Aerate the soil periodically to reduce compaction and increase water absorption. Landscape fertilization should be based on soil tests. The University of Wisconsin Extension recommends applying 3 - 4.5 lbs. of nitrogen per 1000 square feet, per year. The lower rate is recommended when lawn clippings are not removed. Avoid excessive fertilization which can stress the grass during droughts and lead to pollution from runoff.
Healthy turf competes with weeds for water and nutrients.
The height allows the turf to shade out weed seedlings. Weeds can be pulled manually at any time. Remove as much of the weed as possible, including roots. Smaller weeds are easier to kill than larger ones. Follow directions on the manufacturer's label when using herbicides.