# spraying nitrogen?



## vnephologist

[Edited title since thread discusses more than ammonium sulfate]

Spoon feeding small amounts of N over my small lawn (even with ammonium sulfate vs urea) make applications seem very irregular and I feel like I'm getting really good at spraying with my constant PGR, Fe, and fungicide apps. That said, what are the thoughts on spraying ammonium sulfate? I know its already a small part of some folks FAS applications and I read up on foliar N apps in this thread, but I don't see much other discussion of it. Is it just more work over granular for folks with more sqft? I see reference to "spray grade" ammonium sulfate, but when I purchased my bag at Landscape Supply, the guy actually mentioned that it should work well to use for a spray application. What are the downsides?


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## Mightyquinn

vnephologist said:


> Spoon feeding small amounts of N over my small lawn (even with ammonium sulfate vs urea) make applications seem very irregular and I feel like I'm getting really good at spraying with my constant PGR, Fe, and fungicide apps. That said, what are the thoughts on spraying ammonium sulfate? I know its already a small part of some folks FAS applications and I read up on foliar N apps in this thread, but I don't see much other discussion of it. Is it just more work over granular for folks with more sqft? I see reference to "spray grade" ammonium sulfate, but when I purchased my bag at Landscape Supply, the guy actually mentioned that it should work well to use for a spray application. What are the downsides?


I've been researching this topic extensively recently and would really like to know more as information is very limited. Ammonium Sulfate(21-0-0) and Urea(46-0-0) are both water soluble and will generally dissolve in cold water fairly easily. They can be sprayed as a foliar or soil application but will volatize in the soil upon application. Urea is more prone to this then AS since it has to be converted into a usable source for the grass. I've have also read that it will require more carrier(water) when applying liquid fertilizer (3-5 gallons per K) to prevent tissue burn as the fertilizer can dehydrate the leaf. I would do a test area first before applying it to the whole lawn if you are going to do 1 gal/K.

Here are some videos from the Grass Factor which help explain all the nitrogen sources.
[media]https://www.youtube.com/watch?v=QezuN9NkPtQ[/media]

[media]https://www.youtube.com/watch?v=JSgjCLslZoc[/media]


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## vnephologist

Mightyquinn said:


> I've have also read that it will require more carrier(water) when applying liquid fertilizer (3-5 gallons per K) to prevent tissue burn as the fertilizer can dehydrate the leaf. I would do a test area first before applying it to the whole lawn if you are going to do 1 gal/K.


At my current pace, I'm usually right on the money with ~2 gal/K. I wonder if that would be enough dilution with AS at 0.25-0.5 lb/K. Most references to foliar N that I found were for ammonium nitrate. Off the top of my head, I wonder if that's because it needs less carrier?


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## Mightyquinn

vnephologist said:


> Mightyquinn said:
> 
> 
> 
> I've have also read that it will require more carrier(water) when applying liquid fertilizer (3-5 gallons per K) to prevent tissue burn as the fertilizer can dehydrate the leaf. I would do a test area first before applying it to the whole lawn if you are going to do 1 gal/K.
> 
> 
> 
> At my current pace, I'm usually right on the money with ~2 gal/K. I wonder if that would be enough dilution with AS at 0.25-0.5 lb/K. Most references to foliar N that I found were for ammonium nitrate. Off the top of my head, I wonder if that's because it needs less carrier?
Click to expand...

You may be OK then but I would still tread lightly at first so as not to damage anything. Will be curious with your results.


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## vnephologist

For sure. Not doing anything until I get some more feedback first. Even then, I'll be super careful. Just getting things looking like I want.


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## osuturfman

No problem at all melting down and spraying Ammonium Sulfate. A higher carrier volume (2.5+ gal/M) will help to reduce and/or eliminate any risk of tip burn. If you have it dialed in at 2.0 gal/M, perhaps you could cut your rate in half and spray over the lawn twice. With the rates you are suggesting, I would try 2.0 gal/M and see how the turf responds.

