Nitrate of Potassium Granular Fertilizer

Manufacturers typically make potassium nitrate fertilizer (sometimes referred to as nitrate of potash or NOP by reacting potassium chloride (KCl) with a nitrate source. Depending on the objectives and available resources, the nitrate may come from sodium nitrate, nitric acid or ammonium nitrate. The resulting KNO3 is identical regardless of the manufacturing process. Potassium nitrate is commonly sold as a water-soluble, crystalline material primarily intended for dissolving and applying with water or in a prilled form for soil application. Traditionally, this compound is known as saltpeter.

Agricultural use

Growers value fertilizing with KNO₃ especially in conditions where a highly soluble, chloride-free nutrient source is needed. In such soils, all of the N is immediately available for plant uptake as nitrate, requiring no additional microbial action and soil transformation. Growers of high-value vegetable and orchard crops sometime prefer to use a nitrate-based source of nutrition in an effort to boost yield and quality. Potassium nitrate contains a relatively high proportion of K, with an N to K ratio of approximately one to three. Many crops have high K demands and can remove as much or more K than N at harvest.

Applications of KNO₃ to the soil are made before the growing season or as a supplement during the growing season. A diluted solution is sometimes sprayed on plant foliage to stimulate physiological processes or to overcome nutrient deficiencies. Foliar application of K during fruit development advantages some crops, since this growth stage often coincides with high K demands during the time of declining root activity and nutrient uptake. It’s also commonly used for greenhouse plant production and hydroponic culture.

Non-agricultural uses

Potassium nitrate has long been used for fireworks and gunpowder. It’s now more commonly added to food to maintain the quality of meat and cheese. Specialty toothpastes often contain KNOs to alleviate tooth sensitivity. A mixture of KNOs and sodium nitrate (NaNOs) is used for storing heat in solar energy installations.