QuestionsHow to growVegetable GrowingSite and Soilvery heavy claggy soil 0 Vote Up Vote Down SylviaLucy Giles asked 17 years ago I have been told its a good idea to dig in old ashes from the fire, coal, wood, briquettes etc, is this true? 1 Answers 0 Vote Up Vote Down Gerry Daly Staff answered 7 years ago Gritty ashes from a coal or wood fire do help to open up a heavy soil, but peat ashes and some coal ashes are very soft and would not help. Dig in plenty of organic material, or for a small area, dig in 5cms of coarse sand in the top 20cms.