FERTILISER GUIDELINES FOR THE WINE INDUSTRY

namely general yellowing, is consequently mostly present on older leaves. It only becomes visible once there has already been a negative impact on crop load, making it prudent not to wait for the appearance of such symptoms before intervening. In practice it is found that excessive N-nutrition occurs more frequently than deficiencies. This results in the rapid enlargement of leaves which induces a temporary Kdeficiency (the socalled spring fever of the Californians) and high levels of nitrate accumulation in leaves which can lead to shiny blemishes and leaf edge necrosis. Long, flat internodia, bunch abortion and shattering of ber ries are further symptoms, as in the case of the growth-arrested phenomenon on N-rich soils along the Orange River.

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FIGURE 4: Symptoms of excessive N. Leaf edge necrosis (induced Kdeficiency), shiny blemishes and necrotic lesions.

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