174 



THE PRINCIPLES OF SOIL MANAGEMENT 



of water at any point by a rootlet is made up by move- 

 ment of water from the adjacent soil zones. But the 

 plant is not dependent entirely on the movement of 

 water to its roots. The roots are themselves constantly 

 pushing into fresh soil zones, where the moisture, and 

 perhaps also the food, have not been so thoroughly 



Fig. 53. Penetration of root-hairs through the soil, (h, h') root-hairs; (T 7 ) 

 soil particles; (s, j) air-spaces. Water is indicated by concentric lines. 



withdrawn. The roots go to meet the capillary advance 

 of the soil water. This advance of the fine rootlets is 

 rapid, and of great consequence in the nourishment 

 of the plant. It also enables the roots to come into 

 more intimate contact with the soil; for, as the water 

 is extracted, it is lost first and most readily from the 

 large pores. The latter amount of water is found in 

 the smaller spaces, and consequently the roots are 



