Potassium nitrate is used in fertilizers as a source of nitrogen and potassium – two of the macronutrients for plants. When used by itself, it has an NPK rating of 13-0-44.

Potassium nitrate has been a common ingredient of salted meat since antiquity or the Middle Ages. The widespread adoption of nitrate use is more recent and is linked to the development of large-scale meat processing. The use of potassium nitrate has been mostly discontinued because it gives slow and inconsistent results compared with sodium nitrite preparations such as “Prague powder” or pink “curing salt“.

• Used in some toothpastes for sensitive teeth. Recently, the use of potassium nitrate in toothpastes for treating sensitive teeth has increased.
• Used historically to treat asthma. Used in some toothpastes to relieve asthma symptoms.
• Used in Thailand as main ingredient in kidney tablets to relieve the symptoms of cystitis, pyelitis and urethritis.
• Combats high blood pressure and was once used as a hypotensive.

• Used as an electrolyte in a salt bridge.
• Active ingredient of condensed aerosol fire suppression systems. When burned with the free radicals of a fire’s flame, it produces potassium carbonate.
• Works as an aluminium cleaner.
• Component (usually about 98%) of some tree stump removal products. It accelerates the natural decomposition of the stump by supplying nitrogen for the fungi attacking the wood of the stump.
• In heat treatment of metals as a medium temperature molten salt bath, usually in combination with sodium nitrite. A similar bath is used to produce a durable blue/black finish typically seen on firearms. Its oxidizing quality, water solubility, and low cost make it an ideal short-term rust inhibitor.
• To induce flowering of mango trees in the Philippines.
• Thermal storage medium in power generation systems. Sodium and potassium nitrate salts are stored in a molten state with the solar energy collected by the heliostats at the Gemasolar Thermosolar Plant. Ternary salts, with the addition of calcium nitrate or lithium nitrate, have been found to improve the heat storage capacity in the molten salts.
• As a source of potassium ions for exchange with sodium ions in chemically strengthened glass.
• As an oxidizer in model rocket fuel called Rocket candy.
• As a constituent in homemade smoke bombs.