SOIL REMINERALISATION FOR HORTICULTURAL/AGRICULTURAL/FORESTRY APPLICATIONS
HISTORY AND OVERVIEW
THE ORIGIN OF SOILS
The soils of the world have been derived from rocks that have been crushed/ground by glaciers, or expelled by volcanoes, and subsequently subjected to the weathering action of climate by wind, water, variation in temperature or by modern day mechanical crushing.
THE AVERAGE AGE OF SOILS
Most of our soils are over 10,000 years old. This time frame coincides with the last period of glaciation. There are exceptions where glaciers are still actively grinding rock and releasing the fine particles into rivers which flood low lying areas regularly.
The most dramatic demonstration is the Alluvial valleys in the Hunza region of the Himalayas where two modern day phenomena occur - firstly, the natural fertility of the soil, and secondly, the age to which the population live (up to 140 years of age).
The linkage between these two situations is related to the freshly-ground rock which forms the Alluvial soil in as much that silt is slowly releasing a balanced range of minerals, which in turn stimulate the multiplication of micro organisms, which in turn recycle essential plant nutrients. This culminates in the establishment of a fertile environment for plants to grow vigorously and healthily with the ability to be more resistant to disease.
THE DEGENERATION OF SOILS
Since their formation, soils have been losing their inherent fertility (demineralisation) by natural processes (percolating rainfall leaching nutrients to the drainage system and wind and water erosion removing topsoil) and man's cultivation, which results in the removal of soil nutrients in crops for human consumption.
Today, most soils have lost many of the essential nutrients and are unbalanced. Nutrient levels have declined in most areas of the world with many tragic examples of total degradation - the deserts of North Africa and the Middle East and recent examples of rapidly declining soil fertility such as the Murray River area in Australia. This unbalanced soil situation is known as 'demineralised soil', where, because of the lack of imbalance of minerals being released, micro organisms are less active with little or no nutrient recycling occurring. Therefore, the soil fertility chain is destroyed, resulting in undernourished and disease-susceptible plants.
Soil demineralisation occurs through natural processes:
(a) The percolating rainfall leaching nutrients to the drainage systems (streams/rivers/ oceans).
(b) Wind erosion removes the soil to other areas. Again, we have seen dramatic examples in recent times of increased damage by wind erosion. Accelerated by the breakdown in soil fertility (demineralisation) one such example is the wheatland in the Mallee in Victoria.
(c) Water erosion removes top soil, and depending on the state of demineralisation, water erosion will accelerate the more an area is demineralised. For example, in poorly mineralised soils, where the micro organisms are less effective, there will be less fibrous material to hold the soil.
Soil is demineralised through the artificial means of:
(a) Man's cultivation of the soil for food crops. The historical effects of cultivation in this matter are covered later.
(b) Irrigation practices on poorly-structured and demineralised soils have lead to salination - the biggest soil problem in Australia today.
(c) Industrialised man has created pollution in various forms, but as related to demineralisation of the soil, acid rain is the best example.
ACCELERATION AND RETARDATION OF SOIL DEMINERALISATION
Soils known to be fertile and actively cultivated 10,000 years ago are now invariably deserts as a result of nutrient removal and subsequent topsoil erosion.
Although demineralisation is a natural process there are many examples of when man's influence has accelerated or retarded this process:
(a) The deserts of North Africa were once fertile, producing healthy crops. Man's harvesting of the forest and subsequent cultivation has caused a decline in rainfall with increased wind activity, resulting in erosion of the topsoil. Further acceleration resulted from continued cropping with little or no return of nutrients to the cropped soil.
(b) Soils in China that were derived from wind blowing glacial flour (high in natural nutrient sources) were cultivated by the Chinese, under a system of organic recycling, thus slowing down the process of demineralisation.
(c) The Murray river region is a good example of modern day practices leading to rapid demineralisation of soil. At the turn of the century, such soils were already poor (highly demineralised). With tree removal, excessive application of water (flood irrigation) and artificial fertilizers, we have successfully accelerated a situation which will be very difficult, but not impossible to retrieve.
