Study Of Impacts Of Amendant Plant Residues On The Missions Of Green House Gases And NO From Typical Saline Soil

Emissions of carbon dioxide (CO₂), nitrous oxide (N₂O), nitric oxide (NO) and methane (CH₄) from typical saline agricultural soil in south Shanxi were measured from June 19 through October 6, 2008. Air samples were collected with static and opaque chambers and analyzed with a gas chromatograph and a chemiluminescent NO_x analyzer. The investigated fields were applied with 3 treatments of wheat residue application, which were zero (NR), moderate (HR) and high (FR) rates. Based on the measured data, we investigated the overall global warming potential (GWP) at the seasonal scale, which integrates: a) the net emissions of N₂O and CH₄ and, b) the balance of soil organic carbon. The later item is calculated as the sum of the accumulative CO₂ emission and the incorporated residue carbon. We also investigated the molar ratio of NO to N_O fluxes (NO: N₂O). The GWP significantly was reduced by 32% at HR (p < 0.05) and 40% (p < 0.01) at FR, as compared to NR. This indicates that incorporation of harvested wheat residues into the saline soil can increase the sink of green house gases. The cases with NO:N₂O <1 occurred at a frequency far less than 50%, which showed a negative linear correlation with incorporation rates of wheat residues (p < 0.05). A prime effect appeared in soil carbon decomposition when the incorporation rate of wheat residues was increased from HR to FR (p < 0.05). A similar effect also appeared for emissions of N₂O and NO, but reasons are not clear. The average direct emission factors of N₂O-N are 0.39% at FR and 0.19% at HR. This suggests that the emission of N₂O due to incorporation of wheat residues into a saline soil may be overestimated if using the default direct emission factor (1.0%) provided by the IPCC guidelines.