FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY

CHAPTER 2

2 COLLECTION OF SOIL AND LEAF SAMPLES SO I L SAMPLI NG The purpose of soil sampling and soil analysis is: • to predict the probability of a profitable reaction to application of fertiliser; • to evaluate and improve soil fertility; • to recommend practices for fertiliser and lime applications, and • to detect and correct imbalances in nutrient concentrations. 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. The most important benefit of soil analysis in existing vineyards is that changes in soil fertility can be observed and corrective measures may be applied, before nutritional problems that may harm grapevine performance, can develop. 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 commencement of sampling, the site should be divided into its various cultivation units. These units are areas which will be managed similarly because of soil form, soil depth and the incidence of coarse fragments. Separate samples are collected from each of these cultivation/management units and samples from the different 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 P I ETER RAATH

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