# Polymer coated sulfur coated urea?



## Green

I learned a lot from a few articles, as well as @thegrassfactor's awesome video on Nitrogen sources. Before that, I didn't know how PCU and SCU differed in terms of performance. I now see why SCU and methylene ureas are the generally preferred controlled release Nitrogen sources for cool-season lawns...and why PCU is not as useful for cool-season lawns.

However, one thing I'm still trying to understand, is where PCSCUs fit into the picture. On Wikipedia, I read that they're simply a lower cost alternative to thicker polymer coats on PCU, and tend to perform identically to PCUs (in other words, temperature-dependent release curves). But, I have trouble believing this. Wouldn't PCSCU perform intermediate between PCU and SCU, and not be as temperature dependent as PCU, since it uses both types of coatings? Or is the polymer coat still the limiting factor that governs the N release?


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## j4c11

My understanding is that with SCU you get catastrophic release - the coating fails and all of the urea inside is then dissolved released at once. With PSCU you get a polymer coat on top of the sulfur coat, so when you get that catastrophic release from the SCU it happens inside the polymer capsule - now you basically have PCU.

So:

- PSCU vs PCU is cheaper to manufacture as the polymer coat is thinner
- PSCU vs SCU better controls the release of N, and probably withstands blending much better than SCU


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## Green

Those are valuable pieces of information, but I'm still skeptical, and here is why...

With SCU, while it's true that you can get catastrophic release, this does not mean that all of the capsules release at the same time and that it's therefore not an effective vehicle for gradual controlled release over time. Since the coatings aren't uniform on every single capsule due to the manufacturing process, they actually release N at different times/moisture levels, and this "defect" is an advantage which makes SCU a true controlled release N source that is only loosely moisture-level dependent.

I can picture in my mind how PCSCU might work...as you say, the sulfur/wax coating might break down first, followed later by a hole in the polymer coating when temperatures reach a certain level, and then ensuing osmosis causes the fertilizer to flow out of the capsule. But, I wonder if that's actually how it works in practice. It's not totally intuitive whether it's any different than PCU.

Also, some CUs have multiple coatings...polymer, wax, sulfur...I've heard that some have a lot of micro layers. I wonder how these alter the N release characteristics.


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## Suburban Jungle Life

I was wondering the benefit of these coated ureas. Is it just so you can do a one a done approach? I figure a bi weekly urea app would be better or even a bi weekly AMS app instead of trying to slow release syn. I know the cost is much higher but an org source in my opinion would be a better slow release anyway combined with a syn for quick results.


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## j4c11

The main problem with SCU is that the sulfur coating is often times imperfect/cracked, or the whole prill is cracked. This is due to the manufacturing process, mixing with other fertilizers, transport etc. You can expect 30% of your N to be immediately released as a result from SCU. The polymer coating on top "seals" the cracks and protects the sulfur coating underneath, giving you better control over the release curve.

I think the main difference between PSCU and PCU is price, less/thinner polymer means lower cost to manufacture.


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## j4c11

Suburban Jungle Life said:


> I was wondering the benefit of these coated ureas. Is it just so you can do a one a done approach? I figure a bi weekly urea app would be better or even a bi weekly AMS app instead of trying to slow release syn. I know the cost is much higher but an org source in my opinion would be a better slow release anyway combined with a syn for quick results.


If you have time to spoon feed you can definitely achieve the same results, but for lawn care companies for example it may not be cost effective to stop by their clients house weekly. There's also agricultural type uses for it where again labor-wise it's much better to apply less often.

As far as organics being better, ultimately N is N. If you pay double or triple per pound of N from Milorganite vs PSCU it's just a hole in your pocket. The plant doesn't care where its ammonium or nitrate comes from.


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## Suburban Jungle Life

j4c11 said:


> As far as organics being better, ultimately N is N. If you pay double or triple per pound of N from Milorganite vs PSCU it's just a hole in your pocket. The plant doesn't care where its ammonium or nitrate comes from.


While N is N, Milo has many other minerals including iron, calcium, P, and also serves to add organic matter, not just N.

https://www.milorganite.com/using-milorganite/safety

If you are only looking at N, yes milo is very expensive. With milo, you are paying for more than just N.


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## j4c11

Suburban Jungle Life said:


> While N is N, Milo has many other minerals including iron, calcium, P, and also serves to add organic matter, not just N.
> 
> https://www.milorganite.com/using-milorganite/safety
> 
> If you are only looking at N, yes milo is very expensive. With milo, you are paying for more than just N.


Well, I didn't really want to get into the nitty gritty, but yes you are correct there's other stuff in there. There's P and iron and micronutrients in synthetic fertilizers as well, still at a much lower cost.

