Three simplified methods for estimating the volatilization of ammonia from flooded rice.fields were assessed when the plants are small and sparse in the field at Lianhu Farm,China.The most accurate and reliable technique involved the measurements of wind speed and anmonia concentrations in the atmosphere at 0.8 m above the floodwater surface.A slightly less reliable estimation could be obtained with a specially designed ammonia sampler which gave a measure of the horizontal transport of ammonia at a fixed height.In remote locations the sampler method may be preferred because electrical power,pumps,flow meters and anemometers are not required.