Potassium Fertilizer for Corn

Potassium Shortage

• Corn shows clear symptoms of nutrient deficiency when it is low on potassium. Soil testing is still valuable because, according to the University of Minnesota, corn also shows the same symptoms when it is lacking zinc, magnesium or sulfur. When the leaf starts to lighten in color and exhibit a striped pattern, the corn is signaling a shortage of these nutrients.

Availability

• Even if you provide fertilizer that is rich in potassium, the corn needs to be able to utilize that potassium to create healthy plants. Dry conditions or compacted soil can limit the plant's ability to take in potassium through the roots. Any gardens or fields that have been compacted through any means should be disrupted in the fall so a plant's roots can absorb and use any added fertilizer.

Soil Testing

• Soil testing is the key to understanding from year to year how much potassium you need to add, if any. More potassium exists in soil than what shows up on a soil test, but the results measure the potassium that plants can actually access. Anything lower than 150 parts per million indicates a deficiency in potassium for corn growth. Anything above 250 is considered ample, or even too much when it gets to around 800. Excessive potassium is not usually harmful to corn, however.

Application

• Potassium fertilizer for corn should be applied as a starter product when the corn is seeded. Apply the amount of potassium fertilizer recommended for your area based on your soil tests in a 2 inch band beside and underneath the corn seeds. If you fertilize using the "Popup" method -- where the seed is in direct contact with the fertilizer -- don't exceed 5 pounds of K2O per seeded acre, the North Dakota State University recommends. K2O is the measurement of potassium content standardized for use in the fertilizer industry. When you see the measurement of potassium on a fertilizer label, it is referring to K2O, not pure potassium.