290 IRRIGATION PRACTICE 



furrows. Many soils "wash" easily, and if connections 

 are made with the main supply ditch by simply hoeing out 

 a small opening, the water is likely to make the opening 

 larger, or by shifting, even to close it, so that the water 

 does not for any length of time flow down the furrows as 

 intended by the irrigator. In many sugar beet fields and 

 orchards, small boxes, made of lath or lath-like boards, 

 about an inch square on the ends and 24 to 30 inches long, 

 are placed at the head of each furrow-opening, connecting 

 the furrow with the head supply ditch, and establishing a 

 permanent opening into each furrow, not easily disturbed 

 by the moving water. These boxes can be placed a little 

 higher or lower with very little effort, so that practically 

 the same quantity of water may enter each furrow. With 

 devices of this kind it is possible for one man to irrigate 

 a very large tract in a very short time. 



Roeding determined the relative yields obtained when 

 the same quantity of water was applied to a sugar beet 

 field by the open furrow and by the lath-box furrow. When 

 lath boxes were used to carry the water into the furrows, 

 thus providing a slower and more regulated flow, 16.47 

 tons of beets were produced to the acre. When the furrow 

 opened directly through the earth into the supply ditch, 

 making it difficult to control the quantity and even dis- 

 tribution of water, the yield of beets per acre fell to 13.72 

 tons. This emphasizes the value of an even distribution 

 of water over the sugar beet field, and naturally over 

 fields of any other crop. The sub-irrigation of sugar beets 

 has been found feasible only in a few localities where the 

 lands are naturally sub-irrigated. It has not been found 

 profitable to install subterranean channels for water, with 

 outlets at various intervals, for irrigation purposes. 



176. Time to irrigate sugar beets. The beet crop is 



