# Fall Nitrogen in the Transition Zone



## bernstem (Jan 16, 2018)

It is coming up on time to start thinking about how to put a lawn to sleep. There are lots of studies/experience on what to do in the North. Fall Nitrogen Blitz? Winterizer Nitrogen? Something else?

What about those of us who have no or minimal dormancy and no or minimal snow cover? How do the shorter days and lower sunlight intensity affect your decision making? For cool season turf, it can seem like temperatures stay too high for good growth when there is still enough sunlight for the grass. By the time temps drop to ideal levels, sunlight is going away and we never see strong fall growth. The trade off is that growth will continue, though more slowly, much longer and in some cases all winter.

My lawn will continue to grow until at least December, but I will see some snow and likely dormancy for 2-6 weeks. I have tried a lot of things in the past including a early fall Nitrogen followed by a pause and then a winterizer. I did not feel that gave me any benefit over three applications of fall Nitrogen in Aug/Sept/Oct.

This year, I am going to try a Transition Zone variation of the fall blitz. My goal is to try and match Nitrogen applications to growth rate. I am going to use a temperature dependent stabilized slow release Nitrogen. I'll add Ammonium Sulfate applications for immediate release. The idea is to provide a relatively stable base of Nitrogen in the soil that will slow as temperatures drop, but increase more if it warms up. That way, I don't have to be constantly on top of soil temperatures and grass growth as the days get shorter and I have less time to be in the lawn. The Ammonium Sulfate will be mostly for the next 4-6 weeks if the cooler weather breaks and it warms up. If that happens, I can apply a small dose of fast release Nitrogen that is not temperature dependent.

Thoughts on the plan? What are the other transition zone members planning?

Also, an older thread on the topic: https://thelawnforum.com/viewtopic.php?f=24&t=1510


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## 440mag (Jan 29, 2018)

I haven't verified the following scientifically; however; I am sufficiently comfortable going with it until anyone points out where the references may be "off."

<snip>

"The following is a partial list of soil temperatures (F) at the 4-inch depth that should be of the association with certain biological events.

*Cool Season Grasses*

90F Shoot growth ceases.

77F Root growth ceases.

70F Maximum temperature for root growth of any consequence.

70F Time to plant grasses in late summer.

*60-75F Optimum temperature for shoot growth.

50-65F Optimum temperature for root growth.

40F Shoot growth ceases.

33F Root growth ceases.*

20F Low temperature kill possible if temperature subsequently drops rapidly below 20F

<end-snip>

Source: https://www.houzz.com/discussions/1519066/interesting-read-on-soil-temperatures-and-grass-growth
*ORIGINALLY PUBLISHED* by the North Carolina State University Turf Council ("Soil Temperature Reports Aid Managers" March 31, 2005) to show the impact of soil temperature on cool and warm season turf ...

I utilize the above in conjunction with the SCO Map which I use to monitor soil temps on an almost daily basis: https://climate.ncsu.edu/map/

Currently spreading 25lbs of 46-0-0 over 28k sf on roughly a weekly basis, I see myself going through a whole lot of of the stuff between now (soil temps in the low to mid 60's) and when root growth is curtailed! :lol:

Only drawback is I am now wearing a knee brace due to having to push mow the entire acre-and-a-half because the heavy dews rolling off The Great Smoky Mountains every night and morn have the hills and slopes that comprise my property literally soaked every day and too wet for any type rider.

I'll probably be on crutches by then but, next Spring should be epic! :lol:


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## Deadlawn (Sep 8, 2020)

440mag said:


> I haven't verified the following scientifically; however; I am sufficiently comfortable going with it until anyone points out where the references may be "off."
> 
> <snip> "The following is a partial list of soil temperatures (F) at the 4-inch depth that should be of the association with certain biological events.
> 
> ...


@440mag Great info here, thanks!

@bernstem My thought for you is if you are looking for a slow release fertilizer that will release as temps rise, use an organic fertilizer. Organic fertilizers depend on microbes to release them. Microbial action slows down as temperatures fall.


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## sam (Mar 10, 2018)

OP:
Sounds reasonable to me (in theory at least - haven't tried exactly this)
I agree that in the transition zone it's not entirely predictable that the lawn will go to bed once and stay in bed all winter. I never go months without mowing, it's just not that black and white.

Anyway, I thought latest thinking on winterizer was that there was nothing special in doing a winterizer (anywhere, not just in transition zone). The only difference between a winterizer app and doing Fert at other times being that a winterizer just is less efficient. i.e. high percentage of it will get wasted off into the environment so you have to hammer it with more Fert to get the same benefit

I'm not expert but I agree it always seemEd more logical to me to match Fert to the plants natural cycles;

My 2 cents


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## 440mag (Jan 29, 2018)

Good points sam and one of the other natural cycles that has me focusing on nitrogen feeding Oct-Dec is the cycle of fungus in my area - I learned the painful, hard (and expensive) way; woe unto he/she that does not heed the UNC Turf Lab advice to NOT feed TTTF nitrogen after March *in my locale* lest one set their turf up for almost guaranteed fungal disease outbreaks, all summer long.

