MODIFIED DRIS-SYSTEM FOR LEAF ANALYSIS TO OPTIMISE FERTILIZER INPUTS - FURTHER DEVELOPMENTS WITH GRAPEVINES

For annual plants, leaf analysis cannot replace soil testing in order to determine their fertilizer requirements. In contrast, leaf nutrient concentrations of perennial plants, since they grow in rotations of 10 to 30 years, with no change in species and with changing soil test values, often reflect, excepting annual fluctuations, the fertility status of sites. The compositional nutrient approach (CND) is superior to normal DRIS calculations because it is able to reflect the nutritional status of a crop more exactly. In a long term field fertilizer experiment Sufficiency Range (SR), DRIS norms (Beaufils), and the DRIS_CND approach were compared. The CND norms reflected well the responses of different vineyards receiving quite different fertilizer treatments. In a control plot, fertilized only with P and K, over a fifteen years period, the P-index shifted towards the deficiency range. That is most striking because P was supplied annually and the soil P-fertility index was high. Strong interaction was also observed between N and Mg contents in leaves. With CND values it is possible to get a closer insight into the nutrient balance of grapevine and its relationship to final product quality. In grape high yield is far less important than grape quality. The CND approach has the ability to give the right information for quality-oriented production. The system is currently stored on a CD as an EXCEL sheet. It should be helpful for advisory services and for fertilizer recommendations.