Storage and remobilisation of nitrogen by pear (Pyrus communis L.) trees as affected by timing of N supply

Abstract Orchard nitrogen (N) management should aim at reconciling productivity, fruit quality and environmental concerns. Fertilisation strategies should, therefore, maximise the efficiency of N fertilisers, including the choice of the optimal timing of N supply. In the present study, with the aid of labelled [Ca( 15 NO 3 ) 2 ] fertiliser, we assessed: (1) the uptake; (2) the partitioning of nitrogen in 1 year; and (3) its remobilisation the following year, as affected by the timing of N supply. Two-year old Abbe Fetel trees on quince C were grown in pots filled with sand and divided into three groups: one group (A) received 3 g (in total) of labelled N from mid March to mid June, while trees of group B received 3 g of labelled N from late June to fruit harvest (August 20). Trees of group A and B received unlabelled N (3 g/tree) from late June to fruit harvest and from mid March to mid June, respectively. A third set of trees (C) received labelled N (6 g/tree) throughout the season. At fruit harvest, fruits and leaves contained similar amounts of N derived from remobilisation of stored N and from spring uptake (March–June, treatment A) and only a small fraction (around 10%) of N derived from N taken up after June (treatment B). Although abscised leaves contained 10 times higher amounts of N taken up early (A) than late (B) treatments, similar amounts of labelled N were recovered in the tree framework in winter in trees of groups A and B. Remobilisation of N in the following spring accounted for 23–24% of the labelled N in the tree, regardless the timing of N uptake. Trees remobilised with preference N taken up during the previous year than N absorbed earlier. Results indicate that a limited supply of N before fruit harvest does not increase the fruit N content significantly, while it increases N storage in roots during winter to be remobilised the following spring.

[1]  T. Righetti,et al.  Nitrogen partitioning in apple as affected by timing and tree growth habit , 1998 .

[2]  D. Sugar,et al.  Effects of timing of nitrogen application on nitrogen partitioning between vegetative, reproductive, and structural components of mature ‘Comice’ pears , 1992 .

[3]  Peter Millard,et al.  Remobilised nitrogen and root uptake of nitrate for spring leaf growth, flowers and developing fruits of pear (Pyrus communis L.) trees , 1997, Plant and Soil.

[4]  R. Habib,et al.  Mobilizable carbon reserves in young peach trees as evidenced by trunk girdling experiments , 1996 .

[5]  T. Righetti,et al.  Seasonal differences, soil texture and uptake of newly absorbed nitrogen in field-grown pear trees. , 1990 .

[6]  S. Weinbaum,et al.  Quantitative estimates of uptake and internal cycling of (14)N-labeled fertilizer in mature walnut trees. , 1998, Tree physiology.

[7]  T. Righetti,et al.  Postharvest nitrogen application effect on ovule longevity of ‘cornice’ pear trees , 1998 .

[8]  G. Neilsen,et al.  The Influence of Nitrogen Supply on the Uptake and Remobilization of Stored N for the Seasonal Growth of Apple Trees , 1989 .

[9]  M. Tagliavini,et al.  Timing of nitrogen uptake affects winter storage and spring remobilisation of nitrogen in nectarine (Prunus persica var. nectarina) trees , 1999, Plant and Soil.

[10]  Timothy L. Righetti,et al.  Management of Nitrogen and Calcium in Pear Trees for Enhancement of Fruit Resistance to Postharvest Decay , 1992 .

[11]  D. Glenn,et al.  Soil Management Affects Shoot and Root Growth, Nutrient Availability, and Water Uptake of Young Peach Trees , 1991 .

[12]  Timothy L. Righetti,et al.  Recycling of nitrogen in field-grown 'Comice' pears , 1991 .

[13]  Silviero Sansavini,et al.  CANOPY ARCHITECTURE, TRAINING AND PRUNING IN THE MODERN EUROPEAN PEAR ORCHARDS: AN OVERVIEW , 1994 .