Three leafy vegetables, rape (Brassica campestris L.), Chinese cabbage (Brassica chinensis var. Oleifera Makino et Nenoto) and spinach (Spinacia oleracea L.), were grown in plastic pots with 5 kg soil per pot at five nitrate supply rates, 0.00 (N1), 0.15 (N2), 0.30 (N3), 0.45 (N4), and 0.60 (N5) g N kg-1 soil to investigate the effects of nitrate supply on plant growth, nitrate accumulation and nitrate reductase activity (NRA) 9 weeks after sowing. The optimum yield appeared at N3, while above N4, a strong decrease in plant growth occurred. The nitrate concentration increased with nitrate supp...
