不同灌溉方式对设施菜地N2O排放的影响及其年际差异

通过田间原位试验,利用自动静态箱-气相色谱法对设施黄瓜季土壤N_2O排放进行了连续两年的观测,探讨了不同灌溉方式(传统漫灌和滴灌)对N_2O排放的影响及其年际差异,以期为设施菜地N_2O减排提供数据支撑和理论基础。试验设置3个处理,分别为对照处理(CK)、漫灌施肥处理(FP)、滴灌施肥处理(FPD)。CK处理不施氮肥,FP、FPD处理氮肥施用量为有机肥500 kg N·hm~(-2)、化肥700 kg N·hm~(-2),其中化肥根据作物养分需求多次施入。研究结果表明:设施菜地N_2O排放峰主要集中于施肥和灌溉后,基肥持续7 d左右,追肥N_2O排放峰持续3~5 d。土壤温度、水分和气温等因子都能显著影响N_2O排放通量的变化,但不同年际之间对N_2O排放的影响不同,2015年N_2O排放通量的变化主要受土壤温度和气温影响,而2016年主要受土壤湿度和温度影响;改变灌溉方式,对土壤温湿度变化没有产生显著的影响;相同氮肥施用量下,滴灌相比常规漫灌在提高作物产量的同时,能减少N_2O排放总量29.4%~35.1%,并且没有显著年际差异;滴灌相比常规漫灌能减少N_2O排放强度(即单位经济产量N_2O排放量)34.5%~37.5%、排放系数47.2%~47.7%,两年的观测没有显著的年际差异。可见,滴灌相比漫灌在提高蔬菜产量的同时,能显著减少N_2O排放,而且年际之间没有显著差异,是设施菜地值得推荐的一种减排技术,并可为N_2O长期减排效果的估算提供参考。

Effect of irrigation pattern on soil N2O emissions and interannual variability in greenhouse vegetable fields

Greenhouse vegetable(GV) fields are one of the most important sources of N₂O emissions, and drip irrigation has attracted increasing attention as an effective strategy for reducing such emissions. In the present study, we performed a two-year experiment in a GV field, which included two cucumber seasons, and used the static opaque chamber method to quantify N₂O emissions. We also discussed the influences of different irrigation methods(traditional flood irrigation and drip irrigation) on N₂O emissions and its interannual variation, in order to provide data support and theoretical basis for mitigating N₂O emissions in GV fields. Our study involved three irrigation treatments, including control(CK), flood irrigation(FP), and drip irrigation(FPD). There was no N fertilizer input for the CK treatment, whereas the organic and synthetic N inputs rates were 500 and 700 kg N·hm^-2, respectively, for both the FP and FPD treatments, and multiple synthetic N applications were applied according to the nutrient demands of the crops. The N₂O emission peaks of the GV fields were induced by both fertilization and irrigation, and they usually lasted for 7 d after basal fertilizer application but only 3~5 d after topdressing events. Soil temperature, moisture, and air temperature significantly affected N₂O emission flux, but the dominant factors were different in 2015 and 2016; N₂O emission flux was mainly affected by soil and air temperature in 2015 but was mainly affected by soil moisture and temperature in 2016. There were no significant differences in the soil temperature or moisture of the FP or FPD treatments. Compared to FP, FPD increased crop yield also reduced the total N₂O emissions by 29.4%~35.1% on an equivalent N application rate. Compared with FP, FPD reduced N₂O emission intensity(N₂O emission per unit of economic yield) by 34.5%~37.5%, and the emission factor 47.2%~47.7% in two years. Compared to FP, FPD can significantly reduce N₂O emissions while also increasing vegetable yield, and its mitigation efficiency was no significantly interannual variation between 2015 and 2016. Therefore, FPD could be an effective N₂O mitigation strategy in GV fields and could provide reference for estimating the effects of N₂O emission on a long-term scale.