Question
after mowing lawns lately. some are turning yellow with temps in the low 30s, with water turned off do i need to put iron on lawns or whats you recomendation cause all summer the lawns were very green

Answer
Ed, you did not mention where these lawns you were mowing were located - you could be writing from Tokyo, somewhere in Australia, or across the street here on Long Island, NY.  And everywhere in between.  If you were mowing a lawn in December, I am assuming the grass was still growing -- which would leave out all Transition and Cool grass areas.  Therefore, your Zoysia/Bermudagrass/St Augustine grass is shivering in the cold and turning winter beige as a result of the cool temps.  Watering would not help.  If anything, it might be asking for trouble -- any fungus that likes it cool and wet would be ready for action, especially if the lawn had been "treated" for months with products to destroy the natural controls.

I did not know about this Question Pool until this week so forgive me for not seeing this sooner.  You can write me anytime.  A new grass growing season is about to begin.