IRRIGATION AND DRAINAGE 



M3 



the flow to each row of trees. This method is shown in operation 

 in Fig. 63, where a young orchard is being irrigated from |-inch 

 galvanized-iron standpipes connected with a 3-inch wooden pipe. 



Making furrows. The length of the furrow is often governed 

 by the size of the orchard. The rows of citrus trees seldom exceed 

 40 rods in length, but, as a rule, the apple orchards of the North- 

 west are larger. Even in large tracts it is doubtful if it ever pays 

 to run water in furrows that are more than 600 feet long. Where 

 the soil is open and water is readily absorbed, short furrows should 

 be used, otherwise much water 

 is lost in deep percolation on 

 the upper part of the tract. 

 Professor H. Culbertson, San 

 Diego, after a careful investiga- 

 tion of this subject, has reached 

 the conclusion that on sandy or 

 gravelly soil having a steep slope 

 the proper length of furrow is 

 200 feet, while on heavier soils 

 and flatter slopes the length 

 may be increased to 600 feet. 



The grade of the furrows va- 

 ries with the locality. In flat 

 valleys it is often impossible to 

 obtain a fall greater than 1 inch 

 in 100 feet, while on steep 

 slopes the fall may reach 20 

 inches in 100 feet. On ordinary soils a grade of 3 or 4 inches is 

 to be preferred, and where the fall exceeds from 8 to 10 inches in 

 100 feet the trees should be set out in such a way as to decrease 

 the slope of the furrows. 



The number of furrows in orchards depends on the age of the 

 trees, the space between the rows, the depth of furrow, and the 

 character of the soil. Nursery stock is irrigated by one or two 

 furrows and young trees by two, three, or four. A common spac- 

 ing for shallow furrows is z\ feet, while deeper furrows are made 

 3 or 4 feet apart. The general trend of orchard practice is toward 

 deep rather than shallow furrows, a depth of 8 inches being common. 



FlG. 65. Section of standpipe outlined 

 in Fig. 64 



