Excessive application of compost can cause such problems as plant toxicity symptoms due to high salt concentration and the accumulation of trace metals, and ground and surface water pollution. Therefore, an appropriate application of compost to agricultural fields is predetermined to ensure healthy food production and to prevent soil and water pollution. To evaluate the effect of compost application rates on N uptake efficiency and N leaching potential from agricultural field soils, Chinese cabbages were grown in pot with three different application rates of compost for 40 days. Compost was applied at rates of 0 (C0), 500 (C1), 1000 (C2), and 1500 (C3) mg N kg^-1 soil. With increasing compost application, N uptake of cabbage increased, while dry matter yield did not. The slope from linear regression analysis of N uptake versus compost application rate showed that N uptake efficiency of crops from compost-N was 76 g N kg^-1 compost-N. At the same time, concentration of soil inorganic N increased with increasing compost application rate. Net mineralized-N from compost increased linearly with increasing compost application, and the slope of linear regression analysis showed that compost-N was mineralized at the rate of 122 g N kg^-1 compost-N for 40 days. As soil and compost N have their specific isotopic compositions, the δ¹⁵N can be a possible tracer to interpret their relative contribution to plant N and soil inorganic N. The δ¹⁵N was higher in cabbages receiving compost than in control. However, differences in δ¹⁵N values between C2 and C3 plants were virtually the same, indicating that most N in C2 and C3 plants was derived from compost. In accordance with the variations in δ¹⁵N of cabbage-N, the δ¹⁵N of soil inorganic N increased with increasing application rate of compost, indicating the relative contribution of compost-N to soil inorganic N. Our results suggest a possibility that the use of crop- and soil-δ¹⁵N together with their corresponding N concentrations can evaluate luxury consumption of N derived from compost-N, lest we should contaminate surface and ground water from agricultural field.