Characteristics of ammonia gas emissions from soybean cultivation soils treated with mixed microorganisms

Abstract

This study was conducted to evaluate (i) the characteristics of ammonia gas emissions from soybean cultivation soils amended with varying levels of urea and soil water, and (ii) the rate of reduction in ammonia emissions that could be obtained by applying mixed microorganisms (MM) to the urea-treated soils. The ammonia gas emissions from all treatments except the control were highest on day 2 of a laboratory-scale experiment and decreased gradually thereafter. The ammonia gas emissions from the soils increased with increasing urea and soil water contents. However, there were less emissions from soils treated with MM than those from the urea only treatment, and emissions also decreased significantly as the concentration of MM increased. In a field-scale experiment, the total cumulative emissions of ammonia from soil treated with a combination of chemical fertilizers and MM was reduced to 85.8% of that from the soil treated with chemical fertilizers only. Although we infer that MM can be used as an agent to reduce ammonia gas emissions from actual soils used for soybean cultivation, our knowledge of the processes involved in reducing ammonia emissions using microbial treatment is still limited. Consequently, further studies are required to investigate the efficient control of ammonia gas emissions from agricultural soils through the application of microorganisms.