The experiment stations not only publish comparative analyses of the registered fertilizers but they also compute the market values of the plant food contained in them and compare these valuations with the selling price of the fertilizers.

They also furnish a list of trade values of the plant foods in raw materials for the convenience of fertilizer buyers in testing the values of the brands offered them on the markets.

In the following list are given the “trade values agreed upon by the Experiment Stations of Massachusetts, Rhode Island, Connecticut, New Jersey and Vermont, after a careful study of prices ruling in the larger markets of the southern New England and Middle States.”

Trade values of fertilizing ingredients in raw materials and chemicals for 1904: 

         &nb
sp;                                            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