Your point about excess washing off into environment is a real concern and why I just "suck it up" when spreading such light amounts of urea on a weekly basis - well, well over an hour of pushing a spreader and the granules are barely coming out so that the hopper level going down is too slow to even perceive - it's a constant battle to remind myself that "less is more" in my situation ...


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## bernstem (Jan 16, 2018)

As far as I know, this all just my theory. I haven't seen much from Universities on it. Most information is for farther North and farther South, but I have not done an exhaustive search.

All valid points - especially toward washing off of Nitrogen. There is some good evidence that tailoring Nitrogen to growth rates may be the way to go. If the grass is still growing, then give it Nitrogen in proportion to how fast it wants to grow.

Where I run into problems is the unpredictability of late fall/winter growth in the transition zone. It may drop to 35-55 degrees for half of November with slow growth (but still some), then pop up to 45-60 degrees for a week.

As for soil temps, it is uncommon that I ever get a soil freeze at 4 inches. At most I will see the very surface frozen for a week or so before it thaws again. Even if it snows, the ground often does not freeze below the snow and the snow is gone within 3-10 days.


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## ksturfguy (Sep 25, 2018)

My fert plan has been messed up all Fall by the dry weather. I don't have irrigation so have been waiting for a good rain show and it's just barely rained this Fall. I finally applied about a 1/2 LB of N today via Urea. It's supposed to rain/snow the next couple days. Current soil temps are in the upper 40's but have been in the Mid 50's for the last week. We are supposed to get pretty cold this week, high in the low 30's on Monday and lows in the teens on Tuesday. After that it warms back up into the 60's by late next week and should remain in the 50's and 60's for the next week or so.

I still have a 1/2 bag of Urea left so will probably apply it here in a couple weeks if and when we might get more rain again. Then depending on the weather I might apply some Ammonium Sulfate in mid Nov or I might just call it good.


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## g-man (Jun 15, 2017)

@bernstem 


I used the Climate Chart from PACE Turf to see what the grow potential for the St. Louis area is for cool season lawns. It has a similar curve to the one in Indy, but it has a shorter winter period. For me the Nov thru March is almost 0 GP and this matches with what I see. By mid November, I barely get any clippings (most years). Green up starts in March and I start mowing in April.

Looking at your data and your post, you are mowing in December and should start to see green up in February. Therefore, I think nitrogen into mid November might be good. After that, I think it is fairly dormant and I dont see the benefit of any nitrogen then. But around March/April, I would monitor the lawn and give it a small feeding of fast N if it is not growing at a good rate. Normally during that time we see some nitrogen being released from OM, so it might not be needed.

By the way, your July/August look miserable.


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## Green (Dec 24, 2017)

@bernstem, I haven't looked up the data for my area like that which g-man posted. But I know his growing season is similar to mine...greenup starts in late Feb or March, and we start mowing in April generally. The season slows starting about now, and by mid November most years growth is slow. There is little to no growth by the last day of the Nov or early Dec (except for during brief warmups over Winter, when grass can resume growing slightly for short periods). We are about 30 miles away from the Northern reaches of the transition zone (of which NYC and coastal Southwest CT is now a part according to the latest maps).

As such, you may want to keep an eye on my experiment for this year. It's much simpler than last year's (which didn't work out due to flooding and Nitrogen loss).

Basically, the experiment is going to put simulated self-tapering spoonfeeding against a Fall blitz with a traditional final winterizing app.

The self-tapering approach is something I started thinking about years ago after my first discussions with osuturfman when he started discussing the latest studies in his field.

I also had various anecdotal experience with different timings for Fall N in my area (observing different winterization timings and their results).

I feel like if this method I'm about to try works, it would be ideal for use in your area with some timing modifications. I'm pretty sure it's unlike anything you've seen before, as it attempts to simulate the tapered spoonfeeding promoted by the experts most recently, but with a single final application instead of weekly apps of 0.25 N or less (which would taper down to 0.05 lb or so eventually if done manually).

The app is going down this week. The beauty of it is it (in theory) automatically uses soil temp to spoonfeed in the weeks following the application. If it works, it could be a new type of winterizing application and timing that could work for you. It also has carryover into the Spring that should hasten greenup. All the while being unlikely to leach.

If you want in on this experiment, PM me for the details. You could then modify my formula and app rate/timing to fit your conditions. You could put it up against the spoonfeed and see if the results are similar...something I won't be doing.


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## Pezking7p (May 23, 2020)

Very interesting. The PACE model is really cool. I found their temperature data, but is the info about nutrients needs your own compilation @g-man?

