Our gut health has received a huge amount of press in the last few years. Suddenly, everyone is waking up to the valuable microbial diversity in our guts and the benefits it provides us with. The story is exactly the same with our soils. Soil is absolutely crucial for practically all life on earth and contains a staggering amount of highly diverse microorganisms. These microorganisms are fundamental to the cycling of nutrients, the maintenance of soil structure, delivery of nutrients to plants and even assist in plant immune responses. In short, in order to have healthy, productive plants, we need healthy, productive soils.

What is the soil microbiome?

Microorganisms are everywhere. They include bacteria, fungi, protozoa and algae which coexist together in highly active, numerous and diverse communities. These microorganisms interact with plants via the soil surrounding plant roots (the rhizosphere) and have developed close, symbiotic relationships and are essential for proper plant functioning. These relationships date back millions of years and have helped plants exploit soil nutrients. A great example of this is the evolution of leguminous plants, which developed from a symbiotic relationship with nitrogen-fixing bacteria almost 100 million years ago. In exchange for readily-available nitrogen, the plant provides the bacteria with essential sugars.

Microbes can also be essential for phosphorous uptake (without which only 1% of P would be available), iron uptake and plant hormone regulation, as well as reducing disease pressure by outcompeting pathogenic microbes, producing antibiotic compounds and enhancing plant defence responses.

What’s the problem?

Just like with our gut microbiome, we have unwittingly damaged our soil biodiversity. We are ruining our gut diversity with highly processed foods, artificial sweeteners and the extensive use of antibiotics. We have done the same thing with our soils with deep cultivations, widespread use of artificial fertilisers and chemical pesticides and a lack of organic inputs returning to the soil. We have done this to meet the growing demands of global food production, but the state of our soils is catching up with us. Our damaging agricultural practices are reducing the diversity and abundance of microorganisms in the soil and their benefits to plant growth are disappearing with them.

However, soil health is fast becoming a growing subject and research is being carried out into ways to harness the metabolic capabilities of soil microbiota. If we can exploit this, our reliance on unsustainable and expensive inputs would be reduced, thus increasing global food security. This is particularly important in today’s environmental and socio-economic climate with Russia’s invasion of Ukraine, rising energy prices and accelerating global warming.

How can I get a healthy microbiome back into my soils?

Microbial-based inoculum products are beginning to enter the market, and are actually one of the fastest growing industries in the world at the moment, growing at an annual rate of 17%. They have even been praised by some as ‘one of the most promising long-term solutions… to achieving food security while supporting a healthy environment’. These inoculums can be applied as seed treatments or directly to the soils before drilling. However, we need more research into their efficacy under different environmental conditions.

A much better (and probably cheaper and more sustainable) way to achieve this would be to apply animal manures to your soils. By integrating livestock grazing into an agricultural system, inputs of organic matter (nitrogen, carbon, phosphorous etc) are increased, with the microbes entering the soil along with it. This will also reduce the need for artificial mineral fertiliser; microorganisms seem to be sensitive to chemical fertilisers and should be avoided for microbial diversity.

Cover crops will help to maintain your soil microbiome by increasing soil organic matter, nutrient cycling and maintaining soil structure. Minimal tillage techniques will also reduce damage to fungal hyphae networks and also contributes to soil structure, which decreases wind erosion and keeps your soils healthy, fertile and productive. These techniques can also greatly contribute to making our soils act as carbon sinks, trapping carbon and mitigating against climate warming.

The solution to our food and climate crisis may be right under our feet. These tiny microbes have a huge impact on the sustainability of our food systems and perhaps have greater power in our lives than we realise.

Blog post written by Laura Davey who is currently doing a summer placement with Innovation for Agriculture whilst studying for her Masters degree into Sustainable Crop Production at the University of Warwick.

Sources/further reading:

Beneficial Soil Microbiome for Sustainable Agriculture Production | SpringerLink

Crop microbiome and sustainable agriculture | Nature Reviews Microbiology

State of knowledge of soil biodiversity - Status, challenges and potentialities, Full Report (fao.org)