Tillage Effects on Nitrogen Leaching and Nitrous Oxide Emission from Double‐Cropped Paddy Fields

Tillage practices affect the fate of N fertilizer by influencing its transformation. Few studies have examined N leaching and N 2 O emission from double‐cropped paddy fields in southern China. This study was aimed at assessing the influence of tillage systems on saturated hydraulic conductivity ( K s ), N leaching, and N 2 O emission from double‐cropped paddy fields in southern China. The experiment was conducted with rice ( Oryza sativa L.) during the growing seasons of 2010 and 2011. Four treatments in a randomized complete block design were: no‐till (NT), conventional tillage (CT), rotary tillage (RT), and conventional tillage with residue removed (CT0). Results showed that NT significantly increased K s at the 0‐ to 40‐cm depth relative to other treatments ( P < 0.05); however, there were no significant differences in K s at the 40‐ to 80‐cm depth. Compared with other treatments, the mean K s for NT at the 0‐ to 80‐cm depth increased significantly ( P < 0.05), by 76.3, 44.7, and 64.8% compared with CT, RT, and CT0, respectively. Despite significant differences ( P < 0.05) on some occasions, higher concentrations of NH 4 + –N and NO 3 – –N were observed in soil solutions from NT than from other tillage treatments. Conversion of CT to NT reduced N 2 O emissions, and the magnitude of reduction was usually significant ( P < 0.05) compared with other treatments, especially during the stage of peak emissions. Therefore, in the context of yield increase, environmental concern, and climate change, integrated N management under a NT system in paddy fields is needed to attain high N use efficiency and crop yield.