Determination of the Nutritional Requirements of Rootstock Plantations, in Order to Improve the Quality of Grafting Material
Conradie, W J
Hunter, J J
This project commenced during 1997-1998. Two existing mother plantations, on different soils, are used in the investigation. In the first case, on a relatively clayey soil, R99 and 101-14 Mgt are used as experimental material. In the second case, with Ramsey as experimental material, the soil is sandy, with varying amounts of organic material. Measurements are done separately on sections where the soil contains high and low amounts of organic material, respectively. Nitrogen fertilisation is applied at levels ranging from 100 kg N/ha to 325 kg N/ha.
In practice rootstock plantations usually receive nitrogen fertilisation from middle September to end December to beginning January. Results indicated that this timing should be correct in most cases. However, the amount of nitrogen that should be applied will vary, depending on cultivar, planting width and trellising system. Requirements may vary from less than 100 kg N/ha to 150 kg N/ha. Little potassium is absorbed after the end of January and it is important for this element to be adequately supplied during the early season. Significant amounts of phosphate, calcium and magnesium are absorbed during the latter part of the growing season. Soils should therefore be adequately supplied with these elements at the end of January. Current indications are that excessive nitrogen fertilisation may affect the quality of grafting material negatively for soils with high organic material, while this may not necessarily be the case for soils with low organic material.
Olivier, M P and Conradie, W J. 2000. Effect on cultivar and soil type of the nutritional requirements of rootstock plantations. Poster presented at the 2nd International South African Society for Enology and Viticulture Congress, Cape Town, South Africa.