Magnesium in the soil - Soil Essentials: Managing Your Farm's Primary Asset - page 39

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Magnesium in the soil
Background
Magnesium is a metal element written using the chemical symbol Mg. It is one of a
group of elements referred to as the cations. In soil it is always found in
combination with other elements and molecules in the form of hydroxides,
carbonates, sulphates and chlorides to name a few. In plants it plays an important
part in photosynthesis, being part of the chlorophyll molecule. Magnesium in
plants aids in phosphate metabolism, respiration, the activation of plant enzymes
and in protein synthesis. It is also found in significant quantities in the seeds of
many plants. Magnesium plays a vital part in the health of animals (including
humans), particularly in conjunction with calcium and boron in bone formation,
and in blood serum for metabolic processes.
Magnesium in the soil
Magnesium, in association with other cations, helps form soil structure by
affecting f locculation of clay particles. In an ideal situation it should be in
balanced ratios with the other main soil cations - calcium, potassium and sodium.
The relative proportions are: calcium 65-70%, magnesium 15-20%, potassium
5% and sodium less than 5%. When these cation ratios are in balance the soil is
likely to be soft and crumbly, allowing plant roots to freely grow in the soil and
enabling soil biology to thrive.