Organic Carbon and Nitrogen Amendment Prevents Oxidation of Subsurface of Sulfidic Soil under Aerobic Conditions

Abstract

Managing the surface soil (0−10 mm) is important for microbes and benthic organisms that regulate various ecological services, e.g. regulation of soil or water chemistry, oxygenation, and temperature. In this study, the importance of soil carbon and nitrogen in the subsurface (10–80 mm) of sulfidic soil was investigated following the addition of complex and simple carbon and nitrogen sources. The purpose was to assess the effects of carbon and nitrogen on sulfidic soil chemistry (i.e. redox and pH) so as to establish alternative management strategies to prevent oxidation of the surface soil. Aerobic and anaerobic soil moisture conditions were considered as the most prevalent under any surface environment. The results showed that the presence of both carbon and nitrogen, either under aerobic or anaerobic soil condition, is important to prevent oxidation. Organic matter of plant material origin is complex and contains both carbon and nitrogen; this highly reduces the soil redox and increases the pH, even under the aerobic soil conditions. Simple metabolic substrate like glucose acidified the soil and ammonium had no significant effect on soil pH compared to compounds like urea containing both carbon and nitrogen having the opposite effects. The results of this study have implications for management of the surface soil, which is important for various surface environment chemistry and ecosystem services.