Consider using a little fertilizer now.
This year a lot of the fertilizer you applied in the fall has been used by the grass plants. If your field is yellowish and weak it would be a good idea to encourage it a little so it will be better able to respond to the normal fertilizer you apply later in March. The fertilizer ammonium sulfate is good for an early send off. We would not recommend it a rate of more than 5 lbs./ 1000 square feet. It would be better to apply it just prior to a rain. If the fertilizer is left on the turf without some precipitation on the way you may get a foliar burn.