Why AS and not urea or a combination of the two?


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## vnephologist

osuturfman said:


> Why AS and not urea or a combination of the two?


Well, honestly, only because I hadn't seen reference to urea sprayed before and I had recently switched to AS for a little more safety. I found it hard to evenly apply 0.25 lb N/M of urea via spreader. I actually have both Urea and AS on hand if urea or a combo would be better. I'll be applying weekly starting with 0.25 and ramping up once the new seedlings are further along.


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## LawnNerd

Ok, so I'm glad this came up. I was purchasing my urea today from my local spot, and when I was talking to the guy he wanted to know,if I was going to spray. I said no, because I hadn't planned on it. My biggest question is, does anyone know if spray requires more or less follow up irrigation after?


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## osuturfman

*Urea vs. Ammonium Sulfate (AS)*

The basic premise of why and when is a matter of temperature and chemical characteristics of each material. Urea requires an enzyme, known as urease, that's present in the soil to break it down into plant available forms of nitrogen. Urease is marginally effective at soil temperatures below 50 degrees F. Take that into account along with volatilization issues, spraying on a cold weather day might lead to less than ideal efficacy. Enter Ammonium Sulfate.

Ammonium sulfate excels in uptake during cooler weather seasons because it is an ammoniacal form of nitrogen. Couple that with a hydrolysis reaction of melting it down into your spray tank and you are left with NH4 and NO3 which are both instantly available forms of nitrogen for the turf.

One other item of note is the salt index of each material. Ammonium sulfate has a salt index twice that of urea. What does that really mean? Higher carrier volumes when spraying ammonium sulfate (2.5+ gal/M) and irrigating within an hour of spraying the material. Urea is much safer to apply with lower carrier volumes (0.75-2.0 gal/M) and could stand on the leaf in summertime temperatures for up to 12 hours with no phytotoxicity.

The bottom line is, use AS in the early spring and late fall and urea from late spring through early fall for best results.


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## osuturfman

LawnNerd said:


> Ok, so I'm glad this came up. I was purchasing my urea today from my local spot, and when I was talking to the guy he wanted to know,if I was going to spray. I said no, because I hadn't planned on it. My biggest question is, does anyone know if spray requires more or less follow up irrigation after?


Regardless of whether you apply AS or urea through a sprayer my recommendation would be:

- Quick soaking with the hose or two spins of in-ground sprinklers no more than three hours after application. Basically, wash off the leaf and get excess fertilizer to the soil surface.

- Follow up with 0.25" of irrigation the night of or the morning following the application.

You won't go wrong with that plan.


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## Mightyquinn

osuturfman said:


> LawnNerd said:
> 
> 
> 
> Ok, so I'm glad this came up. I was purchasing my urea today from my local spot, and when I was talking to the guy he wanted to know,if I was going to spray. I said no, because I hadn't planned on it. My biggest question is, does anyone know if spray requires more or less follow up irrigation after?
> 
> 
> 
> Regardless of whether you apply AS or urea through a sprayer my recommendation would be:
> 
> - Quick soaking with the hose or two spins of in-ground sprinklers no more than three hours after application. Basically, wash off the leaf and get excess fertilizer to the soil surface.
> 
> - Follow up with 0.25" of irrigation the night of or the morning following the application.
> 
> You won't go wrong with that plan.
Click to expand...

Great information osuturfman!!!

What are your thoughts on using a Nitrogen Stabilizer when spraying Urea?


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## osuturfman

MQ,

Dr. Bruce Branham at the University of Illinois did some great work on this topic. Basically, his research showed volatilization was inconsequential if you irrigate within 24 hours. Urease inhibitors such as UMAXX were also shown to be ineffective relative to additional cost versus making another application of Urea.


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## CH3NO2

Glad to see osuturfman has found a place to share his knowledge and views. Thank you for the insights.


