BULLETIN 318 THE EFFECTg OP ALKALI ON CITRUS TREKS 323 



THE EFFECTS OF SALINE IRRIGATION WATER AND N a NO : , ON THE 

 REACTION OF SOILS 



In view of the widespread belief tljat sodium carbonate (black 

 alkali) and sodium bicarbonate are the most toxic constituents that 

 occur in alkali soils and of the possibility that the injury to the groves 

 discussed above may have been due to, or at least associated with, 

 excessive alkalinity (Oil-ion concentration), the reaction of a con- 

 siderable number of these soils has been determined by means of the 

 hydrogen electrode. 



It has been found that the use of saline irrigation waters Nos. 119. 

 642 and 643, has not increased the alkalinity of the soil over and above 

 that occurring where good irrigation water has been applied. In each 

 case, the soil is distinctly alkaline in the chemical sense of the term, 

 but not appreciably more so where the saline water has been applied. 

 In the comparisons of unirrigated soil with soil that lias been irri- 

 gated with saline water, it has been found that in two cases, soils T 

 and Y, there appears to have been an appreciable increase in alkalinity 

 as a result of irrigation, while in the case of soil II, there has been 

 a decrease. 



In order to study the effects of sodium nitrate on soil alkalinity, 

 tests have been made on each of the control plots (B and M) that lie 

 adjacent to the sodium nitrate plot (II) . The results leave some doubt 

 whether the reaction has been materially changed as a result of apply- 

 ing sodium nitrate. It should be pointed out, however, that the soil 

 of each of these plots is distinctly alkaline and it does not follow from 

 these results that the application of sodium nitrate to an acid soil 

 might not tend to lower the acidity. 



A determination of the reaction of other soils not reported herein 

 has shown equally as high a degree of alkalinity (Oil-ion) where 

 healthy citrus trees are being grown, as in the severely injured groves. 

 We are inclined to conclude, therefore, that excessive alkalinity is not 

 the cause of the injury, either in the case of saline irrigation waters. 

 or where sodium nitrate has been applied as a fertilizer. Excessive 

 concentration of sodium as such, together with the relationships it 

 bears to the concentration of other constituents present, is probably 

 more fundamentally responsible for the injury. 



DISCUSSION 



The results of recent investigations establish the fact that some of 

 the irrigation waters in use at the present lime on the citrus groves of 

 California are highly charged with alkali; others contain somewhat 



DIVISION OF SUKrwnPKAL HORTICULTURE 

 COLLEGE OF AGRICULTURE 



