With climate change and an increasing global human population, the concept of agroforestry is gaining economic and environmental interest. The practice of growing trees and crops on the same land is mainly applied in (sub)tropical climate and rarer in temperate areas where farmers fear decreased understorey crop yields due to competition with trees. However, whether competition is stronger below- (soil moisture, nutrients) or aboveground (light) in a temperate silvoarable agroforestry system (AFS) is not clear. The effects of different treatments of light, water and nutrient availability on crop production in two temperate AFS in Central Switzerland were investigated, where summer barley (Hordeum vulgare L.) was grown as understorey crop under 90%, 40% and 0% shade nets, with and without irrigation and/or fertilisation in a fully factorial design. Yield was reduced by 26% under heavy shade; yield reductions under moderate shade were not significant. Fertilisation and irrigation increased crop yield by 13% and 6–9%, respectively, independent from shade. Individual seed mass was significantly increased by fertilisation from an average of 0.041 g (± 0.008 SD) in unfertilised treatments to an average of 0.048 g (± 0.010) in fertilised treatments. Fertilisation had the biggest impact on total seed number (p < 0.001) with on average 36 (± 26) seeds per individual in unfertilised plots and 61 (± 33) in fertilised plots. This study demonstrates that moderate shade (as can be expected in modern AFS) was not a major limiting factor for barley yield in these two AFS in Switzerland, indicating that AFS with appropriate management combined with suitable selection of understorey crops are an option for agricultural production in temperate regions without significant yield losses.

Introduction Agroforestry systems provide a number of ecosystem services and are frequently considered as a promising diversification strategy for more sustainable and climate resilient primary production. However, most agroforestry field trials compare only one crop type with a control in open field. Additional comparisons between treatments that influence nutrient and water availability are often not looked at, nor are comparisons between crop species. Materials and Methods To deepen our understanding of the ecological processes underlying the potential benefits of agroforestry for food production, the present experimental study addresses three environmental factors (shade, fertilisation and irrigation) on three functionally different crop species (field bean, summer barley, summer rapeseed) and a C4‐grass (Echinochloa crus‐galli) in a Swiss agroforestry system. Crop performance (physiological traits, yield) between functional groups was analysed among treatment combinations of shade, fertilisation and irrigation. Physiological traits included measurements of chlorophyll content, stomatal conductance, specific leaf area and plant height. Results Summer barley and field bean showed significant yield declines when shaded (−44% and −38%, respectively), similar to summer rapeseed with a significant biomass decline (−35%). Shade significantly increased the occurrence of lodging in barley. Rapeseed in particular performed better when fertilised (+40% biomass). Conclusion The results allow to estimate the range of potential yield losses in the competitive zone near mature trees for functionally different crop groups. The findings serve as a decision‐support for species selection in temperate European agroforestry systems.

Agroforestry systems provide a number of ecosystem services and are frequently considered as a promising diversification strategy for more sustainable and climate resilient primary production. Still, less than 1% of the agricultural land in the European Union is silvoarable agroforestry. Most agroforestry field trials compare one crop type with a control in open field with no additional environmental treatments such as nutrient and water availability, thereby limiting our understanding of the ecological processes underlying the potential benefits of agroforestry for food production. The present experimental study addresses three factors (shade, fertilisation, irrigation) on three functionally different crop species (field bean, summer barley, summer rapeseed) and a C4-grass (Echinochloa crus-galli) in a Swiss agroforestry system. The objective of this study was to assess if and how crop performance (physiological traits, yield) between functional groups varies and if and how shade-induced crop yield reductions diverge between treatment combinations, aiming to provide general functional crop species and management recommendations as a guideline for a successful agroforestry practice in temperate Europe. Summer barley (-44%) and field bean (-38%) showed significant yield declines, similar to summer rapeseed with a significant biomass decline (-35%). Shade significantly increased the occurrence of lodging in barley. Rapeseed in particular performed better when fertilised (+40% biomass). Our results enable to estimate the range of potential yield losses in the competitive zone near mature trees for functionally different crop types and serve as a decision-support for species selection in temperate European agroforestry systems.

In agroforestry systems (AFS), where environmental conditions are highly variable at small spatial scales, the use of uniform genetic material of a single cultivar commonly grown in monoculture cropping might not be optimal. However, the use of composite cross populations (CCPs) that contain an inherent genetic variability might be a promising approach to match the environmental variability created by trees in AFS. In this experimental trial, the performance of a CCP ("CC-2k") of winter wheat was compared to a commercial variety ("Wiwa") in a split-plot design in two AFS (Feusisberg, Wollerau) in Central Switzerland. The factor variety (p < 0.05) and the interactions of site and distance to tree (p < 0.05) and site and variety (p < 0.05) significantly affected wheat yield at the plot level. CC-2k and Wiwa yield (across all distances) amounted to 1.9 +/- 0.7 Mg ha-1 and 2.0 +/- 0.8 Mg-1, respectively, in Feusisberg and to 1.9 +/- 0.9 Mg ha-1 and 0.7 +/- 0.4 Mg ha-1, respectively, in Wollerau. Wiwa had a higher protein, Fe and Ca content than CC-2k. Therefore, while the CC-2k outperformed the commercial organic variety Wiwa in terms of yield in one of the two AFS, Wiwa outperformed CC-2k in terms of quality. The composite cross population might be better adapted to the heterogenous environment of agroforestry systems but fails to reach the high-quality product of modern elite cultivars. Further improvements in terms of quality might make CCPs highly interesting for diversified agricultural systems with larger environmental heterogeneity than common monoculture cropping systems.