Arable Systems Research Articles

Evaluating a trait-based approach to compare natural enemy and pest communities in agroforestry vs. arable systems.

Diversified farming systems, for example those that incorporate agroforestry elements, have been proposed as a solution that could maintain and improve multiple ecosystem services. However, habitat diversification in and around arable fields has complex and inconsistent effects on invertebrate crop pests and their natural enemies. This hinders the development of policy recommendations to promote the adoption of such management strategies for the provision of natural pest control services. Here, for the first time, we conducted a trait-based approach to investigate the effect of farming system on plant, invertebrate herbivore, and invertebrate natural enemy communities. We then evaluated this approach by comparing the results to those generated using a traditional taxonomic approach. At each of three working farms, we sampled within an agroforestry field (a diverse farming system comprising alleys of arable crops separated by tree rows), and within a paired non-diversified area of the farm (arable control field). Each of 96 sample points was sampled between 8 and 10 times, yielding 393,318 invertebrate specimens from 344 taxonomic groups. Diet specialization or granivory, lack of a pupal stage, and wing traits in invertebrates, along with late flowering, short flowering duration, creeping habit, and perenniality in plants, were traits more strongly associated with agroforestry crop alleys than the arable control fields. We hypothesize that this is a result of reduced habitat disturbance and increased habitat complexity in the agroforestry system. Taxonomic richness and diversity were higher in the agroforestry crop alleys compared to the arable control fields, but these effects were stronger at lower trophic levels. However, functional trait diversity of natural enemies was significantly higher in the agroforestry crop alleys than the arable control fields, suggesting an improved level of biocontrol, which was not detected by traditional diversity metrics. Of eight key pest taxa, three were significantly suppressed in the agroforestry system, while two were more abundant, compared to the arable control fields. Trait-based approaches can provide a better mechanistic understanding of farming system effects on pests and their natural enemies, therefore we recommend their application and testing in future studies of diversified farming systems.

Arable lands under the pressure of multiple land degradation processes. A global perspective

While agricultural systems are a major pillar in global food security, their productivity is currently threatened by many environmental issues triggered by anthropogenic climate change and human activities, such as land degradation. However, the planetary spatial footprint of land degradation processes on arable lands, which can be considered a major component of global agricultural systems, is still insufficiently well understood. This study analyzes the land degradation footprint on global arable lands, using complex geospatial data on certain major degradation processes, i.e. aridity, soil erosion, vegetation decline, soil salinization and soil organic carbon decline. By applying geostatistical techniques that are representative for identifying the incidence of the five land degradation processes in global arable lands, results showed that aridity is by far the largest singular pressure for these agricultural systems, affecting ~40% of the arable lands' area, which cover approximately 14 million km2 globally. It was found that soil erosion is another major degradation process, the unilateral impact of which affects ~20% of global arable systems. The results also showed that the two degradation processes simultaneously affect an additional ~7% of global arable lands, which makes this synergy the most common form of multiple pressure of land degradative conditions across the world's arable areas. The absolute statistical data showed that India, the United States, China, Brazil, Argentina, Russia and Australia are the most vulnerable countries in the world to the various pathways of arable land degradation. Also, in terms of percentages, statistical observations showed that African countries are the most heavily affected by arable system degradation. This study's findings can be useful for prioritizing agricultural management actions that can mitigate the negative effects of the two degradation processes or of others that currently affect many arable systems across the planet.

