A 50 lbs bag of 50-0-0 has twice as much N or nitrogen as a 50 lbs bag of 25-0-0. If you apply the same amout of each produce you will get different N/area applied.

dbw7, if you'd read my post carefully, you'd seen that I addressed that. Most people do not apply anything different than what the bag says on the back of it.

If I may, I may be the biggest advocate of what (I believe I coined the term here, on this site, and I wish I'd coined a more typing-friendly term) I call big-first-number fertilizer (yes, with all those hyphens). That refers to, oddly enough, a fertilizer that has a big first number. A 16-2-3 would qualify, as would a 20-2-1, or a 24-3-6, etc (notice that big first number?), while an 8-8-8 or a 10-10-10 would not. Specifically, I believe I coined that term because I often recommend Milorganite, which is a 5-2-0, as are most sewage sludge based fertilizers. Those (sewage sludge) ferts are very good in the heat of summer and late spring, while a big-first-number fert would be, could be, a disaster in the heat of July.

So my usual admonishment/lecture/rant sounds like this: You want to use a big-first-number fertilizer in the fall, at least once, twice is better, and you don't want to use Milorganite in the fall. Would you rather put down a 26-2-4 one time, or put down a 5-2-0 five times, to get as much nitorgen on that lawn? Obv, the answer is 'use a big-first-number fertilizer'. Oh, and I usually point out, you're saving a bundle. There are certainly cheaper ways to get nitrogen onto a lawn than by buying Milorganite. Five times.

Then one of my organic friends here (very competent lawn guys) point out that the use of organics has its own advantages, and that big-first-number fertilizers are actively avoided by some people, for what they perceive to be good reasons: they make their own case, about avoiding some chemicals, natural rate of decomposition, etc, and I'm not going to try to make, or demean, their case here. Their point of view is just as important as mine in the ongoing discussion.

The question of urea usually comes up in that context: it's a fairly inexpensive way to put down lots of nitrogen in the fall. Because one type of urea has a forumula of 46-0-0, you are obviously avoiding a too much phosphorus situation, as there is no phosphorus in a 46-0-0. But I think the point that was made was based on price, and ease of application, rather than the urea being somehow a 'superior' thought or a 'superior' fertilizer for all things, at all times of the year. (It's not.) There is another type of urea that has a twenty-something first number, perhaps one type is coated and the other uncoated, but I'm not sure about that. But the recommendation could easily have been made on that basis. And there are some, on the 'organic' side of the fence, that use organics all year long, but use a urea in the fall, just for the 'Big Momma' dose of nitrogen that urea provides (and that the lawn needs).

So if there was some recommendation as to one form or another of the urea, I don't think it was to confuse people: it may well have been to avoid a potential overdose of phosphorus, it may well have been to recommend a convenient way to get a lot of nitrogen at once (which you can only do safely in the fall of the year), or it may have been to discuss the relative benefits of coated vs. uncoated urea.

So stick around awhile, read a few (or a great deal) of the older, archived, posts and discussions, they can be very instructive. We've had some outlandishly refreshing discussions in past days that I really wish we could easily call back, for re-reading, but they can be hard to find if you're looking for one specific thing; but if you're new to the forum, and don't mind wading through a bunch of them, I can promise you, they're well worth your time.

philes, thanks for the insight.

skizot, I think you are correct in that irregardless of what the ratio on the bag is you will put down the same amount of nitrogen. A pound of nitrogen is a pound of nitrogen. I agree with you, the difference is in the total amount of product and in the total amount of P and K that you'd apply. Which is how I understand philes first-big-number term is a lot of nitrogen without a lot of total weight or big P & K numbers. You'll apply more by weight of total product with a 20-0-0 than you will a 46-0-0.

But there is a lot more to fertilizer than just the ratios. I wish there was a way for a "sticky" or a FAQ on fertilizer basics here. It can be a very confusing and daunting part of lawn care and one that can cause some damage if mishandled. I certainly would like to learn more about water insoluable nitrogen (WIN), slow release coatings, sulpher coated versus IBDU, application according to soil tests, and then the range of nutrients that the grass needs like calcium.

Thanks for the info as well, soccer_dad. This forum is definitely awesome. I really wished more people (like my neighbors, hehe) would take the time to visit forums like this. I know not everyone posting here is an expert, but the wealth of knowledge shared between people is truly amazing. Helpful people are what make internet forums, like this one, flourish.

My only complaint about GardenWeb is that their forum software is very outdated. There are many other excellent forum applications out there, that are available for free, and provide many updated and useful features (such as stickies). I'm a computer programmer and I'd be more than willing to help them convert their current software over.

Well let me take a shot at this, it is all about economics period. Which cost less?

40 pounds of 39-0-0 @ $27.
50 pounds of 15-0-0 @ $20

It is a no brainer the 50 pound bag of 15-0-0 is roughly 75% higher in price. You have to look at the cost of application per 1000/ft2.

in this example the 39-0-0 cost $1,72 per 1000/ft, and the 15-0-0 cost $2.66

If you really want to know how much, meassure off an area and apply a known amount ( weight product first) of product. Weight it again and that is how much product you have put down.

dbw7, I have no problems calculating rates. I think you may have just completely misread my entire post. :-) The post was just me commenting on the fact that I've seen several threads where people have posted advice on using a higher N fertilizer, but mentioned nothing of changing the spread rate. If you do not change the spread rate, and just follow the directions on the bag, then you are not putting down any more N with a bag of 43-0-0 than you would be with a bag of 22-0-0 (it's just that you'd physically need less of the 43-0-0 material to get your 1.0 lb. N / 1,000 sq. ft., which may, or may not be cheaper).

