THE TILLAGE OP THE SOIL 65 



stirring is confined to the one, two or three 

 uppermost inches of the soil. 



2. What Tillage Does 



87. Tillage improves the physical condition of 

 the soil : by fining the soil and extending the 

 feeding area for roots (53) ; by increasing the 

 depth of the soil, or loosening it, so that plants 

 obtain a deeper root -hold ; by causing the soil 

 to dry out and warm up in spring ; by mak- 

 ing the conditions of moisture and temperature 

 more uniform throughout the growing season. 



88. It aids in the saving of moisture : by 

 increasing the water-holding capacity of the soil, 

 or deepening the reservoir (79) ; by checking the 

 evaporation (or conserving, or saving, moisture) 

 by means of the surf ace -mulch (83). The for- 

 mer is the result of deep tillage, as deep plow- 

 ing, and the latter of surface tillage. 



89. It hastens and augments chemical action 

 in the soil : by aiding to set free plant-food ; by 

 promoting nitrification (Chap, vi.); by admitting 

 air to the soil ; by lessening extremes of tempera- 

 ture ; by hastening the decomposition of organic 

 matter, as of green -crops or stable manures 

 which are plowed under ; by extending all these 

 benefits to greater depths in the soil. In a very 

 important sense, tillage is manure. 



