146 Bulletin 394 



and thus it seems proper to use them in computing the value for percentage 

 nitrified. The probable error of a given value for the latter was obtained 

 according to the formula given by Mellor,^ 



in which A is the divisor with a probable error a, and B is the dividend 

 with a probable error b. 



It appears unwise to make any very definite statements regarding 

 the data in table 12, both because of the computations involved in con- 

 structing the table and because of the large probable error attached to 

 many of the values. It is believed, however, that the table is useful 

 in showing the approximate amount of nitrification resulting from turning 

 under the various crops. The values for percentage nitrified for the 

 unlimed pots vary widely, and nothing can be said about them except 

 that they show that the added material nitrified less rapidly than in the 

 limed pots. There is no consistent difference shown by the two forma 

 of lime, neither is there any evidence to show that the crop grown for 

 the shorter period nitrified more rapidly. For the three periods of 

 growth the figures showing the percentage nitrified for the crop treated 

 with slaked lime agree very closely; on the other hand, the figures for 

 the pots receiving ground limestone vary rather widely. As a rough 

 figure to indicate the percentage of the added nitrogen nitrified in the 

 limed pots, 50 per cent might be chosen. 



SUMMARY 



In an investigation such as the one described in this paper, repetitions 

 of the experiments under field conditions are desirable before general 

 conclusions are drawn. The results obtained in the present study must 

 be interpreted with respect to the experimental conditions maintained. 

 This fact should be borne in mind in considering the summary given. 



These experiments show that sweet clover will make a satisfactory 

 growth for use as a green manure in three or four months on a worn-out 

 soil, provided the lime requirement is satisfied. When the crop is harvested 

 at either of these periods it compares favorably in nitrogen content with 

 other legumes, and sufficient fiber has not developed to inhibit rapid 

 decay. Growing the crop for the longer period does not result in an 

 increased proportion of fiber. The plant responds readily to inoculation 

 with the appropriate organism. To secure a good stand, the seedbed 



' Mellor, J. W. Higher mathematics for students of chemistry and physics, p. 529. 1905. 



258 



