ALKALI RESISTANCE OF DATE PALM. 117 



the very important peculiarity of being able to withstand large amounts 

 of alkali at the surface of the ground without the crown being injured 

 thereby. Probably this is to be explained by the fact that, like other 

 palms, the date tree has no bark and no delicate cambium layer just 

 beneath; a date palm may be cut all about without dying when an ordi- 

 nary fruit tree so girdled would perish. 



In consequence of the ability of the date palm to endure great 

 accumulations of alkali at the surface of the ground, the "rise of 

 alkali" from the subsoil, so dreaded by growers of other crops, is often 

 not at all dangerous to this plant and may even be advantageous in 

 some conditions, provided thereby the alkali content of the subsoil in 

 which the feeding roots extend is reduced. It is conceivable that in the 

 Salton Basin, California, where, in consequence of the very slight rain- 

 fall, the alkali is often very uniformly distributed throughout the soil 

 to great depths, it may prove desirable to draw the alkali to the sur- 

 face rather than to try to wash it down beyond the reach of the roots 

 at the risk of raising the level of the ground water and suffocating 

 the roots. Once accumulated at the surface, the alkali could be largely 

 removed, as suggested by Professor Hilgard, by scraping together 

 the surface crust and carrying it off the field. The difficulty is that if 

 by judicious irrigation the alkali should be brought to the surface 

 from the subsoil at a depth of, say, 4 to 6 feet, there is always danger 

 that a subsequent irrigation, especially if followed by an exceptionally 

 heavy shower, would bring up alkali from still deeper layers of the 

 subsoil and counteract the beneficial influence of the previous manipula- 

 tion. The theoretical advantage of bringing about a rise of alkali is 

 shown by the following comparison of a Saharan soil with one from 

 the Salton Basin. In the Salton Basin, at boring 133, about 5 miles 

 north of Imperial (Means and Holmes, Circular 9, Bureau of Soils), the 

 alkali is, as usual in this region, rather evenly distributed throughout 

 the soil. In the Sahara, at Fougala, Algeria (station No. 2), the 

 alkali was largely accumulated at the surface, doubtless in part because 

 of three years' irrigation, but also because the rainfall in this portion 

 of the Sahara Desert is much greater than in the Salton Basin. The 

 following table shows the distribution of the alkali at these two points: 



TABLE 45. Distribution of alkali at different depths in the Sahara and in the Salton Basin. 

 [Alkali expressed in percentage of weight of soil.] 



