Emissions of N2O and NH3, and nitrogen leaching from direct seeded rice under different tillage practices in central China

Tillage practices affect the fate of fertilizer nitrogen (N) through influencing transformations of N, but few studies have examined N2O and NH3 emissions, and N leaching from different rice tillage systems. Thus the objective of this study was to assess N2O emission, NH3 volatilization and N leaching from direct seeded rice in conventional tillage (CT) and no-tillage (NT) production systems in the subtropical region of China during the 2008 and 2009 rice growing seasons. Treatments were established following a split-plot design of a randomized complete block with tillage practices as the main plot and N fertilizer level as the sub-plot treatment, and there were four treatments: NT + no fertilizer (NTO), CT + no fertilizer (CTO), NT + compound fertilizer (NTC) and CT + compound fertilizer (CTC), respectively. Results showed that N fertilization significantly increased (p < 0.01) N2O emissions, NH3 volatilization and N leaching from rice fields in both years. In general, there was no significant difference in N2O emissions and NH3 volatilization between NTO and CTO in both years, while NTC had significantly higher (p < 0.05) N2O emissions and NH3 volatilization compared to CTC. Over the two rice growing seasons, NTC showed 32% and 47% higher N2O emissions, and 29% and 52% higher NH3 losses than CTC. Higher (p < 0.05) N2O emissions from NTC than CTC were presumably due to higher soil organic C and greater denitrification. Total N and NO3- concentrations were higher (p < 0.05) in CTC than NTC, but larger volumes of percolation water in NTC than CTC resulted in no significant difference in leakage of total N and NO3-. Hence, application of N fertilizer in combination with NT appeared to be ineffective in reducing N losses from N fertilizer in paddy fields. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.