How Many Pounds Of Phosphorus Would be in an 20-lb. Bag. Of 7-22-8 Fertilizer?
In a 7-22-8 fertilize, 22% is phosphorus. 20 lbs X 0.22 = 4.4 pounds of phosphorus in this bag.
I would break this up into two applications next season using about 1.3 pounds per 100 square feet. This will supply you with nearly 2 lbs of Nitrogen , 5.6 lbs of phosphorus and 2 lbs of potassium. Space this about 4 weeks apart.
You can come back in another 4 weeks with a nitrogen only fertilizer such as 12-0-0 and apply about 3/4 lb per 100 square feet.
These fertilizers will leave you short on potassium by 1 lb which could be fixed by applying 0-0-50 (sulfate of potash) applying 3 ounces per 100 square feet. This could be applied very early in the season before planting or in the fall after the season is completed.