Grassland Management Affects Vegetation Structure, Bats and Their Beetle Prey

Agricultural grasslands provide vital habitats for many species. Yet despite representing a significant proportion of European land use, they are disproportionately understudied compared to arable systems. Increases in productivity and intensification have led to changes in management practices, which are likely to affect grassland habitats and the ecological communities that they support. This study simultaneously monitored three trophic levels to assess the impacts of permanent versus temporary pasture (leys) on vegetation composition, carabid and dung beetle abundance, and the activity of beetle-feeding bats. Leys had lower abundances of soil-inhabiting dung beetles, which may be explained by the more recent exposure to tilling compared with permanent pasture. Beetle-feeding bat activity was also greater in leys, with positive relationships between E. serotinus activity and Onthophagus abundance across both pasture types. However, the lack of any positive relationships between beetle-feeding bat activity and Aphodius, a well-known prey genus, suggests that other key prey orders (Lepidoptera) may be of more influence on bat activity. As well as the management of pasture, differences in cattle management between pasture types can have a significant impact on vegetation and soil structure, which influence invertebrate communities and potentially dictate habitat suitability for bats.

Significant structural evolution of a long‐term fallow soil in response to agricultural management practices requires at least 10 years after conversion

AbstractAgricultural practices can have significant effects on the physical and biological properties of soil. The aim of this study was to understand how the physical structure of a compromised soil, arising from long‐term bare‐fallow management, was modified by adopting different field management practices. We hypothesized that changing agricultural practices from bare‐fallow to arable or grassland would influence the modification of pore structure via an increase in porosity and pore connectivity, and a more homogenous distribution of pore sizes, and that this change exerts a rapid evolution of soil structure following conversion. Soil aggregates (<2 mm) collected in successive years from field plots subjected to three contrasting managements were studied: bare‐fallow, bare‐fallow converted to arable, and bare‐fallow converted to grassland. Soil structure was assessed by X‐ray computed tomography on the aggregates at 1.5 μm resolution, capturing detail relevant to soil biophysical processes. The grassland system increased porosity, diversity of pore sizes, pore connectivity and pore‐surface density significantly over the decade following conversion. However, measured at this resolution, the evolution of most of these metrics of soil structure required approximately 10 years post‐conversion to show a significant effect. The arable system did not influence soil structural evolution significantly. Only pore size distribution was modified in grassland in a shorter time frame (2 years post‐conversion). Hence, evolution of soil structural characteristics appears to require at least a decadal timescale following conversion to grassland.Highlights The physical structure of a compromised soil was modified by adopting plant‐based field management practices. Conversion to grassland increased pore size diversity after 2 years. Porosity, pore connectivity and pore surface density showed a significant modification between 7 and 10 years after conversion.

Recent spatio-temporal changes of land sensitivity to degradation in Romania due to climate change and human activities: An approach based on multiple environmental quality indicators

The analysis of land degradation based on sensitivity models has become a widely used scientific method for understanding the spatial pattern of this complex environmental process that is affecting numerous countries globally, including Romania. However, most specialized studies have been dealing with a static analysis of land sensitivity to degradation, and studies focusing on the process from a dynamic perspective are extremely rare or even lacking altogether in certain states, such as Romania. Given this knowledge gap, the study performs the first dynamic analysis of land sensitivity to degradation across Romania, in the key-period 1990–2018, marked by considerable changes in climate and anthropic driving forces of land degradation. This approach is based on the analysis of spatio-temporal trends of land susceptibility to degradation over the past three decades, based on the Land Degradation Sensitivity Index (LDSI) geospatial tool, computed for the years 1990 and 2018, and analyzed in detail in terms of the cartographic and statistical differences between the two analyzed years. Our investigations showed an expansion of ~1300 km2 (<1% of Romania’s territory) of the LDSI classes critically sensitive to degradation, the national spatial footprint of which was estimated in 1990 at ~67,300 km2 (28.4%), and at ~68,600 km2 (29%) in 2018. Although this recent net expansion does not seem to be exceedingly high, our results are in fact alarming considering the very high territorial differences in the intensification of land degradative conditions throughout the country. The most apparent such territorial discrepancies were detected in Romania’s extra-Carpathian regions, which, post-1990, seem to have become the most susceptible to degradation nationally, amid intense climate change (intensification of aridity) and anthropogenic changes (various changes in land use/cover classes and other unsustainable anthropogenic activities). These findings are alarming, considering, first and foremost, the large-scale presence of arable systems in these regions of the country, the agricultural productivity of which can be seriously eroded due to the intensification of land degradation. Our results can be useful for a more effective implementation of measures against land degradation, which can be applied throughout the country as a priority based on the recent accelerating national trends of land degradation.