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## vnephologist

Thanks so much osuturfman! This is going to set me up perfectly to get everything grown in once I get my DIY walking boom built... http://thelawnforum.com/viewtopic.php?f=4&t=1145


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## Ridgerunner

osuturfman said:


> *Urea vs. Ammonium Sulfate (AS)*
> 
> Urea requires an enzyme, known as urease, that's present in the soil to break it down into plant available forms of nitrogen. Urease is marginally effective at soil temperatures below 50 degrees F. Take that into account along with volatilization issues, spraying on a cold weather day might lead to less than ideal efficacy.


What happens to the urea under those conditions over time?

I think I'll start a new thread to avoid any chance of derailing your thread.


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## vnephologist

On the topic of N sprays, I'm wondering if there are any issues tank mixing PGRs and fungicides? I know Fe should be okay, given the FAS some guys are using.


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## vnephologist

vnephologist said:


> On the topic of N sprays, I'm wondering if there are any issues tank mixing PGRs and fungicides? I know Fe should be okay, given the FAS some guys are using.


After some further research, I think I can answer my own question and say that there are no issues with PGRs (will edit for fungicides when I find references). In fact, I found a recommendation to tank mix soluble N with PGR in this great article... http://gsr.lib.msu.edu/article/bigelow-plant-4-13-12.pdf.

"Another suggestion when using any of these PGRs is to tank-mix a small amount of soluble nitrogen, such as urea and/or a liquid chelated iron source. This will minimize discoloration and continue to stimulate growth/density without excess clipping production."

I guess this is why I see a lot of folks doing PGR+FAS.


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## zeus201

Random question, can this applied to wet grass? Like to apply this in-between the break in rain later this afternoon.


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## vnephologist

As I understand, the answer is yes. I think there's some foliar absorption of AS, but think majority is root absorbed anyway. I think it's definitely okay for urea. Don't forget to water in if it happens to not rain again.


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## vnephologist

After several weeks of spraying urea, I just wanted to mention that I'm finding ease of application and coverage far superior to spreading granular. I realize I only have a small lawn, but for others with a small area, I'd absolutely recommend it. Particularly if you're already spraying other chemicals.


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## LawnNerd

After this thread came up, and a great explanation from osuturfman, i started to spray my urea as well. The consitancy of the application can't be beat. I don't know that I'll go back to granular urea after this year.

Im spraying .5#N/M every two weeks. I spray 1# urea in 2 gallons of water per 1k sqft. This enables me to spray North - South and then East - West. I then walk through the yard with the hose and "rinse off" the grass. Its superiour coverage for sure!

Thanks for starting this thread vnephologist. And thanks osutrufman for the "encouragement"!


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## osuturfman

Glad it has worked out well for you, gentlemen!

As for the foliar absorption of urea or AS into the plant; the critical period is 4 hours after application. If you can get through that period without irrigating or rainfall, you'll get the most bang for your buck on N entering the plant through the foliage. It continues thereafter, however, the curve flattens out significantly. There has also been research work showing seasonal changes in foliar absorption, with a reduction in absorption through the summer and into fall. The thought is that that cuticle, or surface, of the leaf blade becomes more hydrophobic thus not allowing as much to enter the plant. This makes sense as the plant is encountering heat or drought stress through the summer, then entering senescence and hardening off in the fall.

What does that mean for all of you sprayable nitrogen converts? Continue doing your apps as discussed above and have plans for rainfall or irrigation to wash in your N within 4-24 hours after application.


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## Sinclair

Great topic.

I have a small ~1000sf front lawn, and I feel like my pellet spreader urea apps weren't as uniformly distributed as the could have been.

Do Urea and Iron Chelate make good tank partners? It is easier for me to get these separately than it is to get FAS.


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## osuturfman

Should have no problems. Do a jar test just to be sure.


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## vnephologist

Sinclair said:


> Do Urea and Iron Chelate make good tank partners? It is easier for me to get these separately than it is to get FAS.


