How long does the fertilizing effect of wood ash last?

The fertilizing effect of wood ash generally lasts more than 10 days. Wood ash is a common farmyard fertilizer, containing elements such as potassium, calcium, magnesium, sulfur, phosphorus and iron. Wood ash has many functions, including protecting against cold, sterilizing and disinfecting, suppressing the occurrence of pests and diseases, promoting sturdy crop stems and enhancing crop stress resistance.

The main component of wood ash is potassium carbonate (K2CO3), with a relative molecular mass of 138. Because wood ash fertilizer comes from the ash left after plants are burned, it contains almost all the mineral elements found in plants. The most abundant of these is potassium, generally 6-12%, of which more than 90% is water-soluble and present in the form of carbonate; next is phosphorus, generally 1.5-3%; it also contains trace nutrient elements such as calcium, magnesium, silicon, sulfur and iron, manganese, copper, zinc, boron and molybdenum. The ash of different plants has different nutrient contents, with sunflower stalks having the highest potassium content (see table). When wood ash is applied at an equal potassium rate, its fertilizing effect is better than that of chemical potassium fertilizer. Therefore, it is an inorganic farmyard fertilizer with a wide range of sources, low cost, complete nutrients and an obvious fertilizing effect.