Potassium Nitrate
Potassium nitrate (KNO₃) is a soluble source of two major essential plant nutrients. It’s commonly used as a fertilizer for high-value crops that benefit from nitrate (NO₃-) nutrition and a source of potassium (K+) free of chloride (Cl⁻).
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.
Potassium nitrate accounts for only a small portion of the global K fertilizer market. It’s primarily used where its unique composition and properties can provide specific benefits to growers. Further, it’s easy to handle and apply, and is compatible with many other fertilizers, including specialty fertilizers for many high-value specialty crops, as well as those used on grain and fiber crops.
The relatively high solubility of KNO₃ under warm conditions allows for a more concentrated solution than for other common K fertilizers. However, farmers must carefully manage the water to keep the nitrate from moving below the root zone.
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 KNO₃ to alleviate tooth sensitivity. A mixture of KNO₃ and sodium nitrate (NaNO₃) is used for storing heat in solar energy installations.