I tank mix 5% Iron Glucoheptonate (T-Growth/Simple Success Sugar Iron) and PGR with my urea without issues.


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## andrew_suff

vnephologist said:


> After several weeks of spraying urea, I just wanted to mention that I'm finding ease of application and coverage far superior to spreading granular. I realize I only have a small lawn, but for others with a small area, I'd absolutely recommend it. Particularly if you're already spraying other chemicals.


I'm interested in using Urea to spray my lawn. So far some people on here have recommended application of 0.5 pound of Urea per 1,000 square ft (1 gallon). Any tips you could offer for app rates and did you irrigate after applying? Thanks!


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## vnephologist

andrew_suff said:


> I'm interested in using Urea to spray my lawn. So far some people on here have recommended application of 0.5 pound of Urea per 1,000 square ft (1 gallon). Any tips you could offer for app rates and did you irrigate after applying? Thanks!


So, I think for most (and definitely me) its ~1lb of Urea per 1,000. I think the the 0.5 you're seeing 0.5 N. Urea is almost 50% N, so that's how it works out to about a pound per 1k. I'll usually water it in within 30 mins or so until it starts to cool down more. I think I remember there's no need leaving on leaf longer than 4hrs.


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## 7474

@osuturfman Thanks for the information presented in this thread.

I see you offered 2 recommendations for watering in the sprayed urea. One says a light watering to wash off leaf blades right after application and the other states no rain/irrigation for 4 hours to maximize efficacy.

Thanks for any clarification you can offer.


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## osuturfman

7474 said:


> @osuturfman Thanks for the information presented in this thread.
> 
> I see you offered 2 recommendations for watering in the sprayed urea. One says a light watering to wash off leaf blades right after application and the other states no rain/irrigation for 4 hours to maximize efficacy.
> 
> Thanks for any clarification you can offer.


Thanks for your question, @7474.

As I said in earlier posts in this thread, the critical window is that 3-4 hours after application. If you have applied a proper rate of N with a high enough carrier volume, there should be no ill effects within that period. After 4 hours, upwards of 80% of N that is capable of entering the leaf will have done so by that time. At that point, the best practice is to irrigate to wash the remaining fertilizer residue through the canopy and into the soil for any additional uptake.


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## vnephologist

@osuturfman I'm about to give Calcium Nitrate a try. Any specific tips?


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## CarolinaCuttin

Calcium Nitrate is great, but you have you be very careful tank mixing it. I don't use any other salt because It doesn't play well together with most fertilizers. When I spray it, it's always with dye, surfactant and nothing else. Also, the calcium doesn't really get into the plant through the leaves, so your foliar window is for the ammonium and nitrate. But the calcium can still be absorbed through the roots when it gets washed off with rain or irrigation.


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## Rooster

I'm planning to jump into this practice now that I have a very small bermuda lawn. I think it'll just be more consistent to spray rather than spread.

So, my plan is to do ~0.25 lb/k of nitrogen via dissolved Urea every 7-10 days starting in May, but I plan to do this with a hose-end sprayer instead of a tank sprayer. If I apply this at a moderate flow rate, I figure most of it will get in the soil but I'll get a little bit of a foliar application in the process if I don't wash it off. Does anyone see an issue with this plan?


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## jha4aamu

Bermuda_Rooster said:


> I'm planning to jump into this practice now that I have a very small bermuda lawn. I think it'll just be more consistent to spray rather than spread.
> 
> So, my plan is to do ~0.25 lb/k of nitrogen via dissolved Urea every 7-10 days starting in May, but I plan to do this with a hose-end sprayer instead of a tank sprayer. If I apply this at a moderate flow rate, I figure most of it will get in the soil but I'll get a little bit of a foliar application in the process if I don't wash it off. Does anyone see an issue with this plan?


