466 SOILS. 



from the surface to bottom water at seven feet depth. The land on 

 which these observations were made are apparently level to the eye, 

 though probably the alkali belts on which the sugar beets were " poor " 

 are slightly depressed swales. 



It will be noted that here the beets were " good " where the 

 sulfate (Glauber's salt) ranged up to .8%, with .10 to .20 of 

 common salt ; but that so soon as the latter rose above .20, the 

 beets were poor despite the low percentage of Glauber's salt; 

 then became " good " again so soon as the common salt fell 

 below .20%, although the Glauber's salt increased. 



TOLERANCE OF VARIOUS CROP PLANTS. 



The following table, compiled by Dr. R. H. Loughridge 

 mainly from his own observations, 1 gives the details of the 

 tolerance for various culture plants as ascertained at the several 

 experiment substations in California, as well as at other points 

 in that State and in Arizona where critical cases could be 

 found. It is thought preferable to investigate analytically such 

 cases in the field, rather than to attempt to obtain results from 

 small-scale experiments artificially arranged, in which sources 

 of error arising from evaporation and other causes are most 

 difficult to avoid. 



The table is so arranged as to show the maximum tolerance thus far 

 observed for each of the three single ingredients, as well as the maximum 

 of total salts found compatible with good growth. In view of the ex- 

 tremely variable proportions between the three chief ingredients found 

 in nature, this seems to be the only manner in which the observations 

 made can be intelligibly presented, until perhaps a great number of such 

 data shall enable us to evolve mathematical formula? expressing the 

 tolerance for the possible mixtures for each plant. For it is certain 

 that the tolerance-figures will be quite different in presence of other 

 salts, from those that would be obtained for each salt separately ; or for 

 the calculated mean of such separate determinations, proportionally 

 pro-rated. It must also be remembered that in all alkali soils, lime 

 carbonate is abundantly present, as is, nearly always, a greater or less 

 amount of the sulfate (gypsum). As already stated, according to the in- 

 vestigations of Cameron not only these compounds, but also calcium 

 chlorid, exert a protective influence against the injury to plant growth 

 from compounds of sodium and potassium. The figures here given can 

 1 Bulletins Nos. 128, 133 and 140, Calif. Expt. .Station. 



