THE DATE PALM COUNTRY 86 



may be taken as a practical limit for alkalinity; 

 if there is a layer of soil with less salt than this, one 

 may grow dates profitably, but if the soil at all depths 

 contains more than this, another location should be 

 found. Best results will be secured if the alkali does 

 not exceed 0.6%, and 3% may be conveniently taken 

 as a limit beyond which the palm will not grow. 



If the irrigating water is free from alkalinity, it 

 will, of course, help to counteract that of the soil. 

 On the other hand, if the water is brackish it is 

 essential to keep well within the limit of alkali resist- 

 ance in the soil, otherwise the combination of salty 

 soil and brackish water will be too much for the 

 palm, even though neither one were excessively 

 alkaline, taken by itself. Salt on the surface of the 

 ground is most conspicuous but does the least harm, 

 and one frequently sees palms flourishing in a soil 

 which is incrusted with alkali on the surface, so that it 

 looks as if covered with snow. In such cases it is 

 certain that there is fairly good soil underneath. The 

 so-called black alkali, consisting of carbonates of 

 sodium and potassium, is much more dangerous than 

 the more or less neutral chlorids, sulfates and nitrates 

 of sodium, potassium and magnesium, which go by 

 the name of white alkali. 



It need hardly be mentioned that young plants 

 are more affected by alkali than old ones, and that 

 seedlings will fail in a soil that yet might give good 

 results with adult palms. It is also to be noted that 

 some varieties of date are much more resistant to 

 alkali than others: Ghars and Zahidi are particularly 

 valuable in this respect. 



To sum up: one should investigate before he 

 begins, and should not try to grow varieties of dates 



