62 AGRICULTURE 



the topography of the field, and the kind of farming to 

 be undertaken. Two principal methods of applying the 

 water are (1) by flooding, and (2) by the use of furrow- 

 ing, or corrugation, of the field. 



When flooding is used, the water is spread from the 

 source of supply over the entire field at regular or neces- 

 sary intervals. It seeps into the soil and around the root 

 systems of the plants from every point of the surface. 

 When furrowing is employed the water is turned into the 

 furrows from the head lateral ditches. From the furrows 

 it seeps through the soil to the roots of the plants. It is 

 evident that for the successful use of either of these meth- 

 ods the fields must be relatively level and only a trifle slop- 

 ing. 



Saving the water. The only methods known to pre- 

 vent lavish waste of water through surface irrigation are 

 (1) by economy in the application of water, and (2) by 

 keeping a light surface mulch and by frequent and shallow 

 cultivation. This system will produce a greater amount of 

 plant products at less water cost. For most of the fruit, 

 trucking and grain crops the furrow, or corrugation, method 

 is conceded to be more practical and economical than flood- 

 ing. 



Sub-surface irrigation. Under favorable conditions 

 sub-surface irrigation proves most satisfactory, chiefly be- 

 cause there is little or no waste of water, and because the 

 supply can be more easily controlled. 



In this system the water is applied by means of pipes 

 placed beneath the surface. The pipes are full of small 

 holes through which the water enters the soil. A serious 

 objection to this method is that clay soil and small plant 

 roots are likely to clog up the holes. Hence the sub-surface 

 pipes are adapted only to light open soils. Another sub- 

 surface method is by a system of tile or drainage pipes from 



