A SIMPLE-MODEL FOR THE PREDICTION OF NITRATE CONCENTRATION IN THE POTATO ROOT-ZONE

A functional submodel for predicting solute movement and an analytical solution to the steady state convection-dispersion equation for estim ating solute concentration were combined to predict nitrate concentrat ion in the root zone of potatoes. The necessary inputs to the model ar e initial water content, water content at field capacity, days to reac h field capacity, daily irrigation, precipitation and transpiration, h ydraulic conductivity and plant root absorption functions, initial con centration of solute input, molecular diffusion coefficient, dispersiv ity, and width of initial solute pulse. The model was tested with reas onable success based on data collected from four irrigation and nitrog en treatments in experiments conducted in 1990 and 1991 at Aberdeen, I daho. The model predictions were most sensitive to the value of held c apacity and least sensitive to the width of the solute pulse. the mode l is useful in recommending proper timing and amount of irrigation and nitrogen applications to maintain optimum amount of nitrogen in the r oot zone and consequently minimize nitrogen leaching.