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Enhancing diversity within crop systems can have benefits including increased resource use efficiency and productivity, and increased control of weeds, pests and diseases. Some benefits are expected to operate through biodiversity-driven insurance effects, whereby enhanced diversity increases the chance that a system component can compensate for the impacts of adverse environmental conditions. Studies of insurance effects in natural and agricultural systems have provided equivocal results. As insurance effects are expected to play a key role in helping to maintain crop production in more variable future climates (for example under periodic drought), it is essential to know when and how they operate and interact with other potentially beneficial biodiversity-function effects. Using barley as a model crop, and pot-based plant communities, we studied the interactive effects of barley cultivar diversity and drought stress on plant productivity and the response of agricultural weeds, fungal disease, and aphids. Drought reduced barley and weed biomass, but there were no interactive effects of drought and cultivar diversity on plant productivity. Increased cultivar diversity enhanced weed suppression, potentially as a result of reduced functional space availability, and reduced disease severity on a susceptible cultivar; these effects were consistent irrespective of drought. Aphid responses were more complex, with idiosyncratic response patterns on individual cultivars. Overall, we found no evidence of an insurance effect of enhanced cultivar diversity for the negative impact of drought on crop productivity, but our results indicate that other positive biodiversity effects (weed and disease suppression) are maintained under drought. However, it is clear that not all potentially-beneficial biodiversity effects respond in the same manner. Field trials are now needed to explore whether a range of responses also occur in crop field settings, whether these can be expected to occur predictably under a range of environmental conditions, and how these then impact on crop production. [ABSTRACT FROM AUTHOR]

• Increased crop diversity and reduced management intensity promote arthropods. • Pollinators and natural enemies, but not all herbivores, benefit from intercropping. • Mostly, total grain yield is higher in mixtures than in monocultures. • Intercropping can obtain high yields and increase arthropod abundance and diversity. Arthropod diversity of different taxonomic groups and ecosystem services are declining, yet current measures to counteract losses are often restricted to small areas of land or field margins, particularly in agricultural systems. At the same time, large areas of land will be required to feed a growing global population. Intercropping has been proposed as a potential solution to maximize both biodiversity and yield at large scale, but experimental evidence is scarce. In a three-year field experiment, we manipulated crop diversity and management intensity in a cereal-legume intercropping experiment in Germany, where 50% of wheat was replaced by faba beans. We measured arthropod abundance and diversity of different functional groups (pollinators, natural enemies, herbivores) and crop yield. We found that increasing crop diversity increased abundance and diversity of arthropods. Notably, pollinator and natural enemy abundances increased in intercropped systems. Low management intensity generally had positive effects on arthropod abundance and especially on pollinator diversity, indicating benefits of reduced inputs of fertilizers and herbicides. While wheat yield was higher in monocultures and for high management intensity, total grain yield of the intercrop (indicated by land equivalent ratio) was higher in mixtures. We found that trade-offs were stronger between arthropod diversity and wheat yield than between arthropod abundance and wheat yield. Specialist wheat herbivores and generalist herbivores were more abundant at higher wheat yields. Conversely, pollinator and natural enemy diversity were negatively associated with wheat yield. Our results show that diversification can promote both higher yields and greater diversity of arthropods. Intercropping can thus be an opportunity to support biodiversity without risking significant yield losses. [ABSTRACT FROM AUTHOR]

The principal dietary source to humans of the essential cationic mineral elements potassium, magnesium and calcium is through edible plants. The accumulation of these elements in edible portions is the product of selective transport processes catalysing their short-distance and long-distance movement within a plant. In this article we review recent work describing the identification and characterisation of the molecular mechanisms catalysing the uptake and distribution of potassium, magnesium and calcium between organs, cell types and subcellular compartments. Although potassium and magnesium are redistributed effectively within the plant, calcium concentrations in phloem-fed tissues, such as fruits, seeds and tubers, are generally low. However, limitations to the redistribution of mineral elements within the plant, and its consequences for the biofortification of edible crops, can be overcome by appropriate mineral fertilisation and plant breeding strategies. The techniques of ionomics can help identify better genotypes. [Copyright &y& Elsevier]

Herbivorous insect pests living in the soil represent a significant challenge to food security given their persistence, the acute damage they cause to plants and the difficulties associated with managing their populations. Ecological research effort into rhizosphere interactions has increased dramatically in the last decade and we are beginning to understand, in particular, the ecology of how plants defend themselves against soil-dwelling pests. In this review, we synthesise information about four key ecological mechanisms occurring in the rhizosphere or surrounding soil that confer plant protection against root herbivores. We focus on root tolerance, root resistance via direct physical and chemical defences, particularly via acquisition of silicon-based plant defences, integration of plant mutualists (microbes and entomopathogenic nematodes, EPNs) and the influence of soil history and feedbacks. Their suitability as management tools, current limitations for their application, and the opportunities for development are evaluated. We identify opportunities for synergy between these aspects of rhizosphere ecology, such as mycorrhizal fungi negatively affecting pests at the root-interface but also increasing plant uptake of silicon, which is also known to reduce herbivory. Finally, we set out research priorities for developing potential novel management strategies. [ABSTRACT FROM AUTHOR]

• APSIM was calibrated and validated for pure cultures of wheat and faba bean. • APSIM was evaluated for wheat-faba bean pure cultures and intercrops in Europe. • APSIM reproduced pure culture aboveground dry matters and, for wheat, yields. • APSIM overestimates faba bean performance relative to wheat in intercrops. • APSIM must incorporate an alternative approach to simulate height growth. Cereal-legume intercropping can increase yields, reduce fertilizer input and improve soil quality compared with pure culture. Designing intercropping systems requires the integration of plant species trait selection with choice of crop configuration and management. Crop growth models can facilitate the understanding and prediction of the interactions between plant traits, crop configuration and management. However, currently no existing crop growth model has been calibrated and tested for cereal-legume intercrops throughout Europea. We calibrated the Agricultural Production Systems sIMulator (APSIM) for pure cultures of wheat and faba bean using data from Dutch field trials, and determined the phenological parameters to simulate pure cultures and intercrops from seven field experiments across Europe. APSIM successfully reproduced aboveground dry matters and, for wheat only, grain yields in pure cultures. In intercrops, APSIM systematically overestimated the aboveground dry matter and grain yield of faba bean and underestimated those of wheat. APSIM was reasonably capable of simulating plant heights in pure cultures, but respectively overestimated and underestimated the height of faba bean and wheat in intercrops. In order to simulate wheat-faba bean intercrops better, APSIM should be improved regarding the calculation of biomass partitioning to grains in faba bean and of height growth in both species. [ABSTRACT FROM AUTHOR]