478 SOILS. 



lemqn trees are even more sensitive to common salt than 

 oranges, since a total content of 8,000 pounds per acre, about 

 one-third of which was common salt, seemed to render the 

 trees wholly unprofitable. 



In view of these facts, showing that common salt is the por- 

 tion of alkali by far most injurious to citrus trees, great care 

 should be taken in the use of irrigation waters to exclude those 

 charged with that compound ; and also to avoid locating citrus 

 orchards on land already impregnated with common salt. 



The olive tree, as the table shows, is among the most re- 

 sistant to alkali salts, approaching the grape in this respect. 

 This might have been anticipated from its extended culture in 

 the arid regions of the old world, including Palestine and 

 northern Africa, where alkali lands abound. It is probable 

 that the figure given in the table does not yet show the extreme 

 limit of its endurance. 



California experience with the date palm, as the table shows, 

 credits it with an endurance not exceeding 8320 pounds of 

 total salts. This is doubtless an underestimate, for in the 

 Sahara desert and Egypt it is credited with being the culture 

 which will succeed in stronger alkali than any other cultural 

 plant ; and, according to Mr. Means of the United States De- 

 partment of Agriculture, it is sometimes irrigated with water 

 containing as much as 200 grains of salts per gallon. It should 

 be remembered, however, that these trees always grow in very 

 sandy lands ; and in the desert regions it is often grown below 

 the surface of the ground, so as to render it wholly independ- 

 ent of the alkali accumulations on the surface. The extreme 

 limit of its endurance must therefore remain in doubt until 

 more extended experiments have made more definite data 

 available. 



Deciduous OrcJiard Trees. 



Among deciduous orchard trees, strangely enough, the 

 almond stands alongside of the fig in alkali-resistance, as indi- 

 cated in the table. The pcacJi seems to be much more sensitive, 

 ranking near the apricot and prune, whose tolerance is less 

 than half as high. That the pear and apple, generally counted 

 among the more northern fruits in the humid region, should 

 excel these stone fruits in endurance of alkali, is rather unex- 



