FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY

CHAPTER 6

the Cl – in swimming pool salt to Cl + in OCl − ). Therefore, there exists no logical reason why the use of KCl should be discouraged due to the sterilising effect that is claimed to have on soil life. ORGAN I C FERTI LI SERS Various organic materials can be used as a source of nutrients. The most used are, (i) manure, (ii) compost and (iii) grape skins and pips. Due to the low nutrient concentration of these materials, relatively large amounts are required to meet the nutritional requirements of the grapevine. Also note that the nutrients in the respective sources occur in relatively constant ratios, e.g. 3.5% N, 1% P, 2% K for broiler chicken manure. These ratios are not always optimal for a specific plant/soil requirement, and high/prolonged applications may lead to the development of imbalances in the soil. Particularly P and K can build up to needlessly high levels in the soil. Applications of organic fertilisers should therefore be managed, similarly to inorganic fertilisers, in a responsible manner. However, organic fertilisers do have a positive impact on the microbial activity in the soil. Apart from being rich in micro-organisms, it also serves as a nutrient source for organisms that are already in the soil. There is increased realisation of the importance of the soil health effects of diverse microbial life in the soil, also in terms of nutrition. For these reasons taking care of the organic component of the soil becoming increasingly important in fertiliser programmes. If the application (manure/compost) is done in the spring, an application of 1 ton per hectare on the vine row should be adequate. The N application is approximately 10 kg N for 1 ton of compost. Furthermore, 1 ton comprises approximately 2.5 m 3 organic material, which can make a measurable difference, if it is concentrated on the vine row. On the other hand, one ton of chicken manure contains approximately 35 kg N. At an availability of 50% during the first year, such an application should be able to supply half of the post-harvest fertiliser requirement. Depending on the results of the chemical analysis of the soil, this application can be combined with the maintenance applications of gypsum and/or lime. Autumn applications of manure and compost are most effective if it is used in combination with the establishment of a cover crop, where it can be sown in the vine rows. In order to satisfy the nutritional requirements of the cover crop, applications of 3 to 5 ton ha –1 are required. Here it can also be combined with lime and/or gypsum applications, in order to facilitate the application of small volumes of lime and gypsum. Regular application of lime counteracts acidification and eliminates the need for maintenance liming. It is also a slow releasing source of Ca and Mg (35% Ca in calcite and 25% Ca + 12% Mg in dolomite). Gypsum, on the other hand, improves water infiltration and is also a source of Ca (22%) and S (18%). The use of grape skins has no negative effects. It is a source of organic material and NPK, although in low concentrations. Grapes skins also contain sugar which serve as a source of nourishment for microbes. The most effective manner for utilisation is

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