Measures to increase the nitrogen use efficiency of European agricultural production

Inputs of nitrogen to agricultural production systems are necessary to produce food, feed and fibre, but nitrogen (N) losses from those systems represent a waste of a resource and a threat to both the environment and human health. The nitrogen use efficiency (NUE) of an agricultural production system can be seen as an indicator of the balance between benefits and costs of primary food, feed and fibre production. Here, we used modelling to follow the fate of the virgin N input to different production systems (ruminant and granivore meat, dairy, arable), and to estimate their NUE at the system scale. We defined two ruminant meat production systems, depending on whether the land places constraints on farming practices. The other production systems were dairy, granivore and arable production on land without constraints. Two geographic regions were considered: Northern and Southern Europe. Measures to improve NUE were identified and allocated to Low, Medium and High ambition groups, with Low equating to the current situation in Europe for production systems that are broadly following good agricultural practice.The NUE of the production systems was similar to or higher in Southern than Northern Europe, with the maximum technical NUEs if all available measures are implemented were for North and South Europe, respectively, 82% and 92% for arable systems, 71% and 80% for granivores, 50% and 36% for ruminant meat production on constrained land, 53% and 55% for dairy production on unconstrained land and 46% and 62% for ruminant meat production on unconstrained land. The values for NUE found here tend to be higher than reported elsewhere, possibly due to the accounting for long-term residual effects of fertiliser and manure in our method. The greatest increase in NUE with the progressive implementation of higher ambition measures was in unconstrained granivore systems and the least was in constrained ruminant meat systems, reflecting the lower initial NUE of granivore systems and the larger number of measures applicable to confined livestock systems.Our work supports use of NUE as an indicator of the temporal trend in the costs and benefits of existing agricultural production systems, but highlights problems associated with its use as a sustainability criteria for livestock production systems.For arable systems, we consider well-founded the NUE value of 90% above which there is a high risk of soil N depletion, provided many measures to increase NUE are employed. For systems employing fewer measures, we suggest a value of 70% would be more appropriate.We conclude that while it is feasible to calculate the NUE of livestock production systems, the additional complexity required reduces its value as an indicator for benchmarking sustainability in practical agriculture.

Erratum to 'Measuring the unmeasurable? A method to quantify adoption of integrated pest management practices in temperate arable farming systems'.

Erratum to 'Measuring the unmeasurable? A method to quantify adoption of integrated pest management practices in temperate arable farming systems'.

Agriculture intensification reduces plant taxonomic and functional diversity across European arable systems

Abstract Agricultural intensification is one of the main drivers of species loss worldwide, but there is still a lack of information about its effect on functional diversity of arable weed communities. Using a large‐scale pan European study including 786 fields within 261 farms from eight countries, we analysed differences in the taxonomic and functional diversity of arable weeds assemblages across different levels of agricultural intensification. We estimated weed species frequency in each field, and collected species' traits (vegetative height, SLA and seed mass) from the TRY plant trait database. With this information, we estimated taxonomic (species richness), functional composition (community weighted means) and functional diversity (functional richness, evenness, divergence and redundancy). We used indicators of agricultural management intensity at the individual field scale (e.g. yield, inputs of nitrogen fertilizer and herbicides, frequency of mechanical weed control practices) and at the landscape scale surrounding the field (i.e. number of crop types, mean field size and proportion of arable land cover within a radius of 500 m from the sampling points). The effects of agricultural intensification on species and functional richness at the field scale were stronger than those of intensification at the landscape scale, and we did not observe evidence of interacting effects between the two scales. Overall, assemblages in more intensified areas had fewer species, a higher prevalence of species with ruderal strategies (low stature, high leaf area, light seeds), and lower functional redundancy. Maintaining the diversity of Europe's arable weed communities requires some simple management interventions, for example, reducing the high intensity of field‐level agricultural management across Europe, which could be complemented by interventions that increase landscape complexity. A free Plain Language Summary can be found within the Supporting Information of this article.