THE INTRODUCTION OF ARTIFICIAL FERTILIZERS
For the past two hundred years, man has been able to exploit soils that had become nutrient-deficient (by natural processes) by the application of chemical fertilizers. To date, we have concentrated on supplying those nutrients required in relatively large amounts (Nitrogen, Phosphorus and Potassium) with some notable example of trace elements, (those required in relatively small amounts) use in specific soil types, for example, Zinc and copper in the pastoral 'deserts' of South Australia and Victoria and Molybdenum in the high-rainfall pastoral soils of Eastern Australia.
THE PLANT DENIAL EFFECT
As we cultivate more intensively (e.g. vegetables and other irrigated crops), so we find the need to add additional nutrient elements to the soil. Such addition of individual nutrients can upset the balance and often renders the dwindling supply of inherent nutrients unavailable to soil micro organisms and plants, thus the expected yield responses are not always achieved.
Many foliage sprays of 'balanced' nutrients are on the market to attempt to improve vegetable yields. Such measures are only temporary, for the life of the crop, and can often produce tasteless, soft, pest-susceptible crops.
The cost of growing crops in unbalanced soils are:
(a) Having to combat pests and diseases.
(b) The excessive water requirements (up to 4 times of those required for well-balanced soils).
(c) The dissipation of costly human resources.
(d) The cost of human/animal health, with crops not taking up sufficient minerals to meet human and animal nutritional needs.
THE ELEMENTS OF BALANCED SOIL
Rocks (e.g. basalt, lava, granite, shale, slate) supply the nutrients necessary for plant (and animal) growth. A soil derived from a nutrient 'balanced' rock is said to be fertile. Soil-supplied plant nutrients (at least 13) are required in specific proportions. Plants take up additional elements that are essential for animal and human health (at least 8).
(See Table 1). Plants, in turn, take up additional elements that are essential to human and animal health: Sodium, Selenium, Iodine and Cobalt. As well, although not essential, some elements appear to have beneficial effects on some plants e. g. Silicon, Vanadium, Chromium and Aluminium. But excesses of any other than the essential beneficial elements can have a toxic effect on plants, rendering a lesser abundance of nutrients.
REMINERALIZATION OF SOIL-PROCESS
Remineralization is the incorporation of original rock (finely-ground) to the growing zone of nutrient exhausted and eroded soils.
In order to rebuild fertility, as stated in the 'History and Overview', we in theory, could spread rocks on to our soils. However, the more practical way to achieve successful remineralization is to further mill rock dust, as found in our commercial quarries, to an estimated size of 200 mesh fineness. This product, applied at various rates to the plant growing zone of nutrient exhausted and eroded soils, should provide us with the basis of developing and remineralized balanced soil.
TABLE 1.
| TABLE OF ESSENTIAL PLANT NUTRIENTS | |||||
| MACRO-NUTRIENTS | MICRO-NUTRIENTS | ||||
| Supplied from Air and Water | Supplied from Soil Solids | Supplied from Soil Solids | |||
| Carbon | (C) | Nitrogen | (N) | Iron | (Fe) |
| Hydrogen | (H) | Phosphorus | (P) | Manganese | (Mn) |
| Oxygen | (0) | Potassium | (K) | Zinc | (Zn) |
| Calcium | (Ca) | Copper | (Cu) | ||
| Magnesium | (Mg) | Boron | (B) | ||
| Sulphur | (S) | Molybdenum | (Mo) | ||
| Chlorine | (Cl) | ||||
THE PURPOSE OF APPLYING GROUND ROCK
Ground rock applications are aimed at restoring the original balance of fertility that existed in the soil when it was formed 10,000 or more years ago, thus duplicating the environment to as near its original state. Once achieved, food production increases will improve economic returns to the treated land. Perhaps more importantly, further decline can be arrested.
REMINERALIZATION LOWERS COSTS
Remineralisation will provide a balanced environment for plants to grow efficiently, resist the ravages of pests and diseases and produce high yields (many times that on exhausted soils). The direct benefit lowers cost of total production. In Australia's case, this will enhance the country's ability to be export competitive.
QUALITY BENEFITS
Crops grown in remineralised soils will provide the necessary nutrient balance for human requirements and be attractive in taste as well as appearance. From a quality aspect, commercially higher prices will result. In addition, a wider range of markets become available.
Because the crops are of a higher quality in the total sense, stock will conserve energy, the health of both humans and animals will show a marked improvement due to more minerals being made available.
DATE: May 1992
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