NATURE AND PROPERTIES 



OF SOILS 



CHAPTEE I 



SOME CONCEPTIONS OF THE SOIL AND ITS RELA- 

 TIONS TO PLANTS 



Due to the action of climatic agencies the outer solid por- 

 tions of the earth readily pass into a loose and disintegrated 

 condition. This layer, although superficial and insignifi- 

 cant in comparison to the bulk of the earth, has performed 

 and is still performing a marvelous function. Life on the 

 earth has been slowly but steadily developing and changing 

 until we see about us the forms that characterize our age. 

 This evolution has depended to no small degree on this super- 

 ficial layer of decomposed rock with its admixture of de- 

 caying organic matter which together form the soil. In 

 this medium many and varied organisms have lived and from 

 it have drawn, wholly or in part, their sustenance, leaving 

 as a recompense a contribution of Organic debris, which in its 

 turn has given rise to reactions of almost unbelievable com- 

 plexity. 



Like the life which it has sustained and nourished, the 

 soil has been changing and evolving. The soil of today 

 is not the soil of yesterday nor will it be the soil of tomorrow. 

 It is never still. It is continually seeking a mechanical and 

 chemical adjustment with the forces which surround it or 



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