Considerations

• A dense grass will look lush and full. Too much grass seed, however, and the grass will compete for survival and prove slow to establish and thrive. The same is true of fertilizer; as food to the grass, not enough will starve the soil and growing turf of nutrients. On the other hand, too much fertilizer can result in brown grass, bare spots and other damage.
  
  

Grass Seed

• It would be nice if there was a "one size fits all" when it comes to planting grass seeds, but the truth is, there are many types of grasses, each with a varying amount of seed needed per acre. While some seeds might require as little as 175 to 200 lbs. per acre, others might need 400 lbs. per acre. As a rule of thumb, plan to use 350 lbs. per acre as the professionals do, indicates Greg Pierce of Lawn Masters. (If you really want to get down to the nitty-gritty, that's around 16 seeds per inch.)
  
  

Fertilizer

• Fertilizers vary by ratio of the ingredients nitrogen (N), phosphorous (P) and potassium (K). In general, you should use about 40 lbs. per acre of the nitrogen content. To calculate, depending on your fertilizer's ratio of N, "divide 100 by the percent nitrogen in the bag (first number expressed a whole number) to figure how much is needed per 1,000 square feet," as suggested by the University of Illinois Extension. Then, multiply that number by 43 (since there are 43,560 square feet in an acre). For instance, a fertilizer with 20 percent nitrogen would be applied at a rate of about 215 pounds per acre.