The "Yeast of the Soil" 



or Soil Bacteria 



How One 



Order of 

 Life Helps 

 Another 



Why a 

 Soil Is 

 Cold 



How 



Yeast 

 Works 



"The yeast of the soil," as we shall consider it, is not plant 

 food, but low organisms of life which exist in the soil and but 

 for which ctiltivated soils would be practically barren. "The 

 yeast of the soil" is what is scientifically known as bacteria — 

 organisms which thrive in the soil and by means of which 

 unavailable plant food, especially nitrogen in the form of organic 

 matter, such as stable manure (leaves, stalks, etc.), is rendered 

 available. The great discoveries of Hellreigel, the leading 

 investigator along this line, demonstrate that higher orders of 

 plant life are dependent upon lower orders of life. We could 

 not profitably grow a corn or potato crop unless these organisms 

 were growing at the same time in the soil, or had previously 

 existed there and done their work. 



We speak of a soil as being cold and non-productive. It 

 may be cold from an excess of water, or because it is too com- 

 pact and heavy, but the moment we drain it or lighten it by 

 cultivation, it becomes productive. The real reason it be- 

 comes productive is that we admit air and warmth, which are 

 necessary to develop the crop and also the "yeast plants" 

 (bacteria), which, in turn, attack the stable manure or other 

 organic matter (humus), and break it down, rendering it avail- 

 able to plants. Farmers say that they can hear corn grow on 

 warm days and hot nights, which is almost literally true. It 

 is because the weather is favorable to the growth of the nitri- 

 fying plants (bacteria of the soil), Vv^hich convert the unavail- 

 able nitrogen into available and soluble forms. 



It is a well-known fact that the yeast used in making bread 

 and the "mother" used in making vinegar are nothing but an 

 aggregation of bacteria, "yeast plants," as it were. When the 

 yeast is added to bread under warm, favorable conditions, it 

 begins to grow, and in its growth liberates carbonic acid gas, 

 which causes the bread to rise and become light and porous. In 

 the case of vinegar a ferment, or "yeast plant," attacks the sugar 

 of the cider and converts it into alcohol; then the "mother" of 



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