Biochar and Extreme Weather Resilience: Building Resilient Soil for More Extreme Weather

As our weather becomes more unpredictable, plants and soils are increasingly having to cope with extremes — long dry spells followed by intense rainfall, sudden temperature changes, heatwaves and damaging frosts.

Healthy soil provides an important buffer against these fluctuations. Rather than simply trying to protect plants from each individual weather event, we can create healthier, more resilient soils that are better able to support plants when conditions become difficult. Biochar can play a valuable part in this.

Holding Water Through Drought

Biochar's highly porous structure can help soil retain water, particularly in lighter, free-draining soils. This creates a larger reservoir of moisture within the soil for plant roots to draw upon as conditions become dry.

It doesn't make plants drought-proof, but it can help reduce the speed at which growing conditions swing from adequately moist to severely dry. Alongside organic matter, good soil structure and appropriate planting, biochar can therefore help create a more resilient root environment during prolonged periods without rain.

Keeping soils moist and plants growing has wider benefits too. Healthy vegetation shades and protects the soil, roots help maintain soil structure, and plants continue moving water through the landscape via transpiration.

Preparing Dry Ground for the Rain That Follows

Perhaps surprisingly, drought and flooding are closely connected.

After prolonged hot, dry weather, some soils can become hard, compacted or even water-repellent. When intense rain finally arrives, the ground may struggle to absorb it quickly enough. Instead of infiltrating into the soil, water runs across the surface, carrying soil and nutrients with it and contributing to localised flooding and erosion.

This is why we like to think of healthy soil as a sponge.

Biochar can contribute to soil porosity, water retention and, depending on the soil, infiltration. Combined with organic matter, roots and healthy soil biology, it can form part of creating ground that is better equipped to receive rainfall when it comes, retain more of it, and make that water available during the next dry period.

So drought resilience and flood resilience aren't really separate problems. Both depend partly upon what happens to water when it reaches the soil.

Helping Plants Through Heat

Extreme heat places plants under considerable stress, particularly when it occurs alongside a shortage of water.

As soil dries, plants close the tiny stomata in their leaves to reduce water loss. This also restricts the movement of carbon dioxide into the leaf, reducing photosynthesis and ultimately slowing growth.

Keeping more plant-available moisture within the soil can therefore help plants continue functioning for longer during hot, dry conditions.

Healthy vegetation also protects the ground beneath it. Leaves shade the soil, roots hold it together, and water moving through plants and evaporating from their leaves helps dissipate solar energy through evapotranspiration.

The aim isn't simply to keep individual plants alive through a heatwave. It is to help maintain living, vegetated, biologically active soil and landscapes when conditions become challenging.

Supporting Plants Through Frost

Biochar can also be relevant at the opposite temperature extreme.

Frost damage is complex, and biochar cannot prevent freezing temperatures. However, a plant's ability to withstand cold conditions is influenced by its overall health, root development, nutrient status and the physical environment surrounding its roots.

Soil moisture also influences the way soil gains, stores and loses heat. Very dry soil contains more insulating air spaces and generally transfers heat less effectively than appropriately moist soil. Maintaining healthy soil moisture can therefore influence the temperature environment immediately around plants during cold weather.

Biochar should not be thought of as a frost treatment in itself. Rather, its contribution to water retention, nutrient retention, soil structure and root-zone conditions can form part of creating healthier plants that are better equipped to withstand environmental stresses, including periods of cold.

Holding Onto Fertility When Weather Becomes Unpredictable

Extreme weather doesn't only threaten plants — it can also affect the fertility of the soil itself.

Heavy rainfall can wash soluble nutrients down through the soil profile or carry fertile topsoil away through erosion and run-off. Drought, meanwhile, reduces biological activity and can interrupt the microbial processes responsible for cycling nutrients through living soil.

Biochar's porous structure and reactive surfaces can help retain both water and certain nutrients within the soil system. Its pores and surfaces can also provide habitat for microorganisms involved in nutrient cycling.

This means that improving soil resilience isn't simply about keeping more water in the ground. It's about helping the soil hold onto the resources that make healthy plant growth possible.

Creating a Buffer Against Extremes

No soil amendment can protect plants completely against drought, flooding, heatwaves or severe frost.

But we can make the soil itself more resilient.

Biochar can form part of a wider approach that includes compost and organic matter, healthy soil biology, good plant cover, appropriate planting and careful water management.

Together, these practices can help create soils that are better able to absorb water when it is abundant, retain it when it becomes scarce, hold onto nutrients, support healthy roots and maintain living vegetation through increasingly unpredictable conditions.

Rather than responding separately to every drought, downpour, heatwave or frost, the aim is to build something more fundamental:

soil with the capacity to buffer change.