Minimizing Our Impact & Maximizing Fall Fertilizer Applications
If you are growing cool-season grasses the time to apply fertilizer is now. Unequivocally, the fall is the best time to fertilize our cool-season grasses, but the window to maximize how much fertilizer actually gets into the plant has been determined to be much smaller than what we once thought.
There is a long-standing turfgrass industry assumption that "anytime" in the fall is a good time to fertilize cool-season grasses. There is a caveat to this assumption. Many may also believe that fertilizing later will promote earlier spring green-up. This belief is completely false. There have been numerous studies showing no difference in early fall vs. late fall fertilization on spring green-up.
If you will, let me clarify a couple of items. Yes, the fall is the best time to fertilize, but the caveat is that in order to minimize nutrient losses and increase plant uptake we need to have all of our fertilization finished no later than the last week of October. Why you may ask, would fertilizing in November be detrimental? Temperature and turfgrass growth have a direct relationship. As temperatures begin to fall into the 50's and below, turfgrass growth starts to slow drastically. If the turf is not growing, it will not have the ability to actively take up the fertilizer you may have just applied. The fertilizer, especially nitrogen, has to go somewhere. So, if the grass isn't growing and not taking up the fertilizer then I'll give you one guess where it can potentially go. You got it, lost to the environment.
In closing, there is no agronomic benefit to fertilizing in late fall. The recommended time for applying fertilizer is the first week of September to the last week of October.
If you have any other questions feel free to reach out to me anytime.
By John Emerson, Turfgrass Nutrient Management Planning Extension Agent at University of Delaware