g N. H. AGR. EXPERIMENT STATION [Bulletin 196 



Prices of Plant Food Materials. 



Per unit. Per pound. 



Phosphoric acid (P2O5) available $1.20 $0.06 



Nitrogen 6.00 0.30 



Potash (K2O) water soluble 2.50 0.125 



Either the unit or the pound method can be used to cal- 

 culate the commercial value of the fertilizer. If we have 

 a fertilizer with the following guaranteed analysis: 



Phosphoric acid (P2O5) available 3.00% 



Nitrogen total 8.00% 



Potash (K2O) water soluble 2.00% 

 by the unit method we find : 



Nitrogen 3 X $6.00 = $18.00 



Phosphoric acid available 8 X 1.20 = 9.60 



Potash water soluble 2 X 2.50 = 5.00 



Total commercial value $32.60 



By this method we multiply the per cent of each plant 

 food by the cost per unit and then add these figures to give 

 the total value. 



Employing the pound method we obtain : 



3 X 20 = Number of pounds of nitrogen in a ton 60 X $0.80 =: $18.00 



8 X 20 ^ Number of pounds of phosphoric acid 



in a ton 160 X 0.06 = 9.60 



2 X 20 = Number of pounds of potash water soluble 



in a ton 40 X 0.125 = 5.00 



Total commercial value $32.60 



The per cent means the number of pounds in 100 pounds. 

 Since there are twenty hundred pounds in a ton we multi- 

 ply the per cent by twenty to find the number of pounds 

 of each plant food in a ton. Then by knowing the value 

 of these per pound we can figure the value of each plant 

 food per ton. 



CLASSIFICATION OF SAMPLES ANALYZED. 



Table 1 gives the number of samples collected and ana- 

 lyzed in each of the respective classes. 



