Understanding Fertilizers

This article was originally published on May 12, 2009 and expired on June 1, 2010. It is provided here for archival purposes and may contain dated information.

Before purchasing fertilizer for the garden, read the label. Commercial fertilizers are labeled in percentages with the three major nutrients always in this order (N) nitrogen, (P) phosphorous and (K) potassium.

A bag of 6-24-24 does contain 6% (N) nitrogen which is for leaf development. The other two major nutrients are equal in this example with 24% (P) phosphorous and 24% (K) potassium. To keep it simple a 100 lb bag of 6-24-24 has 6 lbs of nitrogen, 24 lbs. of phosphorus and 24 lbs. of potassium fertilizer in it.

The phosphorous is for root development. This major nutrient needs to be high at planting time for transplanting plants. So a soluble 10-50-10 would be high in phosphorous and should be used at planting time. Potassium (K) is the nutrient which aids in the retention of water, overall vigor and helps disease resistance. The three major nutrients are present in a complete fertilizer such as 10-10-10.

There are occasions when an incomplete fertilizer could be used like 34-0-0. This fertilizer has 34% (N) nitrogen and is sold as ammonia nitrate. The product has no (P) phosphorus or (K) potassium in it. This would be used on your sweet corn to increase yield or green foliage plants to improve plant vigor.

There are several options for more natural products such as bone meal or green sand. Bone

meal is used often to supply phosphorus. This product is usually around 4% nitrogen and 30%

phosphorus. Green sand does contain about 3% potassium. Wood ashes would also supply approximately 3% phosphorus and 9% potassium. So for those gardeners who burn wood use those ashes on the garden.

Plants need nutrients to grow properly so use them to help plants flower, yield vegetables or to grow green foliage for enjoyment.

When purchasing fertilizers in local garden stores, nutrients are expressed in percentages.

Purchase the product that will do what you expect it to do and apply them wisely.

Source: Ed Billingsley, County Extension Director, Williamson County and Interim County Extension Director, Jefferson County, edb@illinois.edu

Pull date: June 1, 2010