轮作制度对农田氧化亚氮排放的影响及驱动因子

 于2003年6月至2004年5月进行田间试验，2003年夏种植大豆、玉米和水稻，后季种植冬小麦。观测项目包括农田N2O排放、土壤温度、湿度及生物学因子。观测结果表明，在不同的轮作方式中，玉米（施氮）-小麦（施氮）轮作农田的N2O年度排放量最高，为(18.5±0.7)kgN·ha-1；大豆（不施氮）-小麦（施氮）处理次之，为（13.2±0.4）kgN·ha-1；水稻（施氮）-小麦（施氮）轮作最低，为（11.7±0.7）kgN·ha-1，三者之间存在极显著差异（P =0.001）。相对于耕翻处理，稻茬麦田播前免耕在冬前促进了N2O排放（P＜0.001），但并未增加季节性排放总量(P＞0.1)。大豆、玉米、水稻、小麦田N2O通量的自然对数值（y）与土壤温度（T）、湿度（W）和叶面积指数（L）的关系可用逐步回归方程y=a·W＋b ·T＋c·L＋d表示（a、b、c、d为回归系数），其中玉米田y与L关系不明显，c值为0；大豆田y与W、T关系不显著，a=0，b=0；灌溉稻田a值为0，且y与L关系不明显。大豆、水稻、小麦田N2O通量均与生态系统呼吸速率呈极显著正相关关系（P＜0.0001），而玉米田不存在类似关系。

Nitrous Oxide Emission from Cropland and Its Driving Factors Under Different Crop Rotations

Field experiments were carried out from June 2003 to May 2004. Three crops of maize, soybean and rice were planted in summer season of 2003 followed by winter wheat. A static opaque chamber-GC technique was used to detect the emissions of N2O and CO2 in situ. Soil temperature, moisture and relevant crop parameters were measured. Results showed that there was a significant difference in the annual N2O emissions from different rotation plots. Higher N2O emission was observed in the plot of maize-wheat rotation with an annual amount of (18.5±0.7) kgN·ha-1. Lower N2O emissions were found in the plots of rice-wheat and soybean-wheat rotation with the annual amounts of (11.7±0.7) kgN·ha-1 and (13.2±0.4) kgN·ha-1, respectively. The soybean-growing season did not receive any additional fertilizer in the soybean-wheat rotation. In the rice-wheat plot, no-plowing practice before wheat sowing enhanced N2O emission significantly (P<0.001) in wheat-growing season from sowing to the winter as compared with that from the plowing plot, while no significant increase was observed over the wheat-growing season. A further investigation suggests that a stepwise regression function of y=a·W+b·T+c·L+d can be employed to quantify the influence of soil moisture (W), temperature (T) and leave area index (L) on N2O emission. The y is expressed as ln (FLUXN2O). The function did not show significant correlation between y and L for the maize plot, and thus c=0. The y did not correlate with W and T for the soybean plot, and thus a=0 and b=0. In the irrigated rice paddy, the y did not correlate with L. In addition, N2O emission was generally correlated to ecosystem respiratory rate for the plots of soybean, rice and wheat, while no significant correlation was found for the maize plot.