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MADE POSSIBLE BY
THE MAIZE TRUST
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trace elements in place. The plants can use these nutrients when required
during the various vegetative and seed forming growth stages.
Cations are positively charged chemical entities that are always
found in conjunction with other chemical entities or on the soil col-
loid. The various entities are in constant motion, changing from one
combination to another within the dynamic basic soil colloid struc-
ture and complex of microorganism life cycles.
Soils are tested for Calcium (Ca), magnesium (Mg), potassium (K),
sodium (Na), ammonium nitrogen, other cations and several essential
trace minerals. These positively (+) charged nutrients are generally
known as bases. They can have one or two positive charges. Nega-
tively (-) charged entities are known as anions.
If you think of two magnets each with a north and south pole – when
you bring the north poles or south poles together the two ends are
repulsed by a magnetic force. A north and south pole brought together
will have a strong attraction and be strongly held together. Likewise, in
simplistic terms, the positive charged plant nutrients or cations will be
strongly attracted to a negatively charged surface.
The negatively charged surfaces are found in the soil colloid and
especially soil humus fractions. The cation molecules differ in size
and charge. The mix or percentage of each within all the cations at-
tached to the soil colloid complex is known as base saturation. Or in
simple terms how much of each nutrient needed by the plants is held
in a particular soil.
An ideal balance determined by Dr Albrecht and other research-
ers is as follows:
Calcium 60% to 70%, magnesium 10% to 20%, potassium 2% to
5%, sodium 0,5% to 3%, other cations or bases 5%.
The acidity or pH levels of soils and a liming programme will
largely determine whether the above ideal balance of nutrients is
achieved. The above balances are now shown by many laboratories
or can be calculated from the separate amounts shown in the soil
test report. Compare your soil test to the ideals above. The amounts
are usually shown in milligrams of each nutrient per kilogram of soil.
The CEC is thus a measure of how good your soil is at holding
the essential plant nutrients. Some labs show this as Total Exchange
Capacity (TEC). A very sandy soil with very little or no organic matter
or humus will show a very low CEC and a highly fertile organic soil
will have a high CEC or TEC.
CONCLUSION
Look at your soil test results and see how your soils match up to the
ideal. Then make the changes needed in your cultivation and fertilisa-
tion practises to improve your soils for a sustainable future.