Healthy New Zealand soil

Photo: Ted BaghurstHumus, worms, and deep roots; the signs of healthy soil.

Primary industry: Healthy soils are the basis of all life on land and the essential building blocks of sustainable farms and nutritious food.

SOIL SCIENCE

A few weeks back, while having my hair cut at a local salon, I was asked about my profession. I said that I taught farmers around the world how to grow with less need for chemicals. I explained that I was constantly researching the links between soil health and human health, with an emphasis upon the importance of nutrient-dense food. The hairdresser responded: 'What has the soil got to do with food?'

The price of depletion?
We are what we eat and what we eat comes from soils that are a shadow of their former selves. The loss of minerals, microbes and humus from our soils has necessitated ever-increasing levels of chemical intervention which has, in turn, further exacerbated the losses. It is the proverbial vicious cycle and unfortunately we are the big losers in this equation. The sustainability of continuing down the current path is questionable. This is best illustrated by the fact that we have used more chemicals every year since we began the "chemical experiment" in agriculture (ten decades of extractive farming) and yet every year there has been a global increase in pest and disease pressure.

Last year was a record year for chemical usage around the globe (involving a 14% increase) and this significantly eclipsed the previous year, which was also a record. Dowsing our soils and food with more chemicals each year, with less and less response, is surely the definition of unsustainability.

What determines a healthy soil?
The cornerstones of a highly productive, disease-resistant soil, as previously mentioned, are minerals, microbes and humus. Minerals are the plant's building blocks for the phytonutrients (vitamins, carotenes, antioxidants and protective compounds like sulfurophane, lycopene and anthocyanins) that determine medicinal qualities in fresh food.
The availability of minerals to plants is determined by supply, balance and biology.

For decades, we mined minerals from our soils through crop removal and only replaced three or four. We also ignored the biology that delivers these minerals and protects the plant. We regularly assaulted soil life with salts and biocides and rarely replaced or nurtured those that remained. However, it is more than the simplistic, nitrogen, phosphorus, potassium (NPK) approach and neglect of biology which has impacted soil health, mineral delivery and associated farm profitability. No mineral is an island and each mineral impacts several others. It is all about balance.

The Goldilocks factor
The starting point in the balance equation is always calcium, the trucker of all minerals. Whether you are a primary producer or a home gardener, your first priority is to lime up to your soil's calcium requirements.

Each soil has a different calcium storage capacity based upon its clay component. A good soil test will provide base saturation details (the percentage of storage space available on the clay colloid) and an associated indication of appropriate calcium applications. An understanding of this balance is essential because over liming can actually be worse than ignoring calcium requirements.

It is all about getting it 'just right', hence the Goldilocks analogy. An oversupply of calcium can negatively impact the uptake of seven other minerals. The correct amount of calcium in relation to magnesium (the Ca/Mg ratio) effectively determines how well a soil can breathe and this impacts everything. An open, breathing soil facilitates improved photosynthesis (the most important process on the planet) and provides the optimum terrain for earthworms and other members of your aerobic, microbial workforce. Plant roots expand unimpeded in this medium and moisture moves in freely from above and below.

So, it is calcium as a starting point, and then all other major and minor minerals that need to be addressed for high production fertility. Zinc for leaf size (the solar panel), copper for resilience, boron for reproduction, molybdenum and cobalt to access free nitrogen from the atmosphere and silica (for the cell strength that helps the plant resist both disease and insect attack) In concert, a good supply of these and other minerals will ensure healthy livestock, healthy humans and a healthy planet. When we include planetary health in the equation we are now talking about the third, and most important cornerstone of soil health, humus.

Humus saves the world
Humus is the sweet smelling, chocolate-coloured substance that is produced by micro-organisms and serves as their home base. This product of decomposition is the soil glue that determines whether our streams run brown following rain storms, but it is also the storage system for minerals and moisture.

Humus is the only storage medium in the soil capable of latching on to all minerals, including the highly leachable nitrate form of nitrogen. Humus holds its own weight in water and a simple increase of 1% organic matter (humus) confers 170,000 litres of extra water storage per hectare. The New Zealanders who have nurtured soil biology and increased humus levels saw the obvious gains of their strategy during the recent destructive drought. Humus prevents nitrate leaching, cleanses soil contaminants and houses the predatory organisms and microbe exudates that protect plants from pests.

However, the most important "understanding" in relation to humus relates to reversing climate change. When we build organic matter in our soils, we are intervening in the carbon cycle and sequestering CO2 from the atmosphere. This CO2 sequestration is actually the only way we can effectively address global heating within an increasingly small timeframe.

How do we regenerate our soils?
Mineral balance, inexpensive microbial inoculums and compost are three keys to improving profitability, plant resilience, stock health and our health. The microbe most missing in most soils around the world is actually the most important creature of them all at this point in time.

Mycorrhizal fungi burrow into the plant roots and then create a massive root extension that effectively provides ten times more root surface area. These symbiotic fungi allow the plant greater access to key minerals like phosphorus, potassium and calcium and they produce immune supporting bio-chemicals for their host. They also produce a sticky substance called glomalin that is now known to be the triggering mechanism for 30% of the humus in the soil.

Extractive agriculture has done more than increase our likelihood of growing substandard, chemically contaminated food, it has also knocked out 90% of the all-important mycorrhizal fungi in our soils. These creatures can be reintroduced for as little as ten dollars per hectare and we need to initiate this repopulation exercise, yesterday.

Composting needs to become the mantra for every food producer, home gardener and council. Composting involves humus production and the addition of compost to the soil sparks further humus creation by re-energised soil life. It is now time that we revisit the ancient wisdom that defined the words "humus" and "human" as the same thing. Both words mean "of and for the earth", with the profound implications of that understanding.

New Zealand-born author and educator Graeme Sait is CEO of Australian company Nutri-Tech Solutions (NTS). He travels the world training farmers, consultants and medical practitioners in the importance of nutrient dense, medicinal food and the strategies to produce this food with less chemical intervention. Sait has trained many thousands of farmers on four continents with his four-day, NTS Certificate in Sustainable Agriculture, scheduled for Napier in November.

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