BULLETIN 318 THE EFFECTS OF ALKALI ON CITRUS TREES 309 



trees reach their usual size on soil that contains injurious amounts of 

 alkali. 



It has been found that orange trees affected by alkali are unusually 

 susceptible to injury from adverse climatic conditions. Hot winds 

 burn the- young leaves and frosts produce more serious injury than 

 with normal trees. Alkali injury is also accentuated by the lack of 

 care, such as improper tillage, the insufficient use of manure or other 

 fertilizers, and withholding irrigation, thereby allowing the soil 

 to become too dry. If the soil by allowed to dry out excessively, the 

 concentration of alkali in the soil moisture may become harmful, 

 while a more abundant supply of water would so dilute the salts 

 present as to reduce the concentration to a point where normal growth 

 could take place. 



THE EFFECTS OF IRRIGATION WATER 



Despite the wide publicity that has been given the subject of 

 irrigation waters and the many analyses that were published by 

 Hilgard in the reports of the California Station, our studies in the 

 different citrus districts suggested the desirability of making a survey 

 of the irrigation water in use at present. More than a thousand 

 samples have been analyzed. It lias been found that the vast majority 

 are practically free from alkali. Especially is this true of the water 

 that is drawn from points located near the large watersheds, such, for 

 example, as the Sierra Nevada and the San Bernardino mountains. 

 Usually the wells that are located near the course of streams that 

 originate in those mountains are also sufficiently pure. 



On the other hand, wells located at some distance from the large 

 watersheds and relatively large streams that themselves originate 

 directly in the mountains, show a wide range in composition. A con- 

 siderable number of such wells contain notable amounts of salts. 

 These are widely distributed over a considerable number of citrus dis- 

 tricts in several counties. In certain localities the dissolved salts are 

 predominantly chlorides, others sulfates and in still others bicarbon- 

 ates. A few wells have been found to contain large amounts of 

 nitrates. 



The results of this survey are, on the whole, in close agreement 

 with the published conclusion of Dr. Ililgard. We ([note from him 

 as follows : r> 



"The investigations made by the Station have shown that aside 

 from the frequently saline character of the well and even the artesian 



Calif. Ajjr. Exp. Sta. Bull. 128 (l!00), p. :il. 



