An elementary model of nitrogen uptake and redistribution by annual plant species.

A model is presented that simulates nitrogen uptake and response to nitrogen deficiency by a growing annual plant canopy. It is a descriptive model as it is not based on a detailed definition of the biochemical processes involved. It does incorporate a considerable amount of experimental knowledge about these processes as well as some tentative concepts concerning the availability of soil nitrate and the relation between rates of growth, death and nitrogen translocation to the seeds. The model simulates the effect of nitrogen deficiency on plant growth, seed development, death of vegetative tissues and changes in the nitrogen concentration of the different plant parts. The results warrant a verification and development study under specific field conditions. The model is meant to be used in conjunction with another model that simulates the water balance and transpiration of an annual plant canopy under moisture limiting conditions. The nitrogen balance in the soil is not yet treated in either model.