FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY

CHAPTER 5

Fertilisation according to vigour From the foregoing it is clear that vine’s N status and growth is not only determined by the organic material content of the soil, because factors like soil characteristics, irrigation management, scion/rootstock combination and climate may also play a role. Vegetative growth is therefore regarded as the most reliable indication of a vine’s N status, because it reflects all the above-mentioned factors. Where grapevines show insufficient vigour, the problem must be identified, because it is often not due to under fertilisation of N, but as a consequence of other factors like physical soil constraints, under irrigation, nematodes and salinity or soil acidity. The norms that are used for the evaluation of vigour, together with the appropriate fertilisation guidelines are shown in Table 12. For vineyards with poor vigour, N fertilisation is applied according to the seasonal demand (Table 8) in a minimum of three instalments, i.e. approximately three weeks after bud break, shortly before flowering and/or at pea size berry stage, and lastly just after harvest. In vineyards with ideal vigour the N application at fruit set can be largely eliminated, if the canopy is already fully developed at the time of flowering and if active growth still occurs. For more vigorous vineyards the application after bud break may also be eliminated. Post-harvest fertilisation will only be eliminated for excessively vigorous vineyards.

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