THE EFFECTS OF ALKALI ON CITRUS TREES : 



BY W. P. KELLEY AND E. E. THOMAS 



INTRODUCTION 



It is generally believed that citrus trees are especially sensitive to 

 alkali. One of the best known investigations on the effect of alkali on 

 citrus was published by Loughridge in 1898. 1 In this paper it was 

 pointed out that orange trees may be severely injured by the use of 

 saline irrigation water. From studies on certain groves near Corona, 

 California, it was found that severe injury had been produced a.s a 

 result of irrigating with saline water from Lake Elsinore for a period 

 of from three to four years. 



Analysis of the water showed it to contain 917 parts per million 

 sodium chloride (common salt), 377 parts per million sodium sulfate 

 (glauber.salt), and 391 parts per million sodium carbonate (black 

 alkali). Loughridge concluded that the injury to the trees was due 

 directly to the corrosive action and puddling effect of the black alkali 

 and indirectly to the antiseptic action of the sodium chloride on the 

 bacterial processes of the soil. 



The effects were more pronounced in certain groves than in others. 

 Inherent differences in the soil apparently exerted an influence on the 

 depth to which the water penetrated and, therefore, caused the salts 

 to accumulate in greater quantities in the upper layers of the soil of 

 certain groves than of others. On the whole, the effects were roughly 

 proportional to the concentration of the alkali salts that had accumu- 

 lated in the zone occupied by the roots of the trees. 



The results of this investigation indicated that citrus trees are 

 quite sensitive to alkali, and that the length of time a given supply 

 of saline irrigation water may be used without producing injury 

 depends mainly on the rate the injurious constituents accumulate in 

 the layers of soil occupied by the roots of the trees. 



In 1900 Hilgard- pointed out that citrus trees are especially sensi- 

 tive to sodium chloride. He called attention to the previous work at 



* Paper Xo. 53, University of California, Graduate School of Tropical Agricul- 

 ture and Citrus Experiment Station, Kiverside, Calif. 



1 Effect of Alkali on Citrus Trees. Annual Keport, Calif. AT. Exp. Sta. 

 1897-8, pp. 99-113. 



2 Nature, Value and Utilization of Alkali Lands. Calif. Ar. Exp Sta Bull 

 128 (1900), p. 28. 



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