NET PRIMARY PRODUCTIVITY AND PARTITIONING OF ABSORBED NUTRIENTS IN FIELD-GROWN APPLE TREES

Abstract

Modern agriculture requires both, attention to crop yield and quality and to environmental issues. Among farmers’ practices, fertilization can play a pivotal role in alleviating environmental pressure without affecting the production. In this work we present the study of nutrients budget spanning six years of apple trees cultivation and we propose a model for tree nutrient uptake as a tool to guide fruit trees fertilization. The survey has been carried on a typical apple orchard of the Po Valley, Italy, with Gala/M9 planted in February 1997 at a density of 2632 trees/ha. Each year trunk diameter, fruit yield and pruning wood production were recorded. The biomass of abscised leaves was estimated. A sample of 3 trees was excavated in November 2002. Nutrient concentration has been obtained for fruits, pruning wood, leaves and the whole excavated trees. In 6 years from planting, trees accumulated 16 Mg ha-1 of dry biomass in the framework, 8.5 in the pruning wood, 28 in fruits, and 8.3 in the abscised leaves. Nutrients absorbed in higher amounts were Ca (462 kg ha-1) and K (406 kg ha-1), but most of them returned to soil by abscised leaves and pruning wood. Potassium was mostly partitioned to fruits. Nitrogen was also absorbed in high amounts (345 kg ha-1). The results of this study have been integrated in an electronic spreadsheet (www.isafruit.org) able to estimate apple tree nutrient uptake.