Cents per lb. Nitrogen in Nitrates 16 Nitrogen in Ammonia Salts 171/2 Organic Nitrogen in dry and fine ground fish, blood, and meat, and in mixed fertilizers 171/2 Organic Nitrogen in fine ground bone and tankage 17 Organic Nitrogen in coarse bone and tankage 121/2 Phosphoric Acid soluble in water 41/2 Phosphoric Acid soluble in ammonium citrate 4 Phosphoric Acid in fine ground bone and tankage 4 Phosphoric Acid in coarse bone and tankage 3 Phosphoric Acid (insoluble in water and in ammonium citrate) in mixed fertilizer 2 Potash as high-grade sulphate and in mixtures free from muriate (chloride) 5 Potash as muriate 41/4 For example, in calculating the commercial value of the plant food in a fertilizer we will take the formula mentioned on page 205, namely: Ammonia 2 to 3 per cent. Available Phosphoric Acid 8 to 10 " Total Phosphoric Acid 11 to 14 " Total Bone Phosphate 23 to 25 " Actual Potash 10 to 12 " Sulphate of Potash 18 to 20 " This fertilizer is evidently a mixture of bone meal and sulphate of potash and the plant food contained in it is as follows: Nitrogen 1.65 per cent. Available Phosphoric Acid 8 " Insoluble Phosphoric Acid 3 " Potash 10 " One hundred pounds of the mixture would contain: Pounds. Value per 100 lbs. Nitrogen 1.64 value at 171/2c .29 Available Phosphoric Acid 8 " " 4c .32 Insoluble Phosphoric Acid 3 " " 2c .06 Potash 10 " " 5c .50 ----- Total $1.17 In one ton the whole value would be twenty times this or $23.40. Add to this $8, which is about the average charge for mixing, bagging, shipping, selling and profit, and we find that $32 is probably the lowest figure at which this fertilizer could be purchased on the markets, and very likely the price would be higher as we have taken the lowest guaranteed per cent. of plant food for our basis of calculation. Fertilizers are generally mixed and sold to the farmer on the ton basis. LOW GRADE MIXTURES