University Of Tasmania
144639 - Nitrogen use efficiency, allocation, and remobilization in apple trees.pdf (1.86 MB)

Nitrogen use efficiency, allocation, and remobilization in apple trees: uptake Is optimized with pre-harvest N supply

Download (1.86 MB)
journal contribution
posted on 2023-05-20, 23:36 authored by Tan, BZ, Dugald CloseDugald Close, Peter QuinPeter Quin, Nigel SwartsNigel Swarts
Optimizing the utilization of applied nitrogen (N) in fruit trees requires N supply that is temporally matched to tree demand. We investigated how the timing of N application affected uptake, allocation, and remobilization within 14-year-old “Gala”/M26 apple trees (Malus domestica Borkh) over two seasons. In the 2017–2018 season, 30 g N tree-1 of 5.5 atom% 15N-calcium nitrate was applied by weekly fertigation in four equal doses, commencing either 4 weeks after full bloom (WAFB) (pre-harvest) or 1-week post-harvest, or fortnightly, divided between pre- and post-harvest (50:50 split). Nitrogen uptake derived from fertilizer (NDF) was monitored by leaf sampling before whole trees were destructively harvested at dormancy of the first season to quantify N uptake and allocation and at fruit harvest of the second season to quantify the remobilization of NDF. The uptake efficiency of applied N fertilizer (NUpE) was significantly higher from pre-harvest (32.0%) than from the other treatments (-17%). The leaf NDF concentration, an indicator of N uptake, increased concomitantly only when pre-harvest N was applied. Pre-harvest treated trees allocated more than half of the NDF into fruit and leaves and stored the same amount of NDF into perennial organs as the post-harvest treatment. Subsequent spring remobilization of NDF was not affected by the timing of N fertigation from the previous season. A seasonal effect of remobilization was observed with a decrease in root N status and a reciprocal increase in branch N status at fruit harvest of season two. These findings represent a shift in the understanding of dynamics of N use in mature deciduous trees and indicate that current fertilizer strategies need to be adjusted from post-harvest to primarily pre-harvest N application to optimize N use efficiency. This approach can provide adequate storage N to support early spring growth the following season with no detriment to fruit quality.


Horticulture Innovation Australia


Publication title

Frontiers in Plant Science



Article number









Tasmanian Institute of Agriculture (TIA)


Frontiers Research Foundation

Place of publication


Rights statement

Copyright © 2021 Tan, Close, Quin and Swarts. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License (

Repository Status

  • Open

Socio-economic Objectives

Pome fruit, pip fruit