SEASONAL DYNAMICS OF MACRONUTRIENTS IN LEAVES AND SHOOTS OF FRUITING AND NON-FRUITING BRANCHES OF 'MATEUR' PISTACHIO TREES IN RELATION TO CROP LOAD

Abstract

Knowledge of seasonal dynamics of macronutrients in mature trees is an important component of mineral nutrition management of pistachio. The objective of the present work was to determine the dynamic changes of nitrogen (N), phosphorus (P) and potassium (K) in leaves and shoots of fruiting and non-fruiting branches of 40-year-old ‘Mateur’ pistachio trees in relation to crop load in an experimental orchard in central Tunisia. In April, 50% and all floral buds were removed by hand to generate three different treatments: ½-On-, Off- and On-year trees. Crop load had a significant effect on the macronutrients contents in different organs (leaves and current shoots). Leaf contents of N and P declined during stages I and II of nut development to reach a constant level during the stage III, and finally decline during post-harvest for both ‘Off’ and ‘On’ trees. Potassium leaf contents increased during the growing season in fruiting branches. Macronutrients dynamics in current shoot were different. In fact, K concentration was higher early in the season and then decreased rapidly during stages I and II of nut growth. These dynamics were observed in both fruiting and non-fruiting branches. Disbudded trees increased significantly the N, P and K concentrations in all organs through the season compared to the control trees.