78 THE DATE PALM. 



the date palm would be able to grow as well as in the Sahara oasis, since the irrigat- 

 ing water here is of better quality than at Biskra." 



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



In proceeding west from Biskra one traverses the so-called Western Zab, & which 

 is first seen beyond a low mountain range, the Djebel Mendjenaib, adjoining Biskra 

 on the west. The Western Zab, or more accurately, the Zab Dahri (Map, PI. II, 

 p. 76, and PL XV), is a flat plain, 120 to 172 meters above sea level, which 

 slopes gently to the south or southeast. To the north the plain is limited by the 

 foothills of the Atlas Mountains, which rise rather abruptly. Throughout the 

 Western Zab, at least along the route followed between Biskra and Fougala (see map, 

 PL II), there are practically no surface indications of water, the vegetation being 

 very scanty, consisting mostly of the "Zeita" bush (Limoniastrum guyonianum), 

 which usually indicates the presence of much gypsum in the soil where it grows 

 (see Yearbook 1900, PL LIX, fig. 5). In extremely alkaline spots where chlorids 

 predominate the Zeita disappears, and is replaced by saltbushes (Atriplex), sam- 

 phires (Salicornia), etc. 



There occur throughout the Western Zab occasional large springs which are used 

 to irrigate many oases situated at a somewhat lower level to the southward. Begin- 

 ning at Farfar there is seen a most characteristic and most curious system of date 

 culture. The young date offshoots are planted at the bottom of pits about six 

 feet square, and from 4 to 8 feet deep (PL XV, fig 1). An inspection of a freshly 

 made ditch, or "bir," as it is called by the Arabs, shows that the ditch is just deep 

 enough to penetrate an impervious hardpan, composed of marl and gypsum. Below 

 this stratum water is found and the palms are so planted that their roots can easily 

 penetrate to the water level, and after once getting established they are able to grow 

 without being irrigated from the surface. As the palms grow older the ditches are 

 slowly filled up, the palms in the meantime sprouting forth roots all along the lower 

 part of the trunk. In some cases very old trees are seen to be banked up instead of 

 being planted in ditches (PL XIV, fig. 1). Curiously enough the trees planted in 

 such pits are often irrigated, although their roots are in contact with water. As will 

 be shown later on, this is doubtless done in order to aerate the subsoil and to wash 

 out the alkali, which would otherwise be left at the surface by the evaporation of 

 the moisture brought to the surface by capillary attraction. When irrigated, there 

 is of course perfect drainage through the bottom of the "bir" to a practically fixed 

 water level below. 



At Fougala a French company purchased an entire oasis containing thousands of 

 old bearing date palms, and has made in addition extensive new plantations. This 

 property comprised in 1900 some 263 hectares and contained about 18,000 bearing 

 date palms and 6,000 young trees not yet in bearing. On this property irrigation 

 has been practiced on an extensive scale, although the older palms were grown by 

 planting in pits as previously described, and were irrigated when young by the Arabic 

 method, namely, by raising water from shallow wells by means of buckets attached 

 to sweeps ( ' ' kitara " ) c (PL XIV, fig. 2) . The wells on this property are from 9 to 12 

 feet deep and are from 6 to 8 feet square. They yield about 35 gallons per minute, 

 for some three hours, by which time the water is usually exhausted. These sweeps 

 are run at this rate by a single Arab, although on some wells there are double sweeps, 

 and then two Arabs work side by side. The water from such wells is poured into 

 a large receptacle called "jabia," from which it flows into irrigation ditches. In 



o Biskra water contains from 0.075 to 0.235 per cent of alkali and is worst in sum- 

 mer. (See p. 76. ) Colorado Kiver water used to irrigate the Salton Basin contains 

 from about 0.021 to 0.125 percent of salts and is best in quality in midsummer, when 

 the flood occurs. 



& Marked Zibane in the map, PL II, p. 76. 



c See also Yearbook 1900, PL LXI, fig. 6. 



