We bought a 5000 sq. ft. bag of Scotts Lawn Pro phosphorus free fertilizer ($5.44) and used it earlier this summer. It was very effective. Some Hardware Stores, Lumber Stores, and Agricultural Stores in our area carry Phosphorus Free Fertilizer for yards and shrubs.

The label on a fertilizer bag is required to show the percentage by weight of nitrogen, available phosphate (commonly referred to as phosphorus) and sulfate of potash (commonly referred to as potassium):

• The first number is nitrogen, which promotes overall grass shoot growth.
• The second number is available phosphate (phosphorous), which promotes strong root growth.
• The third number is soluble potash (potassium), which helps grass withstand stress, for example, drought or disease.

Also look at this link for much more information.