In Fig. 5a yields of M. sativa are shown as a function of
distance to the hedgerows of R. pseudoacacia. Significant differences
between the yield of M. sativa growing in 2.5m distance
to R. pseudoacacia hedgerows and yields calculated from samplings
in the middle of the alley (10.5m distance) without any
above- or below-ground interference of R. pseudoacacia were
only observed at four out of 10 harvests. In one case the yield
of M. sativa growing next to trees was even higher than in the
centre of the alleys. But in all other cases the yield of M. sativa
growing next to the hedgerows was decreased as compared
to the centre of the alleys. To compare the productivity of
M. sativa with and without consideration of such edge effects
weighted averages of the yield of alfalfa were calculated with
the assumption that 11% of the plot was influenced by aboveand
below-ground interactions of trees and crops. Cumulated
yield of all 10 harvests based on these weighted averages
amounts to 26.7 tha−1. Based on yields from the middle of the
alley the cumulated yield of 27.4 tha−1 clearly indicated that
potential edge effects will not negatively influence the overall
growth performance of crops.