Soil Temperature Feed Timing
Roots do not read calendars. Nitrogen uptake switches on and off against the temperature four inches down, and September in Minnesota is not September in Georgia. Take two probe readings a few days apart and this gives you the window you are in, the rate that belongs in it, and the date the next threshold arrives.
Grass type
Cool-season — tall fescue, Kentucky bluegrass, perennial rye, fine fescue
Four inches deep, mid-morning, in open turf — not in a bed and not in shade.
Optional — turns a verdict into a date.
Five to seven days smooths out one warm afternoon.