FERTILISER GUIDELINES FOR THE WINE INDUSTRY

products are easier to handle with mechanical spreaders, but the powder prod ucts offer the advantage that they can be formulated for specific use/conditions. The use of enriched organic products has become popular due to the addition of an organic component to the normal fertiliser programme, which is regarded as having various benefits to soil and plant health. Although these products are normally used at volumes that will not increase soil organic C-concentration, it does seem to have a stimulating effect on soil microorganisms. Furthermore, the release of nutrients occurs slower from the pelleted product, and prevents undue leaching of nutrients.

ORGANIC FERTILISER

Various organic materials can be used as a source of nutrients. The most com monly used are, (i) manure; (ii) compost and (iii) grape skins and pips. Due to the low nutrient-concentration of these materials, relatively large volumes are consequently required to meet the nutritional requirements of the grapevine. Note also, that the nutrients in the respective sources occur in constant ratios, e.g. 3,5%N, 1%P, 2%K for broiler chicken manure. These ratios are not always optimal for a specific plantsoil requirement, and high/prolonged applications can lead to the development of imbalances in the soil. P and K in particular can build up to unnecessarily high levels in the soil. Applications of organic fertilisers should therefore be managed in the same way that inorganic fertili sation should be managed. The composition of various organic materials are indicated in Table 22.

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Extractable nutrients

C

P K Ca Mg Na Mn Cu Fe Zn B % mg/kg g/kg 0.2 0.7 1.4 0.2 797 72 0.6 106 89 8.2 25 0.5 0.9 0.8 0.3 2159 94 12.4 272 272 9.0 36 0.9 2.2 0.8 0.5 5021 312 13.4 453 453 26.5 37 0.2 0.6 1.3 0.2 1158 209 0.8 92 91 7.1 18

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