202 SOIL CONDITIONS AND PLANT GROWTH 



showed increases for autumn applications but decreases for 

 spring dressings (140^). 



Table LV. — Effect of Dextrose and Sucrose on the Productiveness 

 AND Nitrogen Content of the Soil. Koch (1516). 



Increased yields of sugar cane have followed the applica- 

 tion of molasses to soils at the Station Agronomique and on 

 Mr, Ebbels' estate ^ in Mauritius, where the residual effect is 

 well shown, and also in Antigua.^ Peck in Hawaii, on the 

 other hand, observed marked losses of nitrate, as also did 

 Harrison in British Guiana.^ 



An increase in crop following the application of sugar or 

 starch to the soil is not evidence of nitrogen fixation, but 

 might equally well be adduced to show that sugar and its 

 decomposition products are direct plant nutrients. Only 

 when an actual gain in nitrogen is demonstrated by analysis 

 does the proof become satisfactory. As a practicable scheme 

 the addition of sugar to the soil would be out of the question 

 for field work. Beijerinck (15) has shown, however, that 

 certain compounds producible in the decomposition of cellulose 

 also serve as sources of energy to azotobacter, and Pringsheim 

 (232) found that the same holds true for Clostridium also. 



Hutchinson (140^) has shown that leaves, stubble, etc., 



^ See The Agricultural News, 1908, vii., 227; 1910, ix., 339; and 1911, x., 

 179. 



^ See Manurial Experiments with Sugar Cane in the Leeward Islands, 1908-09 

 and 1909-10. (Pamphlets 64 and 68, West Indian Department of Agriculture.) 



2 West India Bull., 1913, 13, 136. This contains an interesting discussion 

 on the losses of nitrogen from soil. 



