17 



and Demerara it has been found that an occasional flooding with sea water 

 or the application of sodium chloride in certain fields is quite beneficial. 

 This fact is explained by Prinsen Geerligs ( 1 ) on the ground that a 

 treatment with sodium chloride renders the potash, lime and magnesia 

 contained in the soil more available, as was proven by experiments made 

 by himself and also by studies made, independently, by Eckart ( 2 ). It 

 is also a well known fact of plant and animal physiology that certain 

 substances when applied in large doses, are toxic to plants and animals, 

 but have, when used in small quantities, quite the opposite effect and 

 rather act as stimulants. While it is thus true that sodium chloride in 

 small quantities may be quite beneficial in soils with low chlorine content 

 and with small percentages of available potash and lime, it is equally 

 true that there is a certain limit above which sodium chloride becomes 

 detrimental to the growth of cane. On the basis of many analyses 

 Maxwell arrived at the conclusion that in ordinary soils percentages of 

 sodium chloride exceeding 0.15% (0.09% of chlorine) will prevent the 

 normal growth of cane ( 3 ). In soils which are w 7 ell provided with nitrogen 

 the chlorine content may go higher than 0.15% of sodium chloride without 

 causing any harm. If the chlorine is combined mainly with calcium it 

 may also reach higher figures than 0.09%. Eckart concludes from the 

 analyses of several Hawaiian soils that "where the salt content of the 

 soil reaches over 0.1% (0.06% of chlorine) an injurious effect is produced 

 on the cane." ( 4 ). Figures on the tolerance of cane for other salts, like 

 sulfates, carbonates and bicarbonates are still lacking and carefully 

 controlled experiments will have to be made to find out how much of the 

 different salts, by themselves and in mixtures, the cane will stand without 

 harmful effects. In the meantime we shall have to content ourselves with 

 observations made with soils and canes in the field. A beginning in this 

 direction has already been made at this Station and these studies are 

 being continued. From the results obtained so far it seems that the limit 

 of endurance for sodium chloride in our mineral soils is about the 

 same as that found by Maxwell and Eckart in Hawaii ; but it also appears 

 that cane in its later stages of growth may stand much higher quantities 

 cf salt without visible injury. 



It has been said above that not only the growth of the cane is 

 affected by the presence of salts but that its composition is also largely 

 influenced by it, This is well shown by the results of field experiments 

 made at the Experiment Station of the Hawaiian Sugar Planters' As- 

 sociation. A comparison of two plots, one of them irrigated with 

 fresh water and the other with salt water containing 200 grains of salt 



[1J Intern. Sugar Journal, 1905. 



[2] Expt. Sta. of Hawaiian Sugar Planters' Assn., Eeport for 1902. 



[3] Office of Expt. Stations, Bull 90, p. 17. 



[4] Expt. Sta. of Hawaiian Sugar Planters' Assn. Special Bull. B, p. 51. 



