BOTTOM WATER 23 



Average amount. Minimum amount. 

 Tons water. Tons water. 



Clover 400 3 10 



Potatoes 400 325 



Wheat 350 300 



Oats 375 3oo 



Peas -. 375 3 



Corn 300 



Grapes 375 



Sunflowers 6 6000 



The rainfall during the time of growth is frequently 

 less than the amount of water required for the pro- 

 duction of a crop. One inch of rainfall is equal to 

 about 90 tons per acre. An average rainfall of 2 

 inches per month during the three months of crop 

 growth is equivalent to only 540 tons of water per 

 acre, a large part of which is lost by evaporation. 

 Hence it is that the rainfall during an average grow- 

 ing season is less than the amount of water required 

 to produce crops, and hence the water stored up in the 

 subsoil must be drawn upon to a considerable extent. 

 Inasmuch as the soil's reserve supply of water is such 

 an important factor in crop production, it follows that 

 the capacity of the subsoil for storing and supplying 

 water as needed is a matter of much importance, par- 

 ticularly since the power of the soil for absorbing 

 and retaining water may be influenced by cultivation 

 and manuring. Before discussing the influence of 

 cultivation upon the soil water, the forms in which it 

 is present in the soil should be studied. Water is 

 present in soils in three forms : (i) bottom water, (2) 

 capillary water, and (3) hydroscopic water. 



19. Bottom Water is water which stands in the soil 



