WINETECH Technical Yearbook 2019

PHOTO 1. Examples of deficiency symptoms.

• Leaf blade analyses are more accurate to obtain comprehensive element analysis, while petiole analyses provide better values for nitrate monitoring. • The leaf blade should be separated from the petiole immediately after sampling to prevent the translocation of nutritional elements from one organ to the next (Photo 2). • Leaves should not be sampled during the hottest part of the day, in view of the fact that this may impact on the nutrient concentrations. • Samples should be placed in a clean plastic or paper bag and kept cool until delivery at the laboratory. • In uniform growth areas one composite sample per management unit may be taken. The sample should be composed

TIMING OF SAMPLING Leaf samples should be taken annually at the same physiological growth stage in order to collect meaningful management information. Norms exist for fruiting and véraison. Problems may be sampled at any stage. Procedure of sampling: How and where should leaf samples be taken? GENERAL GUIDELINES • During the vegetative growth stage a leaf sample should be taken of the youngest fully developed leaf (Figure 1). • At fruiting a leaf sample should be taken at the opposite side of the fruit cluster (Figure 1). • A composite sample should consist of at least 30 leaves.

FIGURE 1. Graphic guide of how to sample leaves at various growth stages.