Critical nitrogen concentration (Nc), which is defined as the minimum % N in shoots required to maintain the maximum growth rate of top dry weight (W) at any time, was determined for rice plant. Using two rice varietal groups, japonica varieties and an indica ~times japonica "Dasanbyeo", 18 data points fulfilling the statistical criteria for determining Nc were obtained through eight N-fertilization experiments over two years at Suwon (37~circ 16'N), Korea. Nc dilution curve for each variety was obtained by fitting the Nc-W relationship to power function. However, The critical nitrogen curves for the two variety groups were not different statistically. Thus, a Nc dilution curve was fitted for the Nc data points pooled over the two variety groups and proposed in rice as: Nc=4.08, where W＜1.73 t h a-1 , Nc=5.197 W0.425 3/ (R2 =0.964), where 1.73 t h a-1 ＜W＜12 t h a-l . The Nc for W＜1.73 t h a-l were estimated as a constant value of 4.08%, the mean value of the maximum N concentration for N-limiting condition and the minimum N concentration for N non-limiting condition. The model for Nc is applicable to diagnosing the nitrogen nutrition status during the rice growth period from emergence to heading stage. The Nc curve well discriminated the 144 data points between the N limiting and the N non-limiting groups regardless of varieties, cultural methods, and years.-limiting groups regardless of varieties, cultural methods, and years.

본 연구에서는 정지수체에서 다공확산관을 통해 방류된 연직다중의 혼합 및 희석 특성에 대해 규명하였다. 3차원 실험수조에서 실험을 통해 밝혀진 결과는 다음과 같다. 우선 다공확산관의 병합과정을 살펴보면 흐름의 안정조건에 따라 병합거리가 다소 차이가 있기는 하지만 {{{{ { z}_{ } }}}}/{{{{ {l}_{ } }}}}가 대략 3인 지점부터 병합이 시작되어 그 이후에는 평면부력？의 거동에 서서히 가까워짐을 알 수 있다. 최소희석률에 대해 분석해 본