Field validation of DNDC model for simulating greenhouse gas emissions from rice soils of Kedah, Malaysia through DNDC Model

摘要

The laboratory and Denitrification and Decomposition (DNDC) model for assessment of greenhouse gas emission (GHG) and model validation was accurate for Kedah Malaysia as the farmers grow paddy in two seasons and apply nitrogen (N) at 280 kg N ha - 1 year - 1 by splitting twice as well. In the first and second seasons, the crop received 1735.39 and 1507.15 kg C ha - 1 with 44 and 41 C:N ratio observed from harvested straw. The simulated input of yearly C balance was 3242.5, 366.5 and 2508.6 kg C ha - 1 year - 1 through rice straw, crop residues and roots, respectively which contributed 4674.9 kg C ha - 1 year - 1 SOC with decline of - 3.3 kg C ha - 1 year - 1 CH 4 emission. The yearly DNDC simulation for CO 2 flux rate was 4675 kg C ha - 1 and 932.8 kg ha - 1 year - 1 recording - 3 CH 4 flux. The Global Warming Potential (GWP ) for CO 2 flux was 17141 kg CO 2 - eq ha - 1 , N 2 O 454412 kg CO 2 - eq ha - 1 . However, CH 4 was found as sink. Bulk of all these gases had 471460 kg CO 2 - eq ha - 1 net GWP. The uncertainties for future forecast were measured through DNDC by N rates (20% less than recomm ended, recommended N, and 20, 40 and 60% more than recommended N) by fixing SOC rates viz. 0.02, 0.03, 0.04 and 0.05 for NH 3 volatilization. The unit increase in N rate as well as SOC correspondingly increased NH 3 volatilization, N 2 O, NO and N 2 flux. It is concluded that GW is the main cause of GHG.