TO JVZ SOIL
Preparation of vineyard soils in South Africa: A synopsis of 50 years of research information.
Van Zyl, J
Stellenbosch University. Faculty of AgriSciences. Department of Soil Science
Van Zyl, J
Objectives and Rationale
Considering the determining role of soil preparation in the successful establishing of a vineyard and the huge costs involved, it is imperative that all the available information is compiled correctly in one place. The objective of the project therefore is to comprehensively review all literature on preparation of vineyard soils in South Africa and internationally to compile the existing information in a practical condensed handbook suitable for use by wine and table grape farmers, technical advisers and students.
South African as well as international literature has been reviewed, field trips have been undertaken and during a visit to the United States, Dr Hoffman viewed the newest drainage technology in that country. The available information together with relevant photographs were compiled in book form.
The book “Soil preparation for sustainable wine and table grape vineyards” was printed and was launched on 14 August 2019.
A reduction in available soil volume decreases the grapevine root system and subsequently also shoot growth and yield. The first sign of soil compaction is uneven growth which may eventually progress to dead patches in a vineyard. Experimental results showed that the soil must be loosened to a depth of at least 800 mm, but preferably to one meter. Adequate soil depth could compensate for lack of irrigation in the coastal region of the Western Cape. The correct choice of implement for soil preparation is determined by soil type. Effective soil preparation means that the soil is uniformly loosened to a depth of at least 800 mm, that poor subsoil is not brought to the surface and that the loose soil has a good structure i.e., no large clods which cannot be exploited by roots. Conditions for preparation are best when the soil surface is dry to ensure good traction for tractors while the subsoil is still moist. Deep tillage in two directions may be necessary when a uniformly loose medium is not achieved with working in one direction or better mixing is required. Soil preparation provides the only opportunity to apply lime on acid soils, remedy low P contents in the subsoil and incorporate gypsum in the subsoil for the reclamation of saline soils. Loose soil re-compact after soil preparation and such re-compaction is especially harmful in newly planted vineyards.
Key Conclusion of Discussion
Roots visually illustrate what conditions they experience in the soil and therefore their distribution is important when soil preparation is planned or assessed. New technology makes root studies easier but the use of root inspection in soil profile pits is still essential. The penetrometer is the ideal instrument to detect soil compaction and penetrometer resistances of more than 2000 kPa is considered restricting to root growth. Methods to alleviate root restrictions depend on soil type, but an array of implements is available to provide a horse for each course.
Recommendation to Industry / Key take-home message
The correct soil preparation is essential for sustainable and peak grape production. Fortunately, the knowledge to achieve this goal is available in South Africa and is now contained in the new book on soil preparation. This knowledge is interpreted into clear and concise recommendations.