i8o Journal of Agricultural Research voi. xiii, no. 3 



tile soil, changed to ammonia in seven days from one-third to one-half 

 of the nitrogen added as dried blood or as cottonseed meal. In an 

 earlier experiment the same investigator found that the bacteria from 

 the soil of plot 32, when used to inoculate another previously sterilized 

 soil, acted with like ammonifying vigor as those of the first mentioned of 

 these two experiments. 



Without attempting to apply these proportions to the conditions of 

 our own experiments we may at least infer that during the first two 

 weeks a very advanced stage of amraonification might be reached in the 

 case of the highly fermentable fresh green manures. 



INCREASE OF LIME REQUIREMENT AT LATER PERIODS 



The facts presented in Tables III and IV show, as already has been 

 pointed out, several general increases of limestone requirement in the 

 manurial mixtures. 



It is well known that among the oxidation processes of general occur- 

 rences in ordinary plowed land is that bacterial fermentation which re- 

 sults in the transformation of ammonia to nitric acid. The effect of such 

 a change is clearly to increase the limestone requirement, because the 

 nitric acid must combine with basic materials to form neutral salts. The 

 degree of effect varies, however, for each unit quantity of nitric acid pro- 

 duced, according to the conditions in which the requisite nitrogen exists 

 at the beginning of the period of observ^ation. If, on the one hand, it is 

 present in a body that has little or no effect on the reaction of the soil 

 medium, then the conversion to nitric acid will change the acidity only in 

 such measure as the nitric acid itself contributes to the acidity; on the 

 other hand, if the nitrogen is already present as ammonia, it serves in 

 the measure of its quantity to reduce the limestone requirement at that 

 time, but upon conversion to nitric acid it not only adds to the acid but 

 subtracts in like measure from the previous series of the alkaline sub- 

 stances, so that, in this case, it works a double effect. In the former of 

 these alternatives 28 pounds of nitrogen would make enough nitric acid 

 to require 100 pounds of carbonate of lime for its neutralization; in the 

 latter case the same quantity of nitrogen in the form of ammonia would 

 perform the neutralizing serv^ice of 100 pounds of carbonate of lime, but 

 upon conversion to nitric acid would not only lose its former power but 

 would require the direct action of an equal quantity of the calcium car- 

 bonate, so that the net effects of the conversion of the 28 pounds of am- 

 moniacal nitrogen to nitric nitrogen are to increase the calcium carbonate 

 duty of 200 pounds. There are several other alternative conditions pos- 

 sible. In one ammonia might be formed from a neutral body at the 

 same rate as the nitric acid itself is generated. Of course, in this case 

 the one substance exactly balances the other in its effect upon the lime- 

 stone requirement. 



