Wood ash is the fine powdery residue left after burning wood. It consists mainly of minerals like calcium, potassium, and magnesium, which are released during combustion. This byproduct can vary in color from light gray to dark brown, depending on the type of wood burned. Wood ash is often used as a natural fertilizer in gardens and farms due to its nutrient content. It can help improve soil pH and provide essential nutrients for plants. Additionally, it can be used for other purposes, such as making lye for soap or as a cleaning agent.