The influence of fertilizers and season on nonsymbiotic nitrogen fixation in Brookston and Bedford silt loams
1942
Roberts, J.L. | Olson, F.R.
The rates of nonsymbiotic nitrogen fixation in variously ferilized plots on Bedford and Brookston silt loams were determined during 1938 and 1939. From the results obtained, the following conclusions are drawn: 1. The higher soil nitrogen content of the fertilized Bedford silt loam, as compared with unfertilized, is not due to stimulated nonsymbiotic nitrogen fixation. 2. Phosphatic and potassic fertilizers had no influence on rates of nonsymbiotic nitrogen fixation in Bedford or Brookston silt loams. However, if mannitol were added to Brookston silt loam, plots fertilized with phosphorus were found to have a higher rate of nonsymbiotic nitrogen fixation than the unphosphated plots. This was not the case with Bedford silt loam. 3. Relatively few Azotobacter were found in the samples studied and can not be judged responsible for a significant portion of the observed nitrogen fixation. 4. There was considerable seasonal variation in rates of nonsymbiotic nitrogen fixation in each of the soils studied.
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