SOIL INOCULATION 



285 



reported on pot experiments were clearly in favor of the inoculated 

 plant. Stoklasa was one of the first to study in detail the commercial 

 preparation "alinit" which was placed on the market as a result of 

 Caron's work. His findings were fully as favorable as Caron's, 

 but the work of others soon demonstrated that "alinit" neither in 

 the laboratory nor in the field had the ability to fix nitrogen. When 

 Beijerinck discovered the free-living aerobic nitrogen-fixers, the hope 

 that soil inoculation may be so perfected that it would be beneficial 

 to crops was revived, and since that time many investigators have 

 attempted to inoculate soil in order to increase its crop-producing 

 powers, but usually with negative results. Stoklasa has made 

 great claims for soil inoculation. He found that soils, inoculated 

 with Azotobacter chroococcum and adequately supplied with carbo- 

 hydrates and lime, showed an increase in the number of nitrogen- 

 fixing organisms, and also an increased yield both in quantity and 

 quality of the crop. Stranak also obtained a pronounced increase 

 in the production of beets, grain, and potatoes on inoculating with 

 Azotobacter. 



There may be a decrease in the crop during the first year when 

 carbohydrates and Azotobacter are added to the soil with a marked 

 increase in crop during the second and third year. Even then, the 

 soil may be left richer in nitrogen than it was at first. 



The effect of dextrose and sucrose on the productiveness and nitro- 

 gen content of the soil is shown below: 



It is often the case that the addition of starch to a soil during the 

 first year retards plant growth. This injurious action may be due 

 to the augmented bacterial activity in the soil brought about by the 

 carbohydrates which injure the roots of the plant by withdrawing 

 oxygen and by forming hydrogen sulphid in the deoxygenated 

 atmosphere of the soil through the reduction of sulphates by the 

 bacteria. 



The effect produced by the carbohydrate applications also varies 

 with the season. If applied to the soil in the spring when the soil 

 temperature is low and wh e R other bacteria are more active than 



