76 



THE DATE PALM. 



The very unusual ability of the date palm to withstand alkali is of 

 the utmost importance, since it permits it to be grown profitably in 

 soils unfit for any other paying crop and where ordinary vegetation 

 can not grow at all. The date palm is also of great value in aiding in 

 the reclamation of alkaline lands; for once planted to dates and reg- 

 ularly irrigated the soil improves by a washing out of the alkali if the 

 irrigation water is of good quality and if drainage facilities exist. The 

 importance of the alkali-resisting power of this plant is so great that 

 the results of the examination into the alkali conditions in the Algerian 

 Sahara are given in detail, as they constitute the most trustworthy 

 evidence so far in existence as to the amount of alkali the date palm 

 can stand without injury. 



ALKALI CONDITIONS IN RELATION TO DATE CULTURE AT BISKRA, ALGERIA. 



The first important oasis planted to date palms seen in entering the Sahara by 

 the railway is at El Kantara (see map, PI. II), where a narrow gorge separates the 

 Algerian high plateau from the Sahara, and in a few moments the train passes from one 

 region to the other. At El Kantara, however, the date palm is chiefly valuable in 

 furnishing a shelter and partial shade to other fruit trees, and it is at Biskra that the 

 date palm is first seen under conditions permitting its best growth. This oasis con- 

 tained some 95,000 palms in 1882, and now has a total of about 100,000 bearing 

 date palms. The two near-by oases of Filiache and Chetma contain 35,000 more. 

 Biskra is situated in a plain near the west bank of the Biskra River. The irrigation 

 water is furnished by large springs, situated in the bed of the river, which yield 

 about 13,000 liters, or 3,434 gallons, per minute. This water has been analyzed fre^ 

 quently, with fairly concordant results, the content of dissolved salts being given 

 as follows by various chemists: Vatonne, 0.216 per cent; Buvry, 0.2236 per cent; 

 Lahache, 0.226 per cent; Moissonnier, 0.2346 per cent. 



The detailed analyses by Moissonnier and Buvry are as follows: 



TABLE 11. Composition (in percentage, by weight] of spring water used for irrigating 



the oasis of Biskra, Algeria. 



1 Moissonnier, Recueil de mem. de medicine mil., 3 ser., vol. 31, pp. 260-267. 



2 Buvry, Zeitschrft. f. allgem. Erdkunde, N. F., vol. 4, p. 200. Vide Fischer, Die Dattelpalme, p. 41. 



In winter, when there is a flow of water in the Biskra River, the water in the irri- 

 gating canals may contain as low as 0.075 per cent of dissolved salts, largely gypsum 

 (0.0437 per cent), according to Moissonnier. 



The very good quality of the water in winter, together with the shortage of water 

 in summer there being only 0.1 liter per tree per minute when 0.3 is needed (see 

 p. 45) favors the practice of winter and spring irrigation commonly followed in this 



An analysis of the river water mixed with the spring water after a rainstorm in 

 April, 1880, as reported by Holland, showed only 0.04 per cent of salts, nearly half 

 calcium carbonate (0.01852 per cent). 



