Soil analysis results - Soil Essentials: Managing Your Farm's Primary Asset - page 68

example, Sodic Mesotrophic Yellow Dermosol. (At this stage this terminology is
probably more useful to soil scientists than farmers.)
(2) Soil pH . The pH describes the level of acidity or alkalinity of the soil, with
1 being extremely acid, 7 being neutral and 14 being extremely alkaline. The tests
will be done with either one part of soil in five parts of water, reported as pH water,
or as one part of soil in five parts of dilute calcium chloride solution reported as
pH CaCl 2 . A good report will also specify the desirable pH level for the crop to be
grown.
(3) Electrical conductivity ( EC ). This is a way of measuring how much salt is in
the soil. As salty soil conducts an electric current better than a soil without salt,
the higher the conductivity reading, the saltier the soil. This is an important
reading as many crops have a low tolerance to salt (see 'Total soluble salts' below).
The unit of measurement is microsiemens per centimetre or decisiemens per
metre.
(4) Total soluble salts ( TSS ). This is a measure of all the soluble salts in the soil,
including water soluble plant nutrients, and will be measured in parts per million
or milligrams per kilogram.
Nutrient elements
Nutrient elements may be measured as plant available or as total amount of the
element present in the soil. The amount of each element actually available to the
plants will vary with soil pH, so when considering fertiliser programs it is best to
get the pH right first if possible, before adding other nutrient elements. Modern
thinking is that the soil cations should also be brought into balance before adding
other nutrient elements. These consist of calcium, magnesium, potassium, sodium
and, in acid soils, hydrogen, aluminium and manganese.
Nutrient elements are measured in parts per million (ppm), milligrams per
kilogram (mg/kg) or milliequivalents per 100 grams of soil (meq/100 g). They may
also be expressed as a percentage of the soil. Irrespective of the way they are
written, a good soil report will show the desirable level in the same units, so it is
easy to see if more is needed or if there is too much of a particular element.
(1) The soil cations . These consist of calcium, magnesium, potassium, sodium,
hydrogen, aluminium and manganese. In a soil report the quantities present will
usually be expressed as the plant available amount. The exception is hydrogen that
determines soil pH. A good soil report will show the amount of the cations present
and a recommended level for the crop for that site.
(2) Cation exchange capacity ( CEC ). This refers to the capacity of the soil to
hold the cation elements, and is a measure of the potential nutrient reserve in the
soil and thus an indicator of soil fertility. An imbalance of soil cations, especially
calcium and magnesium, can cause soil structural problems and high levels of