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DCA rapport, nr. 163, 2019

Af Chresten Duus Børgesen, Peter Søensen, Gitte Blicher- Mathiesen, Kristian M. Kristensen, Johannes W.M. Pullens, Jin Zhao and Jørgen E. Olesen

A new updated version of the empirical nitrate leaching model NLES is presented in this report. The NLES5 model is designed to estimate nitrate leaching from the root zone of agricultural land in Denmark. The previous version NLES4 was redesigned to better capture effects of nitrogen inputs in fertilizers, manure and biological N fixation as well as crop sequences and autumn and winter vegetation cover.
NLES5 is based on measured nitrate leaching in both experimental fields and farmer fields. 2053 field observations from 1991 to 2017 were used for the calibration of the model. The model is validated using data from independent field measurements (856 observations) and by cross validation. Uncertainty analysis and scenario analysis of both nitrate leaching and marginal nitrate leaching response to increased N application is presented. The model can estimate average marginal nitrate leaching response to mineral nitrogen application, total nitrate leaching and the effects of a number of field N mitigation measures. Nitrate leaching depends on soil type, crop type and precipitation. The Marginal nitrate leaching was estimated at national scale with a mean of 17%.

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