Sometime last year I read a wonderful book called Soil by Matthew Evans. It is one of the best books I have ever read.[i]  I wanted to blog about it but quite frankly put it off because it is fascinating but complex. I have decided to grasp the nettle and have a go. At the very least I hope it leads some of my readers to want to read the book.

The subject perhaps for most people seems uninteresting but we should all be interested because the importance of soil cannot be overstated. There is no human health without plant health and there is no plant health without soil health. There are more living things in a teaspoon of healthy soil then there are humans on earth. Soil hosts a startling array of life. Despite being relatively unstudied, about a quarter of all living things that have been identified, anywhere, live in soil. The majority of wild bees nest in soil - a full 14,000 species - as do other pollinators such as native wasps. Soil houses ants and spiders and termites, in numbers and mass that make aboveground creatures look sparse. Living healthy soil is pivotal in good ecosystems. It allows plants to communicate with each other. The billions of microbes in each teaspoon of healthy soil can form the genesis of rain.

Plants do something no animal can do: they make their own food. In the early 1600s Flemish physician and scholar Jan Baptista van Helmont decided to investigate the growth of plants in a long-term study that was the first of its kind. He planted a 5-pound willow in 200 pounds of soil and kept it indoors for five years, adding a measured amount of water as needed. After the five years, the tree was weighed again. It now came in at 170 pounds and the soil had lost only 2 ounces. Van Helmont was the first to identify carbon dioxide and invented the word gas to describe previously unknown components of air. In 1782 Swiss botanist Jean Senebier showed that, in the presence of sunlight, plants take in carbon dioxide and release oxygen. In other words, that the miracle of photosynthesis exists.

Using sunlight as its energy source, a plant converts water and carbon dioxide into carbohydrate – sugar. Plants make sugar out of thin air. Without sugar, there would be no fungi. There wouldn’t be much bacteria. There’d be no animal life as we know it. The vast majority of life on land is dependent on plants. If plants didn’t make sugar, there’d be little else. But plants aren’t just made of sugars. They also contain other things which in nutritional terms are expressed as macronutrients and micronutrients. For humans there are only three macronutrients, carbohydrates, proteins and fats. Micronutrients include vitamins and minerals and even smaller elements such as antioxidants. Plants, like us, need micronutrients and macronutrients to live. A plant’s macronutrients are different from ours and include nitrogen, phosphorus, potassium, magnesium, sulphur and calcium. We know from eating avocado and using olive oil that plants also make fats. So where do all of these other micronutrients come from? The answer is soil.

Soil isn’t just dirt. It can be divided into the physical (rocks and dead organic matter), the biological (the living part), and the chemical – the interplay of elements from both the physical and biological parts with plant roots. Where there is no soil, there is limited life on land. Very few things of any size can exist in our terrestrial environment without soil. But it’s a wafer-thin veneer on the surface of the earth. Only about 7.5% of the Earth’s surface is available as potential agricultural land. The rest is ice, water, stone, too dry, too wet, too hot, or covered with cities.

This thin veneer is in peril. In countries like China in just a short period agriculture has moved from being run predominantly on organic principles with only moderate use of herbicides and pesticides to modern destructive industrial type farming. Now even in China’s official report the pollution of China’s arable land is reported as “rather severe” with nearly 20% of its farmland contaminated. China has less than 10% of the world’s arable land but has to feed about 20% of the world’s population and if 20% of that land is poisoned by substances such as cadmium, nickel and arsenic it means the food system is also contaminated. Official estimates are that China produces 12 million tonnes of grain contaminated with heavy metals a year.

It is not only China that has poisoned its soil. All countries have regions affected by mining or other disturbance. Lots of toxic chemicals that were previously stored safely in the ground have been discovered by humans, and brought to the surface – lead, mercury, uranium. Some of our soils are laced with DDT. We have even thrown dangerous heavy metals at soil, cobalt and lead. It only takes 7 tablespoons of lead to poison one hectare of sole. Much of the contamination of cropland comes from salt. One of the effects of deforestation is rising water tables which increases salinity. As you take away trees, and their deep roots die with them, the subterranean water rises, carrying salt with it. Between the poisoning of land, and erosion, it is estimated that the world has lost a third of its cropland in the last 40 years.

Fungi are the heavy lifters in soil. About 90% of plants and nearly all trees have relationships with fungi. We don’t fully understand fungi despite sharing up to 80% of our DNA with them. Mushrooms are the more visible tangible expressions of fungi, but yeast is a fungus. The white fuzz on the outside of Brie cheese is a fungus and the vast majority of fungi spend at least part of their life-cycle in soil. Fungi provide much of the glue that holds soil together.

Soil sustains life, forms rain, elicits hormones that make us content and is the genesis of many modern medicines. Soil is clearly a giver of life but what we’ve done to soil in the last century has left us worse off. Most people eat the wrong things. Most of the diseases of the developed world are those of consumption. Overconsumption and poor consumption of food can contribute to obesity, diabetes, heart disease, stroke, osteoporosis and a range of cancers. In the less developed world hunger is a massive problem but so are nutrient deficiencies even for those who get enough calories to eat. While about a billion people are chronically malnourished, over 3 billion people are micronutrients-deficient with insufficient iron, vitamin A, zinc and iodine. Over 2 billion people are iron deficient, making it the largest nutritional deficiency on the planet leading to about 20% of maternity deaths. Worldwide it is estimated that 800,000 people die every year from zinc-deficiency, comparable to the global mortality from malaria. Many of the world soils are zinc-deficient and there is a general correlation between areas with zinc-deficient soils and those with zinc-deficient humans. The wheat we eat today is up to 40% less nutritious than it was 100 years ago.

Better soil equals more nutrient-dense food. We know all these phytochemicals and antioxidants are doing us good. We can smell all the biochemicals associated with them. We taste them in our food and we know when something is nutrient-dense or not. When it comes to wine, because it is so valuable, a great deal of effort goes into understanding what kind of soil produces the best grapes and of course anyone who appreciates wine will smell it first before they drink it. But the same biochemistry is taking place in food like the humble carrot and really good carrots grown organically in a proper market garden will smell and taste great but a lousy carrot grown in bad soil in some modern machine age way will taste of not very much and perhaps that’s why children don’t really like them.

With modern agriculture erosion rates are increasingly high. Conservatively something like ten tonnes of soil per person is lost per year around the globe. That works out at about 9 kg of topsoil loss for every single meal we eat and that’s just arable cropping land not including the soil lost by over grazing of livestock. The European Union is losing nearly a billion tonnes of soil per year due to water erosion alone. Soil is lost, currently, about 30 to 40 times faster than it is replaced globally and very clearly that isn’t sustainable.

Home gardeners understand how you can make soil through worms. Charles Darwin, the master of evolutionary theory, produced a modest little book in 1881 called The Formation of Vegetable Mould Through the Action of Worms, with observations on their habits. His studies over 40 years led him to concur with the German physiologist Victor Hensen who estimated there were 133,000 earthworms per hectare. Worms consume earth and organic matter and thus make vegetable mould and as they digest and dig, they bring up other matter to the surface, moving the earth about. Darwin finished his book by saying: “When we behold a wide, turf covered expanse, we should remember that its smoothness, on which so much of its beauty depends, is mainly due to all the inequalities having been slowly levelled by worms… It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organised creatures.”

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