Alfalfa in Kansas. 



279 



ings are usually sufficient, but in some cases more will be required. In 

 the latter case the final floating should always be in the same direction as 

 the water will be carried across the field. 



THE DISTRIBUTING SYSTEM. 



In addition to a level surface, proper ditches to conduct the water over 

 the area to be irrigated are very essential. The main supply ditch should 

 of course be located upon the highest land, ' and from this main ditch 

 laterals or field ditches should radiate over the alfalfa land. A well- 

 located and carefully constructed ditch system is an important factor in 

 the efficient application of water. The main ditch should be as direct as 

 possible and large enough to convey the water. The size of the ditch 

 will depend upon the slope of the land, the quantity of water to be car- 

 ried, and the method of application. The usual pumping plant does not 

 have a high capacity, consequently the main distributing ditches need 

 not be very large. If the field has been previously surveyed the location 

 is easily determined, and an engineer should be consulted to determine 

 the size of cross-section of the ditches. For small quantities of water the 

 judgment of the farmer will usually enable him to determine the required 

 size of channel. 



FIG. 217. Crowder used for ditch construction. 



A common method of construction after the ditches have been located 

 is to plow out the ditch line with a plow or lister. If with a plow the 

 dirt should be thrown away from the center line of the ditch. For the 

 irrigated section of Kansas, however, a lister is convenient. The main 

 ditches may be constructed by plowing out two parallel lister furrows 

 and then "splitting the middle" with a third lister furrow. In this fur- 

 row the erowder (see Fig. 217) is drawn to push the dirt out to form the 



