Limited ammonia volatilization loss from upland fields of Andosols following fertilizer applications

The present study first aimed to investigate the ammonia (NH3) volatilization loss from broadcast ammonium sulfate at an upland field of volcanic ash soil (Andosol) in Hokkaido, northern Japan. Ammonium sulfate was applied for the regrowing stage of wheat at a rate of 300 kg ha−1 (= 63.6 kg N ha−1). A micrometeorological technique (i.e., the gradient method) was used to determine the atmosphere-upland field exchange of NH3. A dynamic chamber method was also tested to separate the contributions of the soil surface and wheat to the exchange fluxes. Although the NH3 volatilization began one day after the fertilizer application, the cumulative loss accounted for only 0.2% of the applied nitrogen. Hence, the present study also examined the features of Andosols in terms of the inhibition of NH3 volatilization. Existing studies support the suggestion that upland fields of Andosols inhibit the NH3 volatilization loss compared to non-Andosols. The following were the key features of Andosols that might inhibit NH3 volatilization: the relatively low soil pH; the relatively high effective cation exchange capacity even at a low soil pH; and the relatively high nitrification potential, signifying a high consumption rate of the applied ammonium.