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Different diversification practices have the potential to reduce pests and therefore pesticide use. Yet, their integration at the agroecosystem level and the evaluation of their multifunctional effects remain limited. Through a two-year field experiment conducted in Germany, we tested whether associating intercropping (faba bean-wheat, followed by breadseed poppy-barley) with pluriannual wildflower strips strengthens the biological regulation of aphid pests and weeds, and enhances cropping system productivity. The contribution of flowering weeds to conservation biological control was also analysed. Aphid but also predator colonization and predation rates on bean and poppy were consistently lower in intercropping compared to sole cropping. Wildflower strips enhanced aphid predation in bean-wheat intercropping, and further reduced aphid colonization at 10 m distance but not at 20 m in poppy-barley intercropping. Weed biomass was consistently reduced in intercropping compared to sole cropping bean and poppy, and did not significantly affect bean and poppy yields in intercropping. The cover of one flowering weed species, Matricaria recutita, was negatively correlated to aphid colonization and positively correlated to predation rate. Matricaria recutita flowers were also visited more often by predatory hoverflies in plots adjacent to wildflower strips. Finally, land equivalent ratio was consistently higher than 1, and the highest in bean-wheat intercropping associated to wildflower strips. The study demonstrates the benefits of associating wildflower strips to intercropping to strengthen biological control and cropping system productivity. Flowering weeds, maintained at an acceptable level through intercropping, turn out to be relevant functional biodiversity in interacting with wildflower strips for conservation biological control. [ABSTRACT FROM AUTHOR]

Cropping system diversification through annual intercropping provides a pathway for agricultural production with reduced inputs of fertilizer and pesticides. While several studies have shown that intercrop performance depends on the genotypes used, the available evidence has not been synthesized in an overarching analysis. Here, we review the effects of genotypes in cereal/legume intercropping systems, showing how genotype choice affects mixture performance. Furthermore, we discuss the mechanisms underlying the interactions between genotype and cropping system (i.e., sole cropping vs. intercropping). Data from 69 articles fulfilling inclusion criteria were analyzed, out of which 35 articles reported land equivalent ratio (LER), yielding 262 LER data points to be extracted. The mean and median LER were 1.26 and 1.24, respectively. The extracted genotype × cropping system interaction effects on yield were reported in 71% out of 69 publications. Out of this, genotype × cropping system interaction effects were significant in 75%, of the studies, whereas 25% reported non-significant interactions. The remaining studies did not report the effects of genotype × cropping system. Phenological and morphological traits, such as differences in days to maturity, plant height, or growth habit, explained variations in the performance of mixtures with different genotypes. However, the relevant genotype traits were not described sufficiently in most of the studies to allow for a detailed analysis. A tendency toward higher intercropping performance with short cereal genotypes was observed. The results show the importance of genotype selection for better in cereal/legume intercropping. This study highlights the hitherto unrevealed aspects of genotype evaluation for intercropping systems that need to be tackled. Future research on genotype effects in intercropping should consider phenology, root growth, and soil nutrient and water acquisition timing, as well as the effects of weeds and diseases, to improve our understanding of how genotype combination and breeding may help to optimize intercropping systems. [ABSTRACT FROM AUTHOR]

While many pesticides are detrimental to human health and the environment, drastically reducing their use and risks in agriculture has been set as a key target for global environmental policies. To this end, redesigning agroecosystems by increasing plant diversity at the cropping system and landscape levels is increasingly seen as imperative. Positive evidence that diversifying agroecosystems suppresses pests is accumulating and many ecological mechanisms driving pest suppression are known. Yet, variability in effects, risks of failure, and the limited adoption of diversification practices, call for improving diversification science. The overarching challenge lies in shifting from homogeneous production systems targeting yield at the cost of high input uses, to complex biodiversity-based environments resilient to pest pressure and delivering multifunctional performances. Therefore, a new conceptual umbrella to guide future agroecosystem design is proposed, which consists of integrating four principles: (i) embracing complexity, by jointly considering the multiple pests and their enemies; (ii) considering traits, in mobilizing the functional grammar; (iii) stacking diversification practices, by strategically combining the multiple facets of plant diversity at multiple scales; (iv) translating ecological processes into socio-economic benefits to adopt a multifunctional perspective. While addressing the associated implications for science and research, the present review critically discusses how to mobilize the spatio-temporal cross-scale dependencies of interactions in agroecosystems. Promoting synergies and building on the functional complementarities of ecological processes is proposed as a way to strengthen agroecosystem resilience to pest outbreaks. • Although diversifying effectively suppresses pests, there is room for improvement. • A new conceptual umbrella consisting of four principles is proposed. • The maximization of their effects depends on their strategic integration. • The objective of redesigning is to enhance synergies and resilience against pests. • Framing the interdependencies of socio-ecological relations in agroecosystems is key. [ABSTRACT FROM AUTHOR]

High stability of crop yields is a key objective in crop production and breeding, especially under the conditions of a changing climate. Reliable indices are therefore needed for quantifying yield stability. Recently it was shown that some frequently used indices of yield stability, such as the coefficient of variation (CV) may be wrongly interpreted if there is a systematic dependence of the variance σ² from the mean yield μ following Taylor’s power law. Here we propose a method to adjust the standard CV to account for the systematic dependence of σ² from μ. This adjusted CV can be used as a stability index that is expressed in units that are equivalent to the standard CV, as a percentage of the mean, and can therefore be used in agronomic studies that aim to provide guidance for farmers and advisors. Applying this adjusted CV (called aCV) to FAO cereal yield data, we show that the temporal yield stability of both wheat and rye has weakly but significantly decreased over the last five decades and this trend was not picked up with the standard CV in wheat, and was more marked with the aCV than with the standard CV in rye. For the intensifying research on yield stability in agronomy, the suggested method is a novel alternative to estimate yield stability more conclusively, allowing straight-forward interpretation and providing the basis for developing cropping systems with higher yield stability in the future. [ABSTRACT FROM AUTHOR]

This study investigated the effects of increased genetic diversity in winter wheat ( Triticum aestivum L.), either from hybridization across genotypes or from physical mixing of lines, on grain yield, grain quality, and yield stability in different cropping environments. Sets of pure lines (no diversity), chosen for high yielding ability or high quality, were compared with line mixtures (intermediate level of diversity), and lines crossed with each other in composite cross populations (CCP n , high diversity). Additional populations containing male sterility genes (CCP ms ) to increase outcrossing rates were also tested. Grain yield, grain protein content, and protein yield were measured at four sites (two organically-managed and two conventionally-managed) over three years, using seed harvested locally in each preceding year. CCP n and mixtures out-yielded the mean of the parents by 2.4% and 3.6%, respectively. These yield differences were consistent across genetic backgrounds but partly inconsistent across cropping environments and years. Yield stability measured by environmental variance was higher in CCP n and CCP ms than the mean of the parents. An index of yield reliability tended to be higher in CCP n , CCP ms and mixtures than the mean of the parents. Lin and Binns’ superiority values of yield and protein yield were consistently and significantly lower (i.e. better) in the CCPs than in the mean of the parents, but not different between CCPs and mixtures. However, CCPs showed greater early ground cover and plant height than mixtures. When compared with the (locally non-predictable) best-yielding pure line, CCPs and mixtures exhibited lower mean yield and somewhat lower yield reliability but comparable superiority values. Thus, establishing CCPs from smaller sets of high-performing parent lines might optimize their yielding ability. On the whole, the results demonstrate that using increased within-crop genetic diversity can produce wheat crops with improved yield stability and good yield reliability across variable and unpredictable cropping environments. [ABSTRACT FROM AUTHOR]