Fertilizers that Contain Potassium

Potassium Sulfate

Potassium sulfate, also known as sulfate of potash is one of several white, grey or pink potassic (potassium-containing) salts. These are all powders that dissolve easily.

It consists of about 50 percent pure potassium and is easy to mix with other fertilizers.

Potassium sulfate is most effective when used on heavy soils or under glass.

Like all potassium salts, potassium sulfate is best applied in the fall.

It is also useful in spring.

1½ to 1 ounce of potassium sulfate should be applied per square yard. Less should be used on clay soil.

Potassium Chloride

Potassium chloride, also known as muriate of potash, contains about 45 percent pure potassium

Because it contains chloride ions, which are poisonous to many crops, it must be used with caution.

It is always better to use potassium sulfate than to use potassium chloride.

Kainit

Kainit is made of about 34 percent salt (sodium chloride) 14 percent magnesium sulfate (sulfate of magnesia) and 12 ½ percent pure potassium

It should be used applied in autumn wherever there are winter rains that will later wash away some of the harmful salts.

This fertilizer is especially helpful to crops that require magnesium as well as potassium, such as potatoes, clovers and marigolds.

Kainit also helps to prevent insects and fungus from invading the soil.

It destroys the texture of heavy soil, so it should not be used on the same plot of heavy soil too often.

1 to 3 ounces of Kainit should be applied per square yard.