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GRAANGIDS
2017
GRAIN GUIDE
Soil survey process
Like with the taking of precision samples, a grid pattern is distributed across the field with the aid
of a GPS. The grid size is usually the same as for precision samples. Point observations are usually
done with the aid of a mechanical soil auger or manual soil auger by determining the soil type
at each GPS point and indicating the soil properties on the GPS and/or on an enlarged aerial
photograph of the farm. Soil borders should be indicated on the aerial photograph during the
mapping process by indicating visible soil differences in the field on the map and by correlating
soil differences by way of aerial photograph interpretation with the topography of the field and
drawing this on the aerial photograph.
It is also good practice to describe additional soil properties in profile holes in the dominant soil
units. Soil samples are taken of the different soil horizons and analysed as representative of the
soil unit concerned.
Map processing and report
The soil borders drawn in on the aerial photograph are captured in a geographical computer
programme (GIS) and all the chemical analysis data and physical soil data (texture data) are
linked to the GPS points as point data. A soil map is now processed, indicating the geographical
spread of soil types in the farm on the basis of a soil legend. A report should be drafted on the
basis of the soil map, containing, among other things, the aim, methods, results and discussion of
the soil survey.
Application maps
Different application maps are compiled with the survey data as basis. Examples are potential
maps that indicate the differences in yield potential for different crops, with prescription maps for
differential fertilisation recommendations on the basis of the potential differences, as well as the
varying plant establishment. These prescription maps are then loaded into differential equipment
in agricultural implements, which apply the prescription as required across the field, as needed
per area.
BE ON THE LOOKOUT FOR
QUALITY
PRECISION SERVICES
Continued from p. 41