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Discussion in 'Soils, Fertilizers and Composting' started by LilSprout, Oct 21, 2009.
How much Ammonium Sulphate (21-0-0) is required to apply 3 pounds of Nitrogen to 2392 square yards?
A 100 lb. bag of fertilizer will contain 21 lbs. of nitrogen. So, a simple ratio calculation tells us you need 14 lbs. of fertilzer applied over your garden area to give you 3 lbs. of nitrogen.
100 - 21
x - 3
x = 300 / 21
x = 14.3
True enough, but since the answer is independent of the 2392 figure, I suspect that the questioner meant something like "3 lbs per thousand square feet".
Soccerdad, you may well be correct but I answered the question as it was asked.
Certainly 3 pounds of nitrogen over 21,528 square feet (just under 1/2 acre) is not very much. If this application is for a lawn, then 3 pounds per 1,000 square feet is about right. Spread over two or three applications would be my choice.
The other question would be, "Why all the sulfur?"
Ammonium sulfate (21-0-0) in an acid environment (coastal BC) is not adviced unless you have acid loving plants or need the sulfur to balance nitrogen - i.e., you are trying to improve protien in your crop. Sulfur is not really deficient here. I would suggest calcium nitrate or urea are better sources of nitrogen. 3 lbs of nitrogen per 100 sq ft is ample for individual applications to lawn. You may wish to consider a slow release nitrogen for grass so you don't get flushy growth. The numbers on a fertilizer bag refer to the percentage nitrogen (as N), phophorus (as P2O5) and potassium (as K2O). 21-0-0 also contains about 24% sulfur.