How do different functional groups of crop perform in temperate silvoarable agroforestry systems? A case study

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.