Tools for assessing vine nitrogen status; role of nitrogen uptake in the “terroir” effect

Among the numerous nutrients vines extract from the soil, nitrogen is the one that interferes most with vine vigor, yield, berry constitution and wine quality. Many studies relate on the influence of various levels of nitrogen fertilization on vine growth, yield and berry constitution (KLIEWER, 1971; BELL et al., 1979; DELAS et al., 1991; SPAYD et al., 1993; SPAYD et al., 1994). Other papers deal with the depressive effect of cover crop on vine nitrogen supply, which can partly explain the quality-improving effect of this technique (SOYER et al., 1996).
Vine nitrogen uptake is likely to vary to a considerable extend with soil parameters, even when no nitrogen fertilization or cover crop occurs. Figuring among those parameters are: soil organic matter content, C/N ratio of soil organic matter and soil organic matter turnover. The latter depends mainly on soil temperature, soil aeration, soil pH and soil moisture content. Despite considerable empirical evidence, almost no literature is available on vine nitrogen status as a function of soil characteristics and the impact of this status on vine development, berry constitution and wine quality. This might be explained by the lack of accuracy of currently available indicators of vine nitrogen status, such as petiole or leaf blade nitrogen content, or their lack of accessibility, as is true for cane arginine content. In this paper we discuss the use of several forms of nitrogen in grape juice (must) as indicators of vine nitrogen status. The accuracy of these indicators provides the means to differentiate nitrogen offer by the soil in “terroir” studies and assess its impact on berry quality potential.