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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #151598

Title: EFFECTS OF SPRING SOIL NITROGEN APPLICATION ON NITROGEN REMOBILIZATION,UPTAKE AND PARTITIONING FOR NEW GROWTH IN ALMOND NURSERY PLANTS

Author
item GUIHONG, BI
item Scagel, Carolyn
item CHENG, LAILIANG
item FUCHIGAMI, LESLIE

Submitted to: Journal of Horticultural Science and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2003
Publication Date: 4/1/2004
Citation: Guihong, B., Scagel, C.F., Cheng, L., Fuchigami, L.H. 2004. Effects of spring soil nitrogen application on nitrogen remobilization,uptake and partitioning for new growth in almond nursery plants. Journal of Horticultural Science and Biotechnology.

Interpretive Summary: In deciduous fruit trees, nitrogen (N) used for new growth in the spring may come from two sources: N stored from the previous year and N uptake during the current year. The internal remobilization of N from storage tissues provides N needed for early new growth before significant root uptake occurs and as the season progresses, root uptake of nitrogen plays a more important role in satisfying the tree N demand. Understanding the effects of spring soil N availability on N remobilization, uptake, and growth in nursery trees is important for optimizing the timing of fertilizer application to meet tree uptake and demand. One-year-old 'Nonpareil' almond trees on 'Lovell' rootstocks were used to evaluate the effects of soil nitrogen (N) availability on N remobilization, uptake, partitioning and tree growth. After transplanting in spring, trees received fertilizer with or without NH4NO3 for 12 weeks. During the first 4 weeks, N used for new growth mainly came from N remobilized from storage. Approximately 49% of the N was remobilized for new growth by 12 weeks. The amount and duration of N remobilization was not dependant on N availability. Trees receiving N fertilizer had more new growth than those that did not receive any N. Uptake of N by roots occurred two weeks after transplanting. Rapid uptake of N from soil occurred during the period of rapid shoot and leaf growth and leaves were the major sink for N from both root uptake and storage. The remobilization of N for spring new growth takes place irrespective of the current external N supply. However, the new growth of young almond plants is highly dependent on soil N availability which indicates the importance of N fertilizer applications in spring to almond nursery trees after transplant.

Technical Abstract: One-year-old 'Nonpareil' almond (Prunus dulcis (Mill) D. A. Webb) trees on 'Lovell' rootstocks were used to evaluate the effects of soil nitrogen (N) availability in the spring on N remobilization, uptake, partitioning and tree growth. After transplanting to an N-free medium in spring, trees received a modified Hoagland solution with or without N from 15N-depleted NH4NO3 twice a week for 12 weeks. Sequential harvesting and determination of biomass, N and 15N contents allowed estimation of new growth, N remobilization, uptake and distribution. During the first 4 weeks after transplanting, N used for new shoot and leaf growth mainly came from N remobilized from storage tissues. At the end of the experiment, about 49% of the total tree N at transplanting was remobilized for new shoot and leaf growth. There was no significant difference in the amount and duration of N remobilization between N-fertilized trees and trees that received no N. Trees receiving N fertigation in the spring had significantly more new shoot and leaf growth than those that did not receive any N. Uptake of 15N by roots occurred two weeks after transplanting. Rapid uptake of N from soil occurred during the period of rapid shoot and leaf growth and leaves were the major sink for N from both root uptake and storage. Whole tree N content was significantly higher in N-fertilized trees than those receiving no N approximately six weeks after transplanting. We conclude that the remobilization of N for spring new growth takes place irrespective of the current external N supply. However, the new growth of young almond plants is highly dependent on soil N availability which indicates the importance of N fertilizer applications in spring to almond nursery trees after transplant.