Modeling of Nitrogen Discharge from a Barley Field

Abstract

Development of a simulation model to estimate quantitative nitrogen discharge from a field presents difficult problems due to the impossibility of measuring the absolute contents of several nitrogen forms in the field. The objectives of this study were to develop a simulation model of nitrogen transformations in a barley field, making reference to our examination in the field and many investigations of nitrogen transformations in soils that have been done in the past, and to estimate nitrogen discharge from the field. The unique features of this model are: (i) nitrogen contained in a field exists as six forms-stable organic N, unstable organic N, insoluble ammonium N, soluble ammonium N, nitrate N and urea N; (ii) various transformation processes-nitrification, denitrification, mineralization, organization, urea hydrolysis, and ion exchange-were assumed-to obey first-order kinetics; (iii) Arrhenius's law was applied to the temperature dependence of transformation rates; and (iv) nitrogen concentration of the field drainage is assumed to be in direct proportion to nitrate nitrogen content in the field. It is possible to trace the observed data on nitrogen discharge from an underdrain observed for two time periods in a barley field. This model can be contribute to predicting the nitrogen discharge from a field linked to a field drainage model.