BULLETIN 318 TIIK AFFECTS OF ALKALI ox CITKCS TREES 327 



chlorotic. More or less mottle leaf may also occur. Lemon trees are 

 apparently injured by lesser amounts of alkali than oranges. 



On the whole, the observations and conclusions of Ililgard and 

 Loughridge have been strikingly confirmed. It has again been shown 

 that citrus trees are quite sensitive to alkali and especially to sodium 

 chloride. It is a matter of practical importance for citrus growers 

 to recognize this fact, for sodium chloride is the one constituent most 

 commonly found in irrigation waters that are drawn from wells in 

 the citrus sections of California. 



As for the treatment of the injured groves, nothing more than the 

 most general suggestion can be offered at present. Where saline irri- 

 gation water is being applied, the first consideration should be to 

 secure an adequate supply of pure water. In fact, so long as the 

 application of saline water be continued, it will be difficult to over- 

 come the harmful effects by any method that may be devised. 



As suggested by Forbes" an occasional flooding may improve the 

 conditions, by leaching the salts below the reach of the roots, but 

 before flooding be undertaken, the irrigator should assure himself 

 that the subsoil is of such character as will permit deep penetration 

 of the water and allow it to drain away. Otherwise, his efforts will 

 be wasted. After the salts have been washed down below, the soil 

 should be thoroughly cultivated in order to reduce evaporation and 

 thereby check the rise of salts. 



Where saline water is the only irrigation supply that can possibly 

 be obtained, it may be found desirable, in some cases at least, to dis- 

 continue the furrow system of irrigation entirely and adopt some form 

 of basin or flooding irrigation instead. By that means, the tendency 

 will be to leach the salts down into the subsoil and possibly below the 

 reach of citrus roots. The success of such a scheme will depend largely 

 on the nature of the subsoil drainage and the thoroughness with which 

 it is executed. In addition, the leaching effects of the winter rains 

 should be taken advantage of to the greatest extent possible. As a 

 means to this end, the soil should be put into such condition previous 

 to the rainy season, as will prevent surface run-off and enable the 

 rain water to penetrate deeply. 



It should be borne in mind, however, that alkali salts are being 

 driven down into the subsoil and that there is a constant danger of 

 the salts rising up around the roots. Furthermore, the continued 

 addition of such large amounts of salts as occur in some of the irriga- 

 tion waters, will materiallv increase the salt content of the natural 



Ariz. \gr. Kxj>. Sta. Bull. 44 (1!02\ pp. 1<>7 170. 



