When to Apply Potash to Lawn

Maintaining a lawn with a well-balanced fertilizer program is key to its health and long-term growth. When we speak about fertilizers, there are essential nutrients that play a vital role in promoting a strong, healthy lawn – nitrogen (N), phosphorus (P), and potassium (K). 

Even though actual nitrogen including slow-release nitrogen and other forms of nitrogen content and iron is important for your lawn, potassium is a nutrient that is necessary to withstand weed and insect infestations as well as suppress diseases and help your lawn better resist harsh weather and drought, especially during the winter season.

A question I often get from readers is when to apply potash to lawns, and the short answer is in the fall so that the grass can withstand the harshness of the winter weather.

However, there are several other factors that determine whether your lawn can benefit from a dose of potassium and the exact time to apply potassium to your lawn. 

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When to Apply Potash Fertilizer to Lawn?

Just like applying nitrogen to turf, potash should be applied during the plant’s active growth, which is usually between early spring to late summer. 

You can also apply potassium roughly once a month during the winter and late spring to prevent your plants from becoming invaded by diseases. 

With regard to how much potash to apply, the answer varies by brand so be sure to check the back of the package for application rates. 

When to Apply Potash to Lawn

How Do I Know if My Lawn Needs Potassium?

There are several key signs your lawn needs potassium salts, most notably grass plants turning brown or wilting at any time of year including mid – spring and summer months. 

Other signs your lawn grasses including cool-season grasses, warm-season grasses, and other turfgrass species need potassium include:

  • yellowing edges of leaves,
  • leaves that appear burnt,
  • and excessive weeds.

However, a sure-shot way of knowing when to apply potassium to lawns is with a soil test

How Much Potash to Apply to Your Lawn?

The amount of fertilizer to apply to your lawn with a spreader or other tool depends on the results of a soil test.

While applying potash in excess isn’t necessarily harmful to your lawn, it can affect your lawn’s ability to consume other nutrients such as calcium and magnesium over a period of time. 

There are several ways to take a soil test including taking soil samples and sending them to a lab or using a home soil test kit during the warm months when the temperatures are more than 50 degrees Fahrenheit. 

The University of Perdue says that lawns typically require six pounds of muriate of potash per 1,000 feet. Once you know how much potassium to apply to your lawn, apply the potassium fertilizer evenly when the ground is dry. 

Check the weather to ensure there is no rain in the forecast for at least the next day after you fertilize because water can wash away your efforts.

However, you can water the grass after fertilization as doing so will wash away the fertilizer from the grass blades and to your soil and help the lawn fertilizer reach the roots faster. 

How Much Potash to Apply to Your Lawn?

Potash Fertilizer NPK

Shopping for the right potassium fertilizers can be overwhelming, given that there are several options to choose from, more specifically NPK values. 

NPK values are a set of three numbers listed on fertilizers including liquid fertilizers, organic fertilizer labels, and granular fertilizer labels that represent the concentration of three macro-nutrients used by plants namely nitrogen, phosphorus, and potassium. 

Since we’re talking about potassium, a good potassium fertilizer will have a higher potassium concentration, therefore an NPK of 10-10-20. 

Fertilizers that are rich in potassium include different types of potassium like sulfate of potash, wood ash, potassium sulfate, and/or potassium chloride. Here’s a table that summarizes various potassium fertilizer types and their nutrient content. 

Potash Fertilizer NPK

What Soil pH Level Is Best?

The best soil pH varies by plant because each plant prefers a different level of acidity. But one thing’s clear, having the right soil pH is important to growing a high-quality turf. 

And having the wrong soil pH is detrimental to your lawn’s health. The correct soil pH is between 5.5 and 7.5 so you should do a soil assessment regularly to ensure it is within this range. 

Early identification of soil pH issues makes it easier to correct nutrient deficiencies in poor-quality soils than late identification. 

Sandy soils will have a different pH than clay soils. If you have a vegetable garden or flower garden in sandy soil, the optimal soil pH is between 5.8 and 6.3. 

But if you’re growing lettuce, chard, snap beans, and other plants that can benefit from clay soil type, the pH should be between 8 and 10. 

PH Level Soil Test

Where to Buy Potassium for Lawns

Potassium for lawns is easily available in a 50-pound bag or other quantities at your nearest garden center or online. But here are my top three picks including a granular potassium fertilizer and a product in a water-soluble form that provides healthy plant growth.

See also my detailed article on the different types of potash.

High Potassium Fertilizer

No products found.

The Down to Earth high potassium fertilizer is rich in both potassium and sulfur and features a 22-11-22 NPK. Best of all, the 3-in-1 combination is a naturally occurring source of these 3 vital nutrients and can be applied with either a drop spreader or broadcast spreader. 

No products found.

Granular Potash for Lawns

Osmocote Granular Potash

The Osmocote granular potash features 15-9-12 NPK and a single bag covers up to 37.5 square feet. This slow-release fertilizer should not be applied during wet periods but during dry periods followed by light watering. 

