No. 4.] SOIL FERTILITY. 131 



from the soil ; and that the nitrogen found in this crop is 

 wholly additional to the stock of nitrogen which the soil 

 contained before the crop was grown. We have no proof of 

 this, and any statements in this direction are pure assump- 

 tions. All we have learned definitely is, that under certain 

 conditions leguminous plants have the capacity for taking 

 up atmospheric nitrogen ; but when the soil is fairly well 

 supplied with available nitrogenous compounds, we do not 

 know to what extent the legume will utilize the nitrogen of 

 the air. We have observed this, however : that, when a 

 field of alfalfa is properly supplied with phosphatic and 

 potash manures, it will continue to })roduce abundant crops 

 tlirough a long series of years, without the addition of any 

 nitrogenous fertilizers whatever. This has been illustrated 

 beyond question on the farm of the New York Agi'icultural 

 Experiment Station. I wish it were possible for the alfalfa 

 plant to become extensively used in the State of Massachu- 

 setts. To what extent your conditions are adapted to the 

 growth of this valuable forage crop 1 do not know. 



When we come to consider the question of bacterial organ- 

 isms, not associated with the plants of the leguminous family, 

 but which we have good reason to believe may cause the 

 fixation of atmospheric nitrogen in the soil, we are, it must 

 be confessed, in the field of theory so far as practical results 

 are concerned. Professor Burrill of Illinois, who is an ex- 

 pert in the field of bacteriology, makes the following state- 

 ment in a recent paper : ' ' After many tests upon numerous 

 self-inhabiting species, certain kinds of bacteria have been 

 found which undoubtedly have the power of building the 

 aerial nitrogen into combinations which subsequently serve 

 as food for the higher plants.'' Professor Burrill subse- 

 quently states that the anu)unt of nitrogen thus fixed is 

 small, and that exj)eriments with an artificially pre[)ared sub- 

 stance, called alinit, which is a pure culture of one species 

 of bacteria, have not shown any considerable increase in 

 crops, although favorable rcimrts have been received in some 

 instances. 



But such researches as these ()\)vn up an outlook upon great 

 possibilities. When we remember that some of our soils 