Just my two cents but i think hose end spraying N wouldn't be a good idea vs tank spray. I don't feel like your coverage would be even enough for such a small amount of N


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## Rooster

jha4aamu said:


> Just my two cents but i think hose end spraying N wouldn't be a good idea vs tank spray. I don't feel like your coverage would be even enough for such a small amount of N


I'm less worried about even coverage _because _it's a small amount of N. I'm more worried about burn than shortchanging an area a little N. But that's a good thing to stay aware of, and I would definitely need to make sure I don't systematically shortchange the same spots every week.


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## liamjones

osuturfman said:


> As I said in earlier posts in this thread, the critical window is that 3-4 hours after application. If you have applied a proper rate of N with a high enough carrier volume, there should be no ill effects within that period. After 4 hours, upwards of 80% of N that is capable of entering the leaf will have done so by that time. At that point, the best practice is to irrigate to wash the remaining fertilizer residue through the canopy and into the soil for any additional uptake.


So is it beneficial to spray with a setup to target foliar, eg. a TeeJet XR nozzle and leave for 4 hours (assuming urea/ 1 hour AMS), or should i be setup to target soil with a TeeJet TTI nozzle and leave whatever happens to sit on the leaves for 4 hours (assuming urea/ 1 hour AMS), knowing most of it is already at the soil, then wash the remaing off after 4 hours?

I've always targeted soil for N applications and washed in immediately, will be interesting to see your thoughts on this. I'm applying 0.2lbsN/M weekly and feel like its not enough, maybe foliar is the answer.


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## CarolinaCuttin

@liamjones Target the foliage, use small droplets and lower carrier volumes. 1 gallon per thousand is great. TeeJet XR series is what I use at home and at the golf course.

Also, you're going to get better results with urea since it is much more easily absorbed by the leaf, it is a true foliar. The exception is when outside temperatures aren't getting above 50° F, in that case foliar absorption is going to suffer no matter what you use.


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## liamjones

CarolinaCuttin said:


> @liamjones Target the foliage, use small droplets and lower carrier volumes. 1 gallon per thousand is great. TeeJet XR series is what I use at home and at the golf course.
> 
> Also, you're going to get better results with urea since it is much more easily absorbed by the leaf, it is a true foliar. The exception is when outside temperatures aren't getting above 50° F, in that case foliar absorption is going to suffer no matter what you use.


Thanks for that, looking forward to seeing the improvements of going foliar.


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## osuturfman

liamjones said:


> osuturfman said:
> 
> 
> 
> As I said in earlier posts in this thread, the critical window is that 3-4 hours after application. If you have applied a proper rate of N with a high enough carrier volume, there should be no ill effects within that period. After 4 hours, upwards of 80% of N that is capable of entering the leaf will have done so by that time. At that point, the best practice is to irrigate to wash the remaining fertilizer residue through the canopy and into the soil for any additional uptake.
> 
> 
> 
> So is it beneficial to spray with a setup to target foliar, eg. a TeeJet XR nozzle and leave for 4 hours (assuming urea/ 1 hour AMS), or should i be setup to target soil with a TeeJet TTI nozzle and leave whatever happens to sit on the leaves for 4 hours (assuming urea/ 1 hour AMS), knowing most of it is already at the soil, then wash the remaing off after 4 hours?
> 
> I've always targeted soil for N applications and washed in immediately, will be interesting to see your thoughts on this. I'm applying 0.2lbsN/M weekly and feel like its not enough, maybe foliar is the answer.
Click to expand...

@CarolinaCuttin is correct, if you want to target a foliar application, then a finer droplet at a lower carrier volume is ideal. 0.5-1.0 gal/M carrier volume with an XR tip will be the ideal setup. Just remember, in doing this your misses and overlaps will be magnified.

Here's some top-notch work from the University of Arkansas by Dr. Mike Richardson and the late Dr. Chris Steigler.

https://acsess.onlinelibrary.wiley.com/doi/pdf/10.2135/cropsci2010.06.0377

I think the graph you'll be most interested in is this one below.



