150 STATE BOARD OF AGRICULTURE. 



soil-bactcrioloj^v liaw liiilt-oi- no pijicMcnl valiip fm- applied ajiricnllure. 

 These iiivestigatious ma^' be classilied a.s iulloN\s: 



T. Niiinoiical defoiniiiiaiion of baoteria in soil, 

 II. Dctoniiinatiou of .species in soil. 

 III. Transformation ex])eiinionis after Keniy, Lolinis, etc. 



Those oxporinienls, however valuable tlio.v may bo thoorotieally, have 

 practically no value for a practical aijriculture, because they fail to 

 consider the fact that the bacterial content of the soil is determined al- 

 most entirely by the physical and chemical conditions of the soil and 

 that the microfloi'a in the soil exists in the soil solution. If it is our 

 final aim to aid a<iiicuUure, then soil bacteriolojiy can be successfully de- 

 veloped onl.y by a thorongh study of the soil solution and by influencing 

 this solntion intelligently so as to make the work of the soil bacteria 

 more j^rofi table. 



In pln'siology we recognize the influence of eii\ iioiiineiit on the single 

 cell. Not only if we take the high water content of the living substance 

 into consideration, but also if we consider metabolism as the manifesta- 

 tion of the phenomona of life, the importance of water in the life process 

 is made clear. Without water there is no life. By adding to or diminish- 

 ing the water of the living substance within certain limits, we increase, 

 diminish, or limit the intensity of life p)rocosscs. The environment of 

 bacteria is water, and soil bacteria form no exception. There, whei-e 

 there is little or no water at their disposal, the metabolic processes are 

 reduced to a minimum. Spores, cysts, and other defensive organs are 

 the results of the dryness of the medium. In a former publication^, 

 the author has tried to make a numerical comi)arison between the water 

 content of the soil and the activity of the soil bacteria. As an indi- 

 cator the carbon dioxide production in soils was chosen, a metabolic 

 j)roduct that is formed in nearly all life j^rocesses in compai-atively 

 lai'ge quantities, and in easily detected form. Without going into detail 

 with tliese experiments, I Avill say that if the soil contained only 4.4% 

 ()( water, the soil bacteria Avould be nnable to attack the easily broken 

 down dextrose which was added to the soil. I take this as an exani])le 

 illustrating the overwhelming imi>ortance of the water content for the 

 biochemical action in soils. 



From the foregoing it is clear that water is the medimn of soil bac- 

 teria. Although one cannot make in ])ractice a sliai-p distinction be- 

 tween the rpiantity and the nature of the water, 1 should like to cite 

 the exi;eriments of Be.yerinck- as evidence of the influence of the nature 

 <»f the water, on the microiirganisms. His exj>eriments deal chiefly with 

 unicellular organisms, and let us say here that the "ecological method" 

 proved to be of especial value, in tlie case of the lower organisms, be- 

 cause they are nnicellular and expose in com])arison with their content 

 such an enormous surface, on which the medium can act. 



In his classical investigations lleyerinck showed the dominating in- 

 fluence of the nalui-e of the water enviroumeui on the behavior of 

 the microorganisms. IIow uniform was the material willi which he 

 started must be noted, for il w;'s in many cases the mud of the canal 



>F. ITesselink van Siifhtolon, Ccuir. hi. f. Bakt. II Abt. Bd. 28. S 4.5. 

 *F. Stockhausen, Oekologie Anhaufungeii nach Beyerinck. 



