Soil: the foundation of life on Earth

Issue #32; Winter 2019-2020

In 2014 Maria-Helena Semedo, Deputy Director General of the Food and Agriculture Organisation told a forum marking World Soil Day that we only have 60 years of farming left.

As we learn more and as we witness the alarming rates of soil degradation and erosion across the globe it becomes clear that soil is more than dirt.

Without soil, there’s no food. Land plants cannot move to find better conditions, they rely fully on the soil to sustain growth, development and reproduction. Soil is often treated as an inert material, a foundation into which roots can grow and expand. It is used and abused by humans. We forget that it is the basis of all life on earth, and that it is an important store of carbon in a world facing a climate crisis.

All life on earth depends on the top 20cm of soil, and we are losing soil at an alarming rate. With non-optimal agricultural practices, you can lose several centimetres of soil in a single season. In optimum conditions and a mild climate, it takes between 200-400 years to form 1cm of new soil, and that’s if you don’t try to grow anything in it. In wet, tropical areas soil formation is faster; here you can create 1cm in a mere 200 years. That means we’re losing soil faster than it can be replaced.

Just because soil has nutrients in it, doesn’t mean those nutrients are available to the plants. To be available they need to be soluble. Soluble nutrients require organic matter to break down over a long time. To make a soil fertile takes around 3,000 years, so we really need to look after the soil we have.

Soil is an even richer environment that the one we see above the surface; there are millions of bacteria beneath our feet, many of which we know nothing about. Here at the John Innes Centre two researchers are digging into the world of soil.

We need to stop treating soil like dirt

Postdoctoral researcher Dr Maria C. Hernandez-Soriano and PhD Student Marco Fioratti are passionate about soil, and they think that we need to start treating soil with respect.

Dr Maria C. Hernandez-Soriano previously worked on carbon sequestration, understanding how carbon is stored in the soil and how to keep it there. She says, “Humans – despite their artistic pretensions, their sophistication, and their many accomplishments – owe their existence to a six-inch layer of topsoil, and the fact that it rains.”

She has moved her research into nitrogen, how plants control how much nitrogen is available within soil and how to make the most of the nitrogen that is there. Currently Maria is investigating how plants and soil bacteria communicate by producing and releasing chemical compounds in the rhizosphere and how this communication aids an efficient use of the nutrients available in the soil.

Dr Hernandez-Soriano has already identified a trait in ancient cultivars of wheat from the Watkins Collection held in the John Innes Centre Germplasm Resource Unit that allow plants to make more efficient use of the nitrogen in soil, which could be introduced into modern crops. This, and other potential traits can make plants more independent and better able to communicate with the soil, so they can thrive with less chemical fertilisers.

Alongside this, her work also looks at the rhizosphere, the soil directly in contact with the plant roots, and how plants communicate with that on a molecular level. The rhizosphere is the place where the plants absorb water and nutrients. It’s also where they release compounds that can control the activity of the organisms in the soil. Plants and microbes communicate in the rhizosphere and can help each other out.

Marco Fioratti is a soil ecologist, which means he studies what is going on below the surface of the soil. He is currently investigating how different agricultural practices, for example different tilling techniques or fertilisers affect the soil organisms and what the consequences are for soil health.

All processes in soil are mediated, catalysed or directly provided by soil fauna; from earthworms, down to bacteria. The trophic chain under the soil is as complex as the one above the soil and up into the atmosphere. By enhancing our understanding of this really complex trophic chain, we might one day be able to engineer soil communities by adopting suitable agricultural practices, so that we are enhancing, not degrading soil.

Soil organisms can do everything that traditional agricultural practices do. They can open up the soil, improve the structure, improve infiltration, improve resistance to erosion, balance pH and nutrients levels, make nutrients available to plants when the plant needs it. They can even provide weed and pest control.

Understanding how this all works is the first step. Once we understand it, we can think about how to engineer it and reduce our reliance on inorganic fertiliser and aggressive cultivation techniques, so there is an economic benefit and environmental benefits.

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