird species, notably the grey partridge, Perdix perdix . Thus weeds have a role within agroecosystems in supporting biodiversity more generally. An understanding of weed competitivity and the importance of weeds for insects and birds may allow the identification of the most important weed species. This may form the first step in balancing the needs for weed control with the requirements for biodiversity and more sustainable production methods.

An experiment was conducted to test the hypothesis that phenotypes differing in germination rate and the presence or absence of secondary dormancy at low temperature were not genetically different. Seed of oilseed rape was germinated at 4, 10 and 19 degrees C, where selections were made in the percentile ranges 1-10 (early), 45-55 (intermediate) and 91-100 (late). Secondary dormancy occurred only in the late selections at the two lower temperatures. Thermal weighting of curves of cumulative germination on time gave circumstantial evidence that early percentiles were similar at all three temperatures and that seeds with secondary dormancy came largely from later percentiles above the 50th. To test for genetic differentiation between phenotypes, 5'-anchored simple sequence repeat primers were used to generate DNA marker profiles of seedlings raised from seed from each category. Principal coordinate analysis, and more detailed comparisons using the most discriminating markers, confirmed that the early germinators at the three temperatures were not associated with different banding profiles, but seeds entering secondary dormancy, particularly at 10 degrees C, were genetically distinct from germinators at the same temperature. Secondary dormant seeds at low temperature appear to originate mainly from the late germinating seed at higher temperature. Effects of temperature history and the requirement for alternating temperatures to break secondary dormancy were quantified. The results confirm the existence of genetically discrete sub-populations differing in ecologically significant traits.

Recent developments in molecular methods for assessing diversity, particularly the analysis of randomly Despite extensive research for several decades, there amplified polymorphic DNA fragments, have made it remains a lack of understanding of the processes that possible to obtain estimates of intra- and inter-specific determine the dynamics of natural plant communities. diversity from nuclear genomes of natural plant populaIn this paper some current concepts in vegetation tions with relative ease. However, methods for applying dynamics are reviewed and an attempt is made to the results of such analyses to improve our understanding provide a perspective of the way in which data for of the ecology of natural vegetation are still relatively molecular diversity might be used to help in developing poorly developed. This is due, in part, to the diYculties an understanding of population processes. It is pro- which arise in relating molecular marker data to importposed that data from assessments of general popula- ant ecophysiological traits in natural plant populations. tion diversity, and specific ecophysiological traits can The relationship between the traits displayed by indibe used to assess the potential for individual species vidual species and their role in the ecological community to compete and substitute for each other in a is a further poorly researched subject. Recent publications community.

Chapitre 2; International audience; The biological characteristics of a crop together with the way it is managed in the field determine the rate at which genetic material moves by seed and pollen between crops, crop-derived weeds (volunteers), feral plants, and wild relatives. The EU FP6 project, SIGMEA, collated and compared data on the transmission of genetic material in relation to coexistence thresholds for three contrasting species in Europe. The conclusions are: 1) Coexistence will be feasible for maize, because transmission is mostly by pollen flow, which decreases rapidly with distance. 2) Coexistence will also be feasible for sugar beet because, while volunteer beet may be abundant, most crop beet is harvested when vegetative so will not exchange genes during the year of harvest. 3) Coexistence will be difficult or even impossible for oilseed rape, because persistent seed is a major route of transmission. Field management may alleviate the problems of gene transmission in oilseed rape, but will be insufficient to counter the influence of this species' biology.

Grain admixture due to gene flow of oilseed rape (OSR) could be economically damaging. Different strategies are currently used or proposed to manage grain quality, ranging from homogenisation at the silo level to tactical decision rules at the field level. The relevance of these general strategies was appraised in the case of genetically modified (GM) OSR in three contrasted regions in Europe: Beauce Blesoise (France), Schleswig-Flensburg (Germany), and Fife (UK). Field patterns, crop allocation and agricultural practices were derived from existing datasets and complementary field surveys. Then a gene flow simulator was used to assess how the local contexts influenced the grain admixture between GM and non-GM OSR (without separation measures). The simulations showed that grain admixtures in fields followed a leptokurtic curve. While, however, the worst case was similar in the three regions, the median differed greatly depending on contextual factors such as the size and arrangement of fields. Grain admixture very rarely exceeded the 0.9% threshold for non-GM products if assessed at the level of the silo, at which the grains from all non-GM crops were combined, while maintaining crops below the threshold at the field level required management of a few high risk situations. Analysing grain admixtures and commercial risks at different decision levels (field, silo) demonstrated the efficiency of “flexible” as opposed to “rigid” measures, but this technical analysis did not take other criteria like regulatory issues into account.

