EFFECT OF VARIOUS NITROGEN FERTILIZERS ON MANGANESE AND IRON AVAILABILITY AS MEASURED BY INCUBATION AND SAND CULTURE STUDIES

Abstract

After two months of incubation, soils treated with inorganic nitrogen fertilizers contained more available manganese than those treated with organic sources, except for thiourea which increased it very considerably. Changes in manganese availability were partly due to pH changes and partly to the oxidation-reduction influence of the nitrogen carriers. Changes in iron availability were very small and this is presumably due to the chelation effect of the humic substances released during incubation of soil at room temperature. Nitrogen sources influenced not only manganese availability, but also manganese uptake by potato plants grown in sand cultures. Manganese uptake was about the same with nitrate and ammonium salts; however, plants supplied with physiologically neutral and basic nitrogen compounds contained appreciably less manganese than those supplied with acid compounds, although the pH of the solution was the same in all treatments.