EXPEEIMENT STATION REPORT. 279 



ferment, and they afterwards, by a system of cultivations, 

 isolated and identified the specific form as a member of the 

 family of bacteria. 



The experiments on nitrification made by Warington at 

 Rothamstead in 1877, 1878, and 1879, have fully substan- 

 tiated the claims of the French chemists, and furnished ad- 

 ditional information of practical value in regard to the role 

 of the bacterium that performs such an important part in the 

 process of vegetable nutrition. 



These bacteria abound iu every fertile soil, and as a func- 

 tion of their vital activity are constantly transforming the 

 nitrogren of organic substances and of ammonia, in the sur- 

 face soil, into nitric acid, when the proper conditions of 

 moisture and, temperature are present. 



The bacteria of nitrification are most active at a temper- 

 ature of about 99° F. — they act slowly when the tem- 

 perature is lowered to near the freezing point, or when it is 

 raised to 122° F., and at 131° F. their peculiar function as 

 a ferment ceases. 



Another important condition is essential to rapid nitrifica- 

 tion, namely, the presence of an excess of some salifiable base, 

 as carbonate of calcium, so that nitrates can be readily formed. 

 This accounts for the action of lime when applied to peaty 

 soils, which has not heretofore been satisfactorily explained. 



The nitrates, as found, may be at once taken up by the 

 roots of living plants, or, in their absence, they will ba 

 washed by the rains to the lower strata of the soil beyond 

 the reach of shallow-rooted plants, or they may be lost 

 entirely in the drainage waters. 



It must therefore be seen that the nitrification of soils, and 

 the conservation of the nitrogen in the form of nitrates 

 are biological processes involving the activities of living 



organisms. 



During the summer the process of nitrification is carried 

 on rapidly, and the nitrates are taken up by the growing 

 crops ; but after harvest, on cropped land — and where land 

 is fallowed — the nitrates accumulate in the surface soil until 

 the fall rains wash them down to the lower strata. 



A few examples from the experiments at Rothamstead will 

 sufliciently illustrate the behavior of the nitrates in the soil. 



