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

Abstract

Tillage practices affect the fate of N fertilizer by influencing its transformation. Few studies have examined N leaching and N2O emission from double‐cropped paddy fields in southern China. This study was aimed at assessing the influence of tillage systems on saturated hydraulic conductivity (Ks), N leaching, and N2O 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 Ks at the 0‐ to 40‐cm depth relative to other treatments (P < 0.05); however, there were no significant differences in Ks at the 40‐ to 80‐cm depth. Compared with other treatments, the mean Ks 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 NH4+–N and NO3––N were observed in soil solutions from NT than from other tillage treatments. Conversion of CT to NT reduced N2O 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.