There have been several mathematical models for the transportion of nutrient ions in soil towards single root or root system of a single plant. But wheather these models can match the root systems of the rice plants grown in a clump remaines to be verified. In order to test the models, rice plants were grown in a box consisting of two compartments separated by a sheet of nylon sieve to form a plane of rice roots. A comparison was made between the values of relative concentration of potassium ion in soil near the root surface predicted from Nye's model and those measured with a miniature potassium selective electrode. The results obtained showed that the measured values of relative concentration of potassium ion in the soil of rice rhizosphere were approximate to the theoretically calculated values, and their agreement was even better when water flue increased. It is possible to predict ion concentration near root surface using mathematical modelds even under more complex situations. In this experiment it was also observed that there were a deficit zone of potassium and a neutral or weakly alkaline pH environment in micro-areas of rhizosphere of rice plant.