Simulation and Influence Factors of Nitrous Oxide (N2O) Gases Emission under Different Straw Retention Depths

Straw retention is an important practice increasing crop production worldwide. It also can reduce nitrous oxide (N2O) gas emissions from agricultural soils. But it is very difficult to predict N2O gas discharge amounts when straw is incorporated at different soil depths. This research combined wheat growing season data from the Agricultural Meteorological Experiment Station of Nanjing University of Information Science and Technology, China, with the denitrification-decomposition model (DNDC model) to determine whether the DNDC could simulate the N2O emission rate, annual discharge, and effect of incorporation depth on N2O emissions. Straw was retained on the soil surface, and incorporated at 10, 20, and 30 cm depths. The sensitivity of N2O emissions to several site-specific and environmental factors was also examined. The results were as follows: (1) the DNDC model was able to simulate the N2O emission rate and annual emission rate from different straw incorporation depths; (2) N2O gas emissions are sensitive to annual mean temperature, soil pH, and amounts of soil organic carbon, fertilization, and retained straw, which have different impacts under different straw incorporation depths; and (3) the direct influence of soil internal factors was more important than environmental factors in the surface and 10-cm treatments; however, the influence of straw retention decreased and the influence of environmental factors increased in the 20- and 30-cm treatments.