土壤溶解性有机物对CO2和N2O排放的影响

Abstract

农田土壤是温室气体的重要排放源，溶解性有机物作为土壤微生物容易利用的基质，其含量变化与温室气体的产生和排放密切相关。基于室内培养试验，对溶解性有机物影响土壤CO₂、N₂O的排放过程进行了分析。设置空白（CK）、单施秸秆（S）、单施氮肥（N）、秸秆和氮肥（S+N）4个不同的处理，对添加不同物质条件下土壤溶解性有机碳（DOC）、溶解性有机氮（DON）和CO₂、N₂O的排放动态进行了研究，对DOC和DON影响CO₂、N₂O的排放过程进行了探讨。结果表明：不同处理的温室气体排放通量和土壤DOC、DON含量差异显著；各处理的CO₂排放通量和DOC动态随培养时间的延长呈现逐渐减小的趋势，S和S+N处理的N₂O排放和DON动态呈现先增大后减小的趋势； S+N处理的CO₂排放量最高，DON含量也显著高于其他处理，单施秸秆（S）处理的N₂O排放量和DOC含量显著高于其它处理，单施氮肥（N）对土壤CO₂的排放量和DOC含量的影响较小；土壤CO₂和N₂O的排放通量与土壤DOC和DON含量呈显著的相关性，相关系数（<em>R</em>²）达0.6以上，说明溶解性有机物的含量和动态对CO₂、N₂O的排放过程产生显著影响。;Agricultural soil is the main emission source of greenhouse gas. Dissolved organic matter (DOM) in agricultural soil is the labile component of organic matter and the most available substrates for microbial. Its concentration and dynamic change is closely related to the production and emission of greenhouse gas. The aim of this study was to estimate the effect of soil DOM concentration on the emission of CO₂ and N₂O after materials addition. And the relationship between the dynamics of DOM concentration and the emission of CO₂ and N₂O was evaluated after that. An incubation experiment was adopted in this study with the soil sampled from the tillage layer in the field at Yucheng comprehensive experimental station, Chinese Academy of Sciences. Four treatments, which were soil with or without material addition, i.e., straw only (S), nitrogen only (N), straw with nitrogen (S+N), and control (CK), respectively, were set. The amount of these added materials in this study was estimated based on the conventional application of N fertilizer and straw return in the North China Plain. The emissions of CO₂ and N₂O, and the concentrations of dissolved organic carbon and nitrogen (DOC/DON) were measured at different time interval during the 342 days incubation. The results showed that there was significant difference between these four treatments (<em>P</em> < 0.05) for the concentration of DOM and the emissions of CO₂ and N₂O. It presented a gradually decreasing trend in the emission of CO₂ and the concentration of DOC in soil for all these four treatments. However, the emission of N₂O and the concentration of DON increased at first and then decreased with time for these two treatments of S and S+N. In addition, the treatment of S+N showed the highest average concentration of DOC and DON. The lowest mean concentration of DOC and DON was found in the treatment of N and CK, respectively. In the treatment of S+N added with N fertilizer and corn straw, the cumulative CO₂ emission was 1668.11kg/hm² during the incubation period, which was much higher than the other three treatments. In the treatment of N added with N fertilizer only, the cumulative CO₂ emission was 196.01kg/hm², which was much lower than the other three treatments. The highest cumulative N₂O emission, 495.75g hm^-2, was found in the treatment of S with the addition of straw only, and the lowest cumulative N₂O emission, 136.93 g hm^-2, was found in the treatment of CK. A logarithmic equation was fitted between CO₂ emission and the time for each treatment (<em>R</em>² > 0.57, <em>P</em> < 0.05). There was a significant correlation between the emission of CO₂ and the concentration of DOC(<em>R</em>² > 0.65). It also happened between the emission of N₂O and the concentration of DON in soil (<em>R</em>² > 0.62), indicated that the concentration and dynamics of DOC and DON in soil caused by the addition of straw and N fertilizer had a significant influence on the emission of CO₂ and N₂O.