ISHS Acta Horticulturae 646: International Symposium on Irrigation and Water Relations in Grapevine and Fruit Trees
EFFECTS OF CROP LOAD ON TREE WATER USE IN APPLE (MALUS X DOMESTICA BORKH.) |
| Author: | T. Lakatos |
| Keywords: | sap flow rate, leaf area, fruit growth |
| Abstract:
Sap flow rate measurements were carried out during two consecutive (’on’ and ’off’) years in an apple orchard cv. ’Florina’/M.26 to analyse the effects of various crop loads on tree water use. Sap flow was measured by the thermal dissipation method in trunks of nine trees from June to the harvest period. Crop load was between 0.2-9.0 fruits xcm-2 of trunk cross section area (equal to 0.5-35.0 fruits·m-2 of leaf area), trunk diameter varied between 4.7-8.7 cm. Total leaf area was estimated by leaf counting or using shoot girth and leaf area relationship. In both years, fruit growth rate was determined by measuring diameter of 280 marked fruits with 7 days frequency. Fruit volume was calculated as a function of fruit diameter based on a previously determined relationship. Total leaf area of trees ranged from 4.4 to 19.5 m2 and it was closely related to trunk cross section area. At high crop loads the fruit growth rate peaked in August with 0.5 l·tree-1·day-1 and the leaf area specific total fruit volume reched 6 l·m-2 before the harvest. There was a linear relationship between total leaf area and daily water use, while the leaf area specific water use was influenced by crop load rate. The relationship was described by piecewise linear regression with the breakpoint at a crop load rate of 12 fruits·m-2 of leaf area. At low crop loads the slope of the fitted regression line was less than at high crop load rate. | |
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