422 THE SMALL GRAINS 



series of rectangular basins. On steep or irregular slopes, 

 the levees are run on contour lines. Water is applied 

 in a similar manner to that in border flooding, but on a 

 larger scale. The checks are usually 1 to 2 acres in size. 

 Levees must be broad and low enough for harvesting ma- 

 chinery to cross them. They are sown with grain, and 

 usually receive enough water through seepage and rainfall 

 to mature the crop. This is the method used in rice 

 irrigation (699). 



449. Furrow or corrugation method. In the extreme 

 northwestern states, grain and alfalfa are commonly 

 irrigated by the corrugation method. The water is run 

 in small shallow furrows, from which it percolates laterally 

 through the soil, but does not run over the surface. It is 

 a slow method, that can be used at night, and is proper 

 for heavy soils which take water slowly. On the other 

 hand, it may be better sometimes on light soils, with 

 much slope, to prevent soil washing. It will work on 

 considerable slopes, as the furrows can be run at any 

 angle necessary to give the required grade for the desired 

 velocity of water. The furrows are made just after 

 seeding. Preparation of the land is more expensive than 

 that for flooding, but less labor is required in applying the 

 water. In grain fields, the furrows are made if to 3 feet 

 apart (McLaughlin, 1910). In Utah it appears that irri- 

 gation by flooding is commonly practiced in the northern 

 part of the state, while the furrow method is more 

 common in the southern part. The merits of the two 

 methods have not been determined experimentally for 

 small cereals. 



450. Comparison of methods. No well (1908, pp. 18- 

 19) experimented with the three irrigation methods as 

 to cost, and concluded that the furrow method was most 



