We priced fertilizers with our local dealer. Nitrogen (N), Phosphorous (P), and Potassium (K) are the macro elements we are usually most concerned with. I’ll list the fertilizer, the percent of each nutrient, and the price per ton. The percent of each nutrient is listed in this order: Nitrogen, Phosphorous, Potassium, and Sulfur.
Urea 46-0-0-0 $462/ton
Ammonium sulfate 21-0-0-24 $343/ton
Monoammonium phosphate (MAP) 11-52-0-0 $673/ton
Potassium chloride (Potash) 0-0-60-0 $537/ton
Which source of nitrogen, Urea or Ammonium sulfate, is a better deal. We need to calculate the nitrogen cost per pound.
What is 46% of a ton? Multiply .46 times 2000 equals 920 lbs. nitrogen per ton of Urea. Divide $462 by 920 lbs. equals $.50 per lb. of nitrogen.
Ammonium sulfate is 21% nitrogen. .21 times 2000 equals 420 lbs. nitrogen per ton. Divide $343 by 420 lbs. equals $.82 per lb. of nitrogen.
The Ammonium sulfate is higher priced per lb. of nitrogen. Ammonium sulfate also contains sulfur, which is needed by plants, and it is more stable, releasing its nitrogen more slowly than Urea. Urea will volatilize, turn into a gas, in hot, dry, conditions. Urea is best spread before a rain, or when the ground is cool and moist. So someone may want to use Ammonium sulfate even though it is more expensive.
I realized when I started writing, this is part of a much larger post about the philosophy of fertilizer. For our farm, animal manure is our preferred fertilizer. We just purchased a new manure spreader which I’m excited to use, and will show in a post soon.