118 THE DATE PALM. 



Although the total alkali content of the soil to a depth of feet is 

 slightly greater at the Fougala station than at boring 133, the roots 

 of the date palm would reach a layer of subsoil containing only 0.38 

 per cent of alkali at Fougala, whereas in the Salton Basin station the 

 lowest amount of alkali is 0.61 per cent, or over one-half more than at 

 Fougala. Were the alkali at boring 133 to concentrate at the surface 

 in the same proportion as at Fougala, the lower subsoil would contain 

 something like 0.37 per cent of alkali. However, the soil at 5 and 6 

 feet in depth at boring 133 contains 0.58 per cent, which alkali con- 

 tent probably continues downward for many feet, so that in order to 

 bring about a diminution of the alkali content at any given depth it 

 is essential that the soil lying deeper is not wetted. Whether such an 

 operation can be carried out in practice is doubtful. 



The view outlined above, that the accumulation of alkali at the sur- 

 face may be beneficial to the date palm in some soils but that such 

 accumulation may be dangerous to the plant if dislocated by unusually 

 heavy rains, is confirmed by the following remarkable observation of 

 Vogel, made at Moorzook in Fezzan, in the interior of the Sahara 

 Desert: 



A heavy rain is considered a great disaster, as it destroys the houses that are built 

 out of mud, and also kills the date palms by dissolving the great quantities of salt 

 which are contained in the soil. For example, about twelve years ago [in 1843?] 

 about 12,000 date palms were destroyed in the vicinity of Moorzook by a rain which 

 lasted seven days. rt 



Moorzook is said to have no regular rainy season, though light 

 showers occur in autumn. There is an abundant supply of under- 

 ground water near the surface. Rohlfs says: "The palms do not 

 require artificial irrigation [in Fezzan], since the roots seem to reach 

 water everywhere." 6 Date palms are said not to be watered except 

 during the first six months after they are set out; Under these con- 

 ditions a great accumulation of alkali near the surface is to be expected, 

 and the disastrous result of a heavy rain in washing the alkali down to 

 the level of the roots is not surprising. 



This indifference of the date palm to surface accumulations of alkali 

 constitutes one of its greatest advantages over other crop plants for 

 culture on alkaline soils. 



RESISTANCE OP THE DATE PALM TO CHLORIDS. 



The date palm seems to be resistant to all kinds of alkali, with the 

 possible exception of the soluble carbonates, or black alkali. Common 

 salt and the other chlorids, including the very poisonous magnesium 

 chlorid so injurious to most cultivated plants, are resisted very well 



Vogel, Ed. In Petermann's Geogr. Mitth., 1855, p. 250. 



& Reise durch Nord-Afrika von Tripoli nach Kuka. In Petermann's Geogr. 

 Mitth., Ergiinzungsheft No. 25. 



