FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY

CHAPTER 5

FIGURE 19: General Mn toxicity symptoms (Photo: D. Saayman).

The norms for Mn content of grapevine leaf blades and petioles are indicated in Table 23. Where deficiencies are present or are expected a 0.4 – 0.6% Mn sulphate solution can be used as foliar nutrition. By adding urea (0.5% solution), the efficacy of uptake is increased. The use of Mn containing fungicides may suppress latent Mn deficiencies, but is insufficient in the case of visible deficiency symptoms. TABLE 23: Norms for the Mn contents (mg kg –1 ) of leaf blades and petioles of grapevines. Fruit set Leaf blade Petiole Minimum Sufficient High Toxic Minimum Sufficient High Toxic 10 30 – 60 250 > 650 20 30 – 60 100 > 500 Veraison Leaf blade Petiole Minimum Sufficient High Toxic Minimum Sufficient High Toxic 20 30 – 80 300 > 750 20 30 – 60 200 > 1500

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