S16 - Session O3 - Effect of different reflective ground covers on light reflection and on the coloring of apples at harvest

Authors: Luis Gonzalez Nieto *, Terence Robinson

We conducted three field studies in 2020 and 2021 to compare the light interception (LI) and light reflected (LR) with 2 types of reflective ground cover (GC; Mylar and Extenday) using different deployment configurations with four apple cultivars ('Evercrisp', 'Honeycrisp', 'NY1' and 'NY2'). The second objective was to evaluate the effect of the reflective GC on fruit red coloration. In the first experiment using 'Evercrisp' apple trees we compared the effect of Extenday with control plots (without GC). Extenday increased the average of LI by 23-24% in comparison with control in a sunny and cloudy day. Extenday increased red blush area by 13% in comparison with the control. In experiment 2, we compared Extenday and Mylar in a 'Honeycrisp' orchard with 5 training systems (Tall Spindle, Fruiting Wall, Bi-axis, V-Trellis and planar Cordon). Both reflective films increased total canopy LI with Extenday having a slightly greater improvement in LI than Mylar for all 5 orchard training systems. LI was similar among all training systems except for the V-trellis which had higher LI values. The smallest improvements in LI from the reflective films were with the Cordon and the V-trellis systems, followed by the Tall Spindle and, finally, the Fruiting Wall and the Bi-Axis. LR with Extenday always was higher than with Mylar. In experiment 3 we compared five strategies: UTC, Extenday with 80% and 90% of reflection and Mylar in the herbicide strip, or between the tree rows with 'NY1' and 'NY2' apple trees. Our study showed there are important differences between reflective GCs, with the highest percentage of the LR from Extenday 90%, followed by Mylar in the herbicide strip and extenday 80% and, finally, Mylar between the tree rows. Moreover, all reflective GCs increased red blush area and increased the profitability of the orchard.