182 SOILS: PROPERTIES AND MANAGEMENT 



PLASTICITY 



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FIG. 28. Diagram showing the moisture limits for successful plowing 

 in soils of different class, cc and hh' represent the moisture limits 

 within which successful plowing may be accomplished on a clay and 

 humus clay respectively. 



tions is necessary in order to determine what is just the 

 right moisture content for good plowing. That this 

 condition must be carefully gauged and immediate use 

 made of the advantages it offers is shown by its narrow 

 limit- A few days may suffice for the moisture to drop 

 through such a narrow area of fluctuation. A clay soil is 

 so difficult to handle at best that no opportunities such as 

 are offered by optimum moisture conditions should be lost. 

 Moreover, a heavy soil plowed too dry or too wet does not 

 regain its normal granular condition for several seasons. 

 In a sandy soil no such difficulties are encountered. 



