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. The data show that blade analysis 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 nitrogen differ markedly, depending on the organ considered. For phosphorus and potassium, the differences in nutrient content between vineyards as well as the seasonal variations are better reflected by petiole analysis. This effect, which should be favourable 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 cannot be recommended, whether for the blade ...