The ability to add organic matter to the soil via milorganite is very overrated, in my opinion. Up to 90% of carbon is quickly lost in the form of CO2 as it decomposes, so you have to apply vast amounts of the stuff per thousand sq feet before you see any significant increase in your soil OM%, maybe. What does increase your OM is healthy roots in the ground.


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## Turfguy93

j4c11 said:


> Suburban Jungle Life said:
> 
> 
> 
> While N is N, Milo has many other minerals including iron, calcium, P, and also serves to add organic matter, not just N.
> 
> https://www.milorganite.com/using-milorganite/safety
> 
> If you are only looking at N, yes milo is very expensive. With milo, you are paying for more than just N.
> 
> 
> 
> Well, I didn't really want to get into the nitty gritty, but yes you are correct there's other stuff in there. There's P and iron and micronutrients in synthetic fertilizers as well, still at a much lower cost.
> 
> The ability to add organic matter to the soil via milorganite is very overrated, in my opinion. Up to 90% of carbon is quickly lost in the form of CO2 as it decomposes, so you have to apply vast amounts of the stuff per thousand sq feet before you see any significant increase in your soil OM%, maybe. What does increase your OM is healthy roots in the ground.
Click to expand...

You are very correct! The amount of product that you have to put down to increase organic matter is ridiculous and I feel like people obsess over it too much when if you grow healthy turfgrass the roots will increase your organic matter content on its own


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## Green

I just watched another of @thegrassfactor's videos on N sources, and his experience has been that PCSCU is somewhat less temperature dependent than PCU...as I suspected.


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## stuartmccall

I have been meaning to post my 10 cents worth for some time but for one thing or another I just haven't got around to it. The discussion of SCU/PCSCU and PCU is all well and good but the actual manufactured product WITHIN these categories can vary dramatically in release characteristics. Basically not all SCU/PCSCU or PCU are the same and to make matters more complicated from my own personal experience a lot of product marketed as PCSCU os ion fact lower cost, lower quality SCU with its significantly more brittle coating and less predictable release characteristics.





Depending on the manufacturer calibration can take place at either 21C or 25C which can have a major impact on short term release in colder weather and on longevity in warmer weather.


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## jonthepain

> If you are only looking at N, yes milo is very expensive. With milo, you are paying for more than just N.


Like heavy metals?


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## Suburban Jungle Life

jonthepain said:


> If you are only looking at N, yes milo is very expensive. With milo, you are paying for more than just N.
> 
> 
> 
> Like heavy metals?
Click to expand...

Haha. Yeah... Hopefully, you aren't harvesting your grass for consumption... Or, using clippings in your compost which you use on crops... I wouldn't use biosolids on crops. Ornamentals, sure! I say that now but many farmers use biosolids and we buy their crops... :? Ignorance is bliss!!!


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## Green

stuartmccall said:


> I have been meaning to post my 10 cents worth for some time but for one thing or another I just haven't got around to it. The discussion of SCU/PCSCU and PCU is all well and good but the actual manufactured product WITHIN these categories can vary dramatically in release characteristics. Basically not all SCU/PCSCU or PCU are the same and to make matters more complicated from my own personal experience a lot of product marketed as PCSCU os ion fact lower cost, lower quality SCU with its significantly more brittle coating and less predictable release characteristics.
> 
> 
> 
> 
> 
> Depending on the manufacturer calibration can take place at either 21C or 25C which can have a major impact on short term release in colder weather and on longevity in warmer weather.


Interesting. Can you explain what sort of tests we are looking at in these graphs?


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## jonthepain

> Haha. Yeah... Hopefully, you aren't harvesting your grass for consumption...


I don't think i want to load up my soil with heavy metals ( or whatever else comes down the pipes) whether I'm consuming my turf or not


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## PA Lawn Guy

jonthepain said:


> Haha. Yeah... Hopefully, you aren't harvesting your grass for consumption...
> 
> 
> 
> I don't think i want to load up my soil with heavy metals ( or whatever else comes down the pipes) whether I'm consuming my turf or not
Click to expand...

I thought "milo LOADS your soil with heavy metals" had been debunked?

Here's an interesting article (bold excerpt at the start is a good summary)

Heavy Metals Content


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## PA Lawn Guy

Off topic, sorry. And I am not a Milo user just FWIW.


