西北干旱区两种不同栽培管理措施下棉田CH_4和N_2O排放通量研究

CH4 AND N2O FLUXES FROM COTTON FIELDS DIFFERENT IN FARMING PRACTICES IN NORTHWESTERN CHINA

采用静态箱-气相色谱法对西北干旱区当前普遍采用的膜下滴灌和传统的无膜漫灌两种栽培管理下土壤CH4和N2O通量日变化和季节变化特征进行了研究。结果表明,随时间的推移,无膜漫灌栽培管理措施下棉田土壤CH4日变化通量呈先降后升趋势,而膜下滴灌栽培处理CH4排放通量日变化则呈现先升后降趋势;在整个生长季节,无膜漫灌和膜下滴灌土壤CH4季节变化规律不太明显,前者吸收大气CH4 45.2～52.5 mg m-2 a-1,后者释放CH4通量为0.7～23.1 mg m-2 a-1。两种栽培管理措施下棉田土壤N2O通量的日变化和季节变化均随时间的推移均呈现先升后降趋势,但是,无膜漫灌日均排放N2O通量显著高于膜下滴灌。在整个生长季节,无膜漫灌土壤N2O释放量(N2O 99.3～320.0 mg m-2 a-1)显著高于膜下滴灌(N2O60.0～259.0 mg m-2 a-1)。以上结果说明,膜下滴灌栽培管理措施可以改变旱田传统无膜漫灌栽培土壤与大气CH4的交换方向,促进土壤CH4向大气的排放,但对N2O通量日变化和季节变化规律不产生影响,显著降低土壤N2O的排放量。

Currently, limited information is available regarding the effects of different farmland management practices on fluxes of methane （CH4） and nitrous oxide （N20） from the fields. In this study, diurnal and seasonal variations of CH4 and N20 fluxes from fields under different farming practices, i.e. nowadays commonly used mulched drip irrigation （MD） and traditional mulch-free flood-irrigation （MFF）, were monitored with closed static chambers and a modified gas chromatograph （HP4890）. This study was conducted in a cotton field in Xinjiang, Northwestern China. Results show that the diurnal variations of CH4 in treatments MFF and MD were in sharp contrast. In the former CH4 flux descended first and then ascended, while in the latter it proceeded reversely. Over the whole cotton growing season, however, it had no clear pattern to follow. The soil in the former absorbed a total of CH40.7 -23.1 mg m^-2a^-1 from the atmosphere, while the soil in the latter released a total of cn4 45.2 - 52.5 mg m^-2a^-1. As for N2O fluxes, the two treatments exhibited similar diur- nal and seasonal patterns of a curve going up first and down later. However, in treatment MFF daily N2O flux was muchhigher than in treatment MD. Over the whole cotton growing season, the total N：O emission was higher in treatment MFF （N2099.3-320.0 mgm^-2a^-1） than in treatmentMD （N2060.0-259.0 mgm^-2a^-1）. All the findings suggest that the MD system could alter the direction of the CH4 flux between the soil and the atmosphere of field agro-ecosystem in the arid region. It enhanced considerably CH~ emission, but did not affect much the diurnal or seasonal variation of N2O flu- xes, however, it did reduce N2O emission from the soil quite significantly.