Ammonia Volatilization from Soils1

Abstract

AbstractIf NH4+‐N fertilizers are used, most agronomic crops grow best if the soil reaction is near neutrality. Previous studies have shown that if the soil pH becomes alkaline, NH3 volatilization losses of N occurs. The objective of this study was to determine whether or not a rapidly growing crop could reduce the volatilization losses of N, especially from soils above pH 7 to which large applications of NH4+‐N fertilizers were made. This study was conducted in a greenhouse using a closed system in which all NH3 evolved from the soil was swept away by a stream of air and collected. The amount of NH3‐N evolved from the soils was measured as a function of time, soil pH, amount of N application, and presence or absence of corn (Zea mays indentata Bailey) seedlings. Ammonia losses with or without plants in the system increased as the soil reaction and amount of NH4+‐N application increased. A sharp upward inflection in NH3‐N loss occurred at pH 7.2. Plants reduced NH3‐N losses by atleast 60% in the alkaline soils and by lesser amounts in the acidic and neutral soils. Rapid absorption of NH4+‐N by plant roots appeared to account for the conservation of N.