水肥一体化条件下设施菜地的N2O排放

在保证作物产量的前提下,研究减少农田土壤N_2O排放的水肥统筹管理措施对全球温室气体减排具有重要意义。以京郊典型设施菜地为例,设置了农民习惯(FP)、水肥一体化(FPD)、优化水肥一体化(OPTD)和对照(CK)4个处理,采用静态箱-气相色谱法,对果菜-叶菜(黄瓜-芹菜)轮作周期内土壤N_2O排放进行了观测,并分析了氮肥施用量、灌溉方式、土壤温度和湿度等因素对土壤N_2O排放的影响。结果表明:在黄瓜-芹菜种植模式中,各施氮处理除基肥施用后N_2O排放峰持续10—15d外,一般施肥、施肥+灌溉事件后土壤N_2O排放峰均呈现3—5d短而急促的情形。黄瓜生长季N_2O排放通量与土壤湿度(WFPS)之间呈现显著相关的关系;芹菜生长季N_2O排放通量与土壤温度之间呈现显著相关的关系。观测期内FP处理N_2O排放量为(31.00±2.15)kg N/hm~2,FPD处理与之相比N_2O排放量减少了4.2%,而OPTD处理在减少40%化肥氮量的情况下,N_2O累积排放量比FP处理减少了42.7%,且达到显著水平。说明在水肥一体化条件下,合理改变施肥体系是减少N_2O排放的前提,在此基础上进行水肥优化是设施菜地保持产量、减少N_2O排放的重要技术措施。

N2O emissions from a vegetable field with fertigation management and under greenhouse conditions

Fertigation is an alternative cropping management practice that combines fertilization and irrigation, and it is being employed in China to reduce nitrous oxide (N₂O) emissions while increasing fertilizer use efficiency. A field experiment was conducted at a vegetable field with cucumber and celery planted under greenhouse conditions, in the suburbs of Beijing. The field was divided into 12 plots with 4 treatments. These were a control (CK), routine farmers'' practice treatment (FP), farmers'' practice with drip irrigation treatment (FPD), and optimal fertilization with drip irrigation treatment (OPTD). FPD consisted of drip irrigation with fertilizers dissolved in the irrigation water. OPTD had the same fertigation but N fertilizer was reduced by 40%. Soil N₂O fluxes were measured by static chambers all year round, and the soil temperature, and soil moisture, ammonium, and nitrate levels were monitored in parallel with the N₂O measurements for all the treatment plots. The application event induced N₂O emission peaks that lasted for about 10-15 days in all the plots. However, all the later dressing events caused relatively short N₂O emissions lasting 3-5 days. During the observation period, the accumulative N₂O emissions differed across the treatments. In comparison with the annual N₂O emission rate of (31.00±2.15) kg N/hm² measured in FP, the N₂O emission rates measured in FPD and OPTD were 4.16% and 42.71% lower, respectively. During the cucumber growing season, the N₂O fluxes were significantly correlated with the soil water filled pore space (WFPS) for all treatments, but during the celery growing season, the N₂O fluxes were significantly correlated with soil temperature for all treatments. The results indicated that optimizing fertilization-irrigation by adopting fertigation could reduce N₂O emissions from agricultural systems.