SOME OBSERVATIONS ON SUNLIGHT INTERCEPTION AND DISTRIBUTION BY PEACH TREES AT DIFFERENT PLANTING DENSITIES
Sunlight measurements were made a few days before harvesting by selenium photocells placed above, under and at two points (40 and 140 cm from the soil) within the canopy. For each planting distance sunlight was measured for 50–60 minutes in the morning and for the same time in the afternoon.
From these measurements, values of sunlight interception by trees of 'Stark Redgold' did not show relevant differences at the three different planting distances (86 %, 82 % and 86 % for 2 500, 1 666 and 1 250 trees/ha, respectively).
With 'Suncrest' light interception was similar at 1 250 and 1 666 trees/ha (84 % and 81 %) but much less (71 %) at 2 500 trees/ha. This may be due to poorer tree growth at the lower part of the canopy of the trees planted at 4 x 1 m.
Light penetration within the canopy was generally low for both the varieties. For 'Suncrest' the highest values (21 and 27 % at 40 and 140 cm from the soil, respectively) were observed with the largest planting distance while with 'Stark Redgold' maximum light penetration was 14 % at 140 cm and 6 % at 40 cm from the soil.
Observations of some characteristics of fruits harvested on the higher 2/3 of the canopy (above 140 cm to the top of the tree) and on the lower 1/3 of the canopy (below 140 cm) showed that even if the differences of sunlight penetration between the two parts were not relevant, soluble solids and fruit weight were reduced by 14 % and 17–25 %, respectively. Fruit colour and dry weight of leaves were greatly influenced too.