There are different types of slow release. Usually, the nitrogen will be the only nutrient that will be slow release, but the other nutrients can be as well. Osmocote coats all 3 nutrients with a polymer.

To know what type of slow release is in the bag, you have to check out the guaranteed analysis portion of the label.

GUARANTEED ANALYSIS
TOTAL NITROGEN (N)............................................................24.00%
24.00% Urea Nitrogen (N)*
SOLUBLE POTASH (K2O).......................................................11.00%
SULFUR (S) Total.................................................................... 3.60%
3.60% Free Sulfur (S)
IRON (Fe) Total........................................................................ 2.00%
0.02% Water Soluble Iron (Fe)
MANGANESE (Mn) Total........................................................ 1.00%
0.14% Water Soluble Manganese (Mn)
DERIVED FROM: Polymer Coated Sulfur Coated Urea, Urea, Muriate of Potash, Iron Sucrate, Manganese Sucrate.
CHLORINE (Cl) Max................................................................ 9.00%
*10.80% Slowly Available Urea Nitrogen from Polymer Sulfur Coated Urea.

This one was taken from a bag of Lesco 24-0-11 50%PPSCU 2Fe 1Mn fertilizer. It shows the nutrients, their percentages, and their sources (under the derived from section). In this particular fertilizer, it claims that 10.8 percent of the 24 percent nitrogen is slow release. They will only claim 90% guaranteed slow release because they are scared of an inspection finding less, so this should actually say 12% slowly available nitrogen. So this bag would be sold as a 50% slow release nitrogen fertilizer.

The source is sulfur coated urea with a thin polymer coating. This is most common - they take the nitrogen and coat it with sulfur, so that the sulfur coating has to break down before the nitrogen is released. This requires water. Another source that breaks down when interacting with moisture is IBDU (isobutylidene diurea).

Other sources, such as methylene urea and urea formaldahyde require microbial activity, so soil temperature is the main element in getting the nitrogen available to the plant.

Another source is polymer coating. A polymer surrounds the particle and the pores open up when soil temperatures get warm - this allows water to get in and the fertilizer seeps out, so to speak. So both water and temperature are factors in this type of slow release fertilizer getting used up.

Knowing the way it releases will help you pick out your fertilizer. If you want to put a slow release down in the fall when the soil temperature is cool, you probably wouldn't put down methylene urea, urea formaldahyde, or polymer coated urea because they require soil temperature to be high enough for release. You would use sulfur coated or IBDU since they are reliant upon water and temperature will have little to no effect on release.

Hope this helps - I think there is another thread on slow release fertilizer on this site. There are multiple other forms of slow release mechanisms for fertilizers.

Denverdude gave a good explanation about why the sulfur coated or IBDU slow-release fertilizer is better than the other coating type slow-release fertilizer or how to select the slow-release fertilizer. I want to make sure whether the slow-release fertilizer is usually better than the quick release nitrogen fertilizer. The answer seems "yes". Is it correct? Does anyone know the Ground Work Weed and Feed slow-release fertilizer sold in a tractor store, by the way?

One really isn't better than the other - they each have their place. And just because something says slow release on the bag, that doesn't tell you how much and what kind. It could have 1% slow release nitrogen and they could call it a "slow release fertilizer". The 24-0-11 above has half slow release nitrogen and half soluble or "quick release" nitrogen. So you get a nice kick since half the nitrogen is available right away. Then the slow release portion starts to seep out and spoon feeds the turf with nitrogen over a period of a few weeks.

If there was no slow release nitrogen, then you would get a growth surge at the beginning and then the growth would slow and color would fade. So you would mow like crazy the first couple of weeks and then it would stop growing and the color would fade. This is not ideal for you or the turfgrass health. You are also creating turfgrass that is more susceptible to disease and insect damage.

I use fertilizers such as this during the growing season - with about half "free" nitrogen and half slow release sources. But when October rolls around and top growth has ceased on my cool season grass (this wouldn't apply to bermuda), I don't have to worry about that growth surge, so I use an all quick release or all chemical fertilizer, such as 21-0-0 ammonium sulfate. That way the total amount of nitrogen is available to the plant once it's watered in and - with less slow release, it's cheaper.

I'm not sure what the tractor supply stuff has in it, but armed with this information, you can look at the label in the store and have a good idea of what that product will do for your turf - benefits and short-comings.

This time of year you don't need any fertilizer. Livestock producers (grass farmers) know that the grass will have a growth spurt in the early spring regardless of whether they use fertilizer or not. When that growth spurt is over (usually in April or May), they will apply 1/4 of the nitrogen they think their fields will need. Then in the fall they will apply the other 3/4 of that nitrogen.

As a general rule the slow release fertilizers are better, but you have to know what you are buying and what your goal is.

From Lesco they come in 100%, 75%, and 50% slow release sulphur coated urea. I recommend a 75% as this will give you 25% fast release for imediate use by the turf, and the 75% will be released slowly over a period of time dictacted by water. So instaed of having to fertilize every 2 or 3 weeks, you can stretch it out over 4 to 6 weeks. Depends on what you want to do?

Texas-weed said "From Lesco they come in 100%, 75%, and 50% slow release sulphur coated urea. I recommend a 75%" Is there a way to quickly know the release rate or percentage from the bag label without doing complicated analyses? In other words, what number on the bag label of the slow release fertilizer can quickly tell the release rate or percentage?

Holy cow.

> In other words, what number on the bag label of the slow release fertilizer can quickly tell the release rate or percentage?

HOLY COW is right!

Looking for the percentage symbol next to the number is the quickest for the average person!!!!!!!!!!

Can anyone tell the coating type of the Ground Work slow release Weed & Feed fertilizer and release rate or percentage according to its Guaranteed Analyses of the fertilizer at http://i40.tinypic.com/1415h8h.jpg

This is a 20% slow release derived from poly sulfur coated urea. You figure this out by taking 4.6 (the percentage of slow release nitrogen) divided by 23% (the total amount of nitrogen in the bag) and will get 20.

That means that 80% of the nitrogen will be released immediately and available to the plant and 20% will release mostly depending on water over the next 6 weeks or so.

This is ok if you are applying fertilizer fairly often and wanting to push a decent amount of growth. If you want to feed it slower and not get that much shoot growth, you want to go with something with a higher percentage of slow release.

Can anyone answer two follow up questions?
1) Does the percentage, for example 4.6%, of slowly available on the slow-release fertilizer label mean per every 100 amount of fertilizer, only 4.6 amount is released slowly but the rest of 95.4 are not?
2) I noticed the other composition of the fertilizer has not been mentioned. Is the percentage of the slow release on the label regarding to releasing the nitrogen only?

4.6% of the entire bag or 20% of the nitrogen. Most of the bag is filler and not worth worrying about. You are making this waaaaaaay too hard. This isn't that complicated and you are splitting hairs. You might think about just hiring a lawn service before you fry your brain milling this over so much.

> "You might think about just hiring a lawn service"

I agree with the patient one in CO. because by the time you are satisfied with our answers and the URL's provided for you, the snow will the flying once again

Next Sunday, ask for St. Jude, specifically!