Traditional ‘improver’ could harm you and your soil
Since the start of the first lockdown, sales of barbecues, chimineas and fire pits have soared – as a nation, we like burning things! However, there is a bonfire ash threat to your garden, as we’ll see.
The Telegraph reported that John Lewis‘s outdoor heating equipment sales soared by 77 per cent in two months. Sales of barbecues and fire pits rose by 29 per cent and 35 per cent, respectively. Add in Bonfire Night and traditional burning of garden waste, and that’s a lot of ash we’re creating.
Traditional fertiliser
Gardeners and farmers used to swear by ash as a fertiliser. It is commonly used on acidic soils to raise the pH and make them more alkaline. The word potash originates from the way it was made before it was mined. Pots were used to soak ashes before the liquid was boiled off. Potash in fertilisers nowadays is a generic name for any salt containing water-soluble potassium.
The element is vital for the development of healthy and abundant fruit and flowers and human life. However, you can have too much of a good thing.
Bonfire ash threat – Raising the pH of the soil
Wood ash raises the pH of soil, making it more alkaline. This can be hugely damaging to acid-loving plants (ericaceous) such as blueberries, raspberries, heather and rhododendrons.
There’s a potentially toxic aspect, dependent on what it is that we’re burning. If using wooden pallets, these are usually treated, as is old furniture made from particleboard, which contains adhesives. Painted wood produces toxic fumes, and if the wood is old, extremely toxic fumes because older paint often contained lead. The resulting ashes will contain lead and other potentially toxic elements that can contaminate your growing space – and make you ill.
Contaminants in coal ash
Coal ash is even worse, containing 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 be “likely” so. Short-term exposure 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.
Bonfire ash threat – Beware the risks!
Catherine Mansley of Gardeners’ World offers one potential approach for fans of coal ash and suggests that it is OK to use it with ornamentals, but be aware of the risks should you choose to grow things for consumption later on in that space. Some of the dangerous elements can remain indefinitely – consider running a standard contamination test on your soil to make sure all is well. The best way to dispose of ash is to put it in the council rubbish collection when cold.
Thanks to the expert folk at Safe Soil UK for providing the information for this post.
