Effect of nitrogen fertilizer management and waterlogging on nitrous oxide emission from subtropical sugarcane soils

Considerable potential for N2O emission from Australian sugarcane systems exists from high N fertilizer application rates and periodic waterlogging. To determine N2O emissions, 2 experiments were conducted on ratooned sugarcane grown under field conditions. In the first experiment, crops received 0, 100 or 200 kg N ha(-1) as single or split application. In the second experiment, a sub-set of the single N application plots was subjected to waterlogging. Higher N2O emissions (350 mu g-17 mg N2O m(-2) h(-1)) occurred during warm and wet months (November-February) and coincided with high availability of mineral N in top soil (10-500 mg N kg(-1) soil). Lower emissions (<350 mu g N2O m(-2) h(-1)) were detected in cool and dry months (March-October) coinciding with availability of low mineral N (<10 mg N kg(-1) soil). Regression analysis showed significant positive correlations between N2O emissions and soil temperature, water-filled pore space and mineral N (ammonium and nitrate) content. N2O emissions, soil mineral N content and crop yield followed N application rates (0 < 100 < 200 kg N ha(-1)) and waterlogging amplified N2O emission. Split application of N fertilizer reduced annual N2O emissions in the 200 kg N ha(-1) treatment. We estimate, using the IPCC Tier 1 approach that between 1.0% and 6.7% of applied N fertilizer was emitted as N2O. Our study demonstrates that immediate reduction of N2O emissions can be achieved by avoiding high levels of soil mineral N pools and waterlogging through appropriate fertilizer rates and time of application and soil management. (C) 2009 Elsevier B.V. All rights reserved.