Comparing long-term crop yields of a short rotation alley cropping agroforestry system and of a standard agricultural field in Northern Germany

Alley cropping agroforestry systems (ACS) provide various ecologically positive effects. However, trees and crop plants are competing for essential resources, especially in the transition zone. This study investigated the spatial distribution of oilseed rape and winter wheat yield in the tree-crop competition zone of an ACS with fast-growing poplars and narrow (48 m) and wide (96 m) crop alleys in northern Germany. Furthermore, multi-year crop yield data were compared with those of a corresponding non-agroforestry control field. Crop yields adjacent to the tree strips were significantly lower than at greater distances, mainly due to tree shading and leaf litter coverage. However, the average long-term crop yields of the narrow crop alley, the wide crop alley and the control field did not differ significantly among each other. In conclusion, yield reduction close to the tree strips had no negative influence on the average long-term crop yields of the ACS.