Considerations

• Grass seed germinates best in a neutral soil of about 6.0 to 7.0 pH. A soil test will tell you if your soil is too acidic. If so, it will recommend adding lime. Commonly used products are crushed limestone rock, aglime and ground-up marl.
  
  

Time Frame

• Most experts say it's best to apply lime at least two weeks before dispersing grass seed. The University of Kentucky says the lime should be applied far enough in advance to have time to neutralize acid and react with the soil. According to Clemson University, several months to a year isn't too much time in advance to complete this task. At least six months is needed when applying lime to a forage pasture.
  
  

Potential

• Applying lime at the time of planting grass seed will not cause the grass harm, but you may not end up with a thick lawn. The soil needs time to lose some of its acidity, and if you don't give it that time, the grass may as well be growing in acidic soil.