CO2浓度升高与硝化抑制剂对冬小麦田间N2O排放量的影响

Effects of elevated CO_2 and nitrification inhibitors on N_2O emissions from a winter wheat cropping system

以冬小麦中麦175为供试品种,利用农田开放式CO_2浓度增高(FACE)系统,研究未来大气高CO_2浓度对冬小麦田间N_2O排放的影响,以及施用硝化抑制剂(2-氯-6-三氯甲基吡啶)是否可以起到抑制冬小麦田间N_2O的排放量升高的潜能。试验结果表明:CO_2浓度升高显著提高冬小麦田间N2O的排放增幅达到67.6%,追肥灌溉后小麦田N_2O排放量较大,随着冬小麦生育进程的推进N_2O的排放量逐渐减少,硝化抑制剂对中麦175田间N_2O排放量的影响并不明显。因此,在未来高CO_2浓度环境条件下,可以通过采取相应的耕作制度和栽培技术措施等来降低冬小麦田N_2O的排放量。试验结果对冬小麦田间是否选择施用2-氯-6-三氯甲基吡啶来控制N_2O的排放起到一定的参考作用。

Nitrous oxide （N2O） is one of the most important greenhouse gases emitted from the fertilized agricultural soils. This agricultural greenhouse gas is produced through nitrification and denitrification processes. The possible factors affecting N2O emissions have been widely studied, including the timing and rate of irrigation and nitrogenous fertilizer application, and environmental soil conditions such as temperature, moisture content, and microbial activity. The response of N2 0 emissions to the application of nitrification inhibitors has also been investigated in the last few decades, particularly in the context of climate change mitigation. More recent studies have examined the effects of elevated CO2 on N2O in various agricultural contexts, including a variety of cropping systems. However, there are currently no available reports on thepotential effects of the interaction between elevated CO2 and the nitrification inhibitors on N2O emissions from a winter wheat field under open-air conditions. We therefore measured N2O flux using closed chambers at the Free-Air Carbon dioxide Enrichment （FACE） experimental facility in northern China. The target atmospheric CO2 concentrations were 400 μL/L （ambient） and 550 μL/L（elevated） for treatments with and without the application of a nitrification inhibitor （Nitrapyrin）. Nitrapyrin was applied twice （24% N-serve, 10 mg/kg soil） during the growing season--on day 1 and day 30 after fertilizer application. Measurements （0, 20, and 40 min after chamber closure） were taken from the start of the elongation stage until harvest （Triticum aestivum L. cv. Zhongmai 175 ）. Measurements were taken daily for a week after each nitrapyrin application, and on a weekly basis from the application of nitrapyrin until harvest. The results showed that： 1 ） from the elongation stage to harvest, the elevated atmospheric CO2 concentration increased N2O emissions from the soil by 67.6% overall. Within a week of the first and second applications of the nitrification inhibitor, N2O flux was increased by 58. 1% and 78.7%, respectively, under conditions of elevated CO2. 2） Nitrapyrin had no significant effect on N2O emissions from the winter wheat field. The effect of the interaction between CO2concentration and nitrapyrin application on N2O emissions was not significant. 3） N2O flux was the highest after fertilization and irrigation, before declining gradually over the course of the season. In our study, elevated CO2 stimulated N2O emissions, possibly as a result of higher carbon （C） input into the soil and C substrate availability for denitrifiers. However, the increase in emissions was not mitigated by the application of nitrapyrin. The ineffectiveness of nitrapyrin observed in our study may be due to （i） the fact that the background ammonium （ NH4＋ ） content in the soil was high at our study site, and/or （ii） the adsorption of the active ingredient of the inhibitor into the soil organic matter may be strong enough to reduce contact between the ingredient and NH4＋. Further research is required to substantiate these findings. Our results indicate that under future atmospheric CO2 concentrations, it will be necessary to adopt appropriate agricultural management and cultivation practices in order to reduce N2O emissions from winter wheat fields. This study provides implications for the use of nitrapyrin in the mitigation of N2O emissions from winter wheat fields.