Lawn Fertilizers – What do the Numbers Mean?
Have you ever looked at your lawn and thought that it needed to be greened up? You get in the car and head down to Lowes or Home Depot (we have both in Lincoln) and then start looking at the numerous bags of fertilizer…Which one do you choose? If you don’t know, hopefully this summary will help you next time you feel like making your lawn as green or greener than your neighbors.
All fertilizers use a three number rating system, like 15-15-15 or 21-7-14. The first number represents Nitrogen, the second Phosphorous, the third is Potassium. These numbers are percentages of the total ingredients in the bag. In case you forget the order, the words are alphabetical.
The chemical notations of these elements are N-P-K, an official designation for fertilizer numbers. Triple 15 (15-15-15) has equal amounts of each of these nutrients, or 15% of each. In a rating of 21-7-14, nitrogen has the highest concentration. It is 3 times the amount of phosphorus. Phosphorus is only half of the potassium amount. Technically, this would be called a 3-1-2 ratio.
Look at any set of fertilizer ratios on a label. Notice how the numbers relate to each other by size:
21-7-14 is Big – Small – Medium
21-3-3 is Big – Small – Small
6-20-20 is Small – Big – Big
21-0-0 is Big – Zero – Zero
The NPK rating you want for grass is typically Big – Small – Small. If you follow this, you see that grass needs a lot of Nitrogen and a little bit of the other stuff. That’s the essential part. Here’s what the nutrients do:
Essential for growth of foliage; produces lush, tender green blades. Deficiency results in a yellow-green color and little or no growth.
Stimulates root growth and hastens the maturity of plants, promotes development of seeds. Deficiency can result in slow or stunted growth and discoloration on blades.
Gives vigor to tolerate changing weather conditions and helps resist disease. Strengthens cell wall structure for strong stems. Deficiency can cause weak stems & slow growth.
Now, look at the current status of your lawn. An established lawn needs primarily nitrogen since it is not producing fruit or flowers = Big – Small – Small. A new lawn needs more phosphorous to produce roots = Small – Big – Big. A stressed lawn (preparing for extreme heat or winter) needs more potassium = Big – Small – Medium or Big – Small – Big.
To get that lush, green lawn you’ve always wanted, apply fertilizer in early spring, when the weather begins to warm up for good and plants begin to flourish. Fertilize again in the middle of summer. Fertilize a third time in the early fall after heat waves and droughts have subsided for the year. Remember to always read and follow the product recommendations for fertilizers, or any other garden chemicals. It won’t be long before your lawn is the envy of all your neighbors! Let’s all make Lincoln a more beautiful town to live in!