Smart use of trees and crops brings best yield

Agroforestry systems that combine trees with crops—known as alley-cropping—offer several ecological benefits. These include improved soil quality, reduced wind erosion, enhanced nutrient cycling, and climate change mitigation through carbon capture. However, the presence of trees can also lead to competition for resources such as water, sunlight, and nutrients, negatively impacting crop yields.

Researchers from the University of Göttingen have found that by strategically choosing between winter and spring crops based on the age of poplar trees, farmers can mitigate these negative effects. The study, conducted over six years at four locations in Germany, revealed that spring crops grown near rows of 5-year-old or older poplar trees produced 10-35% less than in open farmland. The greatest yield reduction occurred within four meters of the tree rows, primarily due to limited light from tree shade.

Interestingly, winter crops maintained yields similar to those in open farmland throughout the study period, regardless of the trees' age. This discrepancy suggests that the timing of crop planting relative to tree age plays a crucial role in optimizing agroforestry yields. Furthermore, after the second tree harvest, annual wood production from the poplar trees increased threefold compared to the first two harvests.

Professor Edzo Veldkamp, who led the research, explained that trees provide wind protection, which can offset the reduced harvests close to the tree rows. Dr. Sarah Choe, who conducted the research as part of her Ph.D., concluded that by growing spring crops only during the first three years post-tree harvest and using winter crops thereafter, farmers can significantly improve the overall productivity of alley-cropping systems compared to traditional open farmland.