Modelling Nitrate Formation and Movement in Vineyard Soils – A Contribution to a More Sustainable Viticulture

Ecologically sound production is a catchword used in nearly all viticulture production areas. Besides the pesticides inputs which are unavoidable specific attention is directed to nitrates which can pollute ground water reserves and may have some adverse effects to humans after consumption. There are two main sources for nitrate in vineyard soils: a) mineralization of humic compounds from the soil and b) nitrogen fertilization. In the latter case the inputs can be controlled via balance sheets, which are obligatory in Germany for instance. During a six years period the mineralization process of slowly decomposable organic matter in vineyard soils was evaluated. As a basis STANFORDs equations were used to describe that process but could finally reduced to a zero order equation. These findings were combined with different sub-models from soil science: heat transfer and water movement. Input values are very simple to determine: global irradiation, soil texture (sand, silt, clay) and wet digested organic matter (WALKLEY-BLACK). The compiled model is deterministic. Therefore it is transferable to other, unknown sites. The nitrate dynamic in soils can be followed up with one starting value which under German conditions is determined after harvest or in early springtime: the calculation includes the soils water content, the nitrate concentrations, possibly nitrate losses, and the NO3-content at the point of planned fertilization. Normally the mineral fertilizer input can be reduced without endangering yield and quality of grapevines. The model is now used as a tool for the extension service. On the other hand it is a powerful proof that viticulture, which is mostly carried out in vulnerable land sites, can save the environment for future generations.