[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?

 

[Mightyquinn]

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]

 

[vnephologist]

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?

 

[Mightyquinn]

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?

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.

 

[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.

 

[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?

 

[vnephologist]

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.

 

[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?

 

[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.

 

[osuturfman]

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.

 

[Mightyquinn]

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.

Great information osuturfman!!!

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

 

[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.

 

[CH3NO2]

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

 

[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

 

[Ridgerunner]

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.

 

[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.

 

[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.

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.

 

[zeus201]

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

 

[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.

 

[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.