A simple model approach to simulate nitrogen dynamics in vineyard soils

Mid-European viticultural areas release large amounts of nitrogen into surface water bodies and groundwater, which is due to excessive fertilisation and high mineralisation rates of both, soil organic matter and added secondary raw material. Matching nutrient supply to the crop’s demand is a key measure to prevent further eutrophication of adjacent ecosystems. In order to support nutrient management in viticulture, a simulation model which is able to consider the temporal dynamics of N-uptake and release of nitrogen from organic material in the special environment of a vineyard will be helpful. A simple approach is presented by introducing a plant growth submodel for vine to an established simulation model for agricultural production systems in which the decomposition of fresh organic material is implemented already. The submodel is the result of a few elementary modifications in the basic plant growth submodel to enable continuous plant growth over several growing seasons, independent treatment of the different plant organs, and water and nitrogen uptake adapted to soil depth. The initial validation procedure concentrated on the fundamental ability of the model to reproduce the nitrogen dynamics in a conventionally treated vineyard. The simulated water and nitrogen dynamics were validated on a dataset of four different Rhineland–Palatinate vineyards. With the model bud break could be predicted within a deviation of ±3 days. Grape and shoot dry matter production was simulated with ±13% accuracy. In the case of extreme weather conditions, stronger deviations occurred. Seventy percent of the simulated soil Nmin values ranged within the standard deviation of the observed soil Nmin values, whereas only 40% of the soil water contents could be reproduced at this level of accuracy. However, the results are considered to be sufficient already for practical use in viticultural fertiliser management.