Vibrant soil is crucial to plant health. Soil microbes have a symbiotic relationship with plants - plants provide sugars to microbes and microbes make nutrients bio-available for plants. So by nurturing soil microbes, plants are nurtured, and nutrients and water become available to plants.
Plants produce complex organic molecules like sugars which they exude from their roots to encourage the microorganism populations that comprise a healthy soil. In turn, micro-organisms, by way of their complex ecology, release minerals that are already in the soil so that they are bio-available to plants. Microorganisms such as fungi with their extensive network of filaments, deliver water and nutrients from a wider area than the plant roots cover. These symbiotic relationships between microorganisms in the soil and the plants above are natural processes and will maintain themselves, provided they are not destroyed by excessive chemical or mechanical disturbance.
This natural process of productive plant/soil symbiosis can be fast tracked by inoculating the soil with the biological agents which a soil lacks, and reducing chemical fertiliser and pesticide use. Other factors which limit microbial and plant growth, such as salt, compaction, or extreme lack of available nutrients, can be overcome by the addition of appropriate biological agents and, in some cases, nutrients.
Soil biological methods are much more effective in the long term than applying NPK in an inert form, which is a short term fix. Better to use the living 'nanobots' to mobilise the NPK for you.
Soil is the network of interacting living organisms within the earth's surface layer which support life above ground, that is plants and animals, including humans.
This ecological definition of soil held by HSA is shared by a growing number of soil scientists. It differs from the traditional view held by soil scientists who see physical factors such as climate, topography and underlying (pre-weathered) rock material as key soil components. In the view of traditional soil scientists, soil is merely a porous medium for holding water and keeping plants upright. The role of micro-organisms is seen as a little understood, and certainly not as important as climate, geography and soil chemistry.
Traditionally soils are classified on three dimensions: the nature of the parent material (granite, limestone, basalt etc), the size of inorganic particles (sand, loam, clay etc) and the strata (horizons) in which a sample is located. Soils are tested for the presence or absence of specific nutrients (phosphorus, nitrogen, sulphur, selenium etc) and excessive toxins, particularly salt and aluminium. Significantly, the level of organic matter, which is a key indicator of biological activity and water holding capacity, is generally not measured.
An understanding of soil biology enables the physical factors of soil to be managed. In addition to microbes, plant roots are an active part of soil biology. As is well known, legumes can be used to add nitrogen and make it available for subsequent crops. Other plants directly exude substances from their roots, which through the processes of microbial life in the soil, frees up otherwise unavailable phosphorus and other nutrients. This process can also immobilise toxins such as salt.
Soil is a community of living organisms just as a forest or a coral reef consist of living communities. The physical substrate which supports the soil community is of secondary importance to the network of plant, animal and microbes. Microbial activity controls and manipulates the chemistry of the soil: not the other way around.
Living organisms in soil also ultimately control water infiltration, mineral density and nutrient cycling. Evolution has equipped these organisms to work with plants to apply the laws physics and chemistry for their own ends.
It is not generally realised that the total biomass below ground (that is the dry weight of all living plant, fungi and microbial material) exceeds the above ground plant and animal bio-mass it supports.
Interactions between living organisms (including humans) create soil. An ecosystem is made up of a mosaic of patches with each patch consisting of a relatively stable mix of plants and animals. Patches have sharp edges and distinct communities of soil microbes. Rainfall, climate, soil type, underlying parent rock material and other physical characteristics on either side of the patch boundary are generally the same. Understanding microbial interactions and their differences on the edges of patches is the key to understanding soil and plant growth. What grows above and how it grows is dependent on the relationship it has with what grows below.
Sustainable agriculture is about managing the plant, animal and microbial mix to meet human needs. The living organisms below ground govern the rate of nutrient cycling and are the motor that drives bio-productivity. Sunlight and photosynthesis are merely the energy source - the fuel injection system. The engine that drives land based life is the living soil.
Soil carbon takes three distinct forms:
Sequestered Carbon comprises the fixed carbon plus the total living biomass. Increases in bioproductivity that result in a total long term increase in living biomass are a net carbon sink.
Fossil Carbon is the remains of living organisms that have become trapped in geological formations in the form of coal, oil, and natural gas. The by-product of burning these fossil fuels (mainly carbon dioxide) is accumulating in the atmosphere and oceans. In the atmosphere it exacerbates the greenhouse effect and causes global warming, and in the oceans it creates a weak acid that is having a deleterious effect on a number of organisms.
HSA believes that all current emissions from burning fossil fuels, and the legacy emissions load in the atmosphere can be potentially absorbed by plants and sequestered either as living carbon or fixed carbon (see above).
Food quality is central to human health and well-being.
Soil health determines food quality, land and water resources, and social and environmental welfare. This includes food security, the need for fibre for fuel, clothes and housing, renewable energy sources, clean water, pure air, biodiversity and environmental quality. These factors all depend on soil health. They also determine a nation's long term economic viability and its competitiveness in world markets.
Australian soils are ancient and fragile. The plants, animals and micro-organisms that have maintained them for millennia in the past are stressed mainly through the introduction of European plants, animals and farming techniques. Symptoms of these stressors include areas of erosion, compaction, acidification, rising salinity and most importantly, loss of organic matter and vital nutrients.
Despite these problems, the productivity on Australian farms has continued to improve mainly through the use of chemical fertilizers and irrigation. Both these practices are expensive and unsustainable, especially for broad acre farming, and particularly in the context of a changing climate and water scarcity.
A renewed focus on soil health will not only improve the nutritional quality of food, it will also:
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