250 IRRIGATION FARMING 



Systems of irrigation. - - The most common irrigation 

 system consists of a dam across a stream from which 

 the water is taken, a canal that leads the water to the 

 area to be watered, and the laterals or small ditches 

 through which the water is brought from the canal 

 to the farms. The dam across the stream may simply 

 divert part of the water into the canal, or it may 

 be so large that it converts a part of the valley 

 on the upper side into an immense reservoir in 

 which the flood waters may be stored for irrigation 

 purposes. 



Methods of applying water. - - There are several 

 methods of applying water to the soil. The kind of 

 crop, the size of the irrigated area, and the character 

 of the soil and surface are important factors that de- 

 termine the method of applying the water. 



In aerial irrigation the water is distributed by pipes 

 and sprinklers. Lawns are commonly so watered. 

 Orchards, gardens, and greenhouse benches are often 

 subirrigated ; that is, by underground pipes or tiles 

 the water is carried to the soil around the roots of 

 the plants. 



Pasture grasses and hay and small grains are usually 

 irrigated by flooding. The water is run directly over 

 the surface and around the growing plants. In furrow 

 irrigation the water is run in furrows between the rows 

 of trees or other plants. This is the method by which 

 orchards, com, potatoes, and garden vegetables are 

 usually watered. 



