SOIL WATER AND SOIL AIR 



for the improvement of such soils by securing more rapid 

 percolation will also, to a certain extent, increase the rate of 

 capillary action. 



How to prevent the loss of soil water. There are two 

 sources of loss of soil water. One is the run-off of water that 

 fails to enter the soil; the 

 other is through evaporation 

 of water at the surface. 



Loss of water through 

 run-off may be reduced in 

 two ways: improving the 

 structure of heavy soils by 

 securing granulation through 

 the use of lime, organic 

 matter, tillage, and drainage; 

 or modifying the surface in 



Diagram showing various losses of 

 water. 



A, Through plant and out at leaves. 



such a way that it will be Transpiration. 



B. Evaporation from the surface of 



difficult for water to run tne soil. 



C. Run-off. 



D. Percolation. Drainage. 



E. Mulch preventing loss of water. 



F. Area of capillary water. 



G. Area of free water. 



off. by fall plowing, mak- 

 ing the furrows at right 

 angles to the slope of the 

 land. 



Loss of water through evaporation is shown by the drying 

 of the upper layer of the soil. The extent of this loss may be 

 measured roughly by weighing a pan of damp soil, leaving it 

 in the open air for a few days and then weighing it again. 

 The difference in the two weights represents the loss by 

 evaporation for this period. It is estimated that about one- 

 half of the water reaching the soil by rainfall is lost through 

 evaporation, unless some means is taken to prevent it. 



Since most of the water lost in this way is capillary water, 

 the form absorbed by the root-hairs of plants, it is desirable 



