Looks like Saturday is going to be ideal for final mowing and fertilizer here. Warm temps that night, and a good amount of rain the next day.
This video from GCI is very close to my current philosophy on final mowing:
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Another interesting piece of news: My tweaked Fall fertilizer program, which is only 4 applications, is working very, very well. I'm getting blitz-quality results with fewer applications this year. I'm going to share some knowledge of what is working now, refined over 10 years! Here are the current Fall program details (note this is for fully irrigated, high-income areas, and my low input area does not receive the full late Summer application listed first below):
-Going into Fall, I've already applied a late Summer fertilizer application in early to mid August at 0.50 lb N and K rate. I used Protene 19-0-19 this time with phenomenal results. This stuff has a 2-4 month release (for both the N and the K!). It kept the grass looking good. Prevented a lot of late Summer decline.
-At the very beginning of Fall (mid to late Sept):
I apply another 0.50 lb rate N fertilizer, using something that has a slow or controlled release component of 30 to 60%, but that is not quite as slow as the Protene. Currently, my top choices are Screamin' Green or Anuvia, but anything similar will work, if it has a 4-8 week release duration. Soil temps are likely in the high 60s to low 70s at this point. Latest research indicates this may be the most important app of the entire year, and that it should not be overdone to produce too lush a turf. In Tennessee or NC, where the months are offset by almost plus one from mine, sometime in October would be ideal.
-Several weeks later, during the first part of October:
I repeat the previous app again, 0.50 lb N, same type of fert. Peak daily soil temps should be in the mid 60s. This app holds everything together and serves as a bridge between early and mid Fall.
-Several weeks later, my final mid Fall app:
Around Halloween in my area. I try not to string this out into early Nov. This app uses 46-0-0 urea. The rate is between 0.25 and 0.50 lb of N, and the exact rate in that range is subject to adjustment at the time of application due to factors like cumulative N, grass condition, weather, etc. This can also be considered part 1 of the Winterizer ("initial winterizer app"), which is something I just learned, but that is what it's doing. I aim to apply it 4 or so weeks before I expect growth to stop. Soil temps should be solidly in the 50s. Tree leaves are in Fall color, and dropping. This app ensures enough N gets to grass roots before late Fall, but while soil temps are still fairly ideal for topgrowth and repair. Remember: soil-applied granular urea is an organic compound, and its N is not immediately available to roots**. It requires soil bacteria (microbes) to process it and convert it into plant available N, and this process takes longer the colder the soil is / the later in the season it is. Below 50F, it's very slow, and the urea is stable once watered in assuming there is not excessive rainfall or overwatering occurring. **Currently accepted science of N uptake by roots in plants, but there may be more to the story, as newer research suggests.
Then a pause of 3 to 5 weeks until growth slows/stops.
-And the final app (or part 2 of the Winterizer, or "final winterizer"):
For me, this occurs sometime between mid Nov., and early Dec. The trick here is to wait for growth to stop or at least be at a crawl, but (and this is the new part for me) to also make sure soil temps are still as high as possible (40-50F). The other key element is use of either ammonium sulfate, or a mix of that and urea of at least 30/50. I also like to have methylene urea (MU) in the blend for this app. (This is a very stable form of urea, a true slow release N source that primarily activates in the very late Winter when soil temps are on the climb toward Spring and reach approx 50F again, but some of it may also be available at the very end of the Fall, too). Mistakes I made in the past were: waiting too long until soil was too cold to apply this app, using only urea for it, and using too high an N rate*, all wasteful and not environmentally sound so late in the season. My N rate is once again 0.50 lb, but can be adjusted up to 0.67 lb N if needed. 1/4 to 1/3 of the total N is from "high-activity methylene urea" (e.g. methylene diurea and dimethylene triurea). Scotts 27-0-2 Green Max (30% AMS, 40% U, 30% MU) and 26-0-3 PRO (50% AMS, 25% U, 25% MU) are my products of choice here. Note: If you're using 100% fast release AMS/UREA, 0.25-0.333 lb. N should be sufficient, but I get better results from an AMS/Urea and MU blend in my area. This app helps rejuvenate late Fall color and like the previous app, helps promote Spring Greenup. *Studies show that only around 0.2 to 0.3 lb of N is uptaken by turfgrass so late in the season if a full 1.0 N rate is applied. The rest likely leaches. Don't knowingly be wasteful if you're going to apply a final winterizer; please keep the soluble N rate low!