BLADE OR PETIOLE ANALYSIS AS A GUIDE FOR GRAPE NUTRITION

The leaf opposite the first fruit cluster was used for the investigation of grape nutrition at bloomtime and ripening. Blade and petiole analysis are both suitable for the assessment of the nutrient status in the case of P, K, Mg and Ca. However, the data obtained for N differ markedly, depending on the organ considered. For P and K, the differences in nutrient content between vineyards as well as the seasonal variations are better reflected by petiole analysis. This effect, which should be favorable to the diagnosis, is paralleled by a wider scattering of the nutrient levels; as a result, the differences observed in the petiole are not statistically more significant than those in the blade. Under relatively homogeneous conditions (same variety, same climate), the differences induced by variable parameters (soil type, sampling times, years) appear to be fluctuating, so that nutrient reference levels can not be recommended, whether for the blade or the petiole. Both sampling modes (blade or petiole) are complenentary to each other and could therefore be used advantageously for a better control of grape nutrition and fertilization.