200 



Gardening 



Purdue Univ. Agric. Expt. Sta. 



FIG. 1 1 8. A garden in need of cultivation. The surface crust should be 

 broken to admit air more uniformly to the roots and to conserve the soil moisture. 



preserving a sufficient supply of water for plants that we 

 should thoroughly understand how a surface layer of 

 fine, loose soil keeps the water from escaping into the air. 



How a dust mulch prevents loss of water from soil. 

 The water in the soil can travel in any direction by pass- 

 ing from particle to particle, just as oil travels up the 

 wick of a lamp by passing from thread to thread. It 

 moves from the places where it is most abundant to the 

 places where there is less of it ; hence, when the surface 

 layers of the soil dry out, the water in the damper soil 

 below creeps up toward the surface. In this way the 

 water in a soil is brought to the surface and evaporated 

 into the air. 



But if the surface layer of the soil is cultivated, it is 

 broken loose from the soil below. Then the water 

 finds no direct path from particle to particle upward ; 

 the connection of the upper layer with the soil below is 

 broken. Hence the surface soil soon dries out because its 



