MATHEMATICAL-MODEL OF NITROGEN DYNAMICS IN SOIL

A mathematical model of nitrogen dynamics in the soil was established and verified at three locations differing in soil and climate. It comprises submodels of soil moisture, organic nitrogen mineralization and mineral nitrogen uptake by plants. The input data of the soil moisture submodel constitutes the maximal and critical water capacity, sum of rainfall, average daily temperature, atmospheric pressure, relative air humidity and wind velocity in the height of 2 m. The submodel of organic matter mineralization is based upon the rate of potentially mineralizable nitrogen, presupposes a kinetics of the 1st order for mineralization of potentially mineralizable organic nitrogen. The submodel of the plant growth and of the nitrogen uptake was taken over from the work published by Addiscott, Whitemore (1986). The model was verified at three locations differing in soil and climate and planted with spring barley and winter wheat. A comparison between simulated and measured data well corresponded to the soil moisture data. The relation between simulated and measured values of mineral nitrogen contents in the soil was less close. Even so it is evident that the method of mathematical modelling can contribute to a much more exact estimate of the mineral nitrogen contents in the soil and may serve as a basis for a more precise determination of the need of mineral nitrogen fertilization as well as the risk of washing out the nitrates into underground and surface waters.