Tillage and Its Purposes 135 



rapidly, since the only part of the roots engaged in the 

 absorption of food from the soil is the narrow zone of 

 root hairs just back of the advancing tip of each rootlet. 



In a well-developed corn field, which has been properly 

 plowed and properly tilled afterward, the whole soil is a 

 complete net work of branching rootlets, each with its 

 penetrating root cap and its zone of root hairs. The 

 roots from opposite rows meet and cross each other till 

 hardly an inch of soil is left unoccupied. This also means 

 that an extreme fining of the surface soil is needed, for 

 as the plants develop the roots tend more and more to 

 seek the upper layers of the soil and demand a very 

 permeable material for their minutely divided rootlets, 

 which cannot penetrate hard lumps. 



The fining of the surface soil also favors 

 Retention of the rootlets by retaining the needed moisture 



oisture j.jgj^^ where they are rambhng. A surface of 



he Fining of loosely aggregated clods exposes too much 

 the Surface surface to the air, and dries out rapidly, 

 while the finely pulverized soil acts as a 

 blanket over the soil to check the evaporation of the 

 moisture arising from below by capillary attraction, and 

 to hold it near the surface where the roots can get it. 



While deep breaking is advantageous in enabUng the 

 oxygen to penetrate the soil, the subsequent tillage should 

 always be shallow. As we have shown, the roots, as the 

 crop approaches maturity, tend more and more to branch 

 near the surface, and deep cultivation not only damages 

 the crop by the breaking of the roots, but it turns the soil 

 up to dry out rapidly instead of keeping the shallow 

 blanket of fine soil to act as a check to evaporation. Both 