Temperate agroforestry systems provide greater pollination service than monoculture

Insect pollination is a globally important ecosystem service, contributing to crop yields, production stability and the maintenance of wild plant populations. Ironically, agriculture is one of the major global drivers of wild insect pollinator decline. At the same time, increasing human population is driving ever greater demands on crop production. Agroforestry (AF) – a more diverse farming system integrating woody and agricultural crops – can theoretically reconcile high production with provision of ecosystem services such as pollination. However, empirical studies of pollination in temperate AF systems are almost entirely lacking. We sought to fill this knowledge gap by assessing whether AF can provide increased pollination service compared to monoculture (MC) systems. Six UK sites, each containing an AF and a MC system, were studied over three years. Wild pollinator abundance and diversity were used as proxies for the magnitude and stability, respectively, of the pollinating community. We also directly measured pollination service as seed set in a wild plant phytometer. We found that temperate AF systems can provide greater pollination service than MC: AF treatments had twice as many solitary bees and hoverflies, and in arable systems 2.4 times more bumblebees, than MC treatments. AF also had 4.5 times more seed set compared to MC in one of the two years. At 40% of site-by-year sampling units, species richness of solitary bees was on average 10.5 times higher in AF treatments. This provides evidence in favour of the expectation that AF systems can support higher pollinator richness, and therefore greater potential stability, of pollination service. For the other sampling units, and for bumblebees (Bombus spp.), there was no treatment effect on species richness. Further work is needed to investigate the effect of AF on species richness and its mechanistic basis. Our results also highlight the importance of AF system design, ensuring that ecosystem services outcomes are explicitly planned at the design stage. We suggest that AF has a role to play in improving the sustainability of modern farming and in mitigating the ongoing loss of wild pollinating insects, which is strongly driven by prevailing agricultural practices.

Microorganisms and nutrient stoichiometry as mediators of soil organic matter dynamics

Microbial detritus contributes substantially to the soil organic matter (SOM). Analysis of global literature indicated that microbial detritus carbon (C) contributed 59 and 64% of total soil C in arable agricultural and grassland systems respectively, with a 2.5% greater contribution of bacterial-derived detritus in grasslands and with no difference in the proportional contribution of fungal detritus. Total soil C and nitrogen (N) content was higher in grasslands with an average of 2.8 and 1.6 g N kg−1 soil and 28.8 and 16.8 g C kg−1 soil in grassland and arable systems, respectively. Soil N content explained 11 to 28% of the variance in microbial detritus contribution to soil C. Further, total soil N and C content explained more variance than other factors which are commonly considered to mediate SOM content including precipitation, acidity and clay. Microbial biomass C assimilation and re-metabolism of SOM are affected by nutrient supply and the dissimilarity of the C to N, phosphorus (P) and sulfur (S) ratios between fresh organic matter (FOM), SOM and microorganisms (C:N:P:S 10,000:261:32:48, 10,000:833:200:143, and 10,000:1,494:458:154, respectively). In agricultural systems, stoichiometrically balanced nutrient addition to FOM can increase C transfer to SOM by 6 to 52% and importantly reduce the mineralization of pre-existing SOM by 24 to 50%. Future research to quantify economic and environmental implications is warranted with need for a paradigm shift in thinking to focus on the nutrient requirements of the whole soil–plant system rather than the agronomic requirements of crops alone.

