Author(s):
Neto, Cláudia 
; Carranca, Corina ; Clemente, Josué ; Varennes, Amarilis
Date: 2008
Persistent ID: http://hdl.handle.net/10400.5/5936
Origin: Repositório da UTL
Subject(s): Pyrus communis; Rocha pear; fertigation; fertilizer 15N supply; fertilizer N use efficiency; 15N balance; 15N re-cycling
Description
In newly planted orchards, special attention must be paid to fertilization to build up the permanent
structure of the trees so that high yield and fruit quality can be reached later on. Nitrogen (N) plays a
major role in the fertilization plan, although few studies have assessed its use efficiency in young nonbearing
trees, especially in field conditions. In this work, 1–3 years old ‘Rocha’ pear trees, grafted on
quince BA29, were planted in a Mediterranean region, and fertigated with 6 g N tree 1 year 1 as
ammonium nitrate with 5 at.% 15N enrichment to study the fertilizer N uptake during the vegetative
cycle, the overall fertilizer N use efficiency at the end of each year, and the plant–soil N balance for this
period. Nitrogen remobilization and the re-cycling of N from senescent leaves were also studied by
fertilizing some pear trees with 10 at.% 15N enrichment.
Nitrogen uptake was minimum at bud break and peaked in June/July remainingmore or less constant
until leaf fall. About 25% of the fertilizer N taken up by 3 years old trees in the previous year was found in
the new tissues formed (flowers, leaves and 1-year-old shoots), reaching 27% when fine roots were also
included. In those trees, 32% and 54% of the 15N stored in the previous year in the trunk and older shoots,
respectively, were mobilized to the new growth in the following year.
Fertilizer N use efficiency by trees increased from the first to the third year but was generally small
(6%, 14% and 33%), and estimated N losses were large (89%, 46% and 53%, respectively in the first, second
and third years). Irrigation water and soil provided more N to the trees than fertilizer N.
