Why and How Are Soils Different
As mentioned previously, soils are the result of the interaction of five soil forming factors.
If these factors were precisely the same for all parts of the earth then the soils of the world would all be expected to be exactly the same.
However, even over very short distances one or more of the five factors can change, often quite dramatically.
As a result the appearance and the chemical, physical and biological properties of soils vary from place to place.
Consequently not all soils will have properties suitable for a particular crop or use. It is therefore important to know how each particular soil behaves and its distribution on the lands surface.
Even a cursory look at the soils of a region such as the Waikato illustrates how and why soils can vary:
Soil scientists are able to make a number of interpretations based on observed soil properties:
Analysis of chemical and physical properties usually requires laboratory procedures.
Results can be used to make statements about soil nutrient levels and likely responses to land use.
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many of the mineral soils found in the Waikato are relatively young (less than 12,000 years old), so soil forming materials have had time to alter only slightly - parent materials, therefore, typically dominate soil properties, |
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as most of the mineral soils are formed from alluvium, soil textures are highly variable, ranging from gravel to clay even within a single profile, |
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soils formed on ridges under well drained conditions differ from those formed in lower, poorly drained areas, |
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peat, characteristic of certain areas within the Waikato, forms organic soils. Around the edges of peat swamps soils often have peaty tops on a mineral subsoil. |
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soil colour is used to give an indication on the drainage state of the soil - pale colours and mottles indicate poor drainage, |
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the structure of the soil (ie the size and shape of the aggregates), combined with the ease with which a soil is dislodged from a soil profile, indicates rooting depth of plants and rate of water movement. |