SOIL CHEMISTRY

The chemistry of the soil can be thought of as the service to the soil house and will dictate which tenants live there.

We will now go further and start to explore our soils by looking at soil chemistry, which can also greatly influence the physical and biological nature of the soil.

The subject of soil chemistry involves the investigation of identifying the different elements in a soil and how they influence that soil.

Your soil is "full" of elements which can be divided into positive and negative elements:
The elements that have a positive [+] charge are collectively called cations ["cat irons"].

Major Cations

Calcium	[Ca ++]	Potassium	[K +]	Hydrogen	[H +]
Magnesium	[Mg ++]	Sodium	[Na +]

Minor Cations

Iron	[Fe++]	Copper	[Cu++]
Zinc	[Zn++]	Manganese	[Mn++]

There are other elements that have a negative [-] charge and they are collectively called anions ["an irons"]. For example:

Phosphorous	[P-]	Sulphur	[S-]	Molybdenum	[Mo-]
Chlorine	[Cl-]	Carbon	[C-]	Boron	[B-]

Poor soils are full of the wrong balance of elements. They have an excess of some elements and a deficiency of other. For example in an acid soil there is an excess of Hydrogen. In an alkaline soil there is often an excess of two of the three dominant cations being Calcium [Calcareous soil], Sodium [Saline soils] and Magnesium [black or grey pug clay if high sodium].

Productive healthy soils are full of the correct balance of elements.

So to correct a poor soil and improve the health of the plants and animals we need to duplicate or copy the soil element balance found in productive healthy soils. We can do this by adding or changing the availability of the needed elements.

Dr William Albrecht together with other scientists found that a good soil should have over 95% of the available elements as cations on the Base Saturation Percentage! These cations were needed within certain ranges. The Albrecht cation balance model can act as an international benchmark to assess how close your soil is to a chemically balanced soil. So to correct a poor soil we need to duplicate or copy the required soil element balance that nature requires for each group of plant species that we wish to grow.

Our challenge is to work in harmony with nature to provide the correct chemical balance for the plants that we grow [without forgetting the biological and physical requirements of the soil].

MODERN ALBRECHT SOIL BALANCE

The Albrecht concept is very simple in its basic logic. Tests were initially done on soils that consistently grew the highest quality crop yields and it was found that these soils all had a similar chemistry with Calcium levels being between 60-70%* and Magnesium 10-15%*. Very definite levels were also established for N, P, K, S and the trace elements. Over seventy percent of agricultural crops and high production pastures grow best within this range of soil chemistry. It has been proven, again and again, that a balanced approach to soil chemistry is the key to successful plant growth and that when this occurs soil pH, aeration, drainage, structure and beneficial soil biology also improve. Thus, if we can balance our soil chemistry including the trace elements, improved productivity and plant and animal health will be a natural outcome.

WHAT CALCIUM LEVELS DO YOUR PLANTS NEED?

Calcium levels must meet the requirements of beneficial soil life and plants. Calcium levels are often the dominating cation [+] which influences the chemical [pH], physical and biological nature of the soil.

GENERAL CROPS / PASTURE REQUIREMENTS 68%* Grass 65%Ca* Lucerne 70%Ca*

The secrete to the success of the Albrecht Cation Balance model is that it beneficially affect, not just the chemical [soil fertility], but also the biological [humus formation] and physical [soil structure] nature of the soil. What is why it is so important to developing sustainable agriculture.

CAN SOIL pH INDICATE YOUR CALCIUM [LIME] NEEDS

Over fifty percent of agricultural crops and high production pastures grow best within a critical range of Calcium levels being between 60-70% and Magnesium 10-15% base saturation. It has been proven, again and again, that a balanced approach to soil chemistry is the key to successful plant growth and that when this occurs soil pH, aeration, drainage, structure and beneficial soil biology also improve. Thus, if soil chemistry is balanced, especially with calcium, improved productivity and plant and animal health will be a natural outcome.

In Table 1*, 'A' is a balanced, healthy, productive soil being Ca 68%, Mg 12%, K 5%, & Na>1.5%. As discussed previously, this balance was identified after intensive research based on analysing soils that were naturally productive and healthy, and comparing them with un-productive soils. Notice that Calcium is the major Cation in a healthy soil. Calcium promotes good crumb structure in soil and is important for numerous other soil processes.

When Hydrogen occupies 12% of the CEC [Cation Exchange Capacity], soil pH is 6.2. If the soil fertility balance of soil 'A' is changed by replacing Calcium with Magnesium on 20% of the CEC, the result is soil 'B' with High Magnesium levels. This type of black soil is tight/hard when dry, and sticky when wet. This is a medium productivity soil that is difficult to manage. The Hydrogen % is unchanged so soil pH is still 6.2, but the soil is deficient in Calcium and needs Lime.

Removing Magnesium from 20% of the CEC of soil 'B' and replacing it with Sodium. The results in soil 'C', which is an unproductive saline soil. Note that all three soils have the same 6.2 pH!

The decision as to how much Lime/Dolomite to be applied is calculated by subtracting the Calcium value found on the soil audit from the desired Calcium value [68%] according to the TEC. This ensures that light sandy soils do not get over limed and heavy soil can be budgeted to receive applications over a number of years. This same technique is also used for costly trace elements and can save hundreds of dollars on wasted fertiliser.

As illustrated in the following table it is possible to have the same pH of 6.2 in healthy, productive soils [A], a high Magnesium soil [B] and saline unproductive soils [C].

TABLE 1

	Soil A	Soil B	Soil C
	Balanced	High Mg	High Sodium
Nutrient	Percent of TEC
Calcium [Ca++]	68%	38% 6	38% 6
Magnesium [Mg++]	12.0	42.0 6	22.0 6
Potassium [K+]	5.0	5.0	5.0
Sodium [Na+]	1.5	1.5	21.5 6
Trace Elements	1.5	1.5	1.5
Hydrogen [H+]	12.0	12.0	12.0
TOTAL	100.0	100.0	100.0
pH	6.2	6.2	6.2

*Adapted for Building Healthy Soils and Plants, Tony De Vere [1995] Unpublished.