You might be asking–how exactly am I supposed to fertilize my lawn?

Let’s start with the basics on a bag of fertilizer…. You will see three numbers that are always printed on the label. They are nitrogen-phosphorus-potassium. They are always listed in this order and the number is the product percentage in the 50 lb. bag. For example a 21-7-14 is 21% nitrogen, 7% phosphorus, and 14% potassium. The nitrogen is for shoot growth, color, and turf vigor. Nitrogen in the plant helps it make chlorophyll which provides the grass a beautiful green color. Phosphorus is an essential element for the roots and provides strength for the plant during times of stress. Potassium helps strengthen the plant by making the turf stand denser and stronger. When your potassium is correct your grass can bounce back quicker from injury and wear.

Now that I have explained the basics, let’s discuss how to measure the bag. You will often see on my blog where I list a N-P-K ratio, and then I will tell you how much to put down per 1000 sq. ft. When I give you these amounts, I am often looking to get a certain amount of each into the grass plant for that fertilizer application. The easiest way to do this is to know that if you want 1 lb. of nitrogen, phosphorus, or potassium per 1000 sq. ft., you will divide the percentage by 100. Let’s take the 21-7-14 as an example. If you want 1 lb. of nitrogen per 1000 sq. ft. you need to apply 4.76 pounds (about 5 lbs. product) per 1000 sq. ft. to achieve your goal (100/21% nitrogen = 4.76 lbs.). This will also yield you .33 lbs. of phosphorus per 1000 sq. ft. and .66 lbs. of potassium per 1000 sq. ft. If you wanted 1 lb. of phosphorus you would need to apply just over 14 pounds of product per 1000 sq. ft., and if you wanted 1 pound of potassium you would need to apply a little over 7 lbs. of product per 1000 sq. ft. As you can see it’s an easy and essential calculation to do before you apply your fertilizer.

Once you’ve figured out how much product to apply it will be necessary to calibrate your spreader to achieve these goals. Since you need about 5 lbs. of total product to equal 1 lb. of nitrogen per 1000 sq. ft. it is beneficial to weigh out 5 lbs. in a spreader and mark off a 1000 sq. ft. area. You will walk the area with the spreader and determine if you run out too quickly that your setting is open too far, or if you have lots of extra that you’re setting is too low. You will make the correct adjustments to your spreader and you’re off!

I hope this has helped you out, and it now makes more sense when I’m giving fertilizer rates in my blog.  

Jay