In a gradualist approach to the introduction of crop biotechnology, the findings of experimentation at one scale are used to predict the outcome of moving to a higher scale of deployment. Movement through scales had occurred for certain genetically modified herbicide-tolerant (GMHT) crops in the UK as far as large-scale field trials. However, the land area occupied by these trials was still1% of the area occupied by the respective non-GM crops. Some means is needed to predict the direction and size of the effect of increasing the area of GMHT cropping on ecological variables such as the diversity among species and trophic interactions. Species-accumulation curves are examined here as a method of indicating regional-scale impacts on botanical diversity from multiple field experiments.Data were used from experiments on the effect of (GMHT) crops and non-GM, or conventional, comparators in fields sown with four crop types (beet, maize, spring and winter oilseed rape) at a total of 250 sites in the UK between 2000 and 2003. Indices of biodiversity were measured in a split-field design comparing GMHT with the farmers' usual weed management. In the original analyses based on the means at site level, effects were detected on the mass of weeds in the three spring crops and the proportion of broadleaf and grass weeds in winter oilseed rape, but not on indices of plant species diversity. To explore the links between site means and total taxa, accumulation curves were constructed based on the number of plant species (a pool of around 250 species in total) and the number of plant functional types (24), inferred from the general life-history characteristics of a species.Species accumulation differed between GMHT and conventional treatments in direction and size, depending on the type of crop and its conventional management. Differences were mostly in the asymptote of the curve, indicative of the maximum number of species found in a treatment, rather than the steepness of the curve. In winter oilseed rape, 8% more species were accumulated in the GMHT treatment, mainly as a result of the encouragement of grass species by the herbicide when applied in the autumn. (Overall, GMHT winter oilseed rape had strong negative effects on both the food web and the potential weed burden by increasing the biomass of grasses and decreasing that of broadleaf weeds.) In maize, 33% more species-a substantial increase-were accumulated in the GMHT than in the conventional, consistent with the latter's highly suppressive weed management using triazine herbicides. In the spring oilseed rape and beet, fewer species (around 10%) were accumulated in the GMHT than the conventional. The GMHT treatments did not remove or add any functional (life history) types, however. Differences in species accumulation between treatments appeared to be caused by loss or gain of rarer species. The generality of this effect was confirmed by simulations of species accumulation in which the species complement at each of 50 sites was drawn from a regional pool and subjected to reducing treatment at each site. Shifts in the species-accumulation parameters, comparable to those measured, occurred only when a treatment removed the rarer species at each site.Species accumulation provided a set of simple curve-parameters that captured the net result of numerous local effects of treatments on plant species and, in some instances, the balance between grass and broadleaf types. The direction of effect was not the same in the four crops and depended on the severity of the conventional treatment and on complex interactions between season, herbicide and crop. The accumulation curves gave an indication of potential positive or negative consequences for regional species pools of replacing a conventional practice with GMHT weed management. In this and related studies, a range of indicators, through which diversity was assessed by both species and functional type, and at both site and regional scales, gave more insight into effects of GMHT treatment than provided by any one indicator.Species accumulation was shown to discriminate at the regional scale between agronomic treatments that had little effect on species number at the field scale. While a comprehensive assessment of GM cropping needs to include an examination of regional effects, as here, the costs of doing this in all instances would be prohibitive. Simulations of diversity-reducing treatments could provide a theoretical framework for predicting the likely regional effects from in-field plant dynamics.Accumulation curves potentially offer a means of linking within-site effects to regional impacts on biodiversity resulting from any change in agricultural practice. To guide empirical measurement, there is a scope to apply a methodology such as individual-based modelling at the field scale to explore the links between agronomic treatments and the relative abundance of plant types. The framework needs to be validated in practice, using species-based and functional taxonomies, the latter defined by measured rather than inferred traits.

The EU project SIGMEA mainly addressed issues in GM coexistence, but many of the data set contributed and analysed by around 22 partners also contained information relevant to the ecological impacts of GM maize (Bt), oilseed rape (HT) and beet. SIGMEA partners carried out some of the largest, most comprehensive and most long running GM crop trials in Europe and so are well placed to synthesise the current state of knowledge on ecolgical impacts. This presentation defines which effects are likely to occur and the size of adverse and beneficial effects (if any) relative to differences among other agricultural practices. It finally suggests improvements that might be made in ecological risk assessment. A summarywill be given of the approach andmain findings on GM impacts from the EU SIGMEA project, which combined the findings and expertise from around 25 research organisations. The potential sources of impact – e.g. direct effect of GM organism, gene movement and persistence, associated management –will be considered for data from field experiments on (primarily) Bt maize and HT oilseed rape.

Grain legumes have declined to a low base in many regions of intensified agriculture yet have the potential both to safeguard food security and satisfy rising ethical demands from food consumers. Here, the scope for legume expansion is examined in a long‐established agricultural region in eastern Scotland where grain legumes declined to

BACKGROUND: High erucic acid oilseed rape (HEAR) was tested as a source crop for estimates of regional geneflow. Two methods to detect HEAR in low erucic acid oilseed rape (LEAR) were compared: real-time quantitative PCR (qPCR) and gas chromatography (GC). RESULTS: Fields (2.5 ha) of a LEAR variety (0.028% EA) in Tayside and Hertfordshire were juxtaposed adjacent to and 1 km distant from a HEAR (44% EA) field. The LEAR variety was a varietal association to ensure high cross-pollination (CP). The methods were highly correlated, measuring between 30% and 0.5% CP. However, the qPCR method became unreliable below 0.5% CP, whereas GC was robust enough to detect raised EA equivalent to one F1 seed in 500 (0.2%). A statistical mixture model was fitted to the distributions of EA in samples in order to assign a CP value to each 500-seed sample. Declines of CP from 30% to < 1%, and EA from 5% to 0.2%, with distance up to 150 m in the near fields was best fitted with a power function. The combined mean EA for both far fields was 0.11%, well above the background LEAR value of 0.028%, and mean CP was 0.36%. CONCLUSIONS: The GC method of detection raised %EA should be a reliable and high-throughput means of estimating %CP between fields, provided the %EA of single F1 seed in receptor fields is measured to confirm the presence of F1 seed. Copyright © 2008 Society of Chemical Industry