Grasswood ash is alkaline. Grass wood ash is an ash fertilizer obtained from daily firewood and grass after burning at high temperature, and the main component is potassium carbonate, which is a strong base and weak acid salt. Carbonate ions in grass wood ash undergo a hydrolysis reaction in water, generating hydroxide ions and bicarbonate ions, resulting in an alkaline solution.

Grasswood ash is alkaline and cannot be mixed with acidic fertilizers or pesticides. It is suitable for plants grown in acidic or clayey soils, especially for chlorine-avoidant crops such as sweet potatoes and potatoes, for which grasswood ash can exert its unique fertilizing effect. It can also be used as a mulch for seedlings and nursery plants to provide protection for young plants. When using grass ash, it should not be mixed with ammonia or nitrogen fertilizers. The alkaline substance in grass ash will have a bi bi hydrolysis reaction with ammonia fertilizer or nitrogen fertilizer, leading to a reduction in fertilizer efficiency and even producing harmful substances.