USE OF PHOSPHORUS IN DIFFERENT FORMS 253 



The student or landowner must draw his own conclusions as to 

 which is the better basis upon which to compute the profit. It 

 should be kept in mind that 320 pounds of raw phosphate contains 

 40 pounds of phosphorus, while 320 pounds of acid phosphate con- 

 tains about 20 pounds of that element, so that the raw phosphate 

 is enriching the soil in phosphorus twice as much as the acid phos- 

 phate, while the removal in crops is practically equal. 



An examination of the values of the three crops by plots suggests 

 that the use of the data from plot Ai ($25.02) is unfavorable to 

 the raw phosphate on that series, because of the lower uniform 

 values from plot A4 ($20.61) and plot Ay ($20.03). On the other 

 hand, the use of the data from plot By is favorable to the acid 

 phosphate, by the Ohio method of comparison. 



By the method of direct comparison, by which the total values 

 from plots 15 and 16 (manure alone) are subtracted from the total 

 values from plots 2 and 3 and from plots 5 and 6, respectively, it 

 will be seen that the average value of the increase is $10.59 fr m 

 320 pounds of raw phosphate, and $10.61 from 320 pounds of acid 

 phosphate, the net profit per acre being $9.39 for the raw phosphate 

 and $8.21 for the acid phosphate; or, on the basis of money in- 

 vested, the net profit is 783 per cent for raw phosphate and 342 

 per cent for acid phosphate. For convenient reference, the aver- 

 age actual yields and values are summarized in the accompanying 

 tabular statement. 



TABLE 396. OHIO EXPERIMENTS WITH MANURE, RAW ROCK PHOSPHATE, 



AND ACID PHOSPHATE 

 Average of Twelve Years, with Duplicate Tests on Each Field 



