THE BEET-SUGAR INDUSTRY IN 1920. 25 



Seepage from ditches. — It is sometimes necessary to construct 

 irrigating ditches higher than the surrounding area, to carry the 

 water across low places or to carry it long distances. It is very 

 common for the water to seep through the ditch bank in such cases 

 and to saturate the surrounding fields, especially if the soil in those 

 fields has a high water-holding capacity. Ditches constructed of 

 clay or other close-textured material allow less seepage than ditches 

 constructed of sandy or other porous material. In the case of 

 sandy ditches the holding capacity may be increased very greatly 

 by oiling the surface of the ditch with crude oil ; this can be applied 

 economically only in those localities not far removed from the source 

 of oil supply. Where the oil is available it may be spread over 

 the inner surface of the ditch when the ditch is empty and should 

 be allowed to soak into the soil before the water is turned into the 

 ditch. A second or even a third application of the oil will improve 

 the condition of the ditch. Ditches treated in this manner will 

 carry water with almost no seepage, and when the work is done 

 properly the oiled surface will frequently last for several years. 

 If the oil is spread over the ditch bank, weed growth will be pre- 

 vented, or at least decidedly retarded. There is always some seep- 

 age from the ordinary untreated earth ditch, and the amount of 

 damage clone by this seepage will depend upon the nature of the 

 ditch and the soil of the adjacent fields. The seeped areas may 

 sometimes be rendered tillable by drainage. 



Seepage from earth reservoirs. — The area of land damaged by 

 seepage from earth reservoirs is less than that from ditches, but 

 the total is considerable and is usually progressive; that is, a small 

 area first appears to be water-logged and this gradually increases 

 from year to year until large areas involving fields and sometimes 

 entire farms are destroyed. Seepage from reservoirs depends upon 

 the construction of the reservoir and upon the nature of the sur- 

 rounding country. Reservoirs are sometimes constructed in moun- 

 tainous areas for the purpose of catching and storing flood waters 

 due to melting snows. Generally the location of these reservoirs is 

 such that no tillable soil is injured through seepage; the only loss 

 in such cases is caused by the quantity of water which seeps away 

 and becomes unavailable for irrigation purposes. In other instances 

 reservoirs are constructed of cement, which is nearly impervious to 

 water, and consequently little or no loss from seepage results. The 

 serious injury due to seepage from reservoirs takes place in those 

 localities in which the reservoirs are constructed entirely or in part 

 of earth and in which the surrounding country is composed of tillable 

 land; in such cases the loss due to seepage is sometimes of con- 

 siderable importance. 



Alkali. — As already indicated, one of the serious results of seepage 

 is the accumulation of alkali in the surface soil. In such cases 



