316 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION 



It is interesting to note in this connection that navel orange trees 

 arc being grown on one portion of each of these groves, and Valencia 

 oranges on another. In each case, the navels were injured in a 

 shorter period of time than the Valencias. In fact, some of the Valen- 

 cias of grove T, located in a portion of the field where the soil is six 

 or more feet deep, have not as yet been severely injured, but even that 

 portion of the Valencia trees located on shallow soil similar to the 

 navel area have been less severely injured than the navels. In grove 

 II, the Valtfncias were much less severely injured in 1918 than the 

 navels. It is important to state, however, that many of the Valencia 

 trees in the latter grove have shown seven; injury in 1919. These 

 facts, together with observations in other localities, indicate that 

 Valencia oranges are more resistant to alkali than navel orange trees. 

 But it must not be concluded that the former are highly tolerant of 

 alkali, for such is not the case. The use of irrigation water containing 

 alkali salts will ultimately produce injury to either variety, it being 

 mainly a matter of the length of time. 



A lemon grove located near San Diego has also been studied. The 

 trees are about sixteen years old and have been irrigated from the 

 time of planting with saline water No. 689. During the past two or 

 three years, a portion of the trees have shown signs of injury, many 

 of them severely so. Most of the older leaves throughout the grove 

 have turned yellow around the margins and brown at the tips. A 

 large proportion of the leaves have fallen in certain places, the smaller- 

 shoots have died and the economic value of some of the trees has been 

 greatly impaired. 



Referring again to the table of water analysis, it will be seen that 

 the irrigation water (table 1, No. 689) contains considerable amounts 

 of alkali salts, being composed in this case largely of sodium chloride. 

 Soil samples were drawn from this grove to a depth of two feet 

 and also from an adjacent unirrigated field. Their analyses are given 

 in table 10. In harmony with the results already discussed, it is shown 

 that the concentration of salts has been materially increased as a 

 result of irrigation. The unusually high soluble potassium content 

 of the first foot of the irrigated soil is especially noteworthy and is 

 probably due to the liberal use of fertilizers and manure. 



The irrigation waters discussed above contain relatively large 

 amounts of salts. Some of them contain amounts of alkali salts that 

 might reasonably have been expected to produce injury. Under the 

 conditions of soil and subsoil, as they exist in these groves, it would 

 have been surprising indeed to iind that, injury had not been produced 

 bv these waters. It is interesting in this connection that the effects 