More or less, it looks like you can basically spoon feed (and possibly taper the feedings) until you stop getting clippings?


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## bernstem (Jan 16, 2018)

@g-man The PACE chart fits what I see growth wise to a tee. The lawn slows in mid November, has stopped by mid December, and wakes up in late Feb to early March. I have almost always given a small dose of Nitrogen in mid March/early April as the lawn growth always seems to lag based on where it should be from soil and air temperatures. I am hoping to get something similar to what @Green is discussing. The idea is to build a bank of stabilized Nitrogen in the soil over winter that will be available if it warms up unexpectedly and will still be present in March.

Some of the idea behind this is based on Agricultural practices with a stabilized fall Nitrogen application that will sit in the soil until spring. While I don't think it is great in that setting, and most farmers I talk to don't use it, it may have a better application in turf grass that never really goes dormans but instead slows dramatically. The stabilized Nitrogen should be there and available if needed.

g-man, July and August are striaght up survival mode for cool season grasses here. I just prevent disease and try to keep the grass alive.

Green, I saw your PM. I may see if I can source your blend and try it on half the back lawn and compare to a stabilized Nitrogen on the other half with some light spoon feeding if needed. I am trying to get down to fewer appliations in the fall so the idea of a single application and done that will also give spring green up is attractive. I could also do the whole thing with bi-weekly spoon feeding based on growth predictions using Ammonium Sulfate, but that is a lot of work and days get too short and it becomes a lot of work with limited time.


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## g-man (Jun 15, 2017)

Pezking7p said:


> Very interesting. The PACE model is really cool. I found their temperature data, but is the info about nutrients needs your own compilation @g-man?
> 
> More or less, it looks like you can basically spoon feed (and possibly taper the feedings) until you stop getting clippings?


That table is straight from them. All I did was copy/paste the temps/precipitation from weather base.

I believe that we don't need to make lawn care more complex than it needs to be. Focus on nitrogen in the peaks (eg. Sept) when the grass can use it.


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## Pezking7p (May 23, 2020)

g-man said:


> Pezking7p said:
> 
> 
> > Very interesting. The PACE model is really cool. I found their temperature data, but is the info about nutrients needs your own compilation @g-man?
> ...


I'll have to look a bit more on their site (which looks excellent). I just saw their table for growth potential based on temp and thought you had made your own spreadsheet.

I'm definitely trying to get to a simple lawn program. Least input for the best lawn. But, I'm still learning so I'm feeling out what works best for me.


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## Green (Dec 24, 2017)

@bernstem, there is an eBay seller. They were excellent last year when I purchased. Just search for it and it will come up. I think the price is actually reasonable. They packed it well.

The other blend components were available at local hardware store chains as regular stock or special order.

I like your experiment idea, too.


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## LawnScrub (Jun 4, 2020)

g-man said:


> @bernstem
> 
> 
> I used the Climate Chart from PACE Turf to see what the grow potential for the St. Louis area is for cool season lawns. It has a similar curve to the one in Indy, but it has a shorter winter period. For me the Nov thru March is almost 0 GP and this matches with what I see. By mid November, I barely get any clippings (most years). Green up starts in March and I start mowing in April.
> ...


Thanks for reminding me I had this chart in my spreadsheet, but didn't fully understand it.



Am I reading this right? In my area, the growth potential for cool season grass never stops? Also in the red box, is that the amount of NPK I should be applying monthly? Well mainly the Nitrogen.

If the GP for cool season grass in my area never stops growing, why is everyone around me have warm season grass. I was wondering why the warm season lawns are never fully green.

Here is my GP potential for the year based on this year temperature so far.


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## g-man (Jun 15, 2017)

We are a bit of topic from the OP. You have a nice weather since it doesn't deviate much from 68F. If you can keep it irrigated, you should do a cool season lawn.


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## LawnScrub (Jun 4, 2020)

Sorry if I was getting off topic, I am trying to gauge my fall and winter Nitrogen application. I just did two reno with tttf/kbg this month, different houses, and trying to figure out my fertilizer schedule. Everywhere I read, people are stopping their fertilizer application and since I live in an transition zone that doesn't go dormant much, I am wondering if I should keep my nitrogen application going through winter but at a reduce rate. This topic gave me good information to understand how my lawn reacts to my local temperature.


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## bernstem (Jan 16, 2018)

I think this is on topic. The real question is how do we deal with fall/winter Nitrogen in areas without Dormancy. While @LawnScrub has very different conditions than I do in St. Louis, they are still dealing with the same problem. Most lawn care guides for cool season assume a winter dormancy. How do we deal with areas that don't have it. In his case, it seems easier to me since the winter is basically a nice spring/fall day for me except really dry. The biggest issue they will face is water and that is a very different question.

Assuming adequate irrigation, then I would say LawnScrub can continue with Nitrogen year round based on projected growth. There is no need to winterize or pause there.


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