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Our precious soil
Also availabe in: Afrikaans | Xhosa
Generally, a surface unit of ground is referred to as an acre, a patch, morgen or hectare.
The term used most frequently when referring to the size of such a unit, is hectare. One hectare is approximately the size of a rugby or soccer field and covers 10,000 m2.
The application of fertiliser or irrigation water is usually according to a given quantity per hectare, and crops are planted at a given number of plants per hectare.
The number of animals that can be kept per hectare or the crop yield per hectare gives a good indication of the relative fertility of the soil.
There are different kinds of soil, for example clay, loam and sandy soils.
Sandy soils
They consist of visible loose grains and are very susceptible to wind and water erosion. Sandy soils are very easy to cultivate and make an excellent seedbed for germinating seeds and young plants. These soils usually have a poor water-retaining ability and their fertility is poor.
Clay soils
They consist of very fine particles that cling to each other when they are wet and the soils stick and smear when they are cultivated. If it is cultivated when dry, they form large clods, and they make a poor seedbed that easily clogs. They are slow to absorb water and become waterlogged during the rainy season.
Loam soils
These are regarded as the ideal soils and they do not have the bad properties of sand and clay. They are easy to cultivate, drain well, make a good seedbed and have a crumbly appearance.
When a hole is dug in the ground so that the soil is seen from the side, there are various soil layers with differing thickness, depths, colours, textures and structures.
This total picture is the profile of the soil. The description of the layering and other properties is known as soil morphology.
The upper, cultivated part of the soil, for example, is the plough layer of the profile. A clay layer often occurs deeper down in the soil profile. Underground clay must not be mixed with topsoil. Underground clay does not mix well with topsoil and gives a poor seedbed.
Wet or waterlogged soils usually occur in winter when there is too much water on the soil for all of it to penetrate or drain away. Heavy rain can be the cause.
A compacted, shallow clay layer below the topsoil also accompanies this, and this layer is impenetrable by water. Sometimes it occurs in lower localities where run-off water gathers.
Another cause of waterlogged soils is water that has drained from irrigation dams or canals where the water moves on the clay layer to appear at shallower localities. Plants become waterlogged as a result of poor aeration and a lack of oxygen.
The only way to solve this problem is to get rid of the superfluous water. Soil drainage by means of open furrows, underground drainage pipes or the building of beds are the methods that are employed with the greatest measure of success.
Another common problem is the occurrence of brackish soils. Brackish soil is any type of soil in which an excess of soluble salts occurs. This is usually to be found in places such as Oudtshoorn or Vredendal where the climate is very dry.
It is also to be found in poorly drained and low-lying localities.
Salt-bearing matrixes from which soil is derived, can give rise to brackish soils. Saline irrigation water or drainage water can cause brackishness, and so can the application of too much fertiliser.
There is only one way to improve brackish soil. The soil must be drained and the brackish salts must be washed out of the soil with good-quality irrigation water.
At the end of this process, soil analyses can give an indication of the extent to which the soil has been improved. It is important that soils be analysed before any kind of fertilisation is applied.
Laboratories conduct analysis of soil samples. Analysis can determine the acidity of the soil, the saline content and the quantities of various plant nutrients. In short, analyses give us an idea of the fertility of the soil.
They can, for example, be used to determine how to improve acid soils by liming or to determine which fertilisers and how much of each should be applied for various crops.
Soil samples are usually taken from the cultivated soil depth. For vegetables and other annual crops, it is a depth of 15 to 25 cm (about the depth of a spade). Each sample must represent a particular land or patch of ground. Your local extension officer can advise you on this. Sometimes he is also the best person to deliver the samples to Elsenburg. For more information visit the Elsenburg Plant Laboratories
After the analyses have been performed, the report is mailed to the producer, and a copy is also sent to the extension officer who can explain them more fully.
A soil sample must consist of about 1 kg of soil and be packed in a clean plastic bag. Complete information must be supplied to the laboratory regarding the crops to be planted and the availability of irrigation.
Send the samples to:
The Analysis Laboratories
Private Bag X1
Elsenburg
7607
CP de L Beyers
ELSENBURG / Nitrophoska
