312 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



ably deep and free from hardpan. Throughout this district, the 

 soil is deficient in organic matter and nitrogen, the liberal application 

 of both of which is required for successful citrus culture. 



The orange trees are about twenty-four years old. A number of 

 these groves have been under close observation for a period of about 

 three years. A large portion of the trees irrigated with the saline 

 water have already been severely injured ; some of them are almost 

 dead and a large portion unprofitable. The degree of the injury is 

 much more pronounced at the present time (1919) than it was in 1917, 

 while in 1916 injurious effects had scarcely begun to appear. The 

 accompanying photographs, plates 1 and 2, illustrate the effects and 

 show the appearance of the trees in the spring of 1919. They show 

 the striking contrast between the effects of good irrigation water and 

 water containing alkali salts. In portions of the groves where the 

 saline water has been applied, excessive defoliation has taken place 

 several times. Many of the smaller branches have died and the new 

 foliage has shown excessive mottle leaf. 



Soil samples from a number of these groves have been analyzed. 

 Some of the results are submitted in tables 2, 3, 4, 5 and 6. The data 

 show that the total soluble salt content of the soil and the amounts of 

 certain individual constituents have been greatly increased as a result 

 of irrigating with saline water. The chlorine and sodium content have 

 been increased to the greatest extent. Other constituents have also 

 been augmented considerably. 



The data show a direct relationship between the salt content of the 

 soil and the composition of the irrigation water, and the condition of 

 the orange trees is positively correlated with the salt content. It is 

 evident, however, that orange trees are extremely sensitive. The total 

 concentration of soluble matter in a number of the samples was not 

 more than 0.10 per cent (1000 parts per million), even where the trees 

 have been severely injured. The soil samples represent composite 

 mixtures of a considerable number of cores, taken at random from the 

 spaces between the trees where the irrigation waters have been applied. 

 Under the prevailing system of furrow irrigation soluble salts tend to 

 accumulate in greatest amounts between the irrigation furrows and in 

 the unirrigated spaces between the trees, owing to lateral movement. 

 Consequently, higher concentrations probably occur in localized areas 

 between the furrows, than were found in the samples analyzed. While 

 orange trees are more sensitive to alkali than many other crops, it is 

 reasonably certain that with the continued use of these waters the 

 soil will become so heavily charged with alkali as to impair its useful- 

 ness for the more resistant crops. 



