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Calculating fertilizer amounts based on soil test recommendation #745177

Asked April 19, 2021, 3:55 PM EDT

My recent soil test reported a potassium level of 57 ppm. The test recommended an application of 2.5 lb./1000 sq. ft. of potassium

3.0 lb. of KO2 contains 2.5 lb. of K (the percent weight of K in KO2 is 0.83)

Muriate of Potash (0-0-60) is %60 KO2

5.0 lb. of Muriate Potash contains 3.0 lb. of KO2 which contains 2.5 lb. of K

Therefore, to raise my potassium levels I need to apply 5.0 lb. of Muriate of Potash per 1000 sq. ft. Is this correct? By weight, how much potash can I apply to a Kentucky bluegrass lawn in a single application? How long should I weight between applications? Will I need to apply this much potassium the following year? Or what would be a suggested maintenance dose?


Saginaw County Michigan

Expert Response

Hi Justin, I need the code on your soil test - Thank you!!

An Ask Extension Expert Replied April 19, 2021, 7:33 PM EDT
#B5CR9H

On Mon, Apr 19, 2021, 7:33 PM Ask Extension <<personal data hidden>> wrote:
The Question Asker Replied April 19, 2021, 7:40 PM EDT

Hello Justin,

I looked at your soil test:

Your K soil test value is 57 ppm

Muriate of Potash (KCl: 0-0-60 to 0-0-62) and Potassium sulfate (0-0-50 to 0-0-52)

  1. These fertilizers are potassium sources only (no nitrogen, no phosphorus).
  2. For K soil test values less than 50 ppm, these sources are the best choice for meeting K recommendations. 
  3. Advantages: Fewest applications to meet recommended K rates in a single season. Can be applied in combination with nitrogen only fertilizers or low K analysis fertilizers to meet K recommendations.
  4. Disadvantage: May not be readily available at all stores, can burn turf at high application rates or during hot weather. (To minimize burning potential maximum single application rate is 1.0 lb. K2O or 0.83 lb. K/1000 ft.², irrigation should be applied following application.)

I used the fertilizer calculator to come up with these values

Muriate of Potash KCl: 0-0-60

Based on 1 lb. K2O/1000 ft.²

  • 1.67 lbs of fertilizer to apply 1 lb. K2O/1000 ft.²

Muriate of Potash KCl: 0-0-62

Based on 1 lb. K2O/1000 ft.²

  • 1.61 lbs of fertilizer to apply 1 lb. K2O/1000 ft.²

Potassium sulfate - 0-0-50

Based on 1 lb. K2O/1000 ft.²

  • 2 lbs of fertilizer to apply 1 lb. K2O/1000 ft.²

Potassium Sulfate - 0-0-52

Based on 1 lb. K2O/1000 ft.²

  • 1.92 lbs of fertilizer to apply 1 lb. K2O/1000 ft.²

Hope this helps

An Ask Extension Expert Replied April 21, 2021, 8:16 AM EDT
The report says I need 2.5 pounds of potassium per 1,000 sq. ft. How do I determine how much K20 to apply to get 2.5 pounds of K (potassium)?

On Wed, Apr 21, 2021, 8:16 AM Ask Extension <<personal data hidden>> wrote:
The Question Asker Replied April 21, 2021, 8:53 AM EDT

Sorry, Justin

These are the correct calculations

Muriate of Potash KCl: 0-0-60

Based on 2.5 lbs. K2O/1000 ft.²

  • 4.175 lbs of fertilizer

Muriate of Potash KCl: 0-0-62

Based on 2.5 lbs. K2O/1000 ft.²

  • 4.025 lbs of fertilizer

Potassium sulfate - 0-0-50

Based on 2.5 lbs. K2O/1000 ft.²

  • 5 lbs of fertilizer

Potassium Sulfate - 0-0-52

Based on 2.5 lbs. K2O/1000 ft.²

  • 4.80 lbs of fertilizer
An Ask Extension Expert Replied April 21, 2021, 5:32 PM EDT

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