For the past 5 years or so, our recommendation has been to lightly fertilize turfgrass stands in the Halloween timeframe to bolster root growth heading into winter. That recommendation still stands, however, due to recent extended periods of cool, wet weather, we’re encouraging that an adjustment be made for this year.
Instead of strict adherence to books or calendar dates, the best indicator as to timing for late season fertilization is the growth rate of the turf plants, making the application after the majority of leaf expansion has ceased for the year. Since that slow-down is occurring 2-3 weeks earlier this season, an accompanying fertilizer application should be moved up to mid-October rather than late October.
The rest of the recommendation stands – a light rate, in the 0.25 to 0.3 lbs of N per 1,000 sq. ft. range, use of a quickly soluble N source such as ammonium sulfate, ammonium nitrate or urea, and watering the product off the blades into the soil soon after application.