Potash Fertilizer: Potassium Chloride as a Plant Nutrient
Written by MasterClass
Last updated: Jan 20, 2022 • 3 min read
Potash fertilizer gives plants essential nutrients to grow and thrive. Learn more about the fertilizer and how the product can help your garden.
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What Is Potash Fertilizer?
Potash fertilizer, or potassium fertilizer, is fertilizer made with salts that contain water-soluble forms of potassium. Potassium is an essential nutrient for all life—including plants, animals, and humans—for processing water uptake and turning plant sugars into nutrients. It’s one of three primary macronutrients found in all fertilizers, along with nitrogen and phosphorus (collectively referred to as NPK) and trace minerals like magnesium, copper, and zinc.
The world’s leading source of potassium is Canada, which has large deposits in New Brunswick and Saskatchewan. Other major potash producers include Russia, Belarus, and in the United States, Michigan, New Mexico, and Utah. Together, they produce more than 90 million tonnes, or metric tons, of potash a year.
Potash Production
The word potash refers to its earliest form of production, which dates back to the fifteenth century. A potash burner drew the potassium from wood ash by leaching, and then evaporated the solution in iron pots. Early potash producers called the white residue of potassium salt that remained “pot ash.”
Potash production today comes from potash mining, which involves drilling into deposits found in evaporated sea beds, or by injecting solvents made from water or brine into potash deposits and dissolving the minerals, which are then recovered by evaporation. Potash producers process the mined deposits into compounds in the form of granules.
4 Potassium Compounds in Potash Fertilizer
Potash contains many several types of potassium compounds that serve different purposes.
- 1. Potassium chloride: The most common potassium compound in potash is potassium chloride (KCL), or muriate of potash (MOP). Farmers use potash for carbohydrate crops like wheat when soil chloride content is low.
- 2. Sulfate of potash: The second most common potassium compound is potassium sulfate, or sulfate of potash (SOP), which helps grow fruits in dry climates where soil chloride is low.
- 3. Potassium nitrate: Commonly called saltpeter, this water-soluble compound provides plants with a quick boost of nitrogen.
- 4. Potassium hydroxide: Also known as caustic potash or potash lye, potassium aids photosynthesis by accelerating a plant’s carbon dioxide intake.
How Does Potash Work?
In addition to potash’s use as a plant nutrient, you can use it in recycling, electroplating, and industrial water treatment. You’ll find potash in pharmaceuticals, food products for livestock and in beer as part of the brewing process. When it comes to gardening, potash works in three primary ways:
- Protection: High levels of potassium from potash protect plants from a host of external stressors. It wards off pests like insects and weeds, and helps plants withstand extreme temperatures.
- Prevention: Potash helps plant growth. It produces larger and healthier crop yields by generating enzymes that assist with water retention and food processing. Potash also fosters plant health through drought and disease resistance and corrects potassium deficiencies in the soil.
- Strength: Potash gives plants the essential nutrients it needs to grow and mature. It strengthens roots and stems, and contributes to improved color, taste, and appearance in vegetables and fruits.
How to Use Potash Fertilizer
Here’s a step-by-step breakdown of how to use the fertilizer in your garden:
- Test and check. Before you use potash fertilizer, make sure that your soil and plants need it. Light green, yellow, and brown leaves are clear indications of potassium deficiency. A soil test will also reveal low potassium content and other nutrient deficiencies.
- Choose the right fertilizer. Potassium chloride is the most commonly used form of potash fertilizer. If your soil test determines that you lack other nutrients, look for potassium sulfate or potassium-magnesium fertilizer. Both are especially effective for hardy vegetables like beets or potatoes.
- Apply directly. If your potassium comes in granular form, apply it as topdressing directly and evenly on the soil. You can also till the granules into the soil to reach the plant’s root zone. Add compost or manure to the soil annually to absorb excess potassium, which forms salts that damage plants. Sandy soils need extra organic matter.
- Spray it. Potassium also comes in a liquid form called potassium thiosulfate, which you can spray directly onto flowering plants to boost potassium during the growing season. However, avoid spraying it onto seedlings or into the soil as you’ll risk damaging them.
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