Soils for Life’s resident soil microbiologist, Walter Jehne, has been supporting Urban Agriculture Australia and their display at this year’s Floriade in Canberra, on a mission to encourage people to grow their own food, save money, reconnect with nature and look after their health. Last week the Soils for Life team sat in on Walter’s presentation ‘Why healthy people need healthy food from healthy soils’. Here’s some of what he had to say…

Everything on earth and in our solar system is based on 96 natural elements. Of these, 30 mineral nutrients are the essential elements that underpin all biochemistry and life. These govern the activity of key enzymes and biochemical processes essential to the health of all organisms. Basically, we need these mineral nutrients in order to function properly – and they can only be obtained from rocks or the soils derived from them.

In nature, soil microbes and fungi work with plants to dissolve the minerals and make them available to sustain plant growth. These microbes selectively take up the correct amounts and ratios of mineral nutrients that plants – and animals – need. They also selectively prevent the uptake of toxic elements from the soil solution.

In a cubic metre of healthy soil there can be up to 25km of fungal hyphae – the long, branching filamentous structure of a fungus – working to ensure that the right nutrients are provided to the plants that we eat.

Therefore, the nutrient composition of most plants and animals – our food and our health – has been governed by the ability of symbioses, mostly by mycorrhizal fungi, to selectively concentrate and exclude nutrients from an inert, often toxic, external environment.

Up to World War II, the health and nutrient value of most of our agricultural plants and animals depended on these microbial uptake processes. After World War II, however, inputs of chemical fertilisers and pesticides increased to enhance the yields and profits from ‘industrial’ crops.

These high levels of fertilisers and bio-cides (pesticides, fungicides, herbicides) kill the mycorrhizal symbionts that had previously sustained the natural solubilisation, uptake and cycling of essential nutrients. Heavy cultivation and resultant topsoil loss through wind and water erosion also disturbs these important microbial communities.

Consequently, most plants grown under industrial agriculture today are totally dependent on fertiliser inputs and now take up their nutrients hydroponically – through the liquid or water in the soil, rather than filtered by soil micro-organisms – in whatever concentrations and ratios are present in the soil solution.

As a result, plants contain very high levels of the nutrients added as fertiliser (usually nitrogen, phosphorus and potassium), but little or none of the other 27 essential and trace elements that are not soluble and were previously made available by the microbial symbionts. Accordingly, we also lack these nutrients and trace elements. Selenium, for example, is an essential nutrient – required in minute amounts – for the enzymes that kill cancer cells. Yet the food we generally eat today does not contain such nutrients for us to consume.

Plants often also contain high concentrations of toxic elements because the protective microbial membranes are no longer there to selectively exclude them.

Analyses confirm that much of our industrial food now has a third of the nutrient concentration of equivalent foods prior to World War II. We have to eat three times as much to get these nutrient volumes.

In parallel with our adoption of industrial foods and diets, there have been marked increases in a number of diseases, particularly in the Western world. There is evidence of a direct link between diet and many of these conditions, including cancer, diabetes, heart disease, chronic fatigue, and auto-immune and mental illnesses. We need to change our approach to focus on preventative health.

A key action to reverse our current health crisis is restoring the integrity of our food. It needs to be widely recognised that healthy people need healthy food from healthy soils. Healthy soils grow food with the aid of the natural microbial processes that ensure correct uptake of nutrients and exclusion of toxins.

We need to think about and make conscious decisions with what we eat. Growing our own food or buying it from farmer’s markets or non-industrial sources provides the practical means by which much of the community can ensure they are once again eating healthy food from healthy soil.

A healthily functioning plant – without other external inputs – is the best indicator of a healthy soil. By composting food and organic waste in our vegetable gardens and by using regenerative agricultural practices we can return nutrients to the soil, build soil (and microbial) health and grow plants with the nutrient content to meet our body’s needs.

This is one of the many reasons Soils for Life is encouraging the wide adoption of regenerative landscape management. Make sure you support farmers using regenerative practices and looking after their soil health.

Learn more on the Urban Agriculture website – it has lots of Fact Sheets to download to start getting your own garden growing.

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