130 ELEMENTS OF AGRICULTURE 



A fertilizer containing 2 per cent nitrogen, 10 per cent 

 phosphoric acid and 8 per cent potash is often spoken of 

 as a 2, 10, 8 (two, ten, eight) fertilizer. 



An approximate way to estimate the value of a fer- 

 tilizer in dollars per ton is to multiply the per cent of 

 nitrogen by four and add the per cents of phosphoric 

 acid and potash. This estimates nitrogen at 20 cents per 

 pound and phosphoric acid and potash at 5 cents each 

 per pound. (Prove this rule.) These are higher than the 

 New York prices, but lower than the farmers pay for 

 complete fertilizers, and allow a considerable margin for 

 freight. A 2, 10, 8 fertilizer would therefore be worth 

 approximately 4X2-f-10+8=$26 per ton. 



The labels on fertilizer bags are often confusing, and 

 are doubtless intended to be so. The following is a copy 

 of such a label, and at the right are the facts reduced to 

 their simplest terms: 



Per cent 



Nitrogen 0.82- 1.64 



Nitrogen as ammonia 1.00- 2.00 



Soluble phosphoric acid 6.00- 7 00 



Reverted phosphoric acid 2.00- 3.00 



Insoluble phosphoric acid 1.00- 2.00 



Total phosphoric acid 10.00-12.00 



Per cent 

 Nitrogen 0.82 



Available phos- 

 phoric acid . . .8.00 



Bone phosphate of lime 22.00-25.00 



Available bone phosphate of lime . . 18.00-20.00 Potash. 



Available phosphoric acid 8.00-10.00 



Potash 4.00- 5.00 



Equivalent to sulfate of potash 8.00-10.00 



The higher percentages in the guarantee mean nothing. 

 A guarantee of 4 to 5 per cent of potash is a guarantee 

 of 4 per cent; it would be the same if it said 4 to 50 per cent. 

 Nor do the numerous equivalents mean anything, except 

 for comparison, as that .82 per cent of nitrogen is equiva- 

 lent to 1 per cent of ammonia. 



