vii.] CARBOHYDRATES^ NITROGEN FIXATION 215 



incubator for a month, in order to complete the oxidation 

 of the sugar, the increased yield due to nitrogen fixation 

 was also seen in the first crop. 



At Rothamsted portions of the barley plots, one that 

 had been for a long time unmanured and another that 

 had been receiving phosphates and potash but no 

 nitrogen, were treated with sugar or starch at the rate 

 of 1 ton per acre. In the earlier trials, when these 

 carbohydrates were applied in the spring before sowing, 

 the crop was depressed by the carbohydrate ; but when 

 the time of application was changed to the autumn, a 

 marked increase of yield followed the application of 

 carbohydrate on the plot well supplied with all the 

 elements of fertility except nitrogen, though the effect 

 was small upon the unmanured plot. 



Rothamsted. Effect of Carbohydrate on Succeeding 



Barley Crop. 



* Starch instead of sugar. 



In the earlier trials, with a spring application of the 

 carbohydrate, the normal temperature of the soil was 

 too low to permit of the development of Azotobacter 

 and the fixation of nitrogen. Other organisms attacked 

 the carbohydrate and by their multiplication reduced 



