不同施氮水平下陇中黄土高原旱作小麦农田土壤温室气体的排放特征

Greenhouse gas emission characteristics of dry wheat field in the loess plateau of central gansu under different nitrogen application levels

【目的】研究不同施氮水平对陇中旱作小麦农田不同生育时期温室气体排放的影响,为旱区农业合理施用氮肥、减排温室气体提供理论依据.【方法】试验以长期施氮春小麦田为供试土壤,其中5个处理组氮肥投入量分别为0,52.5,105.0,157.5,210.0kg/hm^2.采用静态暗箱-气象色谱法测定旱作小麦农田土壤N_2O的排放通量,利用EGM-4便携式土壤碳通量测定系统测定小麦农田土壤CO_2的排放通量.【结果】春小麦全生育期内,不同施氮水平下N_2O排放通量变化趋势一致,其中在分蘖期(4月25日)、抽穗期(6月8日)和灌浆期(7月10日)出现排放峰,且灌浆期排放峰明显高于其他时期,出苗期出现排放最低峰.在灌浆期N_5处理组N_2O气体通量最高,其排放值为0.806mg/(m^2·h).CO_2通量变化在不同处理间较为一致,在分蘖期前变化幅度较小,至三叶期开始降低,其中N_1、N2处理组在三叶期到分蘖期CO_2通量变化幅度最大,分别从0.563、0.402μmol/(m^2·s)降低到0.238,0.183μmol/(m^2·s),其他处理变化幅度较小.相关分析发现,N_2O平均通量与各土层土壤温度呈负相关,但相关性不显著;与0～5cm土壤含水量呈负相关,与5～10cm和10～30cm土壤含水量呈正相关,相关系数分别为0.496和0.105.CO_2平均通量与各土层土壤温度呈显著正相关,相关系数分别为0.427、0.419和0.367;与0～5cm和10～30cm土壤含水量呈显著正相关,相关系数分别为0.529和0.385.【结论】在整个生育期内,小麦田N_2O和CO_2的排放量均在一定程度上受到土壤温度和土壤水分的共同影响.同时,小麦田不同施氮水平处理下N_2O的平均排放通量随着施肥量的增加而增加,且N_5处理组N_2O排放量最高;小麦田CO_2的平均排放通量随施氮量的增加而逐渐降低,且N_1处理组CO_2排放通量最高.

【Objective】The purpose of this study was to determine the effects of different nitrogen application levels on the greenhouse gas emissions of dry wheat fields in central Gansu in different growthstages,and to provide a theoretical basis for the rational application of nitrogen fertilizer and greenhouse gas emission reduction in dry land agriculture.【Method】Long-term nitrogen application in spring wheat field was used as the test soil,of which five nitrogen fertilizer inputs were 0,52.5,105.0,157.5,210.0kg/hm2.The N2O emission fluxes in dry wheat field soil were measured by static cable-meteorological chromatography,and the CO2 emission fluxes in wheat field soil were measured by EGM-4portable soil carbon fluxes measurement system.【Result】During the whole growth period of spring wheat,the change trend of N2O emission flux was the same under different nitrogen application levels,and the emission peaks appeared in tillering stage(April 25),heading stage(June 8)and pustulation period(July 10).The emission peak in pustulation stage was significantly higher than that in other periods,and the lowest emission peak appeared in seedling stage.The highest gas flux of N2O appeared in pustulation stage treated by N5 and the emission value was 0.806mg/(m2·h).The change of CO2 flux was more consistent among different treatments,and the change range was small before trefoil stage,and began to decrease in trefoil stage,in which the change of CO2 fluxes in N1 and N2treatment from trefoil stage to tillering stage was the largest,reduced from 0.563,0.402μmol/(m2·s)to 0.238,0.183μmol/(m2·s),while the change range in other treatments was slightly.Correlation analysis showed that the average flux of N2O was negatively correlated with soil temperature in each soil layer,but it was not significant.It was negatively correlated with soil moisture content of 0~5cm,and was positively correlated with soil moisture content of 10~30cm and 5~10cm,the correlation coefficient was 0.496 and 0.105,respectively.There was a significant positive correlation between the average flux of CO2 and soil temperature in each soil layer,and the correlation coefficient was 0.427,0.419 and 0.367,respectively.It was positively correlated with 0~5cm and 10~30cm soil moisture content significantly,and the correlation coefficient was 0.529 and 0.385,respectively.【Conclusion】During the whole growth period,the emissions of N2O and CO2 in wheat fields were affected by the combined action of soil temperature and soil moisture to some extent.At the same time,the average emission flux of N2O increased with the increase of fertilization amount under different nitrogen application levels in wheat field,and the N2O emission load was highest in N5 treatment.The average emission flux of CO2 decreased with the increase of nitrogen application amount in wheat field,and CO2 emission flux was highest in N1 treatment.