Fall lawn fertilization-NPK percentage?

Back in the day, 30-40 yrs ago, the rule of thumb was to fertilize lawns in the Fall with nearly zero nitrogen (N), and heavy on the phosphorus (P), & potassium (K). Reason being one did not want to stimulate leaf growth with nitrogen late in the season that would inhibit dormancy by stimulating leaf growth artificially late in the year, yet on the other hand, fortify root growth and overall plant health with a good shot of phosphorus and potassium for next Spring’s green up.

Flash forward to 2021… Now all the online “experts” insist that massive doses of nitrogen and zero amounts of phosphorus be administered in the Fall to achieve a better Spring green-up and overall superior plant health.

I’ve yet to be able to verify this notion from any reliable source, so, what’s your opinion?

The answer for you is likely to depend on where you live and what your soil profile is.

University extension services tend to recommend fall fertilization of cool-season grasses with formulations relatively high in nitrogen. This seems counter-intuitive since for plants in general you want to avoid stimulating active growth late in the season. But cool-season grasses like KY bluegrass keep growing well past first frost so the high-nitrogen fert. may be useful to aid recovery from summer stress.

I’d go with what horticultural professionals recommend for your area.

Personally I have way more lawn than I need, so I don’t want to encourage it through fertilization. It gets decomposing clippings and shredded leaves, and that’s it.