Sheltered by trees: long-term yield dynamics in temperate alley cropping agroforestry with changing water availability

Abstract

As warm season droughts increase in frequency due to climate change, causing severe yield losses especially among cereal crops, European agriculture is in dire need of adaptation. While agroforestry is widely regarded as a key adaptation measure, little is known on how yield performance is influenced by changing water availability in temperate regions. Therefore, we assessed the yield dynamics of five winter crops (winter wheat, triticale, winter barley, winter pea, and rapeseed) during seven growing seasons (2012 to 2023) in a well-established (since 2007) alley cropping agroforestry trial site in Southwestern Germany. The trial integrated three different agroforestry practices in a randomized block design: (i) willow short-rotation coppice, (ii) walnut trees for nut production, and (iii) diverse hedgerows. The relationship between crop yield and climatic water balance was analyzed using a linear mixed-model. In this unique long-term comparison, we demonstrate that individual alley cropping practices exhibited distinct yield patterns with increased distance to tree rows. In contrast to the willow short rotation coppice, walnut and hedgerows did not evoke significant winter crop yield declines at proximity. While in the walnut plots yields did not significantly vary with distance to tree rows, yields adjacent to hedge rows declined significantly towards the alley center. Moreover, tree rows contributed to stable crop yields under fluctuating water availability in their proximity and up to the alley center on their leeward side while yields significantly varied with changing climatic water balance on the windward side. Our results underline the potential of agroforestry to sustain yields in the face of increasingly variable water availability, further substantiating the contribution of alley cropping agroforestry for farming systems’ resilience to increasingly variable weather conditions. They moreover contribute to planning and policy support for advancing agroforestry as a climate smart solution in temperate regions.