Biochar and Food Resilience: Safeguarding Soils for a More Secure Food Future

Food resilience has never been such a priority for the planet as a whole.

Whether we're talking about a vegetable patch, market garden or farm, our ability to produce food ultimately depends upon the health of the soil. It needs to provide plants with water, nutrients, air and a functioning biological ecosystem — and it needs to keep doing so when conditions are less than ideal.

That is becoming increasingly important as growers face more unpredictable weather, pressure on water supplies, declining soil health and rising costs for agricultural inputs.

Biochar cannot solve all of these challenges. What it can do is help us build healthier, more resilient soils that make better use of the resources already available to them. And because biochar can remain in soil for a very long time, its contribution is fundamentally different from an input that needs to be continually replaced.

Food Resilience Starts With Soil Resilience

Modern food production can sometimes encourage us to think primarily about what a crop needs to be given: fertiliser, irrigation, pesticides and other inputs.

But beneath all of those interventions is the soil itself.

Healthy agricultural soil performs an extraordinary number of functions simultaneously. It receives rainfall, stores and supplies water, holds nutrients, allows roots to breathe and penetrate, supports microorganisms and fungi, cycles organic matter and provides the physical foundation in which plants grow.

A resilient food system therefore needs more than productive crops in a good year. It needs soils capable of continuing to function when conditions become difficult.

This is where biochar becomes interesting.

Making Better Use of Water

Water is one of the most obvious vulnerabilities in food production.

Biochar has a highly porous structure, inherited partly from the cellular structure of the plant material from which it was made. When incorporated into soil, those pores — together with changes biochar can create in the surrounding soil structure — can affect how water is retained and moves through the soil.

Research generally finds that biochar can increase plant-available water, although the size of the effect varies substantially according to soil type and the properties of the biochar. The benefits tend to be particularly significant in coarse, free-draining soils.

This matters for food resilience because rainfall is not necessarily useful simply because it falls.

What matters is how much of that water enters the soil, how much remains there, and how much is subsequently available to crops when they need it.

If we can retain more of the rainfall we receive within healthy soil, crops may have a larger reservoir to draw upon when the weather becomes dry.

Drought and Flooding Are Connected

Periods of drought are increasingly likely to be punctuated by intense rainfall rather than the gentle, regular rain growers would ideally choose.

This creates another problem.

Dry or degraded soils can sometimes struggle to receive sudden heavy rainfall. Instead of infiltrating into the ground, water moves across the surface, taking soil and nutrients with it and potentially contributing to flooding further downstream.

Improving soil structure, organic matter, vegetation and biological activity can all help landscapes become more capable of receiving and retaining water.

Biochar can form one part of this approach.

Rather than thinking separately about drought protection and flood protection, it can be more useful to think about creating sponge-like agricultural soils: soils capable of receiving water when it is abundant, storing more of it within the landscape, and making it available to plants when rain becomes scarce.

For food production, that ability to buffer between extremes is increasingly valuable.

Keeping Nutrients Where Crops Can Use Them

Food resilience isn't simply about water. Plants also need reliable access to nutrients.

Some nutrients are easily lost from agricultural systems through leaching, erosion and run-off. This isn't only inefficient for the grower; nutrients leaving the soil can also contribute to environmental problems elsewhere.

Biochar's surfaces can interact with dissolved nutrients, while weathering of biochar within soil can increase its surface charge and cation exchange capacity.

This allows biochar to influence the retention and movement of positively charged nutrients such as ammonium, potassium, calcium and magnesium.

It is important to be clear about what this means.

Biochar isn't necessarily supplying those nutrients itself.

Rather, it can help change the soil's ability to hold onto and cycle resources that are already present or subsequently added.

That makes biochar particularly interesting when used alongside compost, manure and other sources of fertility.

Biochar and Compost: Building Fertility Together

Compost and biochar do very different jobs.

Good compost contributes nutrients, decomposable organic matter and biological activity. But much of that organic material will naturally continue decomposing over time.

Biochar is much more resistant to biological decomposition.

Combining the two therefore brings together active organic fertility and persistent carbon structure.

Compost can provide nutrients and microbial life, while biochar provides pores and reactive surfaces where water, nutrients and microorganisms can accumulate.

This is one reason biochar is often mixed with compost or other nutrient-rich organic material before being incorporated into soil.

Rather than replacing compost or fertiliser, biochar can help us think about how we retain and make better use of fertility within the system.

