17 



DRAINAGE 



Without natural or artificial drainage, alkali is the inevitable 

 consequence of irrigation wherever the evaporation from the soil is 

 greater than the rainfall. "Irrigation without proper provision for 

 drainage has, in the past, in very many cases, been the cause of 

 abandonment of lands once abundantly fruitful."* 



Without stopping to go into the matter exhaustively, it may be said 

 in general, that those lands most likely to be brought under irrigation 

 are the areas which usually lack good natural drainage. In humid 

 sections the water table may be within three or even two feet of the 

 surface without injurious results. In arid sections the water table 

 should be not nearer than five feet from the surface, while a depth 

 of six or more feet is desirable. This is due to the deeper feeding area 

 of the roots of plants in arid climates as well as greater danger from 

 alkali where the water table is near the surface. No prediction can 

 be made as to the length of time which will elapse before alkali will 

 appear under irrigation. Clay lands usually suffer sooner than sandy 

 ones. There are areas that have been irrigated for more than twenty- 

 five years which do not yet show the need of under drainage. The 

 purpose of this paragraph is merely to warn purchasers of irrigated 

 land that they may be required to add to the purchase price the cost 

 of tile drainage. A complete system of tile drainage may cost as much 

 as forty dollars per acre, while it is possible that sufficient drainage 

 may be afforded in other cases at a cost not to exceed ten dollars 

 per acre. 



Excellent opportunities exist today for the purchase and reclama- 

 tion by tile drainage of lands that have "gone bad" under irrigation. 

 The intending purchaser should be cautioned, however to try to 

 reclaim only lands which are known to have been fertile. Lands which 

 have never been known to have grown profitable crops may well be 

 avoided in the present state of our knowledge. 



GOOD AND BAD LANDS 



The goodness or badness of land is largely in relation to the crop 

 it is intended to grow. Thus there are soils excellently adapted to 

 olives which will return poor yields of wheat or barley. There are 

 vast areas in California well adapted to grains and alfalfa, on which 

 potatoes cannot be grown economically because of the character of 

 the soil, and on which oranges and lemons cannot be grown on account 



* See article by Dr. Hilgard, entitled "Alkali Lands Irrigation and Drainage in Their 

 Mutual Relation," in the Report of the California Agricultural Experiment Station for the 

 year 1890. 



