If you are going to start a lawn fertilizer program, you really do need to have a basic understanding of what you are applying and why. and if you look at your typical bag of fertilizer, there will be three numbers there that illustrated just exactly what the fertilizer will do for your grass. Let’s learn about each one.

In the picture to the left you see a the three numbers on the back and what each one stands for. The first number refers to the nitrogen content, the second the phosphorous concentration and the third is potassium or more accurately potash. These elements each have their use in the typical lawn.

N = Nitrogen. Nitrogen is what makes the grass green and also pushes it to add top growth. The more top growth, the more leaf structure there is to capture sunlight and produce sugars through photosynthesis (remember 8th grade science class?)

It is possible to push too much lawn growth by utilizing too much nitrogen but if you are following the directions on the bag label (VERY important) then you will be fine. As a general rule, however, you should use less nitrogen during the dry, hot months of summer.

If your bag as the number 20 for nitrogen, then that means that 20% of the material in the bag contains usable nitrogen. If you are applying the fertilizer at a rate of 2 lbs per 1,000 square feet of lawn space, then that will effectively give you .4 lbs of N on the lawn. (a little under half a pound). That is a decent amount for later spring. Again, follow the label instructions for “pounds on the ground” keeping in mind that we standardize lawn applications according to square feet.

If the bag covers 5,000 square feet and is 10 lbs, then you are applying 2 lbs per 1,000 square feet of lawn area. Get it?

If that same bag has 20% nitrogen then that means that each 1,000 square feet of lawn area will get .4 lbs of N.

P = Phosphorous or Phosphate – A lot of provinces across the country have gone “phos-free” meaning they have banned its use on home lawns. This is due to the potential of groundwater leaching and contamination. There is some debate as to the usefulness of phos in lawns and I don’t have time to get into it all here. Long story short, phos helps the lawn at its root system. Phos supports root strength and development and assists in moisture intake. If you can get it in your area, DO IT! Just make sure to apply in the proper amount and keep the fert in the lawn and NOT on the driveway or street (called ‘off target application’) where it can run off during rain and into groundwater or sewers!

K = Potassium or potash. Potassium works in conjunction with Nitrogen to strengthen foliage. It also helps the lawn resist and recover from stress such as heat, drought and disease. This one will be in pretty much any fert you get to some degree.

There you go guys, more than you ever wanted to know about the numbers on the bag of fertilizer. What questions do you have?