NURSERY PRACTICE FOR PRAIRIE-PLAINS PLANTING 



63 



many feet per minute for a certain distance. Then the rate of advance 

 gradually slows down until a point is reached where little or no progress 

 can be noted. It is evident that the part of the tree row near the point 

 of diversion at the main ditch is then being overirrigated, whereas 

 the far end of the row will be getting little or no water. For sandy 

 loam soils, a carry of from 450 to 650 feet down a tree row should ordi- 

 narily produce good results. The distance may be increased some- 

 what on tighter soils. The exact distance on a given slope and for a 

 given head of water and type of soil can be determined only by 

 experience with the particular field in question. 



When rapid percolation interferes with the carrying of water the 

 full length of the rows, the best procedure is often to increase the 

 quantity of water entering each row. A second expedient is to plow 



SIDE SLOPES 1 TO 1 



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Figure 13.- — Common type of irrigation ditch used in nurseries, but not suitable 

 for use on slopes in excess of 18 inches per 100 feet. Bottom of ditch may range 

 from 12 to 16 inches. 



a shallow trench or run a canvas hose down one row, through which a 

 fairly large head of water may be carried to the far end of the field, 

 where it may be diverted to the rows not reached by the usual 

 method. 



Ditch construction is not a difficult problem, since the main and 

 lateral ditches used in nursery irrigation are relatively small. In 

 lighter soils, a plowed furrow may be used to make the line, after which 

 a V-shaped scraper or small ditching machine will suffice for the re- 

 mainder of the construction process. In heavier soils, it will be neces- 

 sary to plow the soil loose and then remove it with the blade ditcher. 

 In most instances, a ditch with a bottom width of 12 to 16 inches, a 

 depth of 12 inches, and side slopes of 1:1 will suffice to carry the 

 quantities needed in nurseries (fig. 13). 



Where the water must be carried down slopes in excess of 18 inches 

 per 100 feet to reach some particular area, ditches of the cross-section 

 mentioned above are likely to be damaged by erosion. If the slope 

 is short in length, the water can be conducted in a trough made of 

 1- x 12-inch plank; or a simple drop may be made with sand bags, which 

 can be moved from place to place at little cost and may be used to 

 advantage in many places to prevent erosive action of irrigation 

 water. 