Apart from potash, the Osmocote granular potash also contains 10 other essential nutrients and feeds for up to 6 months. 

Osmocote Smart-Release Plant Food Plus Outdoor & Indoor, 8 lb.
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Osmocote Smart-Release Plant Food Plus Outdoor & Indoor, 8 lb.
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  • OSMOCOTE’S BEST FORMULA: Each homogeneous granule contains 15-9-12 NPK plus micro and secondary nutrients and feeds up to 6 full months.
  • OSMOCOTE’S SECRET: Soil temperature controls how Osmocote releases its nutrients, and more importantly how nutrients are taken up by the plant. Replenishment and feeding are in natural harmony.

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Liquid Potash for Lawns

Simple Lawn Solutions

The Simple Lawn Solutions liquid soluble potash features a 15-0-15 NPK so you get the power of potassium and nitrogen blended with humic acid.

It is formulated with high-quality feed-grade nutrients and is designed to be applied quickly and easily to the soil surface. This product is manufactured in the United States and is a great choice for any soil type. 

15-0-15 32 Ounce and 15-0-15 1 Gallon Bundle - Liquid Lawn Food...
28 Reviews
15-0-15 32 Ounce and 15-0-15 1 Gallon Bundle - Liquid Lawn Food...
  • 15-0-15 Phosphorus-free Liquid Lawn Food Nutritional Supplement: If you want to maintain lawn vigor or if your lawn shows symptoms of a Nitrogen & Potassium deficiency, this is the correct fertilizer for you!
  • The Power of Nitrogen & Potassium Blended with Humic Acid: Intensify green and growth while providing key nutrients for health and strength. Humic Acid conditions soil while helping the transfer of food throughout the plant cell.
  • Made With High Quality Feed Grade Ingredients: Nourish your lawn to with pure liquid Nutrients. Designed to be quickly & easily applied.

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How to Apply Potash to Your Lawn?

 The way to add potash to lawns differs between granular potash and liquid potash. 

Applying Granular Potash to Lawn

Just like granular type of fertilizer, the easiest uniform way of adding granular potash to a lawn is with a spreader.

Assuming you’ve performed soil testing and have determined that your turf is indeed short of potassium and other soil nutrients, choose a granular fertilizer with a high potassium content (read the product labels). 

Fill the drop spreader with the granular potash fertilizer and spread the necessary amount when the ground is dry. Depending on how short your lawn is in potassium, you may need two separate applications – one in the spring and the other in the fall to maintain healthy soil and fertile soil. 

Unlike water-soluble fertilizer, Granular potash fertilizer is systemic meaning it must be watered into the soil to be taken up by the roots for healthy root growth and increased disease resistance.

Applying Liquid Potash to Lawn

Liquid potash works almost immediately toward healthy grass growth. The dilution and application instructions may vary across products so make sure you read the product labels and apply adequate amounts and not excessive amounts. 

Some liquid potash should be dissolved in water before application while other are ready-to-use products that sometimes come with a sprayer. Start by dissolving the potash in water, and use a garden sprayer that attaches to a hose for application. 

Spray the liquid potash fertilizer evenly across your turf and cover all the way to the edge of your lawn but avoid spraying on other areas of your lawn such as garden beds as they may not be potassium-deficient, but may be short of a pound of nitrogen or have an iron deficiency. 

Can You Put Too Much Potassium in Your Lawn?

It’s easy to add excessive amounts of fertilizer to your lawn during any time of the year including the winter months. Even though potash plays a critical role in lawn health, excess potassium can actually do more harm than good. 

Applying too much potash fertilizer can burn or desiccate grass roots, ultimately killing your grass. Additionally, excess potash fertilizer can also be harmful to the environment and cause nitrogen and salt levels in the soil to increase. 

There are several signs of overfertilizing such as browning and wilting grass blades, stunted growth, and a crust of fertilizer on the soil surface. 

Too Much Potassium on Lawn


Q. Can Potassium Burn Grass?

A. Similar to regular fertilizer, excessive amounts of potash whether from slow-release sources or quick-release sources and/or from a single application of frequent applications can burn grass in an established turf. 

This is may result in fertilizer burn, which can be fixed by scooping up the excess fertilizer, rinsing the soil with water, and reseeding the lawn if necessary. 

Final Thoughts 

Applying potassium to your lawn is one of the many key fertilization practices only when your lawn needs it.

Just like applying a pound nitrogen or two, the right time to apply potash is during the plant’s active growth and in dry weather (avoid wet weather), which is early spring to late summer, and not a late spring application or late winter application.

But it’s important to perform a soil test first by taking a soil sample or a home soil test to bring alkaline soils and clay soils within the right pH and ensure that you have a potassium deficiency.

Water-insoluble potash fertilizer takes longer to work than water-soluble fertilizer so you’ll have to be patient to see great results. 

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