Whole system valuation of arable, agroforestry and tree-only systems at three case study sites in Europe

There is an increasing demand to study the long-term effects of land use from both local farm and wider societal and environmental perspectives. This study applied an approach to evaluate both the financial profitability of arable, agroforestry, and tree-only systems and the wider societal benefits over a period of 30-60 years. The biophysical inputs and yields from the three systems were modelled for three case study sites in the United Kingdom, Spain, and Switzerland, using a tree and crop simulation model called Yield-SAFE. A bio-economic model called Farm-SAFE was then used to compare the financial (EAVF) and economic (or societal) equivalent annual values (EAVE) by including monetary values for five environmental externalities: carbon dioxide emissions, carbon sequestration, soil erosion by water, and nitrogen and phosphorus balances. Across the three case studies, arable farming generated higher farm incomes than the agroforestry or tree-only systems, but the arable systems also created the greatest environmental costs. By comparison the agroforestry and tree-only systems generated lower CO2 emissions and sequestered more carbon. Applying monetary values to the environmental externalities meant that the EAVE of the agroforestry and tree-only systems were greater or similar to that for the arable system in the UK case study. In Spain, the slow predicted growth of the trees meant that, even after including the environmental externalities, the arable system created greater societal benefit than the agroforestry and tree-only systems. In Switzerland, including the environmental externalities increased the attraction of the tree-only system, but the high subsidies for arable and agroforestry systems meant that the EAVE for the agroforestry and arable systems were the most attractive from a farmer’s perspective. A breakeven analysis was used to determine the environmental externality values at which the agroforestry and tree-only systems produced the same societal return as the arable system in each case study. In the UK, a carbon price of ₠16 (t CO2)-1 allowed the EAVE of the agroforestry system to attain parity with the arable EAVE. In both the UK and Spain, an environmental nitrogen cost of ₠3-6 (kg N)-1 was sufficient for the EAVE of the agroforestry and tree-only systems to match those of arable farming. Because trees on farms provide ‘‘economies of multifunction’’ for environmental benefits, the breakeven values will be less if environmental benefits are considered together as packages. The described approach provides a method for governments and others to examine the cost effectiveness of new agri-environment measures.

Nitrous Oxide Emissions and Methane Uptake from Organic and Conventionally Managed Arable Crop Rotations on Farms in Northwest Germany

Land-use extensification by shifting from conventional to organic arable farming is often discussed as a measure for reducing greenhouse gas (GHG) emissions from agricultural land. Doubts about the benefits arise when emissions are calculated per product unit, particularly where high yields are possible under conventional management. Among the non-CO2 GHG emissions, nitrous oxide (N2O) is the main contributor from arable land and is controlled by soil type, environmental conditions and management. In order to investigate how land-use change from conventional to organic farming would perform under highly productive site conditions in northwest Germany, and how this would affect the important greenhouse gases N2O and methane (CH4), an on-farm field research was conducted over two experimental years. Two site-specific organic crop rotations, (i) with 25% legumes (grass + clover - winter wheat – winter rye – oats) and (ii) with 40% legumes (grass + clover – winter wheat – winter rye – spring field peas – winter rye), were compared with (iii) a conventional arable rotation (winter oilseed rape – winter wheat – winter wheat – sugar beet – winter wheat) and two reference systems, (iv) extensive grassland and (v) a beech forest), which were chosen as the baseline. The results showed that organic farming had lower N2O emissions of 0.7 N2O–N ha−1 year−1 than the conventional rotation, with 2.1 kg N2O–N ha−1 year−1 (p &lt; 0.05), but higher emissions than the extensive grassland (0.3 kg N2O ha−1 year−1) and beech forest (0.4 kg N2O ha−1 year−1). CH4 emissions were a negligible part of total GHG emissions (as CO2 equivalents) in the two arable systems, and considerable uptake of CH4 from the forest soils showed this was a GHG sink in the first experimental year. Organic systems produced up to 40% lower crop yields, but the emissions per product unit in rotation (iii) was not superior to (ii) during the two experimental years. Thus, arable organic farming showed the ability to produce agricultural commodities with low N2O emissions per unit area, and no differences in product-related emissions compared with conventional farming. Conventional and organic systems both showed potential for further mitigation of N2O emissions by controlling the field level nitrogen surplus to a minimum, and by the optimized timing of the removal of the grass–clover ley phase.

