The third macronutrient is potassium (K) also known as “potash.” Crops contain about as much potassium as nitrogen and more potassium than phosphorus. Potassium helps farmers produce higher quality crops. It is particularly important in carbohydrate and starch synthesis, making adequate potash critical for high-carbohydrate crops like potatoes, sugar beets and grapes. It also helps plants resist wilting longer and helps perennial crops like alfalfa avoid winter kill by ensuring the plants have enough starch in their roots to get through the winter.
Potassium, like nitrogen, also helps plants produce protein as they grow. Potassium helps produce:
- More weight per kernel and more kernels per ear in corn
- Greater oil content in soybeans
- Better milling and baking quality in wheat
Potassium can be plentiful in some soils, but as with nitrogen (N) and phosphorus (P), the problem is availability. Up to 98 percent of K in the soil is unavailable to plants in its existing form. Once again, human ingenuity must produce commercial fertilizers to provide the potassium crops need to grow in adequate amounts and quality.
For more information on potassium as a quality building block, click here.
Important Potassium Fertilizer Products
Potassium compounds found in nature are actually the “salts” evaporated from sea water. Commercial forms of potassium are mined from deposits deep in the earth.
Sources of K for use on crops include animal manure, plant residues, and most importantly, commercial fertilizer products. The most widely used commercial K fertilizer is potassium chloride (KCl), also known as muriate of potash (because the production process involves hydrochloric acid, also known as muriatic acid). Other widely used K products include potassium-magnesium sulfate, potassium sulfate and potassium nitrate. A relatively small amount of potassium-sodium nitrate and various lime-potash mixtures are also applied. All these products release K+ ions in the presence of soil moisture, and potassium nitrate offers farmers a good source of N as well as K.