Reason 1: DEFRA Regulations
DEFRA does not permit grazing on land where ashes are scattered. Our Cranfield University contacts tell us that this is a precautionary principle and that, to their knowledge, the science has not been done to prove it is safe to graze over ashes.
Reason 2: Damaging to plant life
Ashes contain a large amount of salt and phosphates, the combination of which can overload and kill plant life.
Reason 3: Unhealthy soil pH
Plants tend to grow best at a certain soil pH, with most generally needing soil that has a pH range of between 5.5 and 7.5. This is slightly acidic and near the pH neutral level. Scattering ashes, which have a high pH, onto the ground disrupts the pH balance and can make the soil highly alkaline. This change could kill a wide range of plant species and essential soil bacteria.
Reason 4: Build up of ash piles
From a practical and aesthetic perspective, ashes are rarely strewn widely and land as concentrated piles of ash that end up as sticky clayey masses.