Potassium Nitrate — Frequently Asked Questions

Tobacco, where chloride ruins burn quality; potatoes, where it reduces starch content and specific gravity; grapes and stone fruit, which show leaf scorch and quality loss; and many other fruit and horticultural crops. For these, muriate of potash is unsuitable despite being the cheapest potassium source, and potassium nitrate is the standard alternative.

13-0-46, meaning 13 percent nitrogen all in nitrate form, no phosphorus and 46 percent potassium as K2O. It also has a low salt index for the nutrients delivered, which reduces the risk of root burn in fertigation and makes it suitable for saline soils where a higher-salt fertiliser would add to the problem.

Mixed with sodium nitrate it forms solar salt, a molten mixture that stays liquid across a wide temperature range and is stable at high temperature. Concentrated solar power plants use it to store heat collected during the day so electricity can be generated after dark, which is what makes solar thermal dispatchable rather than intermittent.

Yes. It supplies oxygen that greatly accelerates combustion, which is the basis of its long use in pyrotechnics and its historic role as saltpetre in black powder. It must be stored away from combustible material, fuels and organic matter, and its supply is subject to precursor controls in some jurisdictions.