CONTINUOUS FLOW METHOD IN SOIL MICROBIOLOGY. 3. BIOLOGICAL IMMOBILIZATION OF NITROGEN AND PHOSPHORUS.

Abstract

The authors submit the results of study of nitrification in soil samples, using the continuous flow method. The course of nitrification was studied in soil samples continuously enriched with differently concentrated ammonium sulphate solutions and in soil samples of different weights (i.e. soil columns of different heights). The ammonium ions were oxidized after a short lag phase, the length of which depended on the ammonium nitrogen concentration. An exponential phase of nitrite formation was then observed. A steady state in the oxidation of ammonium ions was observed only with a continuous flow of low ammonium sulphate concentrations. After a given time, which was in inverse proportion to the ammonium sulphate concentration, the rate of nitrite and nitrate formation decreased. It was found that the factor limiting the rate of oxidation of ammonium ions was the degree of their adsorption in the soil. It was confirmed that ammonium ions were oxidized in the soil in the adsorbed state. It was also found that the oxidation of synthesized nitrite to nitrate was influenced by the concentration of continuously added ammonium ions and that the rate of oxidation increased with the height of the soil column. The results showed that the bacteria oxidizing ammonium ions to nitrite and nitrite to nitrate were localized in different parts of the soil column.