35 



In discussing the analytical results of the first series of soil samples, 

 the amount of injury to the cane to be expected could be estimated on 

 the basis of the total amount of salts present, chlorine and bicarbonates 

 being the chief factors, since sulfates were found in small quantities only, 

 from 6 to 9% of the total. This manner of interpretation could be used 

 there, since, as stated before, the salts contained in the several samples 

 were present in about the same proportion in each. If in the present 

 series of analyses we should consider the total amount of salts to be 

 indicative of the injury to be expected, we would arrive at entirely 

 erroneous conclusions. In such a case No. 2 would be expected to grow 

 the worst cane, following nos. 1, 4, 3, and 5. The facts show that such is 

 not the case. Nor can the chlorine content alone be used as a criterion. 

 Sample No. 3 had .1% of chlorine, and the cane was dying; No. 1 had 

 .15% of chlorine, and the cane there was vigorous and healthy. 



A further examination of the table shows that the proportion of 

 bicarbonate to chlorine and to sulfate in any one sample is quite different 

 from that in the other samples so that we cannot draw conclusions in 

 the same way as we did in the first series of analyses. 



How are we then to interpret the figures of the table? Returning 

 again to what was said in the discussion of the first series of analyses, 

 chlorides and bicarbonates are about equally injurious while sulfates are 

 much less so. In fact, sulfates are not only less injurious, but, in mixtures 

 with other salts, even exert a protective effect, so that the other salts in 

 the presence of sulfates are less injurious. A good illustration of this 

 phenomenon is afforded by a case cited by Hilgard, concerning the 

 growth of sugar beets in salt land ( Hilgard 's "Soils", page 466) : Beets 

 were "good" where the sulfate (Glauber's salt) ranged up to 0.8%, with 

 .1 to .2% of common salt; but so soon as the latter rose above .2%, the 

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

 "good" again so soon as the common salt fell below 0.2%, although the 

 Glauber's salt increased. Investigations by Cameron have also shown 

 that sulfates, and more especially calcium sulfate counteract the injurious 

 effect of sodium and other soluble salts. As in the soils under investiga- 

 tion lime is present in considerable quantities, the sulfuric acid found in 

 the samples must first be combined with lime, forming calcium sulfate. 

 We shall see how markedly the protective influence of calcium sulfate is 

 shown in our samples. 



Beginning with No. 1, we found a vigorous, healthy cane with a 

 dark green foliage which in seven months had attained a height of six 

 feet. The average sum of chlorine and bicarbonic acid is lower than in 

 any other sample, viz. .234%, and the sulfuric acid, representing the 

 protective influence, is highest, .819%. 



At the next station the sum of bicarbonic acid and chlorine has 

 reached .45% and the sulfuric acid is slightly lower than in the first, 

 .678%. Corespondingly the cane was not as good as in No. 1. The leaves 



