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
journal contributionposted 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 titleFrontiers in Plant Science
Department/SchoolTasmanian Institute of Agriculture (TIA)
PublisherFrontiers Research Foundation
Place of publicationSwitzerland
Rights statementCopyright © 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 (https://creativecommons.org/licenses/by/4.0/).