IRRIGATION 



271 



whore a levee or dike is built around the field and into which the 

 water is turned and left till it is all absorbed. r l his is a common 

 practice in China and Japan. In open field flooding a canvas dam 

 is placed in the ditch and the water forced to run over the banks 

 of the ditch into the field. A moderate slope permits it to run 

 slowly over the field where the surplus water runs into another 

 ditch at the lower side. 



Basin flooding is practiced in orchards, the levee being thrown 

 up so as to occupy the space allotted to each tree. The water is al- 

 lowed to enter the enclosure and left till it is absorbed (Fig. 12'2). 

 Dirt is piled around the base of the tree so the bark will not get 

 wet. This method is gradually passing out of use. 



Fio. 123. Irrigating potatoes by furrows. I". S. Reclamation Service. 



(b) Furrow Irrigation. The furrow method of irrigation is 

 one of the most common and for most conditions one of the best 

 methods practiced. Small furrows lead from the supply ditch and 

 the water is absorbed by the soil ( Fig. 1 :>.'{). The furrows are from 

 five to ten inches deep and from three to eight feet apart, the dis- 

 tance depending upon the soil and the crop. By this method the 

 irrigator may control the quantity of water and a comparatively 

 small amount may be spread over a large area of land. Onlv a 

 small amount of the soil becomes wet. so that injury from puddling 

 is not imminent. The furrows may soon be covered and thus reduce 

 evaporation, preventing or retarding the rise of alkali. Tt is very 

 difficult to obtain uniform distribution, due to the difference in the 

 absorbing power of the soil or length of furrow or both. This 



