410 NATURE AND PEOPBRTIBS OF SOILS 



is more apparent than real. The transformation of nitro- 

 gen has received so much attention and study that more 

 is known regarding the changes involved. The other cycles 

 are probably just as extended and complicated, the lack of 

 knowledge forcing a simpler presentation. 



From the standpoint of soil fertility the compounds that 

 are produced in the nitrogen cycle and the relation of these 

 materials to plant growth are of major consideration. While 

 the organisms involved in the transformation should receive 

 as much attention as is practicable, the approach should be by 

 means of biological-chemistry rather than through bacteri- 

 ology. 



It must not be inferred that the carbon, sulfur and nitro- 

 gen cycles are distinct or that transformations may proceed 

 in one with no activity in the others. As a matter of fact, 

 the cycles are interlocked in a hopelessly intricate manner. 

 The decomposition of proteid matter involves all of the cycles 

 already mentioned. The carbon, sulfur, and nitrogen un- 

 dergo distinctly different transformations, but the changes 

 are so closely related as to make definite lines of distinction 

 very difficult. Proteid matter may produce urea, carbon 

 dioxide, water, and sulfates. Certain of these products often 

 strongly influence the solubility of the soil minerals. Thus, 

 the four cycles already mentioned would be involved in the 

 decomposition of one original compound. 



227. Decay and putrefaction.^ — The decomposition of 

 most nitrogenous matter is very rapid in a normal soil, the 

 putrefactive influences producing partially decayed sub- 

 stances of great variety.^ Some of these materials are very 

 complicated, while others are capable of being absorbed di- 



=^ Deeomposition and decay are general terms, referring to all types 

 of biological degradation. Fermentation refeis to the decomposition of 

 carbohydrates, while putrefaction has to do with nitrogenous materials. 

 The two latter terms are generally very loosely used. 



-* Lathi op, E. 0., FroteMi Deeomposi>t%on %n Boila; Soil Sci., Vol. I, 

 No. 6, pp. 509-532, 1916. 