Soil health cluster analysis based on national monitoring of soil indicators

AbstractA major challenge in soil science is to monitor and understand the state and change of soils at a national scale to inform decision making and policy. To address this, there is a need to identify key parameters for soil health and function and determine how they relate to other parameters, including traditional soil surveys. Here we present a national‐scale dataset of topsoil sampled as part of a wider agri‐environment monitoring scheme in Wales, UK. Over 1,350 topsoils (0–15 cm) were sampled across a very wide range of habitats and a range of physical, chemical and biological soil quality indicators were measured. We show consistent differences in soil physicochemical properties across habitat types, with carbon decreasing and pH increasing across the habitat productivity gradient from bogs through woodlands and grasslands to arable systems. The soils within our dataset are largely within the limits identified as important for supporting habitat function, with the exception of excessive phosphate levels in mesotrophic grassland. Cluster detection methods identified four soil functional classes based on measured topsoil properties, which were more related to habitat type than the genesis‐based soil classification from soil maps. These soil functional classes can be interpreted as phenoforms within the soil genoforms found by traditional soil classification. This shows the importance of land‐use management in determining the soil health and functional capacity of soils. Our work provides an account of the current state of soil health in Wales, its relationship to soil function and a baseline for future monitoring to track changes against agri‐environment and other policy targets.HighlightsWe measured soil physicochemical properties in ~1,350 sites in a variety of temperate habitatsThere was a strong gradient in soil carbon and pH, with other variables being correlated with theseMesotrophic grassland sites had phosphate levels above the identified limit for good functioningSoil classes from topsoil properties were more related to land use than soil map classifications

Using a meta-analysis approach to understand complexity in soil biodiversity and phosphorus acquisition in plants

Current soil phosphorus (P) management is neither environmentally nor economically sustainable. Soil biodiversity has been offered as a solution to unsustainable land management and to promote ecosystem service provision. We know soil biology is instrumental in plant access to soil P, but specific effects of biological complexity, (used here to describe the number of links between different organisms), under different P levels on plant productivity are not well understood. We conducted a meta-analysis on relevant literature, which reported the response of terrestrial plants of economic and anthropogenic importance to P conditions, and controlled for biological treatments across different land-uses (arable, grassland and woodland). We hypothesised that: 1) in arable systems increased biological complexity will enhance plant productivity; 2) in perennial systems such as grassland and woodlands, increasing biological complexity will have no effect; 3) increasing the fertility of the system by addition of P fertiliser will reduce any benefits of biological complexity. We found that soil organisms are not always beneficial to plant shoot biomass, but that the effects of - and interaction among - bacteria, protozoa, nematodes, mycorrhizae, collembola and earthworms differ in their impact on plant biomass (positive or negative) dependent on the presence of other community members, P-level status and time. These findings bring into question existing frameworks that link below-ground biodiversity with above-ground plant productivity. We recommend further experimental work be conducted, which controls for land-use, P status, and soil biological composition and complexity. Such work should be followed by future systematic reviews, which could pragmatically inform more tailored biological management for plant P requirements, land-use and ecosystem service provision. To enable further meta-analyses of this type we recommend habitual inclusion of sufficient experimental detail and data, as a prerequisite for publication and a useful way to utilise increased online publication space.

Using long-term datasets to assess the impacts of dietary exposure to neonicotinoids on farmland bird populations in England.

