OPTIMIZATION OF LIGHT INTERCEPCION IN INTENSIVE SWEET CHERRY ORCHARD

In high density sweet cherry orchards the crop canopy is fragmented, arranged in linear lanes. In between the tree lanes the alleyway provides the space for technology measures and machinery. The area rate of orchard covered by canopy considerably influences the PAR (photosynthetic active radiation) absorption potential of the orchard. Our first step in Hungary towards intensification of cherry orchard was the “modified Brunner Spindle” in spacing 6x4 to 5x3 m, introduced in the 80-es of last century. The canopy covered rate of the orchard area increased from 0.4-0.5 to 0.60.7 with decreasing spacing. The denser “Hungarian Cherry Spindle” with spacing of 4x2m slightly increased the rate of canopy covered orchard area (0.6-0.8) but in this system the leaf and shoot population is more and more crowded in a reduced space. This situation may provide both advantages and disadvantages considering environmental physiology and technology aspects. The total leaf area of trees and the leaf area index (LAI) is considerably influenced by the cultivar and rootstocks. The LAI and so the PAR absorption capacity of orchard shows typical course during the season, influenced by the applied pruning too. On dwarfing rootstock GiSelA 5 or 6 the LAI values of trees reach a maximum of 2 to 3, while the LAI of tree on vigorous rootstocks can achieve 7 to 8. At the stage of LAImax the canopy walls of trees intercept 60-90% of PAR, which means 40-75% PAR absorption calculated for the whole orchard area. Environmental factors considerably influence the performance of net CO2 assimilation of leaves in daily and seasonal course as well. Our investigation confirmed the role of water supply and temperature of leaves affecting the stomatal conductance. The stomatal conductance of leaves on different rootstocks at appropriate water supply showed daily maximum in the Tleaf range of 30 – 40 °C, while in the Tleaf range of 40 – 45 °C the conductance rapidly decreased. This down regulation on dwarfing rootstock is faster, while on vigorous rootstocks slower. Since the water supply of leaves on dwarfing rootstocks due to their hydraulic system is more vulnerable, and the exposition of leaves to solar radiation is higher due to the scarse canopy, the leaves get faster into the critical Tleaf range. In contrary trees on vigorous rootstocks with higher LAI, which is linked with higher shading, may show more efficient PAR utilization. The research was supported by TAMOP-4-2.1.B-09/1/KMR- 2010-0005 project and by Hungarian Scientific Research Funds OTKA 109361project.