USE OF PHOSPHORUS IN DIFFERENT FORMS 265 



acre for the last four years; while the value of the increase pro- 

 duced by $1.05 worth of raw phosphate (above the increase pro- 

 duced by the nitrogen and potassium) was $5.85 per acre as an 

 average of the twelve years, and $8.41 for the last four years. 



As an average of all crops, the raw phosphate produced larger 

 yields than the acid phosphate (dissolved bone black) and prac- 

 tically the same yields as the reverted phosphate (including lime) ; 

 but the bone-meal plots gave slightly larger average yields, the 

 increase from $4.70 worth of bone meal being $8.41 per acre for 

 four years as an average of the entire period, and $11.47 P er acre 

 for the last four years, above the increase produced by nitrogen 

 and potassium alone. 



When used in addition to nitrogen and potassium, $1.05 worth of 

 raw phosphate produced net profits amounting to $4.80 per acre 

 every four years as an average of the twelve years, and $7.36 for 

 the last four years; while the corresponding net profits from $4.70 

 worth of bone meal were. $3. 71 for the twelve years' average and 

 $6.77 for the last four years. Thus, the greatest total net profits 

 were from the raw phosphate. On the basis of money invested in 

 phosphorus, the net profits from raw phosphate were 457 and 700 

 per cent, and from bone meal they were 79 and 144 per cent, re- 

 spectively. 



In no case was the net profit from the use of phosphorus sufficient 

 to cover the net loss from the use of nitrogen and potassium, so 

 that the total result was a net loss in all cases. It must be kept in 

 mind, too, that the effects produced by phosphorus when used in 

 addition to nitrogen and potassium (over and above those produced 

 by nitrogen and potassium alone) are usually greater than the 

 effects produced by phosphorus when used alone, as is fully shown 

 by other experiments hereinafter discussed. 



On the other hand, these Pennsylvania investigations clearly 

 indicate that if the nitrogen were secured from the inexhaustible 

 supply in the air and turned under in the form of farm manure, 

 legume crops, or other residues, and if the potassium can be liber- 

 ated from the practically inexhaustible supply in the soil by the 

 decay of this same organic matter, then the use of phosphorus 

 would not only be profitable in itself, but the total result of the 

 system should yield large net profits. 



