FERTILISER GUIDELINES FOR THE WINE INDUSTRY

EXISTING VINEYARDS: After preparation, samples are collected per management unit. To ensure that the samples are representative of the unit, it is once again constituted from subsamples which are taken from different places in the unit. If the soil has been ridged, the samples should be taken from the ridge only. The first sam pling ought to be done shortly after preparation to determine whether optimal conditions were created during preparation. For maintenance fertilisation, soil samples must be taken at least every three years, except in cases of very sandy or stony soils where leaching can reach serious proportions. Samples should then be collected every two years. These samples are taken in the vine row. Because soil composition can vary drasti cally over short distances, long term trends can be best determined if samples are collected more or less at the same places. Vines should be marked for this purpose to ensure that samples are collected more or less at the same place. Weak patches in the vineyard should be sampled separately. Because the cultivation action often disturbs the transition between soil lay ers, samples should be collected from fixed depths. Samples should always be taken at the same depths in order to establish a history of results, which can be correlated with fertilisation application. If the person who does the rec ommendations does not have records of previous analyses, more than one layer must be sampled. In order to determine the effect of especially lime and phosphate fertiliser which have not yet reacted completely, it is preferable to collect samples at depths of 0-150 mm and 150-450/500 mm. Considering that few roots are found deeper, deeper samples are not necessary. If the soil is shallower than 450-500 mm, sampling should be limited to above the restricting layer. The presence of underlying clay in the sample can affect results to such an extent that they are meaningless. A sample of 1 kg is sufficient. STONEY SOIL: If the soil is very stony and the stones are so large that it cannot be sampled, an estimate of the incidence of stones must be made, i.e. indicate the volume occupied by stones. This information can have an appreciable effect on the fertiliser recommendation and must accompany the soil samples to the labo ratory. A stone correction is used in the estimation of gypsum, lime, potassium and phosphate fertiliser requirements.

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