Farmers should be warned against judging fertilizers by their valuations. A fertilizer, the cost of which comes chiefly from the phosphoric acid present, would value much lower commercially than a fertilizer with a high percentage of nitrogen, and yet the former might be the more profitable for a given farmer to purchase.

Table for converting the fertilizer elements into their usually reported forms, and vice versa (J. P. Stewart)

(a) Converting Elements into Compounds

K X 2.4103 = K20.

P X 4.5806 = P205.

N X 1.2143 = NH3.

Mg X 1.6667 = MgO.

Ca X 1.4000 = CaO.

(6) Converting Compounds into Elements

K2O X .4149 = K. P2O5 X .2183 = P. NH3 X .8235 = N. MgO X .6000 = Mg. CaO X .7143 = Ca.

Computing the trade value.

A simple way of figuring the value of a commercial fertilizer 1 (Cavanaugh)

Example No. 1. Guaranteed Analysis

Nitrogen................     1.60 to 2.00 per cent

Phosphoric acid available...........    7.00 to 8.00 per cent

Potash.................    2.00 to 3.50 per cent

Cost per ton.............    \$29.00

1 In these and the succeeding examples, it happens that the trade values per lb. of chemicals are not those of 1910, given on pp. 47-48 ; but it is intended only to explain the method.

Multiplying the lowest figure representing the per cent of the given element by 20, and calculating the value from the price per pound, we have in No. 1 (remembering that 1 per cent means one pound in a hundred, or twenty pounds in a ton): —

Nitrogen...........1.60 X 20 = 32 lb. @ 150 - \$4.80

Phosphoric acid......... 7 X 20 - 140 lb. @ 50 = 7.00

Potash............2 X 20 = 40 lb. @ 50 = 2.00

Commercial value per ton.............\$13.80

Example No. 2. Guaranteed Analysis

Nitrogen................    3.30 to 4.00 per cent

Phosphoric acid available..........    8.00 to 10.00 per cent

Potash ................    7.00 to 8.00 per cent

Cost per ton.............    \$38.00

Its value is calculated the same as No. 1: —

Nitrogen...........3.30 X 20 = 66 lb. @ 15 = \$9.90

Phosphoric acid.........8.00 X 20 = 160 lb. @ 5 = 8.00

Potash............7.00 X 20 = 140 lb. ® 5 = 7.00

Commercial value................\$24.90

The cheapest fertilizer is the one in which one dollar purchases the greatest amount of plant-food. In No. 1, \$29 obtained \$13.80 worth, which is at the rate of forty-eight cents worth for \$1. In No. 2, \$38 buys \$24.90 worth of plant-food, or at the rate of sixty-five cents worth for the dollar. The difference between the commercial value, as calculated, and the selling price, is to cover expenses of manufacture, bagging, shipping, commission fees, and profits.

How to figure the trade value of a fertilizer in greater detail (Voorhees) It is assumed that the mixed fertilizer is guaranteed to contain

Ammonia...................    4 per cent

Available phosphoric acid..............    8 per cent

Total phosphoric acid ...............    9 per cent

Potash.....................    6 per cent and that the nitrogen exists in three forms, as nitrate, as ammonia, and as organic; the phosphoric acid in three forms, soluble, reverted, and insoluble; and potash in two forms, sulfate and muriate. The 4 per cent ammonia would be equivalent to 3.28 per cent nitrogen, 1 per cent of which is nitrate-nitrogen, | per cent sulfate of ammonia-nitrogen, and 1.78 per cent is derived from organic forms. Of the total phosphoric acid, 6 per cent is soluble, 2 per cent reverted, and 1 per cent is insoluble; of the total potash, 3 per cent is derived from muriate and 3 per cent from sulfate.

The first column in Table A shows the percentage of the constituents contained, which, multiplied by 20, gives the pounds per ton in the second column, which, multiplied by the schedule prices per pound, gives the valuation per ton, as shown in the fourth column.

In the case of ground bone, the guarantee is 4 per cent ammonia and 48 per cent bone phosphate, which are equivalent to 3.28 per cent nitrogen and 22 per cent phosphoric acid. It is assumed that 60 per cent of the material is finer than fa of an inch, and is regarded as " fine," and 40 per cent is coarser than fa of an inch, and is regarded as "coarse."

Table A. — Complete Fertilizer

The first column of figures in Table B shows the percentage, or pounds per hundred, of the constituents, which is multiplied by the percentage of fineness, which gives the percentage or pounds per hundred of fine or coarse in the third column. The calculation is then finished, as in the case of complete fertilizers.