THK TILLA(fK OK THK SOIL 



65 



stirring is eonlineil to the one, two or three 

 ui)p»'rniost inches of the soil. 



'J. What 'rUltif/c Does 



ST. Tilhi,«,'(» iiuprovfs the physical condition of 

 tli«' soil : Ity lininjj: the soil and cxtendini^ the 

 feeding area for roots (53) ; by increasing the 

 dcptli of the soil, or loosening it, so that j)lTints 

 obtain a deeper root-hold ; l>y <'aasiiig the soil 

 to dry out and warm up in sjiriiiu' ; by mak- 

 ing the conditions of moistui't' and temperature 

 nion* uniform throughout the growing season. 



SS. It aids in tlie saving of moisture: l)y 

 increasing the water-holding capacity of the soil, 

 or deepening tlie reservoir (7!)); by checking the 

 evaporation (or <'onserving, or saving, moisture) 

 by means of the surface-nudch (SI)). The for- 

 mer is th«' result of deep tillagt', as deep plow- 

 iuLT, and the latter of surface tillage. 



Sl>. It hastens and augments chemi<al act inn 

 in the soil : by aiding to s(»t free j)lant-food ; by 

 promoting nitrification (Chap, vi.); by admitting 

 air to the soil ; by lessening extremes of tempera- 

 tiu'e ; l»y hastening tlie decomp<)siti<»n of organic 

 matter, as of gre«Mi-erops or stable manures 

 which are plowe<l under; by extendini^ all these 

 benelits to greater depths in the soil. In a very 

 important sense, tillage is manure. 



