FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY

that the petiole is sampled for analysis, but in certain cases it will be necessary to analyse the leaf blade as well. Norms for the elemental contents of leaf blades and petioles are indicated in Chapter 5. Sampling protocol The way in which vines are sampled for analysis has a major effect on the results obtained. As shown in Figure 1, leaves opposite the bunch are sampled at fruit set, or if this has been removed, the leaf between the third and the fifth node on a bearing shoot must be sampled. At veraison leaves must be sampled between the fifth and the eighth node from the growing point. Thirty leaf blades or petioles, immediately separated at sampling, are sufficient. Either one can be analysed although, as already discussed, petiole analyses are generally regarded as more accurate. The phenological stage (e.g. fruit set or veraison) of sampling must be indicated. Leaves should not be sampled during the hottest part of the day, since it can affect leaf composition. It is preferable to collect samples in the morning. Samples must be placed in a clean plastic or paper bag and should be kept cool until delivered to the laboratory. The samples must not be frozen under any circumstances.

Sampling at fruit set

Sampling at veraison

FIGURE 1: Positions where leaves should be sampled for analysis. SKETCHES FROM DAVENPORT & HORNECK (2011).

16 | COLLECTION OF SOIL AND LEAF SAMPLES