From the University of Nebraska-Lincoln’s Turf iNfo blog:
Fall is arguably the most import season for turfgrass managers. While we’re busy preparing for a new growing season in spring and trying to survive stressful conditions in the summer, fall is the time to recover from summer, renovate, and prepare for winter. It’s a season of seeding, cultivation, weed control, and fertilization. While fall is still widely considered the most important time to fertilize turfgrass, the fertilization recommendations have evolved over the past decade. Fall nitrogen applications are essential to promote plant regrowth, summer stress recovery, and maximize carbohydrate storage prior to winter. Previous recommendations were to apply nitrogen during early to mid-September and then make a heavy application of nitrogen fertilization at the end of the growing season (early to mid-November). The rational was the cool weather stunted shoot growth while the nitrogen fertilizer was still taken into the plant because the soils are still relatively warm. Dr. Soldat’s group at UW-Madison actually found that nitrogen uptake was lower during the end of fall compared to earlier in the season. Read it all here