WINETECH Technical Yearbook 2019

of five subsamples taken at various places in the block. • When problem spots occur in a block, at least two leaf samples should be taken in order to make meaningful deductions; one sample in the problem area and one in the healthy area. • If foliar nutrition is sprayed before leaf samples are taken, the laboratory results may be misleading for the purposes of fertilisation. Do not take leaf samples directly after application of foliar nutrients. Leaf analysis results should be interpreted by experts, including soil scientists and viticulturists, who are able to make reliable and accurate recommendations. Leaf analyses are an instrument in the hand of the fertilisation consultant to update existing fertilisation programmes. The intention is to combine the grapevine’s nutritional requirements and production objectives on

scientific and economic levels in a practically manageable programme. Make the effort to take samples correctly and in the right places; any analysis and recommendation are directly dependent on the quality of the sample received by the laboratory. Fertilisation programmes, foliar nutrition and solutions to problems are all based on the analyses of the samples submitted. In order to make the best technical recommendation and obtain optimal economic value, the best possible sample should be analysed. All aspects discussed in the three articles impact on the profitability of the farming enterprise, whether in terms of production volumes, fruit quality, longevity of a block, or production cost. Furthermore it contributes to the ecological sustainability of the farming system, in that it may prevent mismanagement of fertilisation especially (excessive fertilisation).

PHOTO 2. This shows how the leaf has been separated from the petiole.

– For more information, contact Johan de Jager at dejagerj@vinpro.co.za.