© 1989 Heron Publishing—Victoria, Canada
An experimental test of a nitrogen uptake and partitioning model for young trees
R. Habib (1), A-M. de Cockborne (2), P. Monestiez (3) and F. Lafolie (2)
1. Station d’Agronomie, INRA, Domaine Saint-Paul 84140, Montfavet, France / 2. Station de Science du sol, INRA, Domaine Saint-Paul 84140, Montfavet, France / 3. Laboratoire de Biométrie, INRA, Domaine Saint-Paul 84140, Montfavet, France / Received June 21, 1988
Summary
Simulation models of nitrate uptake and total nitrogen partitioning during the exponential growth phase of one-year-old peach
trees (Prunus persica (L.) Batsch.) were tested in an experiment with 88 plants grown in soil-filled containers. Plants were fertilized with 15N-NO3– and nitrate uptake estimated by periodic destructive analysis of plants for excess 15N. Partitioning of N within the trees was followed by the analysis of plant parts for total N and 15N.
The nitrate uptake model, which provides one of the main inputs to the partitioning model, is based on a simplified form of
the Michaelis-Menten equation adapted to describe uptake by roots growing in soil layers. The nitrogen partitioning model
considers each plant part (e.g., roots, trunk, shoots, leaves) as either a sink or a source for nitrogen. The model uses a
flow equation, which is the same for all plant parts, to model the dynamics of nitrogen partitioning in the tree using increases
in dry matter of various plant parts as driving force variables.
The experiment demonstrated an error in the compartment organization of the partitioning model as a result of which the model
failed to simulate changes in root N. A modification of the partitioning model structure to take account of the importance
of trunk nitrogen reserves for root growth at the beginning of the growing season, which was indicated by the 15N data, greatly improved prediction of root N. This modification is discussed in relation to the modeling approach.