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## stuartmccall

Green said:


> stuartmccall said:
> 
> 
> 
> I have been meaning to post my 10 cents worth for some time but for one thing or another I just haven't got around to it. The discussion of SCU/PCSCU and PCU is all well and good but the actual manufactured product WITHIN these categories can vary dramatically in release characteristics. Basically not all SCU/PCSCU or PCU are the same and to make matters more complicated from my own personal experience a lot of product marketed as PCSCU os ion fact lower cost, lower quality SCU with its significantly more brittle coating and less predictable release characteristics.
> 
> 
> 
> 
> 
> Depending on the manufacturer calibration can take place at either 21C or 25C which can have a major impact on short term release in colder weather and on longevity in warmer weather.
> 
> 
> 
> Interesting. Can you explain what sort of tests we are looking at in these graphs?
Click to expand...

The first series of graphs show release curves for different SCU and PCU products and variations by temperature. As temperature increases the concentration of N in solution increases indicating release of nutrient. Two of these basically "dump" with just the smallest increase in temperature.


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## stuartmccall

stuartmccall said:


> Green said:
> 
> 
> 
> 
> 
> stuartmccall said:
> 
> 
> 
> I have been meaning to post my 10 cents worth for some time but for one thing or another I just haven't got around to it. The discussion of SCU/PCSCU and PCU is all well and good but the actual manufactured product WITHIN these categories can vary dramatically in release characteristics. Basically not all SCU/PCSCU or PCU are the same and to make matters more complicated from my own personal experience a lot of product marketed as PCSCU os ion fact lower cost, lower quality SCU with its significantly more brittle coating and less predictable release characteristics.
> 
> 
> 
> 
> 
> Depending on the manufacturer calibration can take place at either 21C or 25C which can have a major impact on short term release in colder weather and on longevity in warmer weather.
> 
> 
> 
> Interesting. Can you explain what sort of tests we are looking at in these graphs?
> 
> Click to expand...
> 
> The first series of graphs show release curves for different SCU and PCU products and variations by temperature. As temperature increases the concentration of N in solution increases indicating release of nutrient. Two of these basically "dump" with just the smallest increase in temperature.
Click to expand...

The second graphs show release of SCU vs PCSCU as the pricks are more brittle with SCU they tend to release more rapidly if damaged

https://gilbasolutions.com/slow-release2.html


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## Green

@stuartmccall, this is good info. Not the first time I've heard stuff along similar lines, but a reminder not to get hung up on the type of coating, but how actual brands perform, if data is available.

@mowww, any thoughts on this topic?


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## flyfishsteve

MESA


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## mowww

@Green absolutely correct. There is a wide variability in the marketplace when it comes to durability and quality of various poly coats. Some release 2-3x as quickly after going through a spreader, some release too slow for northern US soil temps. PCSCU, a slightly different category, is notorious for its catastrophic release which can lead to early release and on the flip side lock-off which leaves nutrients unavailable. I'll try to post some more specific data when I get a chance from university work I have been involved in.


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## ABC123

Feeding the leaf nitrogen is 1000x better than feeding the soil N.


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## Green

mowww said:


> PCSCU, a slightly different category, is notorious for its catastrophic release which can lead to early release and on the flip side lock-off which leaves nutrients unavailable. I'll try to post some more specific data when I get a chance from university work I have been involved in.


Really? I knew this happens with regular SCU...


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## mowww

@ABC123 I don't think it is as clear cut as that. Both have advantages and disadvantages. Both have a million and one variables. When compared head to head in peer-reviewed university research, 25% of the time granular has better quality, 25% the time foliar does, and 50% of the time they're the same. When it comes to micronutrients and any nutrient that is presented with a opportunity to be quickly locked-up, foliar makes a lot of sense. But to say "1000x better" is misleading to everyone that comes here to learn, even if foliar were 2x "better" then granular applications wouldn't be a thing in the turf world.

There are a lot of ways to make grass green. You can make it as simple or complicated as you'd like.


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## Green

@mowww, both interesting and expected.

@ABC123, did you mean efficiency? Because foliar N is generally more immediately efficient (1,000x would be a figure of speech, even then, though).


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## Mightyquinn

ABC123 said:


> Feeding the leaf nitrogen is 1000x better than feeding the soil N.


I know this is a little bit of an exaggeration but I think it's still true regardless. When I was feeding the soil Nitrogen you never knew what you were going to get really as the season went on as the slow release would release fast sometimes an slow other times plus if you reel mow and your lawn is super dense and tight, the prills will just lay on top of the grass and then get broken the next time you mow and then you have a bunch of fast release Nitrogen in your lawn. Don't get me wrong I do believe Slow Release fertilizer has it's place and probably does work just fine for most people but it's not the end all be all, which is why we have TLF and this thread 

I have found that spraying Nitrogen is a lot more efficient and I can tailor my applications to what the grass is telling me and I tend not to waste as much either since I am just give the lawn what it needs at the time. It seems with slow release you have to almost over apply it in order to account for any variations over the release period as you can't really count on when it's going to fee the lawn.

Just my .02 :thumbup:


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