Applying potassium dihydrogen phosphate to orchids this way: why is it both wasteful and causes fertilizer burn?

Potassium dihydrogen phosphate is an indispensable good thing when growing orchids at home, but many orchid growers go against its function when using it, not only causing waste but more easily leading to fertilizer burn.

Potassium dihydrogen phosphate was designed and produced from the outset for foliar application of phosphorus and potassium fertilizer, so it is a dedicated foliar fertilizer. Some orchid growers use it for root application, which is actually about the same as taking medicine meant for an IV drip and swallowing it orally. Although it is not necessarily true that every orchid grower will cause fertilizer burn through root application, the effect of root application is clearly not as good as foliar application, so it is a kind of waste.

On March 26, 2015, Haoshe Farmer, who has a habit of keeping a diary for special cases, grew a pot of cymbidium (Cymbidium faberi) for three years and saw a flower spike for the first time, just emerging from the soil and about the size of half a cigarette butt.

I felt this pot of flowers needed some supplementation of phosphorus and potassium fertilizer (normally done in autumn), so I diluted 98% potassium dihydrogen phosphate with water at 500 times (the concentration may have been a bit high) and watered it on, because when spraying on leaves before I had also used this kind of concentration (generally an 800-times solution, occasionally a 500-times solution) and had never had a problem. But after a week I found the flower spike had stopped growing, and after another week the flower spike's color had gone bad and it fell off with a gentle touch, and the base of the flower spike had already rotted.

What was even more outrageous was that this pot of cymbidium was still continuing to suffer fertilizer burn more than a month later, and in the end more than half of a pot of 15 cymbidium seedlings died. This was the first time I encountered fertilizer burn caused by potassium dihydrogen phosphate, and since then I have never used it for root application again.

The safe concentration for foliar spraying of potassium dihydrogen phosphate is a dilution of 800 times or more, and carbendazim, thiophanate-methyl, mancozeb, dimethoate, fenvalerate, urea and other fertilizers or pesticides can be added to spray together, greatly increasing work efficiency.Do not use foliar fertilizer when orchids are blooming; it can be used both before and after flowering.