Soil is Australia’s greatest asset and it should be protected. Australian soils mirror the continent’s great age and consequently are products of environmental conditions throughout history. Our soils tend to be nutritionally and organically impoverished. The majority of our soils tend to be quite clayey just below the surface which restricts drainage and impedes root growth. In order to change direction from stripping our soils to nourishing them we need to understand the fundamental functions of our Australian soil.
Soil is full of life, there is significantly more life in the soil than there is above it. Soil supports a diversity of animal, plant, fungi, protist and bacterial life. It regulates nutrient cycles and gas exchange with the atmosphere. Earthworms play an important role in the soil by increasing soil fertility and are abundant in healthy soils, approximately one million earthworms can be found in an acre of soil. Earthworms and assorted insects play an important role in soil aeration and assist in soil regeneration by recycling nutrients and detritus. Microorganisms call soil their home as well, there are billions of microorganisms in a handful of fertile soil. These microbes also perform key roles within their soil environment.
In recent years we have placed an increased demand on soil performance. Naturally soils regenerate themselves as plant and animal material breaks down and returns to the soil, however, by harvesting and removing this material we are limiting soil regeneration. Humans have responded to this by using fertilisers to increase soil fertility. These often inorganic forms of nutrients become locked up and unavailable to plants.
Plants evolve by being fed by the soil, so natural sources of nutrients have optimal uptake, while inorganic forms are limited in performance. This has led to soil degradation, depriving them of crucial elements, while other elements become excessive. Now is the time where our soils need remineralising, essentially putting the elements back into the soil and rebalancing those in excess.
To begin the process of building healthy soil we need to start feeding the microbes and avoid harming them with chemicals. Microbes are the soil and plants best friend, but pesticides kill more than just the pest species. Instead soil microbe balance should be supported, which discourages disease outbreaks. Microbes produce humus which is the perfect plant food – mother’s milk for plants – and is nature’s way of recycling nutrients and carbon back into the soil. Microbial life cycles depend on minerals, organic matter and moisture.
Minerals are essential to soil fertility. They provide the life force for all living things and are released in their plant available, ionic forms by microbe activity and are as important as vitamins and proteins in our food. Hence, it makes sense to supply the soil with a healthy balanced diet. If we consistently deprive our bodies of minerals this leads to major health problems. It should be no surprise that we should supply our soils with as many nutrients as possible - at least 70 valuable trace and ultra trace minerals, preferably in non water-soluble form.
Unfortunately today’s technology has devised a way to feed plants by providing manufactured nutritional elements in the form of water soluble nitrogen, phosphate and potassium also known as NPK. These modern fertilisers are water soluble and enter the plants through the drinking roots rather than the feeder roots. Under these circumstances NPK fertilisers leave their residues stored in the vacuoles of plant cells. These vacuoles become saturated with undesirable elements like phosphates, heavy metals and herbicides, instead of the positive storage space they should offer the plant.
When we overdose and force feed the soil with an excess of elements plant tolerance is limited, leading to moisture stress, increased disease susceptibility and early maturity. Instead elements should be available as the plants need them. What would you prefer a well stocked pantry full of variety or the same meal force fed to you everyday? Fertile soils act as plant digestive systems. The undesirable elements become locked up in the soil creating undigested organic matter which renders the soil sick and infertile, consequently plants will not thrive. Plants grown in these soils need protection from weeds that can tolerate harsher situations and insect attack. Healthy plants are disease and pest resistant and will outperform weeds.
The soil stores 1500 gt of soil organic carbon, which is twice that of the atmosphere 770gt (McCarl et al. 2007). Soil carbon sequestration is beneficial for soil health as is increases cation exchange capacity (CEC), structural stability and water retention capacity. When soil is managed correctly, carbon is stored in the soil naturally. Carbon governs moisture content and when carbon is sequestered naturally in the soil it increases the soil’s ability to store moisture. This in turn assists the plants ability to cope better in climatic changes like dry and wet times.
What you put on your soil and plants ends up on your plate. The consequence of poor soil management is ultimately the loss of soil fertility. Great soil management starts with selecting the right microbe food like a balanced mineral fertiliser which then is the catalyst to kick start the cycle of life in the soil, achieving optimal plant health. It is up to each of us to make a difference and take care of our most precious resource, our Australian soil.
McCarl BA, Metting FB, Rice C (2007) Soil carbon sequestration. Climatic Change 80, 1–3.