Over the last 20 years, a new group of systemic insecticides–the neonicotinoids—has gained prominence in arable systems, and their application globally has risen year on year. Previous modelling studies using long-term data have suggested that neonicotinoid application has had a detrimental impact on bird populations, but these studies were either limited to a single species or neglected to analyse specific exposure pathways in conjunction with observed population trends. Using bird abundance data, neonicotinoid usage records and cropping data for England at a 5x5 km resolution, generalised linear mixed models were used to test for spatio-temporal associations between neonicotinoid use and changes in the populations of 22 farmland bird species between 1994 and 2014, and to determine whether any associations were explained by dietary preferences. We assigned farmland bird species to three categories of dietary exposure to neonicotinoids based on literature data for species diets and neonicotinoid residues present in dietary items. Significant estimates of neonicotinoid-related population change were obtained for 13 of the 22 species (9 positive effects, 4 negative effects). Model estimates for individual species were not collectively explained by dietary risk categories, so dietary exposure to neonicotinoids via ingestion of treated seeds and seedlings could not be confirmed as a causal factor in farmland bird declines. Although it is not possible to infer any generic effect of dietary exposure to neonicotinoids on farmland bird populations, our analysis identifies three species with significant negative estimates that may warrant further research (house sparrow Passer domesticus, skylark Alauda arvensis and red-legged partridge Alectoris rufa). We conclude that there was either no consistent effect of dietary exposure to neonicotinoids on farmland bird populations in England, or that any over-arching effect was not detectable using our study design. The potential for indirect effects of insecticide use on bird populations via reduced food availability was not considered here and should be a focus for future research.

Effect of legume and legume-festulolium mixture and their mulches on cereal yield and soil quality in organic farming

ABSTRACT Research was conducted to determine the effects of perennial legume and their mulches on cereal grain yield and the alterations to clay loam Cambisol properties. The perennial legumes (Trifolium pratense L., Medicago sativa L.) as well as their mixtures with festulolium (x Festulolium) were studied in conjunction with their aboveground biomass management methods: removal from the field (cut twice for forage), mixed management (the first cut was for forage, the second and third cuts were mulched) and mulching (four times) in an organic arable farming system. Mulching of legumes biomass resulted in a higher total nitrogen (N) used for green manure. A similar amount of N was accumulated for lucerne and lucerne-festulolium mulch when using mulching and mixed management. Legumes used for mulching caused the amount of mineral N in soil to increase in late autumn (62.7–82.9 kg ha–1) and decrease in spring (39.5–64.0 kg ha–1). This mineral N had a positive impact on crop yield (r = 0.68–0.71*); however, mineral N in autumn had a negative impact on soil sustainable organic compounds (r = −0.71*). The results indicate that the most suitable treatment was the legume-festulolium mixture, which used the biomass under mixed management.

Aphids Influence Soil Fungal Communities in Conventional Agricultural Systems.

Arbuscular mycorrhizal fungi (AMF) form symbioses with the roots of most plant species, including cereals. AMF can increase the uptake of nutrients including nitrogen (N) and phosphorus (P), and of silicon (Si) as well as increase host resistance to various stresses. Plants can simultaneously interact with above-ground insect herbivores such as aphids, which can alter the proportion of plant roots colonized by AMF. However, it is unknown if aphids impact the structure of AMF communities colonizing plants or the extent of the extraradical mycelium produced in the soil, both of which can influence the defensive and nutritional benefit a plant derives from the symbiosis. This study investigated the effect of aphids on the plant-AMF interaction in a conventionally managed agricultural system. As plants also interact with other soil fungi, the non-AMF fungal community was also investigated. We hypothesized that aphids would depress plant growth, and reduce intraradical AMF colonization, soil fungal hyphal density and the diversity of AM and non-AM fungal communities. To test the effects of aphids, field plots of barley enclosed with insect proof cages were inoculated with Sitobion avenae or remained uninoculated. AMF specific and total fungal amplicon sequencing assessed root fungal communities 46 days after aphid addition. Aphids did not impact above-ground plant biomass, but did increase the grain N:P ratio. Whilst aphid presence had no impact on AMF intraradical colonization, soil fungal hyphal length density, or AMF community characteristics, there was a trend for the aphid treatment to increase vesicle numbers and the relative abundance of the AMF family Gigasporaceae. Contrary to expectations, the aphid treatment also increased the evenness of the total fungal community. This suggests that aphids can influence soil communities in conventional arable systems, a result that could have implications for multitrophic feedback loops between crop pests and soil organisms across the above-below-ground interface.

