49, BULLETIN 339, U. S. DEPARTMENT OF AGRICULTURE. 
LENGTH OF’ RUN. 
Water never should be flooded too far between cross ditches on any 
crop or on any class of soil. An even application of water to all parts 
of a field is highly desirable but is very difficult to secure even with 
the best of systefms in use. Where water is run too far between 
cross ditches there is either oversaturation and deep percolation loss 
on the upper end near the supply ditch, or insufficient absorption at 
the lower end near the waste ditch. This is particularly true with 
soils which absorb water readily. Other things bemg equal, water 
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Fig. 12.—Effect of length of ran upon amount required perapplication. (Based upon results from 20 
different plots of porous soil.) 
should be flooded shorter distances on porous soils than on the more 
impervious soils. Experiments conducted upon 20 plots of very por- 
ous soil in the vicinity of Rigby, Idaho, have demonstrated that a 
very great saving of water may be made by flooding shorter distances 
than is usual, and it is thought that a preparation of the land into 
narrower, shorter borders, and the use of larger heads would have 
resulted in a still greater saving. The curve in figure 12 is self- 
explanatory and clearly illustrates the great saving of water which 
may be made on porous soils similar to those near Rigby (PI. II, fig. 
2) by flooding water shorter distances. 
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