OVER-IRRIGATION AND ALKALI 381 



Machines and molds for lining farm ditches are on the 

 market and may be obtained at relatively small cost. 

 Pipes are often most desirable for the smaller ditches, 

 since they eliminate direct loss by evaporation, and also 

 the growth of grass or algae near the ditch banks. Smith 

 has shown that tile may be made of cement at prices so 

 low as to make the method available for the farm irri- 

 gation system. The good irrigation farmer should make 

 the ditches under his control as impervious as is possible. 



227. The economical use of water a remedy. The 

 common custom of allowing water to run hi irrigation 

 canals during the whole year, when it is really needed 

 only a few months of the year, is responsible for much 

 seepage and positive injury to the lower-lying lands. 

 Water, whether taken from reservoir or river, should be 

 allowed in the canals only during the seasons of the year 

 of actual use. Moreover, on the farm, it should be used 

 economically, in harmony with the principles already 

 elaborated in this volume. By the more economical use 

 of water in these two directions the danger of water-logging 

 will be greatly reduced. 



228. Drainage the final remedy. Even in the arid 

 region, where no irrigation is practised, there will be some 

 low-lying wet lands resulting from the natural rainfall 

 seeping through the soil from the highlands and the 

 river beds. When irrigation is established and practised, 

 even under the best conditions, the area of wet land will 

 be somewhat larger than it was before. Naturally, the 

 best and final remedy for this condition is underdrainage. 

 Underdrainage has been well tried out during the last 

 hundred years in Europe and in the eastern United States, 

 and has been found to be a great and helpful factor in 

 making agriculture successful. In spite of the apparent 



