| Ammonia | 3½ to 4 per cent. |
| Available Phosphoric Acid | 3 to 3½ per cent. |
| Actual Potash | 2½ to 3 per cent. |
Just one-half the guarantee of the high grade mixture A. A ton of this contains:
| Pounds. | ||
| Nitrogen | 57.7 value at 17½¢ | $10.10 |
| Available Phosphoric Acid | 60 value at 4¢ | 2.40 |
| Potash | 50 value at 5¢ | 2.50 |
| —— | —— | |
| Totals | 167.7 | $15.00 |
| Add average charge for mixing, etc. | 8.00 | |
| —— | ||
| $23.00 | ||
The selling price of this would very likely be not less than $25.
This seems at first sight to be cheaper and more reasonable. But let us see.
In a ton of mixture A he gets 335.4 pounds of plant food for $40, or at an average cost of twelve cents per pound, while in a ton of mixture B he gets 167.7 pounds of plant food for $25, or at an average cost of fifteen cents per pound.
To put it another way, in a ton of the high grade mixture A, he gets 335.4 pounds of plant food for $40. To get the same amount of plant food, 335.4 pounds, in the low grade mixture, B, it will be necessary to buy two tons at a cost of $50.
A low grade fertilizer is always expensive even if the plant food is furnished by high grade materials.