SOIL WATER 79 



the crop, may reveal an interesting situation. It 

 may show, for instance, that the rainfall in those 

 months is equal to or greater than the water used 

 in producing the crop. This would be all right 

 were it not for two facts; quite frequently there 

 are years that fall much below the average in sum- 

 mer rainfall, perhaps considerably below the 

 amount needed by the crop; it is the average of 

 wet years and dry years that gives the "normal" 

 rainfall. Then, again, not all the rain that 

 falls becomes available for plant growth. 

 Some of it runs off as surface water and 

 fills the creek; some of it passes down through 

 the soil; some of it evaporates. Very often 

 not half of the summer rainfall can be utilised 

 by crops. 



The comparison of figures may show that the 

 total amount of water that falls during the growing 

 season is only about one-third as much as the crop 

 needs. In nearly all sections of the country the 

 situation is that not enough rain falls during the 

 growing season to water the crops after that lost 

 by surface drainage, evaporation and seepage is 

 deducted. The total rainfall may be adequate, but 

 it is unevenly distributed. The problem, then, is 

 to store the abundant rains of winter and early 

 spring against the dryness of summer; this is one 

 of the most important problems in farming. The 

 water may be stored in reservoirs and used for 

 irrigation or it may be stored in the soil itself; 

 the former is a Western, the latter an Eastern 

 method. Soil storage is more common and re- 

 quires more skill. The man who has learned 

 to store water in the soil effectively ha* 

 mastered one of the most important problems in 

 crop husbandry. 