Please let me know if you have any more questions. I hope this helps!


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## uts

@osuturfman Wow. That plateau-ing is fairly steep. Seems like after 2 or 3 hours the benefit is very little.

I am just starting to get into spraying foliar stuff with my 4gallon backpack and I was reading through this with a lot of interest. Thank you for the explaining so well!

My usual spray volume is 0.5-0.6G/M so I can cover 7-8M in one backpack. From what I have read, that should be safe for applying 0.2lb/M of N from urea, right?

I'm planning to tank mix this with feature and spray every 3 weeks or so?


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## ladycage

I am trying to get started with foliar application of nitrogen. I have 34-0-0 water soluble granular fertilizer and also AS 21-0-0. I have bermuda grass, would it be ok to dissolve 1 pound of 34-0-0 in 1 gallon of water and spray once dissolved? I would let this sit on the grass for 3 hours and then water it in. I want to do this weekly to push my bare spots to fill in. Does this seem like a good plan? thanks for your assistance


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## Copat

I'm trying to better understand spraying urea. I'm wanting to do .25LB/ per 1k sqft. For this - would it be recommend to do 1 gallon of water per .25LB of urea? Thank you in advance


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## jha4aamu

Your carrier rate should be 1gal of water per K.

If you are spraying .25lb of urea/k, thats only .125lb of N/k


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## ABC123

As long as it has even coverage you can use however much water per 1k sq ft.

heres a great calculator on how much fertilizer you will need.

http://soils.rs.uky.edu/calculators/mult_fert.asp


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## Alowan

Any problem diluting it With a gallon pr 1000 and spraying it With a quick 1:20 sprayer (mixes 20 amounts water to 1 amount solution)


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## ABC123

As long as it's even coverage it's all good


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## corneliani

Alowan said:


> Any problem diluting it With a gallon pr 1000 and spraying it With a quick 1:20 sprayer (mixes 20 amounts water to 1 amount solution)


Are you referring to a sprayer the likes of these?

If so it's probably the safest way to spray nitrogen, but not very accurate. The issues I've always had with that style is not fully knowing how fast to move across the lawn to apply the product evenly. If you can calibrate yourself to evenly distributing the tank across your yard, it's golden. But it's kind of hit or miss IMO.

Worth noting that this is a soil-application method vs a foliar-app. The accompanying water will wash the fertilizer right off the blades. If you're trying to get some foliar action a finer stream is needed.


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## Alowan

Yep. Something like that. Got a sprayer from a fert company and my lawn is so little that i Can relativly precisly spray it With it (300 sqft).

It might come on a little uneven but as the application space is this small it is fairly even. I spray the lawn in a back and forth motion and then do several passes With the same speed.

Never thought About the potential for unevenness.


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## Theycallmemrr

https://www.turfnet.com/webinar_archives.html/the-ins-and-outs-of-foliar-fertilizers-r27/

Interesting lecture on foliar fertilizers.


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## San

Theycallmemrr said:


> https://www.turfnet.com/webinar_archives.html/the-ins-and-outs-of-foliar-fertilizers-r27/
> 
> Interesting lecture on foliar fertilizers.


Great find! Thanks for sharing.


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## Alowan

Interesting! Thanks for sharing!


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## Wood Chopper

Sorry if I'm repeating the obvious. I got some granular 21-0-0 Ammonium Sulfate from my local Farmer's exchange. I mixed a bit in a mason jar and it mixes quite easily. I have a Strom 4 gallon back pack sprayer. With the recommendations here I am going to measure out 1.20 lbs. of Ammonium Sulfate per gallon of water giving me .25 lbs. of N per 1,000. So I will cover 4,000 sq.ft per tank. I will do a test run with water to make sure I run out at 4,000 sq. ft. To make sure I spray even I am going to spray follow my lawn stripes with my fine spray nozzle tip. I am going to wait 3 hours and then water. What else am I missing? Thanks in advance

Matt


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