no TILLAGEMOVEMENTS OF SOIL WATER [chap. 



manent water level were I foot below, 0-405 if the 

 water had to be lifted 2 feet, and 0-18 inch if the 

 water had to rise 4 feet to the evaporating surface. 

 When the sand was replaced by a clay loam, the lift 

 of water to the surface was somewhat less, but in all 

 cases the amounts were probably less than would be 

 realised under field conditions, because the evapora- 

 tion was not enough to dry the surface, and was 

 further checked by the formation of a saline crust on 

 the surface. Working in the field, King obtained a 

 daily loss at the evaporating surface of 1-3 lb. per 

 square foot, or 01 9 inch of water, the water table 

 being from 4 to 5 feet below the surface. 



The following table illustrates how the subsoil may 

 act as a regulator to the amount of water contained in 

 the surface layer, absorbing the water which descends by 

 percolation during rainy periods, and giving it up again 

 by capillarity to the surface soil during periods of 

 drought. The first line shows the rainfall during the 

 periods indicated, the second line the amount of 

 evaporation during the same period, while the third line 

 shows the changes in the water content of the top foot 

 of soil. As this change is not represented by the 

 difference between the rainfall and the evaporation, it 

 is clear that water must have been in some cases passed 

 down to the subsoil, in others lifted from it, in quantities 

 shown by the last set of figures. 



Water in inches. 



Rainfall ..... 



Evaporation ..... 

 Gain or Loss of Water in top ioot 

 Water furnished by ( - ), or passed 

 on to ( + ) Subsoil 



