Analysis of soils is the determination of the composition of soil by various chemical and
physical methods. Analyses are normally done in the laboratory, though there are kits
available which allow you to test for yourself if the soil is deficient in any of the major
nutrients.
The pH value of soil and other materials can also be tested by the amateur—see
below “Testing for Soil pH”.
The CEC (Cation Exchange Capacity) of a soil measures its capacity to hold the
major cations (calcium, magnesium, sodium and potassium—as well as hydrogen,
aluminium and manganese in acid soil). It is a measure of the potential nutrient reserve
in the soil and is therefore an indicator of inherent soil fertility.
- Chemical Analysis
The purpose of this is to determine the chemical composition of soil, including trace
elements, and to determine its state of fertility. This information helps food producers to
use the correct type and amount of fertiliser.
For the experienced observer a simpler, quicker and cheaper option to chemical
analysis is to check the status of the soil’s nutrients by observing how plants grow in it.
“ TraceElements”, pages 23–29.
- Mechanical Analysis
The purpose of this is to determine the texture and physical properties of soil, which is
mainly of interest for the classification of soils and their land-use.
Results of a mechanical analysis enable the soil texture or soil type to be classified,
by means of the diagram shown on the next page, known as The Soil Triangle:
18 TONY WINCH
Soil may be analysed both chemically and physically (“mechanically”). In both
cases soil samples must be taken that are representative of the area, and sampled from a
large number of sites using standardised procedures. One simple method to take soil
samples is to imagine the field in the shape of the letter “W”; samples are taken at
intervals all along this imaginary line.
Some of the symptoms of nutrient deficiency and toxicity are described in 1Cd.