What is actually in a bag of fertilizer?

[part-time-Farmer-NC]

Was wondering about the ingredients of fertilizer. So for example a bag of 13-13-13 is 13% of each N-P-K or 19.5# of actual fertilizer in a 40# bag (one manufacturer declares those numbers are comprised of Ammonium Nitrate, Diammonium phosphate, Muriate potash KMAG). Some mention of small percentages of other minerals.

So what is the rest of that 20.5#'s (51% of a 40# bag)? Coop dude said it was lime years ago, so I thought a bag of 13-13-13 was all fertilizer and little to no lime (13*3=39#). Which is why I always tried to get the highest triple digits I could this time of year its 17-17-17 (50# bag). I also found in an article that they sometimes put sand in it see below.

So it appears I am right it's about 51% sand/lime per 40# bag. 17-17-17 is 50#of all the N-P-K ingredients I belive.

I did see this site that defines it pretty good.

An Overview of 13-13-13 Fertilizer & Its Meaning

Have you wondered about the 13-13-13 coding on the back of every bag? Does it affect your fertilizer's quality and performance? Find out in this blog post.

fixandfeed.com

I can't verify that by any label though. hmmm. I prefer not to pay fertilizer prices for lime... but it's their game and we just get to play in it...

 

[ning]

They're "fillers"; dry (sand clay limestone) wet (water, surfactants, emulsifiers, stabilizers, thickeners)
pH adjusters
etc

Consider that the actual fertilizing substances may be corrosive or sticky or who knows what, even a fine powder that won't stick together at all; in order to be able to disperse it you need it to be in a nicely pelletized solid or homogeneous liquid, and that's going to take other things.

And, they add stuff to dilute it so you think you're buying more, yes.

 

[WinterDeere]

Ning already got most of it, leaving room for inert ingredients required for pelletization, and possible surfactants, etc. Also, there's value in arranging the product for a consistent application rate, with most turf care programs and equipment already dialed in to a 200#/acre distribution rate. So, it's not a huge surprise that most commercial fertilizers used in turf care are mixed at densities that work well near this application rate.

They're also leaving room for the addition of things like pesticides (Allectus, Dimension, etc.) and selective herbicides, as well as lime and/or Iron.

I can't imagine those packaging fertilizer for commercial applications would see any value in packing out their product for the appearance of "think you're buying more", as ning suggests at the end of his otherwise good post. That might happen with Scotts crap sold at Lowes Depot, but the commercial guys would actually see better value in the opposite, rather reducing hauled weight per pound of active ingredient.

 

[Complete Turf Care]

In a previous job, I formulated and blended thousands of tons of fertilizer used in rice, soybeans, corn, sugar cane, etc.

There are basically 5 or 6 raw materials that are used to formulate a fertilizer blend

You have N-P-K as your macro nutrients in a blend of fertilizer. Lets start with the N which is nitrogen

Sources of Nitrogen include urea which is 46-00-00. So, for every 100 lbs of 46-00-00 you get 46 'units' or pounds of nitrogen
Another source is Ammonium Sulfate which is 21-00-00 12s. So, for every 100 lbs of 21-00-00 you get 21 'units' or pounds of nitrogen and 12 lbs of Sulphur

Now for the "P" which is Phosphorus. Sources of phosphorus include 18-46-00 and 00-46-00. Either one of these will get you 46 lbs of P per 100 lbs

The "K" is potassium, sometimes called potash. The most common source for K is 00-00-60.

The most units you can get in a 'blend' of fertilizer is about 60 'units'

For example: if we mix 33.3 lbs of 46-00-00 and 33.3 lbs of 00-46-00 and 33.3 lbs of 00-00-60 you will get 100 lbs of a 15-15-20 fertilizer blend

46 x .33 = 15 of 46-00-00
46 x .33 = 15 of 00-46-00
60 x .33 = 20 of 00-00-60

Now, if you use more, or less of any of the 3 raw materials, you will get a different blend. This is a very simplified explanation.

But, yes, it is usually best to buy the highest number blend available. Many blenders will use 'filler' to get lower numbers of NPK. For example, a 8-8-8 fertilizer is most likely a 17-17-17 with enough filler to bring it down to the 8-8-8. This means you would have to put out a little over 200 lbs of 8-8-8 to get an equal amount of fertilizer as you would with 100 lbs of 17-17-17. There are sometimes where you would want other formulations, such as when sulphur or other micronutrients are needed.

There is a lot more to it than my brief explanation.

 

[part-time-Farmer-NC]

In a previous job, I formulated and blended thousands of tons of fertilizer used in rice, soybeans, corn, sugar cane, etc.

There are basically 5 or 6 raw materials that are used to formulate a fertilizer blend

You have N-P-K as your macro nutrients in a blend of fertilizer. Lets start with the N which is nitrogen

Sources of Nitrogen include urea which is 46-00-00. So, for every 100 lbs of 46-00-00 you get 46 'units' or pounds of nitrogen
Another source is Ammonium Sulfate which is 21-00-00 12s. So, for every 100 lbs of 21-00-00 you get 21 'units' or pounds of nitrogen and 12 lbs of Sulphur

Now for the "P" which is Phosphorus. Sources of phosphorus include 18-46-00 and 00-46-00. Either one of these will get you 46 lbs of P per 100 lbs

The "K" is potassium, sometimes called potash. The most common source for K is 00-00-60.

The most units you can get in a 'blend' of fertilizer is about 60 'units'

For example: if we mix 33.3 lbs of 46-00-00 and 33.3 lbs of 00-46-00 and 33.3 lbs of 00-00-60 you will get 100 lbs of a 15-15-20 fertilizer blend

46 x .33 = 15 of 46-00-00
46 x .33 = 15 of 00-46-00
60 x .33 = 20 of 00-00-60

Now, if you use more, or less of any of the 3 raw materials, you will get a different blend. This is a very simplified explanation.

But, yes, it is usually best to buy the highest number blend available. Many blenders will use 'filler' to get lower numbers of NPK. For example, a 8-8-8 fertilizer is most likely a 17-17-17 with enough filler to bring it down to the 8-8-8. This means you would have to put out a little over 200 lbs of 8-8-8 to get an equal amount of fertilizer as you would with 100 lbs of 17-17-17. There are sometimes where you would want other formulations, such as when sulphur or other micronutrients are needed.

There is a lot more to it than my brief explanation.

Thanks for cracking the code!

 

[ning]

Sources of Nitrogen include urea which is 46-00-00

This makes sense - the source isn't pure Nitrogen, but the nn-nn-nn values state how much of the particular nutirent is present.
Urea = CH₄N₂O; this roughly is 12+4+2*14+16=60
(N₂=28)/(total=60) = 46% nitrogen portion