32 



SCIENCE 



[N. S. Vol. XLIII. No. 1097 



experiments was undertaken, using soil from 

 a number of plats that had been fertilized 

 differently. The samples were drawn on 

 August 14. Varying amounts of dried blood, 

 bone meal and ammonium sulfate were added 

 and the series arranged so as to make possible 

 a fair comparison of the rates of nitrification 

 when approximately equal amounts of nitro- 

 gen had been acted upon simultaneously.^ 

 The following table sets forth a part of the 

 results obtained: 



Nitrification^ with the Use of Varying Amounts of 

 Materials 



Briefly, it was found that 1 per cent, dried 

 blood failed to undergo nitrification in those 

 soils which had not been consistently fertilized 

 with organic manures and that in some cases 

 0.5 per cent, was not nitrified. On the other 



3 When the experiments were begun the dried 

 blood was thought to contain 13 per cent, nitrogen 

 and the bone meal approximately 3 per cent. 

 Analyses later showed them to contain 13.2 per 

 cent, and 4.25 per cent., respectively. Consequently 

 the amounts of nitrogen added as bone meal were 

 higher than had been intended, but this does not 

 materially modify the conclusions to be drawn, 

 since a wide range of concentrations was provided. 

 The ammonium sulfate was Baker's C.P. 



* The data represent the increase in nitric N 

 over that found in separate portions of soil incu- 

 bated for the same time under similar conditions, 

 but without the addition of nitrogenous material. 

 The minus sign ( — ) indicates loss of nitrate. 



hand, when the concentration was reduced to 

 0.25 per cent, or less, vigorous nitrification 

 took place in every case. It was found, how- 

 ever, that in most cases increasing percentages 

 of the nitrogen added were nitrified as the 

 amounts of dried blood were decreased down to 

 0.0625 per cent. Hence it would seem that 

 even 0.25 per cent, dried blood, which is only 

 one fourth the concentration commonly used 

 in laboratory experiments, may inhibit nitri- 

 fication to some extent in some soils. Similar 

 statements may be made regarding the results 

 obtained from the use of bone meal. The addi- 

 tion of large amounts of this material corre- 

 sponding approximately to the larger amounts 

 of nitrogen added as dried blood, failed to be 

 nitrified in the same soils that showed inability 

 to nitrify 1 per cent, dried blood. The smaller 

 amounts, however, were actively converted 

 into nitrate, but in no case more actively than 

 similar amounts of nitrogen as dried blood. 



In the case of ammonimn suKate, the re- 

 sults show that increasing percentages of the 

 nitrogen were nitrified as the concentration 

 decreased and that this material was most com- 

 pletely nitrified when added in the lowest 

 concentration. Comparing the percentage of 

 nitrification when the materials were added in 

 low concentrations, similar to that employed 

 in field practises, it is interesting to note that 

 with only one exception out of the ten series 

 of studies now made on the subject, ammonium 

 sulfate was nitrified no more vigorously than 

 dried blood, and in every case dried blood was 

 nitrified more actively than such a low-grade 

 nitrogenous material as bone meal. This fea- 

 ture of the results, therefore, is in harmony 

 with common knowledge and experimental 

 data obtained in humid regions. It should be' 

 added that other series of studies conducted at 

 a different time, fully verify the above state- 

 ments. The conclusions seem warranted, 

 therefore, that dried blood will undergo nitri- 

 fication in these soils fully as actively as the 

 other materials studied, provided an excessive 

 concentration is not employed. 



The above data also indicate that before 

 field comparisons on the nitrifiability of diifer- 

 ent materials can safely be drawn, it is neces- 



