施氮水平对太行山前平原冬小麦-夏玉米轮作体系土壤温室气体通量的影响

应用静态明箱-气相色谱法对4 个施氮肥水平N0 0 kg(N)·hm^-2]、N200 200 kg(N)·hm^-2]、N400 400kg(N)·hm^-2]、N600 600 kg(N)·hm^-2]的夏玉米-冬小麦季轮作体系2008~2010 年的土壤温室气体(CH₄、CO₂ 和N₂O)排放通量进行研究, 同时观测5 cm 土层土壤温度并记录降水量。结果表明: 太行山前平原冬小麦-夏玉米轮作农田生态系统为CH₄ 吸收汇, CO₂ 和N₂O 排放源。随着氮肥施入量的增加土壤对CH₄ 的吸收速率降低, 而CO₂ 和N₂O 的排放速率增加。冬小麦季施氮处理土壤对CH₄ 的吸收速率显著低于无氮肥的N0 处理, 而N600处理土壤CO₂ 和N₂O 排放速率显著高于N0 处理(P<0.05)。施肥和灌溉会直接导致土壤CO₂ 和N₂O 的排放通量增加, 同时土壤对CH₄ 的吸收峰值减小。土壤温度升高和降水量增加以及干湿交替加剧均会造成N₂O 和CO₂排放速率增加。同时在持续干燥和低温条件的冬季不施氮处理观测到土壤对N₂O 的吸收现象。N0、N200、N400 和N600 处理土壤CH₄ 年排放总量(kg·hm^-2·a^-1)分别为-1.42、-0.75、-0.82、-0.92(2008~2009 年)和-2.60、-1.47、-1.35、-1.76(2009~2010 年), N0、N200、N400 和N600 处理土壤CO₂ 年排放总量(kg·hm^-2·a^-1)分别为15 597.6、19 345.6、21 455.9、29 012.5(2008~2009 年)和10 317.7、11 474.0、13 983.5、20 639.3(2009~2010年), N0、N200、N400 和N600 处理土壤N₂O 年排放总量(kg·hm^-2·a^-1)分别为1.05、2.16、5.27、6.98(2008~2009年)和1.49、2.31、4.42、5.81(2009~2010 年)。

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^-2]and 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.