I have always told everyone to read and follow the label of any product that you apply on your yard but do you really know what those number on the front of the bag mean?
The first number on the bag represent the total percentage of Nitrogen
Nitrogen promotes overall turfgrass growth. The important fact to understand is that nitrogen is basically what makes your yard green and promotes upright growth. Not all fertilizers are the same. Under this number there will be a percentage of the nitrogen that is readily available or fast releasing and also what is released over an extended period of time. simply put if you want your yard to grow like crazy and mowing every day be careful when selecting a fertilizer that is 100% readily available. You should look for a product that is 50% fast release and 50% or more slow releasing. This will give you an even greening and less time behind a mower.
The second number on the bag represent the percentage of Phosphorus.
In Dane county there is a law in effect that prohibits the the application of phosphorous. You can apply Phosphorus if you have a soil test that show your soil is deficient or at the time of a new seeding. To be honest most soils in our area have plenty and you most likely will not need to apply any. Look for a product that has a 0 for the second number.
The third number on the bag represent the percentage of Potassium.
Potassium helps the turf withstand stress and disease. Also helps build and strong turf and roots system.
Fall is the most important time to apply fertilizer to your yard. This will help you turf develop a strong roots system. I would look for a product that would give you 1 pound of nitrogen per 1000 square feet that has around 50% fast release and 50% slow release. Also, I would recommend at least .5 pound of potassium per 1000 square feet. This will help your yard recover from our summer. Always water in the fertilizer soon after the application and make sure that you do not apply to sidewalks and roads.
I have inserted a picture of a fertilizer that would treat 16,000 square feet with a pound of actual nitrogen and .5 pound of Potassium.
Not all products are the same they may seem like a great deal but when you do the math there are many differences.