FERTILISER GUIDELINES FOR THE WINE INDUSTRY

COLLECTION OF SOIL SAMPLES

The purpose of soil sampling and soil analysis is: • to classify soils in order to suggest practices for fertiliser and lime applica tion; • to predict the probability of a profitable reaction to application of fertiliser; • to evaluate soil fertility; • to determine which specific soil conditions could be improved by applying soil amendments; and • to detect and correct imbalances in nutrient concentrations. The most important advantage of soil analysis is probably the ability to moni tor changes in soil fertility in order to apply corrective action before nutritional stress occurs. Soil analysis is essential before soil preparation to ensure that physical and chemical defects can be corrected during preparation. Regular analysis is required in existing vineyards to ensure that optimal conditions for growth are maintained. SAMPLING FOR SOIL PREPARATION: Profile pits are necessary to evaluate the physical/morphological characteristics and to determine the borders of management units. For smaller commercial areas, sampling should be done on at least a 50 m X 50 m grid. If the initial soil examination reveals that large soil differences occur between points, more pits should be dug to determine where the soil transitions are. Before com mencement of sampling, the site should be divided into its various cultivation units. These units are areas which will require similar management based on soil form, depth and the incidence of coarse fragments. Separate samples are collected from each of these cultivation/management units and samples from the different profile sampling points within the same unit may be mixed in order to obtain representative samples for that management unit. The depth/ thickness of the different horizons/layers, as well as an estimation of the coarse fraction must also be noted. With soil preparation for vineyards it is desirable to collect samples from the topsoil and subsoil separately. It is also often desirable to sample underlying clay material separately, since salts can move upwards to the overlying soil layers during dry periods. The depth of sampling must be indicated. A sample of 1 kg is sufficient.

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