CONCLUDING REMARKS. 257 



the importance of knowing the source of the 

 benefits realized before giving certificates. It 

 may be due to a favorable season, to substances 

 already in the soil, or to the manure, or to all three 

 combined. If the farmer sees a favorable ap- 

 pearance in his crop, he is too apt at once to 

 attribute it exclusively to the bought fertilizer, 

 forgetting what he must have frequently seen, 

 when using stable manure alone, that one year 

 a good crop may be raised, and the next time, 

 though equally well cultivated arid manured, a 

 poor one. It has been shown that the amounts 

 required of the valuable constituents of crops are 

 very small. Hence, if the so-called concentrated 

 fertilizers contain but a little of what is really 

 needed, its effect on the crop would be apparent. 

 But our farmers should bear in mind that they 

 pay exorbitant prices for the benefits received. 

 If they apply 400 Ibs. of a fertilizer costing $50 

 per ton, it would be $10 to the acre, and they 

 should have clear views of the amount of any 

 crop that should be expected from such an out- 

 lay. As an illustration, 25 bushels of wheat 

 with the straw requires : 



27-95 Ibs. of Phosphoric Acid @ $0.12 per Ib $3.49 



39-65" "Potash @ 0.08 " .... 3.17 



46-60" "Nitrogen @ 0.15 " .... 6.99 



' Ifctftl $13.65 



Hence, if an outlay of $13. G5 on aii acre should 



