What kind of fertilizer is wood ash? Composition, characteristics and how to use it

Wood ash is the residue left after plants are burned. Common sources include crop straw, weeds, branches and the leftover ash from wood-fired stoves, and it is a traditional farmyard potassium fertilizer. Its main component is potassium carbonate, and its potassium content is relatively high. It also contains calcium, magnesium, phosphorus and a small amount of trace elements, so it can supply crops with a variety of nutrients.

Wood ash is alkaline, and the potassium in it is readily soluble in water, so its fertilizing effect comes on fairly quickly. It is light in texture and strongly hygroscopic, and spreading a moderate amount into the soil can make the soil looser and more breathable, which is fairly friendly to root and tuber crops such as sweet potato and potato. Dry, fine wood ash also has a certain moisture-absorbing and anti-rot effect, and many flower growers apply it to wounds after pruning to help the cut close up and reduce the occurrence of rot.

In terms of use, wood ash can be applied as a base fertilizer, mixed into the soil when turning the ground or potting up, or soaked in water, with the upper clear liquid diluted and sprayed on as a top dressing. When used on potted flowers, the amount should be small rather than large; a thin layer is enough, as an excess can easily make the potting soil too alkaline and instead affect the normal uptake of the roots.

It should be noted that wood ash must not be stored or used together with ammonium nitrogen fertilizers such as ammonium sulfate and ammonium bicarbonate, or with human feces and urine, because the alkaline components promote ammonia volatilization and cause loss of nitrogen; it also should not be mixed with acidic fertilizers. When caring for flowers that prefer acidic soil, such as rhododendrons, gardenias and orchids, the amount used should be controlled even more carefully, so that the soil does not become alkaline and affect growth. In addition, wood ash should be stored in a dry place and protected from rain, because once the potassium is leached by rainwater, its fertilizing effect will decline markedly.