ALKALI RESISTANCE OF DATE PALM. 121 



which are irrigated with artesian water containing 0.64 per cent of 

 dissolved salts, and it is said that still more alkaline well water con- 

 taining 1 per cent of salts is used to irrigate date palms in some of the 

 other oases. Even the brine which seeps through the alkali soils and 

 runs off in the drains is used to water palms growing at lower levels, 

 and in some plantations no other water is available for irrigation (see 

 p. 98). The alkaline water from Lake Elsinore, which proved so 

 very disastrous to the orange orchards about Riverside, Cal., con- 

 tained only from 84 to 116 grains per gallon, whereas the water used 

 exclusively on the date plantations at Chegga, Algeria, contained 

 374 grains, and substracting gypsum, 250 grains per gallon of harmful 

 alkali. Water, such as that supplied from Lake Elsinore at its worst, 

 would be adapted perfectly to irrigate date palms. Even the intensely 

 brackish ground water under the Sal ton Basin, which lies some 50 feet 

 below the surface at Calexico and only about 30 feet below at Imperial, 

 though it contains some 0.4 to 0.6 per cent of dissolved salts, and 

 though it would prove fatal to most crop plants if brought up near 

 the surface by injudicious irrigation, would not necessarily injure the 

 date palm. Many plantations in the Sahara are irrigated with water 

 more alkaline than this. The chief danger to the date palm to be 

 apprehended from a rise of ground water is the suffocation of the 

 roots because of imperfect aeration of the water-logged subsoil. 



The immense superiority of the date palm over all ordinary crop 

 plants for culture in alkaline lands becomes evident when it is remem- 

 bered that all ordinary useful plants, such as wheat, corn, and alfalfa, 

 peach, orange, and prune trees, etc., are killed by as much as 0.5 or 0.6 

 per cent of alkali in the soil, a which amount is entirely without 

 influence on the date palm. The more resistant crop plants, such as 

 barley, sorghum, sugar beets, grapevines, olive trees, and possibly 

 pomegranate, jujube, and pistache trees, are able to withstand from 

 0.6 to 1 per cent of alkali; but these plants are easily injured by an 

 accumulation of the alkali at the surface, which is perfectly harmless 

 to the date palm. About the only crop plant which can withstand 

 considerably over 1 per cent of alkali is the Australian saltbush 

 (Atriplex semibaccata), and Qven this forage plant can not endure 

 nearly as much alkali as the date palm probably not half as much. 

 As noted on page 115, asparagus is able to endure much alkali, though 

 the limits of its resistance have not yet been determined. The date 

 palm is, then, the most resistant to alkali of all plants now known cap- 

 able of commercial culture in arid regions. 



See Means and Holmes, Circular No. 9, Bureau of Soils, U. S. Department of 

 Agriculture, 1902, and other publications of that Bureau. 



