Beware The Dangers Of Adding Ash To Your Soil: It’s risky and could be harming you and the soil
Among the many things we have learned about ourselves during the pandemic and ensuing lockdown and restrictions, one stands out. We are a nation of fire starters. Whether it was barbecues in the spring and summer or chimineas and fire pits as the nights drew in and the temperatures started to drop in the autumn, it is evident we like burning things a lot.
The Safe Soil UK team love Bonfire Night as much as the next person, and there was a time when a stonking good garden bonfire would have led to a by-product that was considered fabulously useful: Ash. Gardeners used to swear by it. As did farmers. Indeed, we can see the evidence in the aftermath of forest and brush fires as lush green growth starts to spring up and replace the charred landscape in just a few weeks.
Ash had been used as a fertiliser for years and is commonly used on acidic soils to raise their pH and make them more alkaline. Indeed, the word potash originates from the way it was made before it was mined – using pots to soak ashes before the liquid was boiled off. Note that potash is a common ingredient in fertilisers and is a generic name for any salt containing water-soluble potassium. It is also where the word potassium comes from.
Granted, potassium is vital for the advancement of nutrients through plants and consequently the development of healthy (and abundant) fruit and flowers. But remember that wood ash raises the pH of the soil, making it more alkaline, which can be hugely damaging to plants that prefer acidic soil such as many fruits including blueberries and raspberries as well as rhododendrons and roses. And finally, there’s a potentially toxic aspect to all this, which is dependent on what it is that we’re burning. Traditional bonfires tend to be assembled using wooden pallets. The wood in these has often been treated. Likewise, old furniture is often made from particleboard rather than solid wood – this contains adhesives that produce toxic fumes when burned in addition to by-products in the resulting ashes. Painted wood such as disused doors and window frames also produce toxic fumes and, in a worst-case scenario if the wood is old, extremely toxic fumes because older paint often contained lead. The resulting ashes will also contain lead and other potentially toxic elements that, when added to soil, can contaminate your growing space. And make you sick.
And then there’s coal ash, which is even worse. It contains contaminants like mercury, cadmium, chromium and arsenic as well as polycyclic aromatic hydrocarbons (PAHs), a group of chemicals that are produced during incomplete combustion of coal, oil and other organic products. Some PAHs are classified as being carcinogenic and others are deemed to “likely” be so. Short-term exposure to these can result in irritation of the nose and throat, dizziness, vomiting and shortness of breath. Long-term exposure can result in liver and kidney damage, cardiac arrhythmia and multiple cancers.
Some of the dangerous elements can remain in the soil indefinitely. Indeed, anyone suspecting that unsafe ash may have been used on their growing space would be well-advised to consider running a standard contamination test on their soil to make sure all is well. In the end, the best way to dispose of ash left from all those bonfires, barbecues and fire pits is to put it in council rubbish collection. Because, as we like to ask at Safe Soil UK, why chance it?
If you think your soil may have been contaminated by wood or coal ash, Safe Soil UK offers testing suites that can help put your mind at ease.