OT a little but how do I understand fertilizer numbers?

Got my soil nutrient numbers back and their recommendations. I need 265 lbs per acre of K.
If I buy by the 40lb bag lets say 12-12-12 these numbers reflect the NPK % in the bag. How much actual K in pounds would this bag have?
It's 12% so what is the rest of the bag full of?
This is what I don't understand. Anyone know how to figure this out?
Thanks in advance!!!

My guess would be 12% of each of the other items and then a bunch of inert material/micro nutrients.

12% of 40 (.12*40) = 4.8 lbs

N=4.8 lbs
P=4.8 lbs
K=4.8 lbs
Inert/micro=25.6 lbs

You could buy 0-0-60 and get just what you need.

Do they make 0-0-60?
So that 40 lb bag would really be 24 lbs of K then?

1st #= nitrogen 2ond#= phosphorus 3rd#=potasium which is potash. I remember the order by putting the ingredients in alphabetical order. A fifty lb bag of 5 10 10 would have 2 and a half lb of nitrogen and 5 lb of each of the other 2 ingredients. the rest is filler. I once bought corn starter that was 60 0 0.

patsdeere calculations are correct.

You need to find bags that are higher in K aka ...Potassium aka....potash and smaller in N and P. If you use 12-12-12 to satisfy your K, you will be putting on 265 lbs of N per acre. With this rate, you would be shooting for 300+ bu per acre of corn.

Potash is sold as 0-0-62 in my area. With 62% of the total weight as K, you would need to spread 427 lbs of product. (265 lbs/.62= 427)

For starter fert on my corn, I use a 50/50 mix of DAP and Potash. This gives me 9-23-31. I put on 250 lbs per acre so...N 22.5 lbs P 57.5 K 77.5

DAP, diammonium phosphate, is 18-46-0. This means 18% is N 46% is phosphorous and zero K.

There is 4.8 lbs of K in each bag so to get 265 lbs of K per acre you would need over 55 bags or 2200 lbs per acre. This is way to much N and most likely to much P depending on what your test says.

You would be better off finding some Muriate of potash 0-0-60. You would need about 441 lbs of this per acre to provide you 265 lbs of K.

If you are trying to convert this down to a home garden you can use a conversion table that shows differant ratios.
For example 0-0-60 uses a ratio of
100 lbs per acre = .2 lbs or 1/3 cup per 100 sq ft
So to get 265 lbs per acre you would need .88 lbs or 1.45 cups of 0-0-60 for every 100 sq ft.

Unless you are fertilizing a garden plot, WHY are you messing with bags?? Go to local fertilizer dealer and they can custom mix whatever analysis you want or need and put it in a spreader cart and you pull it around to spread with your tractor. LOTS cheaper in bulk than bags. Chris

100 lbs of 10-20-10 converted to weight equals to:
10 - 25 lbs of Nitrogen
20 - 50 lbs of Phosphate(Phosphrous)
10 - 25 lbs of Potassium (Potash)

Here is some information. You will have to check with your local fertilizer people to see what is available in your area. But yeah, when you state how many pounds per acre of K is needed we would assume that is actual pounds. Since any form of potash is not pure the analysis is stated in pounds actual per 100 pounds of product. The rest of the bag is "dirt"

Potash fertilizer is the commonly used term for the soil fertilizer forms of potassium (element K). The name comes from collection of wood ash in metal pots when the fertilizer benefits of this material were first recognized many centuries ago.

Muriate of Potash: It's odd how this old-fashioned name remains in use! Muriate comes from Muria, the Latin for brine. Muriate of potash is potassium chloride containing between 50 and 60 per cent potash. It was deposited eons ago by ancient seas and should be considered a natural product, blessed by organocultists, but it is not. Its chlorine content passes off rapidly when applied to soil. As explained under soil organisms, however, muriate of potash is harmful to certain beneficial bacteria. Some authorities think sulfate of potash makes a better potash fertilizer.

Sulfate of Potash: This contains 48 per cent potash. It is more expensive than muriate of potash but is considered less harmful to bacteria and plant roots.

Wood Ashes: About the only generally-available organic source for potash fertilizer, this material is treasured by organic gardeners. Wood ashes contain about 6 per cent potash, plus considerable lime. Before corn cobs were used industrially, the cobs were burned in huge piles. The resultant ashes were peculiarly rich in potash - up to 35 per cent. Almost any ash resulting from burning organic materials that contain some fiber should be a fair source of potash fertilizer. Wood ashes are particularly good to use for adding potash to a compost heap.

Yeah, I did that and used a 5 ton spreader but now I don't have that much to do. Mostly upkeep.
The bags had me thinking what is the rest of the bag full of and I use it as an example for my question. Sometimes if you catch them on sale, the bags can be cheaper then custom mix bulk depending on what you need.

Your numbers are WAY off, don't believe me go to your local menards, home depot, lowes and read ANY fertilizer (garden, grass, house plant) the numbers are the actual percentage of active material the rest is filler/carrier.