Nitrogen fertilizer status in the rhizosphere varied with different N forms and the soil moisture condition. It was revealed that there existed a depletion zone of NH₄⁺-N in rice rhizosphere under submerged condition. The exponential correlation was found between the depiction rate and the distance from the root surface for both (NH₄)₂SO₄ and (NH₂)₂CO. The depletion of NHS-N was also observed in the area of 1-3 mm from root plane of upland crops, such as maize, barley, and ryegrass. Being different from that of rice, the maximum of depletion value was not near the root surface. In other words, NH₄⁺-N was relatively accumulated in the rhizosphere soil within the rhizosphere area .of 1-3 mm from the root plane. The furthm results showed that a considerable amount of labelled nitrogen was detected in the rhizosphere of upland crops, indicating part of NH₄⁺-N relatively accumulated near the root surface is contributed by the nitrogen exuded from the plant root. The amount of exuded N or the rate of relatively accumulation of N was related to the crop species and soil water condition. On the contrary, in the case of NO₃^--N, significant accumulation of labelled NO₃^--N was found in the zone of 0-5 mm from root plane of both rice and maize under either submerged or dryland condition. It can be considered that NO₃^--N is mainly transferred to the root by mass flow, which is different from ammonium nitrogen by diffusion, and accordingly it is not depleted but accumulated in the plant rhizosphere soil.