194 SOILS : PROPERTIES AND MANAGEMENT 



Percentage 

 of pene- 

 tration 



1. Puddled clay 100 



2. Clay plus 2 per cent CaO 56 



3. Clay plus 4 per cent CaO 43 



4. Clay plus 6 per cent CaO 33 



5. Clay plus 5 per cent CaCOg 98 



6. Clay plus 10 per cent CaCOs Ill 



7. Clay plus 25 per cent CaCOg 95 



In the soil the oxide and hydrate revert to the carbonate, 

 but before this change occurs the flocculating effects have 

 been exerted and the lines of weakness so essential to 

 granulative processes have been developed. Lime really 

 does not produce granulation in a normal soil through 

 its own action alone, but is aided by the other influences 

 already discussed. 



Warington ^ reports a statement of an English farmer 

 to the effect that by the use of large quantities of lime on 

 heavy clay soil he was enabled to plow with two horses 

 instead of three. It is generally true that soils rich in 

 lime are well granulated, and maintain a much better 

 physical condition than soils of the same texture that 

 are poor in lime. 



128. Tillage. — The effect of tillage on soil structure 

 is to produce lines of cleavage, and these, when produced 

 by plowing, are multitudinous and fairly uniformly dis- 

 tributed. Plowing, when the moisture content is suit- 

 able, tends to break the soil into thin layers, which move 

 one over the other like the leaves of a book when the pages 



1 Warington, R. Physical Properties of Soil, p. 33. 

 Oxford, 1900. 



