CHAPTER VI. 



BACTERIA IN THE INDUSTRIES. 



A more careful study into the use made of bacteria in the arts and in- 

 dustries will completely dispel the generally prevalent opinions regarding 

 the pernicious nature of bacteria. This erroneous popular conception was 

 the outcome of the earlier activities in the study of disease germs. Weknow 

 that without the rotting bacteria, higher life, as we know it, would be im- 

 possible. Decayed plants and animals mixed with sand constitutes the 

 soO, the ultimate source of all higher life. 



I. The Function of Bacteria in Agriculture. 



The exact relationship of soil bacteria to soil fertility is not generally 

 understood, although it is well known that bacteria are abundantly present in 

 all soils. In fact, soil would be impossible without bacterial action. The 

 number of microbes in one grarh of dry soil varies considerably, ranging 

 from about one million to six millions and more. That these minute organ- 

 isms must perform some important work is almost self-evident. Recent in- 

 vestigations have demonstrated that the fertility of the soil is approximately 

 proportional to the number or quantity of bacteria present. 



We recognize what is known as potential fertility and kinetic soU fertility, 

 or, in other words, unavailable and available fertility. By potential or un- 

 available fertility, we mean the existence in the soil of plant foods which are, 

 so to speak, locked up and cannot be used by plants in the form or chemical 

 combination in which they then exist. By kinetic fertility we mean that 

 condition of the soil in which foods are direcdy available to the plants grow- 

 ing therein. If all the plant food substances occurring in the soil were directiy 

 or kinetically available, the productiveness of the soil would not lessen appre- 

 ciably for many years, say one hundred years or more. Why then is it 

 necessary to use fertilizers, to rotate crops, to rest the soil, etc., in a few years 

 in order to prevent soil exhaustion? This is simply due to the fact that in a 

 few years the crop plants use up so much of the available food that, unless 

 more is supplied, the crop yield will grow less and less until profitable culture 

 is impossible. 



We are familiar in a general way with soil exhaustion and the beneficial 

 influence of soil tilling, of crop rotation, and the use and value of the various 

 fertilizers. It is known that to let crop lands lie fallow for a season or two 



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