We get this question all the time. The truth is, there are a lot of fertilizers to choose from, and many of them are good. By understanding the basics of a fertilzer label, you have a better chance of finding a quality product.
Guaranteed Analysis: N-P-K
Maybe someone has told you to buy “20-10-10” or “12-12-12”. Do you know what this means? Every bag of fertilzer has a label with a Guaranteed Analysis, in the form of three numbers seperated by dashes. The numbers represent the percentage (in order) of nitrogen (N), phosphorus (P), and potassium (K) contained in that product. Therefore a bag of 20-10-10 contains 20% N, 10% P, and 10% K. These three nutrients are the most essential nutrients for turfgrass health.
The above label is for a 12-12-12, or “triple twelve” fertilizer. This is a balanced fertilizer, providing equal amounts of N, P, and K. This particular fertilizer also provides 15% Sulfur (S), which is considered a secondary nutrient in turf health. A well balanced fertilizer is recommended at the time of sodding or seeding to ensure that your new plants get all three essential nutrients.
Nitrogen is the most important component of a turf fertilizer, and is most responsible for green color and shoot (blade) growth. Nitrogen gives you a lot of “show”. It greens and grows turf in a hurry. However, it also goes away quickly. You might see 3 to 4 weeks of fast growth, then it quits, and your grass loses color.
This problem can be mitigated by using slow-release nitrogen fertilizers. Rather than a quick feed all at once, the nitrogen is released over time. Some high quality nitrogen sources can continue to feed for an entire growing season.
This label is quite different from the first one we looked at. The Guaranteed Analysis is 32-0-4. This fertilizer provides 32% N, no P, and only 4% K. In other words, this fertilizer is mostly nitrogen, designed to provide a quick response, green color, and shoot growth.
However, notice the last line with the asterisk “* Contains 9% slowly available nitrogen . . . “. This is good. It means that 9% of this bag is SLOW RELEASE. With 32% total N, 9% means that over 1/4 of the nitrogen in this bag is in slow release form.
So, which one should I buy?
Even with some knowledge of the labels, this is still an involved question. Variables affecting your decision include grass type, time of year, weather, and soil conditions. Here are a few key tips to remember:
Where do I find high-quality fertilizer?
You can buy good lawn fertilizers in many stores. If you know how to read a label, you may find adequate products at your local hardware store or even a “big box” store. If you are not sure, we recommend going to a local independently owned garden center. There are also some local wholesale supply houses that sell to the general public.