Ammonia Volatilization from Urea Applied to Acid Paddy Soil in Southern China and Its Control

<正> Results showed that ammonia loss from urea broadcast into floodwater and incorporated into soil at transplanting was as high as 40% of applied N, and the corresponding total nitrogen (N) loss was 56%. Ammonia loss was measured with simplified micrometeorological method (ammonia sampler), and total N loss was concurrently measured using 15N balance technique. The experiment was conducted under strong sunshine conditions on acid paddy soil derived from Quaternary red clay. The ammonia loss in this particular condition was much greater than those obtained from previous studies when urea was also applied to acid paddy soil but under cloudy conditions. It is concluded that the strong sunshine conditions with high temperature and shallow floodwater during the period of present experiment favoured ammonia volatilization.Application of stearyl alcohol on the surface of the floodwater reduced ammonia loss to 23% of applied N. However, the effect of stearyl alcohol was short-lived, probably due to the microbiolog