250 THE IRRIGATION AGE, 



from heat, which would be apt to destroy them in spite of the fre- 

 quent use of water alone. This recourse takes the place of mulching 

 and sprinkling and is vastly better for a hot, arid locality. The 

 sprinkled water flies off from the mulch with great rapidity and much 

 water is used with little benefit to the plant, while the filling of the 

 depressed bed from the ditch and spreading the water through and 

 under "the mulch is very economical of water and of most direct ad- 

 vantage to the plant. 



For the hot, dry season of the year, in places where there is no 

 danger of supersaturating the soil, the depressed bed is available for 

 all kinds of vegetables and small fruits and flowers, ani the use of 

 this system is really the secret of success in growing them in some 

 regions. 



It is quite widely employed also by market gardeners and others, 

 even where heat is not excessive, bnt where a light, sandy soil pre- 

 dominates. A prominent example of this is in the sand hills south of 

 San Francisco, where the vegetable growers, who are largely natives 

 of the Mediterranean countries, have transformed large areas of hill- 

 sides into terraces and on these have arranged depressed beds, chiefly 

 of quite small areas, and are growing large quantities of garden 

 truck. The water is raised by windmills and pumps from wells in the 

 low places and delivered into small flumes which run from the wind- 

 mill towers to the opposite hillsides, supported by very light, high 

 trestles. The water, after supplying the highest terrace, is conveyed 

 most ingeniously by troughs or small ditches from terrace to terrace 

 until all the beds have been filled. The terraces are so narrow and 

 the beds on them so small and irregular in shape that depressing 

 them and filling them from time to time seems about the only avail- 

 able way to make use of such little corners of leachy soil. The sys- 

 tem calls for an immense amount of hard handwork, but the Medi- 

 terranean immigrant seems born to it. 



DITCH-BANK IRRIGATION. 



A simple form of depressed-bed irrigation, and one which is read- 

 ily available for home garden work in the arid region, may be called 

 "ditch-bank irrigation." It aims to use the water percolating from a 

 raised ditch, which will moisten the slope of the bank and the soil for 

 a certain distance outward from its base. Its prototype is perhaps 

 the old permanent ditch of the Spanish settlers, which was opened 

 out from a stream on a grade favoring a slow flow, and whatever land 

 on each side was thus moistened was used for a few beans, onions, and 

 peppers, which were about the only vegetables those settlers required. 

 In the depressed- bed system the banks of the water-carrying levees 

 are usually set full of quickly maturing vegetables. 



Ditch-bank irrigation consists in a sort of a combination of the 



