灌水量对温室番茄土壤CO2、N2O和CH4排放的影响

为揭示不同灌水量对温室番茄土壤CO₂、N₂O和CH₄排放及作物产量的影响,提出有效的减排措施,试验设置充分灌溉(1.0W,W_1.0;W为充分供水的灌水量)、亏缺20%灌溉(0.8W,W_0.8)和亏缺40%灌溉(0.6W,W_0.6)3个灌水水平,采用静态暗箱/气相色谱法于2017年4—12月对两茬温室番茄土壤CO₂、N₂O和CH₄进行全生长季监测,分析土壤CO₂、N₂O和CH₄排放对不同灌水量的响应.结果表明: 番茄两个生长季中,土壤CO₂、N₂O和CH₄排放量均随着灌水量增加呈现逐渐增加的趋势(W_1.0＞W_0.8＞W_0.6),除W_0.6和W_1.0处理间土壤N₂O排放具有显著差异外,其他各处理间气体排放差异均不显著.与W_1.0处理相比,W_0.6和W_0.8处理土壤CO₂排放分别减小了12.2%和8.3%,N₂O分别减小了19.1%和8.0%,CH₄分别减小了11.0%和6.2%.番茄产量和由土壤N₂O和CH₄引起的全球增温潜势(GWP)均随灌水量增加而增加;与W_1.0处理相比,W_0.6处理产量和GWP显著减小,降幅分别为17.0%和22.9%,而W_0.8处理对两者未产生显著影响.单位产量GWP随灌水量增加表现为先增加后降低的趋势(W_0.8＞W_1.0＞W_0.6),处理间差异不显著.灌溉水利用效率(IWUE)随灌水量增加而降低,与W_1.0处理相比,W_0.6和W_0.8处理IWUE分别增加了38.3%和9.4%.回归分析表明,土壤CO₂排放通量与土壤水分呈指数负相关关系;土壤CH₄通量与土壤水分呈线性正相关关系;当土壤温度小于18 ℃和大于18 ℃时,土壤N₂O排放通量与土壤温度间均呈指数负相关关系.灌水增加了番茄产量和温室气体排放,但降低了IWUE.综合考虑番茄产量、IWUE和温室效应,推荐W_0.8处理为较佳的灌溉模式.

Effects of irrigation amounts on soil CO2, N2O and CH4 emissions in greenhouse tomato field.

To understand the effects of different irrigation amounts on soil CO₂, N₂O, and CH₄ emission characteristics and tomato yield, and further put forward effective reduction measures, we carried out an experiment with three irrigation levels: full irrigation (1.0W, W_1.0; W meant irrigation amount needed to provide the adequate water), 20% deficit irrigation (0.8W, W_0.8) and 40% deficit irrigation (0.6W, W_0.6). We used static closed chamber and gas chromatography method to measure greenhouse gas emission in two consecutive greenhouse tomato rotation cycles from April to December, 2017. The results showed that cumulative soil CO₂, N₂O and CH₄ emissions increased with increasing irrigation amounts in the two growing seasons (W_1.0＞W_0.8＞W_0.6), and significant difference of N₂O between W_0.6 and W_1.0 was observed, while other treatment effects on soil gas emissions were not obvious. Compared to W_1.0, cumulative soil CO₂ emissions were decreased by 12.2% and 8.3%, cumulative soil N₂O emissions were decreased by 19.1% and 8.0%, and cumulative soil CH₄ emissions were reduced by 11.0% and 6.2% for W_0.6 and W_0.8, respectively. Tomato yield and global warming potential of soil N₂O and CH₄ emissions (GWP) increased as irrigation amount increasing. Compared with W_1.0, W_0.6 significantly decreased tomato yield by 17.0% and GWP by 22.9%, while the difference between the effects of W_0.8 and W_1.0 on these two parameters was not significant. Global warming potential per tomato yield presented an increase then a decrease as irrigation amount increasing (W_0.8＞W_1.0＞W_0.6), but without stanificance. Irrigation water use efficiency (IWUE) showed a decrease with increasing irrigation amount. Compared with W_1.0, IWUE under W_0.6 and W_0.8 was increased by 38.3% and 9.4%, respectively. Soil CO₂ flux was nega-tively and exponentially correlated with soil moisture. The dependence of soil CH₄ flux on soil moisture showed a significantly positive correlation. An exponential negative correlation was observed between the soil N₂O flux and soil temperature when soil temperature was below or above 18 ℃. Irrigation increased tomato yield and soil greenhouse gas emissions, but decreased IWUE. Therefore, W_0.8 was the best mode of irrigation management when synthetically considering tomato yield, IWUE, and greenhouse effect.