Soil greenhouse gas emission in winter wheat/summer maize rotation ecosystem as affected by nitrogen fertilization in the Piedmont Plain of Mount Taihang, China

The effect of soil nutrient augmentation via nitrogen deposition or fertilization on the processes of storing, releasing and re-absorbing of methane (CH₄) carbon dioxide (CO₂) and nitrous oxide (N₂O) greenhouse gases (GHG) in soil ecosystems are poorly understood. This study described an original field experiment for measuring soil GHG flux at nitrogen application rates of N0 0 kg(N)·hm^-2, N200 200 kg(N)·hm^-2, N400 400 kg(N)·hm^-2and N600 600 kg(N)·hm^-2 in winter wheat/summer maize double cropping system in the Piedmont Plains of Mount Taihang. CH₄, CO₂ and N₂O emissions from soils under the winter wheat/summer maize rotation system were measured from July 2008 through June 2010 using the static transparent chamber and gas chromatography technique. The results showed that soils under winter wheat/summer maize ecosystems served as CH₄ sink, and CO₂ and N₂O sources. With increasing nitrogen application, CH₄ absorption rate decreased and CO₂ and N₂O flux rates increased. In winter wheat season, CH₄ absorption rate under N0 treatment was significantly higher than under other nitrogen treatments. Both CO₂ and N₂O emission flux rates under N600 treatment were significantly higher (P<0.05) than under N0 treatment. Nitrogen fertilization and irrigation sharply induced CO₂ and N₂O peak flux emissions and decreased CH₄ peak absorption. Rising soil temperature, precipitation or alternating wet/dry weather increased soil N₂O and CO₂ emission flux rates. Negative N₂O flux rates were observed under low temperature and high evaporation conditions in N0 application treatments in winter. CH₄ emission accumulation for 2008~2009 under N0, N200, N400 and N600 treatments was -1.42, -0.75, -0.82 and -0.92 kg·hm^-2·a^-1, respectively. For 2009~2010, it was -2.60, -1.47, -1.35 and -1.76 kg·hm^-2·a^-1, respectively. CO₂ emission accumulation for 2008~2009 under N0, N200, N400 and N600 treatments was 15 598, 19 346, 21 456 and 29 013 kg·hm^-2·a^-1, respectively. For 2009~2010, it was 10 318, 11 474, 13 984 and 20 639 kg·hm^-2·a^-1, respectively. Then N₂O emission accumulation for 2008~2009 under N0, N200, N400 and N600 treatments was 1.05, 2.16, 5.27 and 6.98 kg·hm^-2·a^-1, respectively. Also for 2009~2010, it was 1.49, 2.31, 4.42 and 5.81 kg·hm^-2·a^-1, respectively.