Modeling soil organic carbon evolution in long-term arable experiments with AMG model

Reliable models predicting soil organic carbon (SOC) evolution are required to better manage cropping systems with the objectives of mitigating climate change and improving soil quality. In this study, data from 60 selected long-term field trials conducted in arable systems in France were used to evaluate a revised version of AMG model integrating a new mineralization submodel. The drivers of SOC evolution identified using Random Forest analysis were consistent with those considered in AMG. The model with its default parameterization simulated accurately the changes in SOC stocks over time, the relative model error (RRMSE = 5.3%) being comparable to the measurement error (CV = 4.3%). Model performance was little affected by the choice of plant C input estimation method, but was improved by a site specific optimization of SOC pool partitioning. AMG shows a good potential for predicting SOC evolution in scenarios varying in climate, soil properties and crop management.

Off‐site impacts of soil erosion and runoff: Why connectivity is more important than erosion rates

AbstractOff‐site impacts of soil erosion are of greater social and economic concern in Western Europe than on‐site impacts. They fall into two related categories: muddy flooding of properties and ecological impacts on watercourses because of excessive sedimentation and associated pollutants. Critical to these impacts is the connectedness of the runoff and sediment system between agricultural fields and the river system. We argue that well‐connected systems causing off‐site damage are not necessarily related to areas of high erosion rates; emphasis should therefore be on the way in which connections occur. In temperate, arable systems, important elements of connectivity are anthropogenic in origin: roads, tracks, sunken lanes, field drains, ditches, culverts and permeable field boundaries. Mapping these features allows us to understand how they affect runoff and modify its impacts, to design appropriate mitigation measures and to better validate model predictions. Published maps (digital and paper) do not, by themselves, give sufficient information. Field mapping and observation, aided by remote sensing, are also necessary.

Simulated seawater flooding reduces oilseed rape growth, yield and progeny performance.

Of the many threats to global food security, one of the most pressing is the increased incidence of extreme weather events. In addition to extreme rainfall, a combination of global sea level rise and storm surge is likely to result in frequent episodes of seawater flooding in arable systems along low-lying coasts. Our aim was to elucidate the effects of simulated seawater and freshwater flooding on the survival, growth and reproductive potential of four cultivars of the important seed crop, Brassica napus [canola, or oilseed rape (OSR)]. Established plants were exposed to 24 or 96 h freshwater or seawater root zone immersion (with a no immersion 'control'). Initial post-treatment performance over 7 weeks was quantified using dry weight biomass. A second group of plants, cultivated until maturity, were used to quantify reproductive yield (siliqua and seed number, and seed size) and subsequent progeny performance (germination and seedling growth). Oilseed rape growth and reproductive responses were unaffected by freshwater, but seawater negatively affected growth and siliqua number for all cultivars, and seed mass for two ('Agatha' and 'Cubic'). In addition to impacts on crop yield, the growth of seedlings cultivated from seed collected from maternal plants subjected to seawater immersion was also reduced. Our results demonstrate the potential impact of seawater inundation on coastal cropping systems; although OSR may survive acute saline flooding, there are longer term impacts on growth and yield for some cultivars. The threat may necessitate changes in land-use practice and/or the development of salt-tolerant cultivars to maintain economically viable yields. In addition, by evidencing a hitherto unknown effect on reproductive performance (i.e. reduced seed yield) and subsequent seedling growth, our study highlights an important potential impact of coastal flooding on plant community dynamics for (semi-) natural habitats.