None of us needs a chemistry degree to translate fertilizer labels and how to use fertilizer, but here's an article that further addresses the value of trace minerals and such in fertilizer. It also includes very basic info about Nitrogen, Potassium and Phosporous.

Here is a link that might be useful: Beyond Nitrogen, Potassium and Phosphorous

Considerations for higher N products:
-Cost per 1,000sqft. Usually higher N products have a lower cost per 1,000sqft.
-Spread rate. A higher N number, such as 46-0-0, requires you to put down a little over 2 lbs per 1,000sqft. Something like a 21-0-0 would require 5 lbs per 1,000sqft to get 1 lb of N down per 1,000sqft. The less product you put down, the worse the particle distribution in most cases.
-Another consideration is the source of N. Ammonium sulfate has a max of 21% nitrogen, Ammonium nitrate 34%, and urea 46%. There are differences in these forms of nitrogen and how turf responds to it.
-% of slow release nitrogen. Just because a bag has 32% nitrogen doesn't mean it will make the grass grow like crazy. If it is 50% sulfur coated urea, it would actually push less growth than a bag of 21-0-0 ammonium sulfate.
-Pound of P and K applied. Most would look at bags of 32-5-7 and 24-5-7 and think that the P and K applied would be the same with both bags. Actually if you are applying it based on one pound of N per 1,000sqft, you would put less P and K down with the 32-5-7 than the 24-5-7. The ratio of the numbers is more important than the actual numbers. Higher N numbers are often used by lawn care companies to reduce costs, but when they do that, they often skimp on the P and K due to less total product being put down per 1,000sqft.

skizot, first of all, there is the law of limiting factors (see Liebig's law) which should determine whether a fertilizer is needed at all. Then there is the ratio of N,P and K in relation to each other. This ratio is the result of field trials and can be different for the same crop grown on different soil types. By far the most 'problematic' is nitrogen; the usual inorganic sources are very soluble and liable to leaching by rainfall or irrigation (inorganic urea will go from a solid product to a gas directly). To counter this, manufacturers are always seeking to extend the availability of nitrogen; this adds to the cost.
I am more interested in the 'N sources' as stated on the fertilizer bag. If the bag proclaimes "16-4-8" and it states "Nitrogen source: 16% derived from urea", then that tells me that I can expect a quick green-up and an equally quick "green-down". If I get a strong shower of rain within a day or two, a great deal of the product will be dissolved and carried to places where it does not need to be at all, really. IBDU is a slow-release form of urea; it will cost more; the application rate will be the same as for untreated urea (lb. Nitrogen/1000sq.ft.) but it will give a more long lasting effect and will be better for the environment.
I feel that the homeowner is misled on this issue. One manufacturer marketed the same "numbers" to commercial operators and homeowners. The difference was in the Nitrogen source. The all-soluble was much cheaper but would have to be put down more frequently to maintain the turf quality.
Guess who this was marketed to.

SCU vs IBDU. My understanding is that SCU is broken down by microbial action and IBDU is water soluable. Is there truth to that or am misunderstanding the marketing hype. I assume that slow release is equitable, just depends on application.

Let me give a caveat first, that I use Lesco Commercial fertilers for my needs for the last four years or so. These products do not provide a "spreader setting" on the bags.
If I read your post correctly, you are asserting that spreader setting bags of fertilizer will list as follows.... 20-10-14 spreader setting of 7. 30-2-11 spreader setting of 3. If this is the case, you guys need to get with the program. What is the benefit of a higher N P or K if you are lowering your spread rate? You should have your spreader LOCKED DOWN on your spread rate and adjust your fertilizer accordingly. Not adjusting your spread rate. Most of you should have enough accumen to know your spread rate simply by looking at your particle dispersion on your turf. Not by reading a setting on a bag. KNOW YOUR PARTICLE DISPERSION, and adjust PRODUCT accordingly. If I need more N on my lawn, I buy a higher N product and leave my spread rate the same. ALWAYS THE SAME. Don't be fearful of Fertilizer.

soccer dad, there are many ways to make the soluble nitrogen sources more slowly available. You are quite correct in the comparison between SCU and IBDU. The practical implications are that one might not realise the full benefit of SCU applied in the cooler seasons when microbial activity is reduced or, application of IBDU might be be less effective under drought conditions. Osmocote and Ureaform are other means to the same end.

reelfanatic, it has been some years since I worked for LESCO but I do remember they marketed a special gauge to be used with their spreader and the gauge setting was printed on each bag, calibrated to apply 1lb. Nitrogen per 1000 sq.ft. Fertilizer recommendations vary mainly because of of soil physical and chemical properties and while one might have good reason to question these recommendations, it is not in the best interest of the environment to increase these rates arbitrarily. Indeed one might be in violation of local laws to do so.