Abstract: By using self-designed lysimeters, the dynamic changes of ammonia- and nitrate N leakage from the plowpan of paddy field under different N supply were studied , aimed to understand the N leakage loss from paddy field during rice growth per iod. A dynamic model was built to simulate the N translocation and transf ormation in rice plant, soil, and water by Vensim software. The data from the field experiment with N fertilization rates of 0, 75, 150, 225, 300, and 375 kg·hm-2 in Yuhan g district, Hangzhou City in 2003 were used for calibrating the model, and the data from the field experiment in 2007 were utilized for validating the model. The simul ated N concentrations in the leakage fitted well with the observed data, suggest ing that the simulated results were reliable and the model was applicable.

Key words: arbuscular mycorrhizal fungi (AMF), nitrogen, metabolism pathway, ecosystem.