42 



BULLETIN 339, IT. 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 systems 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 being equal, water 



At 



\ 



% 



\ 



X 



























































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































zoo -?ao 6ao aao /eeo /zao /&o S6oa /&<x> &>ee jszoa *gtv *saa &st» 



Fig. 12.— EfFect of length of ran upon amount required per application. (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 (PL II, fig. 

 2) by flooding water shorter distances. 



