Fall is the best time to apply fertilizer in Nebraska. The cooler weather allows for active growth while the plant is rapidly storing nutrients in the roots for the following spring. Applying a slow release or organic fertilizer at a high rate late in the fall will allow your lawn to green the fastest the following spring. Typically late in the fall the annual weeds have died off so the fertilizer is focused on the target grass and very little is wasted. If you only receive one application per season this is the time–mid to late September.