EFFECT OF IRRIGATION AND NITROGEN OR POTASSIUM FERTIGATION ON YIELD AND FRUIT QUALITY ON 'CONFERENCE' PEAR TREES IN BELGIUM

In Belgium the necessity of an irrigation system for pear trees under the temperate zone climatological conditions is often discussed, especially for pear orchards on loamy soils. With an annual rainfall of about 760 mm per year, it is not always evident to judge about the investment in an irrigation system in a pear orchard. But with the expected global changes in climate in the near future, more extreme situations of drought with more irregular rainfall periods during the summer are expected. Therefore an increased interest in irrigation systems under pear trees is expected. Another important factor for the pear cultivar ‘Conference’ is the price difference between a fruit of 55 mm and 65 mm where the larger fruit can bring double the price. Also some cultural interventions in the orchards like root pruning for vegetative growth control can increase the drought susceptibility of pear trees. The effects of root pruning on the mineral composition of leaves and fruit and on the fruit quality at harvest and during storage will be discussed. In these trials, soil water content was measured with gravimetric moisture measurements and compared with watermark measurements at different depths in the soil profile. Supplementary applications of potassium and nitrogen were given through the irrigation system during summer with the aim of improving the final fruit quality of the pears. The effect of this supplementary fertigation with nitrogen on fruit quality was more prominent than the effect of a supplementary potassium application.