Abstract:An experiment using monolith lysimeter was conducted to compare dry deep-placement of urea (DPU) in plowed paddy field before permanent flood with wet broadcast of urea (WBU) on puddled paddy field in effect on fertilizer N loss and rice N uptake at the Jiangsu-Changshu National Agroecological Experiment Station (31°33′ N, 123°38′ E). The experiment was designed to have three treatments, i.e. deep-placement, broadcast and CK (no urea applied), and ammonia volatilization, N leaching and rice N uptake were measured during the rice growing season. Results show that NH3 volatilization flux from DPU was significantly lower than from WBU, being 40.1 and 68.8 kg hm-2, or 13.4% and 22.9%, respectively, of the fertilizer N used in the lysimeter in 2007, and 19.2 and 26.2 kg hm-2, or 7.7% and 10.4%, respectively, for DPU and WBU in field trial in 2004. Leaching of total N (TN) in DPU was markedly higher than in WBU, being 14.3 and 4.6 kg hm-2, or 4.8% and 1.5% of the fertilizerN applied, respectively. Nitrogen was leached away mainly in the form of NO3--N in the ricegrowing season, accounted for 73.7%~97.3% of the total N leaching. But NH4+-Nleaching did not show much difference between DPU and WBU. Compared with WBU, DPU reduced net N loss by 19.0 kg hm-2 and increased rice N uptake by 15.2 kg hm-2 and plant apparent recovery of fertilizer-N by 5%, i.e. 34% in WBU and 39% in DPU. DPU raised crop yield slightly over WBU, but did not affect much soil N content. The results indicate that the DPU method is superior to the common practice of broadcasting urea into flooded paddy field and is worth extrapolating.