FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY

CHAPTER 5

SUMMARY Differences in soil type lead to divergent nutrient requirements between the different table grape areas and even within areas. In order to obtain balanced growth and canopy-to-crop ratios, as well as quick ripening of bunches and shoots, and naturally good grape quality, individual nutrient requirements must be addressed in a fertilisation programme. Nitrogen fertilisation requirements are primarily determined by vegetative vigour. On account of P moving so slowly in the soil, P adjustments are done every few years, at which time P levels are raised to a minimum concentration in the soil. However, P tends to be fixed in soils with high pH values, in which case annual applications, according to production, may be considered. For potassium fertilisation the texture of the soil must be taken into account. If the soil is sandy, maintenance fertilisation, based on expected yield, is applied. For clayey soils the K concentration is adjusted to a minimum norm. In general, Ca and Mg fertilisation is unnecessary in soils for which the pH has been rectified, or where free lime occurs. Rectification of trace elements can be done in soils where the pH of the soil is optimal, even though foliar nutrition may also be used successfully to address deficiencies.

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