UTILIZATION OF LIGHT RESOURCES BY HDP SYSTEMS

High light interception is a prerequisite for high yield, but shading reduces fruit bud formation, fruit set and retention, fruit size and fruit quality, especially colour.
Work on the design of hedgerow orchards to optimize light interception and penetration is reviewed.
In the still more intensive continuous-canopy orchard the relative light intensity at any given depth in the canopy can be expected to equal e^{-K (L)} when L is the vertically summed LAI down to that depth and K the light extinction coefficient.
Using measured values of K it is calculated that little useful crop could be produced below an LAI of 3.15 and that with typical trees of Golden Delicious/ M.9 this would be attained with 4773 trees/ha, i.e. a considerable increase in intensification over the conventional hedgerow orchard.
As density increases shade by annual shoot growth at the top of the canopy becomes increasingly serious and actually reduces the volume of the well-illuminated fruiting zone.
For further intensification genetic, chemical or mechanical control of shoot growth is of dominant importance.

Symposium on High Density Planting

J.E. Jackson

https://doi.org/10.17660/ActaHortic.1978.65.7