What Is a Potassium Nitrate Fertilizer?

Potassium nitrate fertilizer is commonly used both in large-scale agriculture and in home gardens. Available in granular or liquid form, it contains two nutrients vital to the growth of plant species: potassium and nitrogen. While nitrogen promotes growth processes, making sure plants mature fully, potassium regulates biological functions.

A naturally occurring mineral, potassium nitrate (KNO₃) forms a thin, white crust and can be found near brine lakes, in caves, or in rich, organic soil. Chile, India, and Spain boast some of the largest sources. Manufactured forms were first made by combining wood with manure. Today, it is created by oxidizing ammonia.

Potassium nitrate is alternatively known as niter or, more commonly in the United States, saltpeter. As it contains high amounts of nitrate and low amounts of salt, this fertilizer works well for growing celery, tomatoes, potatoes, and some fruits. In agriculture, it is often used to support specialty or high-value crops. In home gardens, potassium nitrate fertilizer helps to maintain green, healthy lawns and flowers.

The benefits of potassium nitrate fertilizer are obvious — healthier, more productive crops and more attractive gardens and landscaping. Potassium nitrate fertilizer can also aid in getting seeds to germinate in the first place. More specifically, potassium, also called potash, is important in making plants more resistant to diseases, drought, and even extreme temperature changes. The compound does this by encouraging robust root systems and promoting photosynthesis and energy production. The nitrates in this fertilizer are essential for making protein, and nitrogen is a major component of chlorophyll, the green parts of plants where photosynthesis occurs.

In the past, potassium nitrate was used to make gunpowder, and today it is used in fireworks and grenade fuses. Safety is a concern when using this type of fertilizer. It can cause irritation and even significant harm if it is swallowed, inhaled, or absorbed through the skin. Severe eye irritation is another potential negative side effect. This fertilizer should only be used in well-ventilated areas, and farmers or gardeners should, minimally, wear goggles, a mask, and gloves when applying it.

Recently, concerns have been raised about using potassium nitrate fertilizer over long periods of time. Potassium nitrate is made up of 13% nitrogen, and with continued use, the plants can't always use it all. Excess nitrogen can make plants more susceptible to frost or wind damage. In addition, because it is so water soluble, the nitrogen can leach into the groundwater or wash off into streams and rivers, where it can damage ecosystems.