Non‐Linear Response of Ammonia Volatilization to Periphyton in Paddy Soils

Abstract

AbstractAmmonia (NH3) volatilization from paddy soils is one of the main contributors to agricultural NH3 emissions, however, little attention has been paid to the role of the ubiquitous periphyton in paddy soils on NH3 volatilization. Considering that the composition of periphyton is dominated by autotrophs that directly affect the redox and pH conditions, it is hypothesized that the presence of periphyton may be an important factor affecting NH3 emissions. In this study, NH3 volatilization was determined under six periphyton biomass treatments and under treatments with six different N application rates to evaluate the contribution of periphyton to NH3 volatilization in the laboratory representing the paddy soils system. Results showed that periphyton had trade‐off effects on NH3 volatilization through pH and the NH4+ concentration. Periphyton had net inhibition effects on NH3 volatilization when the periphyton biomass was higher than 110 g·m−2. In contrast, periphyton had net promotion effects on NH3 volatilization when the periphyton biomass was less than 110 g·m−2. The contribution of periphyton to NH3 volatilization increased exponentially with increasing N application rates (i.e., with the increasing nitrogen concentration of the overlying water). In the low‐nitrogen treatments (≤20 kg N·ha−1), periphyton had no significant effect on NH3 volatilization. In contrast, periphyton contributed as much as 47.4% of NH3 volatilization at high nitrogen concentrations (100 kg N·ha−1). This study provides valuable insight into the role of periphyton on NH3 volatilization, offers quantified relationship between periphyton and NH3 volatilization, and improves the accuracy of NH3 volatilization estimation in regional paddy soils.