NUTRIENT DISTRIBUTION AND REQUIREMENT OF ‘FORELLE’ PEAR TREES ON TWO ROOTSTOCKS

Abstract

Accurate water and fertilizer management are essential in modern high intensity orchard systems to enable the manipulation of both reproductive and vegetative development. Studies have been conducted to establish the annual plant fertilization requirements, of several tree crops but there exists little information regarding the requirements of pear trees on rootstocks of differing vigour. Nine- year-old ‘Forelle’ pear trees in a commercial orchard on either vigorous, BP1 or dwarfing, Quince A (QA) rootstocks were completely removed from the soil and divided into various tree parts (roots, stems, leaves, shoots and fruit), each part massed, milled and a mineral analysis conducted. Annual requirements of the nine- year-old trees for macro- (N, P, K, Ca and Mg) and micro- elements (Mn, Fe, Cu, Zn, B) were determined by calculating losses and fixation and their requirements expressed in g or mg element/kg yield respectively. ‘Forelle’ on the more vigorous BP1 shows higher requirements than the more dwarfing QA rootstock mainly because of the higher mass of summer and winter wood removed as prunings as well as a higher mass of young shoots. From these results, and with due consideration given to various production differences, annual minimum and maximum fertilization guidelines based on the yield have been determined.