We carried out a greenhouse experiment to investigate the nitrogen dynamics in an upland soil with low-fertile, applied with waste sludge (N:P:K = 6.9:3.1:0.4%). After amending the sludge and P fertilizer to the soil, a vegetable, Brasssica campestris var. peruviridis was cultivated. For comparison, plot of chemical fertilizer and no application were added. Fate of N from the sludge and soil were estimated by ¹⁵N-dilution method. Plant height and number of leaf in the sludge plot increased as same as in that of chemical fertilizer. But leaf color in the sludge plot changed lower than that in chemical fertilizer. At harvest there is no significant (p = 0.05) difference in dry weight between sludge and chemical fertilizer plots. But they were much higher than no application significantly (p = 0.05). Somewhat higher amount of total nitrogen (1.02 g pot^-1) was taken up by the plant of sludge plot than by that of chemical fertilizer (0.83 g pot^-1). The plant in sludge plot up took 0.77 g pot^-1 of N from the sludge and 0.25 g pot^-1 of N from the soil. Meanwhile, that in chemical fertilizer up took 0.65 and 0.17 g pot^-1 of N from fertilizer and soil, respectively. As results, nitrogen use efficiency of the plot of sludge and chemical fertilizer were 22.5 and 27.2%, respectively. It suggests that amount of the sludge application should increase 21% comparing with chemical fertilizer, in order that plant grown in the soil amended with sludge takes up the same amount of N as that with chemical fertilizer. Soil microbial activity in the sludge plot, measured by enzymatic assay (=esterase activity to fluorescent diacetate), increased and changed higher than the plot of chemical fertilizer and no application.