Supporting the Biology That Supports Our Crops

A fertile soil is also a living soil.

Bacteria, fungi and other microorganisms decompose organic matter and participate in the cycling of nitrogen, phosphorus, sulphur and other nutrients.

Mycorrhizal fungi can form associations with plant roots, extending into the surrounding soil and helping plants acquire resources beyond the immediate reach of their own roots.

Biochar can alter this biological environment.

Its larger pores and surfaces can be colonised by microorganisms and fungal hyphae, while its effects on moisture, nutrients, pH and soil structure can indirectly influence microbial communities.

The response is complex and varies between soils, crops and biochars, so it would be misleading to suggest that adding biochar automatically creates a thriving soil ecosystem.

But biochar can contribute something valuable: long-lasting physical habitat within an already living soil system.

More Resilient Crops in Extreme Weather

The importance of all these characteristics becomes clearer when plants are under stress.

During drought, roots need access to diminishing reserves of soil moisture.

During periods of intense rainfall, they need soil that remains sufficiently structured and aerated rather than becoming persistently waterlogged.

During heat, plants need enough water to maintain physiological processes including transpiration.

During frost and rapid temperature fluctuations, healthy roots, appropriate moisture and adequate nutrition all contribute to the plant's overall ability to withstand stress.

Biochar doesn't provide a protective shield against extreme weather.

Instead, its contribution is more fundamental: helping to create a root environment with greater capacity to buffer fluctuations in water, nutrients and growing conditions.

Reducing Dependence on Inputs

There is another dimension to food resilience: dependence.

A food-growing system heavily dependent on resources brought in from elsewhere can become vulnerable when those resources become scarce or expensive.

Fertilisers, growing media and irrigation all have associated economic and resource costs.

Biochar isn't a replacement for nutrients — plants still require nitrogen, phosphorus, potassium and many other elements.

But improving the soil's ability to retain water and nutrients potentially helps growers make more effective use of the resources they already have.

There is also an important difference between biochar and many other amendments.

Biochar is deliberately resistant to decomposition.

While compost and organic matter need to be replenished as part of healthy soil management, biochar can continue contributing its carbon structure within the soil over a much longer period.

That makes it an investment in the long-term physical and chemical capacity of the soil, rather than simply another annual input.

Food Resilience Can Start at Home

Food security can sound like something that only governments and large farms need to think about.

But resilience exists at many scales.

A vegetable garden that retains water better through a dry summer is more resilient.

An allotment that builds fertility from compost, organic matter and biochar is more resilient.

A community growing project producing food in healthy living soil is more resilient.

A market garden that can retain more rainfall and make efficient use of compost and nutrients is more resilient.

And farms that gradually build healthier, better-structured soils contribute to resilience at a much larger scale.

Individually, these changes may seem small. Collectively, they represent a shift away from simply extracting food from soil and towards building the ecological capacity that allows soil to keep producing it.

Carbon Is Part of the Food Story Too

There is a particularly interesting circularity here.

Plants need atmospheric carbon dioxide to grow. Through photosynthesis, they take CO₂ from the air and use its carbon to construct roots, leaves, stems, fruit and seeds.

Some plants become food. Others produce woody biomass.

When suitable woody material is converted into biochar, a proportion of that plant-captured carbon becomes much more resistant to decomposition.

We can then return it to the soil.

There, that stable carbon can contribute to water retention, nutrient dynamics, soil structure and microbial habitat — helping create the conditions in which another generation of plants can grow.

So rather than thinking of carbon simply as something that needs to be eliminated, we can think about putting plant-captured carbon to useful work within healthy soils.

CO₂ supports plant growth. Plants capture its carbon. Biochar stabilises some of that carbon. Soil gains long-lasting carbon structure. Healthier soil supports the next generation of plants and food.

Building Food Security From the Ground Up

There will never be one solution to food resilience.

We need appropriate crops, diverse farming systems, healthy ecosystems, responsible water management, good growers, secure supply chains and many other things besides.

But all terrestrial food production ultimately comes back to one extraordinary resource:

soil.

Biochar gives us a way of investing in that resource for the long term.

By helping soils retain water and nutrients, supporting soil structure and biological habitat, and putting stable plant-derived carbon back into the ground, biochar can form part of creating growing systems that are less vulnerable to environmental extremes and better able to make use of the resources available to them.

Food resilience isn't simply about producing more this year.

It's about building soils capable of continuing to grow food for the years and generations to come.