The reason why we wait till late March to feed the grass is it's best to allow it to wake up, grow a strong new root system, and fungal diseases tend to be worse if we fertilize too early.
The Time is Nigh for Fertilizing Your Lawn

LSU AgCenter
The reason why we wait till late March to feed the grass is it's best to allow it to wake up, grow a strong new root system, and fungal diseases tend to be worse if we fertilize too early.