Abstract: To understand the impacts of different fertilization regimes on the risk of nitrogen leaching and thus to provide scientific reference for the control of non-point source pollution of chemical fertilizers in basic croplands of Hetao, we monitored the nitrogen leaching of salinized fluvoaquic soil in the growing season of maize in Hetao Irrigation District for two consecutive years by in situ leakage meter method. There were five treatments, including no fertilization (NF), farmer conventional fertilization (CK), conventional fertilization by farmers + bentonite (B), conventional fertilization by farmers + biochar (C), and conventional fertilization by farmers + organic fertilizer (F). The results showed that the total amount of leaching water under treatments B and C decreased by 16.4% and 15.9%, respectively, compared to CK treatment. In contrast, the amount of leaching water was relatively higher under treatment F. For nitrogen leaching, nitrate and ammonium concentrations peaked after the second irrigation. The peak values of treatments B and C were relatively lower and that of treatment F was slightly higher. Except for the NF treatment, the treatment B was lowest in cumulative inorganic nitrogen loss with an average of 65 kg·hm^-2, being 41.3% lower than that of CK. The amounts of nitrogen loss were 73.4 kg·hm^-2 and 96.4 kg·hm^-2 under treatments C and F, espectively, which decreased by 33.7% and 12.9%, respectively, compared to CK. Leaching volume of total nitrogen and total dissolved nitrogen in leaching water following the pattern: NF <B <C <F <CK. The apparent leaching rates of treatments B, C and F (averaged 15.3%, 16.5% and 18.5%, respectively) were lower than that under CK (25.5%). The yield of maize under treatments F, B and C increased by 9.8%, 8.4%, and 6.6%, respectively, compared to CK (P<0.05). All fertilization treatments enhanced maize production during the two years. The amount of nitrogen leaching loss was greater under treatment F. Bentonite and biochar addition effectively inhibited the leaching loss of nitrogen and increased nitrogen fertilizer utilization rate, which would contribute to reducing the non-point source pollution of chemical fertilizers in Hetao Irrigation Area. In conclusion, treatment B is more feasible for application, followed by treatment C.

Key words: fine root functional trait, diameter class, Zenia insignis plantation, rhizosphere soil