Changes in the radiation regime and photosynthesis in the crown of an apple tree when pruning for perennial wood

Abstract

The article presents data on the study of the radiation regime and photosynthesis net productivity in the crown of an apple tree in connection with the regenerative pruning of old-aged trees. The object of the research was an apple tree of the Antonovka obyknovennaya variety, a seed stock (seedlings of cultivated varieties), planted in 1987. The test plot soil is leached chernozem. Options: 1. Established pruning (control); 2. Pruning for 5-6 year-old wood; 3. Pruning for 7-8 year-old wood. The experiment was arranged inrandomized blocks of 6 accounting trees in 3 replicates. The regenerative pruning was carried out in spring 2016. Every year damaged branches were removed in the control variant, while “wolf-like” shoots were thinned in other variants. The solar output was accounted within the daytime with the 2-hour interval from the northern and southern sides of the apple tree crown in its center, as well as under the crown at a distance of 1, 2 and 3 meters from the periphery to the center of the crown. The measurements were carried out after the growth activity cessation in the fine weather in August with a universal albedometer M-69 coming with a galvanometer GSA-1. The net productivity of leaves was determined by the method of A. S. Ovsyannikov in parallel, taking into account solar radiation. It is revealed that the regenerative pruning has a considerable impact on the performance of the solar output. The greatest arrival of solar radiation is noted on the periphery of the crown. In the treatment with pruning branches for 5-6 year-old wood, this parameter was 10.5-13.5 % higher than in the control variant. Pruning branches for 7-8 year-old wood improved lighting conditions by 27.6-31.7 % compared to the control. In the lower part of the crown, the radiation regime is less favorable for the photosynthesis process relative to the central part of the crown. Regenerative pruning increased the photosynthesis productivity significantly. In the central part of the crown, the highest parameters of the net photosynthesis productivity were observed on the periphery on the southern side when pruning for 7-8 year-old wood - 7.81 g of dry basis/m2 *day.