1912] 



on Recent Advances in Agricultural IScience. 



51! 



bacter, this organism derives from the carbonaceous part of the plant 

 residues the energy it requires for the fixation of nitrogen, and a 

 steady addition to the original stock goes on. We have found 

 Azotobacter present in all these rich black soils, from both South 

 and North America, the Russian Steppes, and similar virgin land 

 in all parts of the world, and again we also find an abundance of 

 lime, one of the other necessary factors for the growth of Azotobacter. 

 \'irgin soils are not necessarily rich ; there are miserably poor ones, 

 though they have equally carried some sort of vegetation for 

 hundreds, indeed thousands, of years. Tbey have remained poor be- 

 cause some of the other factors upon which depend the development 

 of Azotobacter are lacking. With this far-reaching conclusion in sight, 

 we have naturally tried at Rothamsted whether we could not bring 

 about a similar heaping up of nitrogen in the soil by simply adding 

 to it a carbohydrate containing no nitrogen, such as starch or sugar. 

 In plots the experiment is perfectly successful, and accordingly we 

 selected one of the plots in the barley field which was in a very 

 nitrogen-starved condition, because it had been manured for fifty 

 years only with mineral fertilizers containing no nitrogen, and treated 

 half the plot with sugar at the rate of a ton to the acre, the other 

 treatment of the two halves of the plot being alike. To our surprise, 



HoosFiELD Barley. 



Effects of Sugar (or Starch) on the Amount of Produce. 

 Plot 4 0. Complete Minerals. 



* Very small crop, not weighed. 



+ Starch applied instead of Sugar in 



the half receiving sugar gave a miserable crop, much below the non- 

 sugar half, for four years in succession, and a bacteriological exami- 

 nation of the soil showed that Azotobacter had not increased in 

 response to the sugar, but that the number of merely putrefactive 

 organisms had gone up greatly. These facts led Dr. Hutchinson 

 to surmise that we had been putting on the sugar at the wrong 

 time of year, in early spring or winter, some time before the barley 

 was sown, when the soil is cold. Now Azotobacter is comparatively 



