Since Roman times, wood ash has been recognized as a useful amendment to the soil. In fact, North America exported wood ash to Britain in the 18th century as a fertilizer, and today, 80 per-cent of the ash produced commercially in the Northeastern United States is applied to the land.
Wood stoves and fireplaces are great for warming gardeners’ chilly hands and feet. So, what can we do with the ashes? Since wood ash is derived from plant material, it contains most of the 13 essential nutrients the soil must have for good plant growth and health.
When wood burns, nitrogen and sulfur are lost as gases, and calcium, potassium, magnesium and trace element compounds remain. The remaining carbonates and oxides are valuable liming agents, raising pH, thus neutralizing acid soils. Soils that are acid and low in potassium benefit from wood ash. However, acid-loving plants such as blueberries, cranberries, rhododendrons and azaleas would not do well at all with an application of wood ash.
Wood ash has a very fine particle size, so it reacts rapidly and completely in the soil. Although small amounts of nutrients are applied with wood ash, the main effect is that it is a liming agent. The average ash is equivalent to a 0-1-3 (N-P-K). The chemical makeup varies with the type of wood burned. Hardwoods produce three times as much ash per cord as do softwoods.
Wood ash should never be applied to areas where potatoes will be planted as ash can pro’mote potato scab. For most garden soil, 20 pounds (about a 5-gallon pail) per 1,000 square feet can be applied safely each year. That equals about 6 pounds of ground limestone applied to the same area.
The best time to apply wood ash is in the spring when the soil is dry and before tilling. In compost piles wood ash can be used to maintain a neutral condition, the best environment for microorganisms to break down organic materials. Sprinkle ash on each layer of compost. This is especially good if you have oak leaves or pine needles in your compost heap.
Ash should be stored in a metal container with a secure lid. This helps prevent accidental fires from live coals and prevents water from flowing through the ash and leaching out the nutrients before the materials are applied to the soil.none