GROWING BY IRRIGATION. 283 



since if they run in a direction across the slope there 

 will be danger of their filling and the water fail 

 of reaching the points aimed at. The furrow method 

 will do more with a small amount of water than any 

 other except subirrigation by means of tiles. 



The Flooding System. The most common way of 

 irrigating alfalfa in our West is by flooding. To 

 prepare land for this system one puts in ditches on 

 contour lines, the upper one to bring water to the 

 field, below another to catch the waste water and 

 collect it for the part of the field below. 



The distance apart of these head ditches, as they 

 are called, is determined by the nature of the soil, 

 slope and the amount of water to be had. Usually if 

 they are from 400' to 1,000' apart it will be well, 

 with an average distance perhaps of about 500'. 

 Much here depends on the nature of the soil. There 

 are soils where it is well to have these ditches as 

 near as 200' feet or even closer together. Much 

 of course depends upon the head available. If there 

 is not much head the leading ditches should be closer 

 than if there is a flood of water. The ditches while 

 following contour lines rather closely ought to have 

 enough fall so that the water will flow freely in them. 



Preparing the Land for Flooding. The contour 

 ditch is made first, strong, with a good bank. Be- 

 low it a lesser ditch, close up; this to distribute the 

 water. The field should be leveled as well as pos- 

 sible. Upon this leveling will depend a lot of the 

 later success or failure of the alfalfa. Work in mak- 

 ing the land level is work well spent. It should next 



