Beginner Gardening: Patchy Grass, 1 by cleeden

cleeden wrote:
I live in Michigan. We had new sod installed last year. We have a sprinkler system and the sod looked pretty good last summer. We did have soil put down before they installed the sod, but under the sod is all clay… We fertilized the grass in late April early May (the spreader that we used sort of striped the grass). so we waited until 2 weeks ago to fertilize again. Now our grass is 8 different shades of green, we water the grass at night, and I think it is getting enough water. You can see in the picture that we have all different colors. We have a riding lawn mower that mulches, we heard that it is good for your lawn to mulch, but I do see dead grass covering the soil. Sometimes we use our push mower that bags the cut grass. Do you have any ideas for what we can do? Should we wait one more month and fertilize again? Do you know of any good fertilizers? How much should we be watering our grass with clay soil? What is the best time to water?

Thank you for your help...