For the vast majority of homeowners, resist the urge to fertilize now. Fertilizing now can encourage too much growth and could lead to problems later this summer such as poor root growth and disease. Additionally, since spring rains play havoc with mowing schedules, nitrogen fertilization can further complicate your mowing schedule by causing grass plants to grow too fast. Instead of applying fertilizer now, it is better for homeowners to wait until mid-to late-May and apply up to 0.75 lbs N/1000 sq. ft. with a fertilizer that contains mostly slow release nitrogen sources like sulfur- or polymer-coated urea, urea formaldehyde, methylenediurea, dimethylenetriurea and natural organic nitrogen. If a preemergence herbicide is justified on your lawn to control crabgrass now, most of those are available combined with fertilizer and you are forced to apply a fertilizer now. Look for a product with low nitrogen and be sure the majority of the nitrogen is a slow release N as listed earlier.