BULLETIN 318 THE EFFECTS OF ALKALI ON emirs TREES 307 



It is commonly held that alkali injury is mainly, if not entirely, 

 due to excessive concentration as such. In the course of this work, 

 it has become evident, however, that injury may be produced under 

 certain conditions where the total concentration is relatively low. 

 The data obtained in a study of this phase of the subject afford the 

 basis for an interesting hypothesis which will be presented elsewhere 

 and further work is in progress. The discussion in this bulletin will 

 be confined mainly to the effects of excessive concentration. 



As this work has progressed, it has become increasingly evident 

 that many of the citrus growers of California have not sufficiently 

 grasped the significance of alkali in citrus culture. Especially is this 

 true in regard to the bearings of impure irrigation water on the 

 accumulation of alkali in the soil. Fortunately, a large percentage 

 of the citrus soils was free from alkali previous to the introduction of 

 irrigation and very much of it still remains free. There are con- 

 siderable areas located in several districts, however, where harmful 

 amounts of alkali have accumulated as a result of applying saline 

 irrigation water and still other areas, not yet seriously injured, where 

 alkali is accumulating at present as a result of orchard practices which, 

 if continued, will ultimately produce injury. 



This bulletin will be devoted to a discussion of results obtained in 

 connection with a study of a considerable number of citrus groves in 

 different localities in California. The investigations reported herein 

 deal mainly with the effects of alkali rather than with means of over- 

 coming the injury. It is undoubtedly a matter of practical importance 

 for citrus growers to be able to r< cognize the effects of alkali and 

 especially to appreciate the relationships between existing orchard 

 practices and the accumulation of alkali. 



Unfortunately, the present state of knowledge does not yet make 

 it possible to predict with as great a degree of certainty as is desirable, 

 what the effects of a given amount of alkali will be, or how long a given 

 saline irrigation water may be applied before producing injury. The 

 extreme variability of soils and the inadequacy of knowledge concern- 

 ing the fundamental relationships between salts and soils, and salts 

 and plant growth, add to the difficulty. Despite these facts, informa- 

 tion of some practical importance has been obtained. 



The investigations reported herein should be looked upon as being 

 preliminary to a study of methods of combating alkali in citrus 

 groves. It is hoped that fhis discussion will enable citrus growers to 

 recognize the effects of alkali, to appreciate the seriousness of alkali 

 in citrus culture, to apprehend more clearly the relationships between 

 irrigation and the accumulation of alkali, and to see that the applica- 



DIVl&ON OF SUblROPICAl HORTICULTURE 



COlUGt OF AGRICULTURE 



btRKlY. CALIFORNIA 



