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A Technical Guide for Wine Producers
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RECENT ARTICLES | WYNBOER HOME
MAPPING VINEYARD
SOILS Establishment of a vineyard is an expensive, long term
investment. Establishment cost, for trellised vineyards, can amount to as
much as R40 000 per hectare. It is well-known that soil, in addition to
climate and viticultural practices, is one of the most important factors
with regard to yield and quality of the vineyard. It is impossible to
modify physical and chemical soil limitations significantly once the
vineyard has been planted. Detailed soil mapping and suitable soil
preparation, before vineyard establishment, are therefore indispensible in
order to accommodate differences in soil type and soil characteristics
which may have a limiting effect on successful viticulture. What does soil mapping entail? A soil survey and accompanying soil map are intended to
provide you, the producer, with information about the soil and land form,
as well as information required to take decisions about the use of the
land and the planning of its development. Soil mapping means that "soil
boundaries" should be indicated in some or other way on a map. Two kinds
of soil surveys are relevant, namely a reconnaissance survey and a
detailed survey. A reconnaissance survey, which also includes the
interpretation of aerial photographs, is initially used to identify
suitable localities and soils for viticulture. A detailed survey involves
a field survey in terms of a specific grid system to provide
representative coverage of soil variations so that mapping units may be
composed. Detailed surveys are usually undertaken on a grid system of 75 x
75 metres. The minimum profile pit depth for soil description is 1,5
metres, unless an impenetrable layer occurs in the subsoil. For detailed
identification and mapping of South African soils the revised system is
used, namely Soil classification: A taxonomic system for South Africa
(Soil classification work group, 1991). This system is based on the
identification of diagnostic horizons and material. The various soil forms
are defined in terms of the type and vertical sequence of diagnostic
horizons and material. A description is given, inter alia, of the depth of
all horizons and material, soil form and family, subsoil limitations and
characteristics, texture and soil water conditions. Soil chemical analyses
are important at this stage to rectify soil chemical limitations prior to
soil preparation. Adding value Soil analysis is essential to determine the suitability
of the land for a specific crop. If suitable for viticulture, the
interpretations and recommendations of the soil analysis should be done by
an experienced soil scientist. Factors influencing suitability of the soil
are texture, structure, chemical composition, mineralogical composition,
parent material, depth, slope and drainage danger due to topographical
position. To a large extent these factors determine the depth of root
distribution and therefore the production potential of the soil. Soil
potential also indicates dangers with regard to tilling, erosion,
cultivation and application of water. Cultivar and rootstock selection,
irrigation design and scheduling, soil and crop management and ameliorant
programmes are facets which rely heavily on soil surveys. For you, the
producer, it is extremely important to discuss the results of soil mapping
thoroughly with a pedologist. Soil usually has one or more physical,
chemical and/or morphological limitation(s) such as clay content,
humidity, occurrence of coarse fragments and compacted subsoil layers,
soil acidity levels and nutrition status. In the course of soil
preparation, aspects such as i.a. compacted layers, soil acidity levels
and nutrition status may be addressed. Since the water holding capacity of
soil is adversely affected by a decline in clay percentage and an increase
in the occurrence of coarse fragments, the initial irrigation design and
scheduling should take this into account. The presence of green/gray soil
colours may indicate periodic water saturation and soil management
decisions should make provision for this. Soil texture refers to the
relative relationship of particle size fractions in the soil and varies
from sand to clay. An increase in clay content affects drainage. Soil
structure degrees vary from apedal (structure-free, e.g. sand), weak,
medium to strong in the case of block structure. Water movement and
aeration as well as root development are influenced by soil structure. To
a large extent the physical condition of the subsoil therefore determines
root penetration. For economic production, vine roots require a minimum
soil depth so that root development and water and nutrient uptake are not
restricted. One of the aims of soil preparation is to increase root volume
in order to buffer vines against unfavourable climatic conditions. Soil and climatic requirements of crops
For a reliable evaluation of the suitability, potential
and production ability of a certain land for a specific crop, it is
essential to know the requirements, adjustments and tolerances of crops
with regard to soil and climatic conditions. The expertise of various
disciplines must be integrated to determine the most suitable use, from an
economic point of view, for a specific piece of land. With economic
conditions and market trends continuously changing, and with new and
improved cultivars and farming practices coming into play, regular
re-evaluation of land use is essential and if required, adjustments must
be made to accommodate changing circumstances. Optimal use of resources For optimal use of your resources, as well as the
preservation thereof for posterity, the producer must have access to
useful, comprehensive knowledge of soil and climate. Various mechanisms,
including the integrated production of wine (IPW guidelines), require the
suitability of soil for specific cultivars and soil preparations to be
based on soil profile descriptions. Soil chemical adjustments are
dependent on a soil chemical analysis by a laboratory. The mapping of a
farm entails a once-off expense and serves as a management tool and
planning document for the future. However, small scale vineyard plantings
are still frequently undertaken without having a soil survey done prior to
planting. It is important to plant cultivars according to soil suitability
so as to maintain sustainable, economic production without exhausting the
soil as a natural resource. This also satisfies the winemaker's
requirements vis á vis quality and quantity. |
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