SRI and Climate Change
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Why soil is the new black gold

What is soil?

To put it simply, soil is the basis of most life on land. It is the ultimate recycler and giver of life. Rather than simply being a step in the food chain, it is the enabler of this procession of energy and nutrients through trophic levels. But in more tangible terms, soil is a salad of organic matter, minerals, gases, and water. It is a sandwich of what is both above it, and below it -  the eroded underlying geology producing the constituent minerals and the decaying plant and animal life providing organic matter and nutrients. The rain and the atmosphere add the rest.

Why is soil vital for life?

Soil is so essential as it provides everything that terrestrial life needs in an easily accessible form, in a similar way to water providing everything that aquatic life needs. For those photosynthetic producers at the bottom of the food chain it gives them the carbon, water and nutrients they need to grow and be healthy. From these plants all other animals (including humans) can subsequently gain their energy and nutrients. The nutrients that the soil provides travel up the food chain until sooner or later plants or animals in which they are contained die, and begin to rot, returning those nutrients back to the soil, where they are decomposed by microorganisms back into their most basic forms, ready to be used, and travel up the food chain again.

In addition to being nature’s pantry, soils store and filter water, protect us from flooding and droughts and capture and store vast amounts of carbon. Locked away in our soils are 2,500 gigatons of climate-altering Carbon, more than three times that contained in the atmosphere. Of our damaging carbon emissions leaking into the atmosphere, a quarter is removed each year by Earth’s soils, where it benefits life, rather than damaging it.

How can soil be unhealthy?

However, soil, like anything that is alive (I’m justifying the term “alive” with the fact that there are more species of organisms in the soil, than there is aboveground), can become sick. And as with any organism, when it becomes sick, it becomes less good at what it does. With soil, that’s providing 95% of human consumed calories worldwide, as well as mitigating climate change.

An unhealthy soil is one that is poor in nutrients, organic matter, water and gas, without these components, or without the required quantity of these components, the plants and crops that utilise the soil are smaller, there’s less of them, and those that there are, are of lower quality. These same adjectives can be applied to those organisms that rely on soil, including humans. Research has shown for over a century that lower quality soil leads to lower quality produce. It is no coincidence that as soil quality has declined over recent decades, there has been a significant reduction in the protein, calcium, phosphorus, iron, riboflavin and vitamin C content of fruit and vegetables produced. In turn, this has resulted in real world health implications such as obesity, stunted growth, eye problems, diabetes, and heart disease.

This lower quality soil now comprises one third of Earth’s productive topsoil. Organic matter, a key indicator of soil health, composes just half a percent of these soils, yet soils need eight times this.

How does soil sequester carbon?

One key solution to both climate change, and degraded soil quality is taking carbon from the atmosphere and locking it away in the soil, where it does not contribute to global warming, and where it does make soil healthier.

Soils sequester carbon by utilising the plants that grow in them. As plants grow, they take carbon from the air and use it to make their physical structures - their leaves, their stems, their roots and everything else. When these plants die, they can be respired by microorganisms, which take the carbon contained in the plant and return it to the atmosphere. However, the carbon in the parts of these plants that are underground, such as the roots, stay there as it is out of reach of the microorganisms that would break it down and return the carbon to the atmosphere.

Soil that has more carbon is healthier and contains more nutrients. This therefore increases plant growth, meaning that more carbon can be trapped in the soil. A positive reinforcement cycle can happen with more and more carbon becoming locked in the soil, making it healthier, making humans healthier, and making the climate healthier.

How can soil health be improved?

Healthier soils help to fight climate change, they increase the nutritional quality of our food,  make us healthier, and they prevent droughts and flooding. So how can we help our soils be healthier? Well the main area that we need to focus on is agricultural soils, as it is the soils that feed us that humans have damaged the most. The easiest way to improve these soils is to increase the amount of organic matter that they contain, and then stopping microorganisms breaking this organic matter down and returning it to the atmosphere.

One method of doing this is by focussing on the roots of plants. By encouraging larger root systems, more carbon is taken from the atmosphere and stored underground. This can be done by changing the varieties of crops grown, changing the growing practices by which they’re grown or by ensuring that the soil is not compacted so that roots can grow well. Once the carbon is in the ground in the form of plant roots, we then want to stop it getting out of the ground. Ploughing, a common practice in agriculture, increases the breakdown rate of carbon in the soil, meaning that more carbon is released into the atmosphere. Although common, ploughing is not required to grow healthy abundant crops and there are many alternative methods that increase soil health rather than damaging it.

Finally, the use of agrochemicals can harm soil. They can damage the microorganisms in the soil, meaning that the soil cannot produce its own nutrients. The use of organic fertilisers can restore the beneficial microorganism community, ensuring that the soil can produce nutrients on its own. Organic fertilisers such as manure also have the advantage of adding to the soil organic carbon content.

Soil and the System of Rice Intensification.

A key component of increasing soil health is making it easy for farmers to do. Switching to farming methods that benefit the planet and people is even more appealing to farmers if it is free to switch and enables the farmers that implement it to make more money. This is where the System of Rice Intensification (SRI) comes in.

SRI is a rice farming method that is based on a number of principles that can be adapted to the most effective practices depending on the environment. These principles are; start with young healthy plants; optimise plant spacing to minimise competition; build up healthy and fertile soil; and apply only the minimum amount of water needed. When implemented, these principles significantly reduce greenhouse gas emissions, they increase the yield of the rice fields, they increase farmer income, and they ensure that crops can more effectively withstand extreme weather conditions.

Importantly, these practices also increase soil health. SRI promotes the use of organic fertilisers, which ensures that the good soil microorganisms aren’t killed off, thus ensuring that the soil can provide the necessary nutrition to the rice plants which grow in it. As well as this, rice plants that are grown according to SRI principles have a much more extensive root network than regular rice plants. This means that more carbon can be taken from the atmosphere and stored underground, making the soil, and the planet healthier.

Soil health is important everywhere. We need healthy soils to ensure we have nutritious food to eat, to prevent flooding and droughts and to take harmful carbon from the atmosphere and to instead make it beneficial, by locking it in the earth. It is in humanity’s interest to look after our soils. They are the foundation of all terrestrial life on Earth. The System of Rice Intensification is a mechanism to increase the health of rice growing soils - soils which cover 10% of global arable land. The benefits of healthy soils can be reaped for this farmland, and for those that rely on it, and the climate and food security benefits can be reaped by everybody.

Oil may have been the ‘black gold’ of the 20th century but surely soil - the source of the world's food, and a major climate change mitigator is more deserving of the title.

Find out more about SRI, and how it benefits both people and the planet together: