342 Annual Report Agricultural Experiment Station 



Mesa. Mechanical analyses and tests of water holding capacities 

 are being made, and parallel pot cultures using inoculated legumes 

 are also included in the investigation. In cooperation with the 

 Horticulturist a series of samples of citrus fruit from the old Blais- 

 dell orchard on the Yuma Mesa have been analyzed with a view to 

 showing their early maturing and other qualities. The details of 

 these several lines of investigation will be found in the report of 

 the commission to the Project Manager of the U. S. Reclamation 

 Service at Yuma. This report, which is a joint report from the 

 three departments concerned will be published as a bulletin by the 

 Experiment Station and is here referred to as forming a part of 

 the Chemist's annual report. 



RESISTANCE OF CROPS TO ALKALI 



A series of soil analyses illustrating the resistance of cotton 

 and other crops to alkali under field conditions have accumulated 

 in the laboratory and are given in Table XIX. 



An inspection of Table XIX reveals the extreme difficulty of 

 attempting to establish limits of tolerance for alkali under field con- 

 ditions. Possible reasons may be oft'ered for some of the dis- 

 crepancies. First should be mentioned the difficulty of getting 

 soil samples that really represent the conditions under which the 

 plants are growing. The surface crust is always very alkaline and 

 should not enter into the sample in greater relative proportion than 

 it occurs. The roots of the plants may be drawing on other zones 

 than the one sampled, alkali being known to vary abruptly with 

 depth. In cultivated fields the variation in concentration also varies 

 greatly within a few feet. The mechanical composition of the soil 

 undoubtedly has much to do with alkali tolerance. In the case of 

 black alkali dissolved organic matter possibly may be poisonous. 

 One salt also influences the effect of another. Water soluble salts 

 due to calcium sulphate are harmless, but calcium chloride or 

 soluble magnesium salts are harmful forms of white alkali. 



The soil 6819 carries excessive amounts of soluble salts, mostly 

 Swdium chloride, but it was said good crops were produced the 

 previous year, and the land had again been prepared for planting. 

 The sample analyzed was moist subsurface when collected. Dry 

 surface clods with capillary contact ran much higher in soluble salt. 

 The high tolerance in this case may be explained by the subirriga- 

 tion which kept the soil constantly wet. 



Barlev soils 682v3 and 6824 show the best growth in the case of 



