[Effect of Water-Fertilizer-Gas Coupling on Soil N2O Emission and Yield in Greenhouse Tomato].

To reveal the effect of water, fertilizer, and gas coupling on soil N2O emissions in greenhouse tomato soil and suggest appropriate measures for increasing yield and reducing N2O emissions, static chamber-gas chromatography was used to study the effects of soil N2O emissions. The variation laws of soil temperature, water-filled pore space (WFPS), NO3--N content, and O2 content and the influence mechanism of N2O emission under the condition of water-fertilizer-gas coupling were analyzed. Aerated conditions comprised two water levels, 0.6 W and 1.0 W (representing 40% deficit irrigation and full irrigation, W represents when sufficient irrigation water was available), and three nitrogen levels (120 kg·hm-2, 180 kg·hm-2, and 240 kg·hm-2, representing low, medium, and high nitrogen, respectively, with 50% F, 75% F, and F, F is the recommended amount of nitrogen application locally). Three levels of fertilization were used as controlled unaerated full irrigation (O representing aeration, and CK representing conventional drip irrigation). Nine treatments were designed in the experiment. The results showed that the tomato field cumulative emission of N2O under full irrigation (W2F1O, W2F2O, and W2F3O) increased by an average of 55.7% compared with the corresponding treatment at W1 level (P<0.05). The N2O emissions of W1F3O, W2F3O, and W2F3CK fields significantly increased by 13.4% and 43.8% compared with medium nitrogen W1F2O, W2F2O, and W2F2CK and low nitrogen W1F1O, W2F1O, and W2F1CK treatments, respectively (P<0.05).Compared with the corresponding unaerated full irrigation, the emissions (W2F1O, W2F2O, and W2F3O) significantly increased by 11.2% (P<0.05). Aeration, the increase of nitrogen rate, and irrigation amount resulted in the increment of tomato yield and yield-scaled N2O emissions. Compared with medium nitrogen, the yield and yield-scaled N2O emission of high nitrogen treatment increased by 12.5% (P<0.05) and 3.9% (P>0.05), respectively. Compared with low nitrogen treatment, the yield and yield-scaled N2O emission of high nitrogen treatment increased by 30.4% and 9.6% (P<0.05), respectively. The yield and yield-scaled N2O emissions of aerated full irrigation significantly increased by 29.7% and 18.7%, respectively, compared with aerated deficient irrigation. Compared with unaerated irrigation treatment, the yield under aerated treatment increased by 10.4% (P<0.05), and the yield-scaled N2O emission increased by 3.9% (P>0.05). Under the conditions of increasing irrigation water, decreasing fertilizer application, and aeration, partial factor productivity, and irrigation water use efficiency (IWUE) can be significantly increased. After comprehensive consideration of cumulative N2O emissions, tomato production, nitrogen fertilizer utilization efficiency, IWUE, and yield-scaled N2O emission, it can be concluded that aerated low nitrogen full irrigation is an optimal management mode. The results provide reference for increasing yield and reducing emissions of greenhouse tomato.

[Effects of irrigation amounts on soil CO2, N2O and CH4 emissions in greenhouse tomato field.] / 灌水量对温室番茄土壤CO2、N2O和CH4排放的影响.

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, W1.0; W meant irrigation amount needed to provide the adequate water), 20% deficit irrigation (0.8W, W0.8) and 40% deficit irrigation (0.6W, W0.6). 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 (W1.0＞W0.8＞W0.6), and significant difference of N2O between W0.6 and W1.0 was observed, while other treatment effects on soil gas emissions were not obvious. Compared to W1.0, 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 W0.6 and W0.8, respectively. Tomato yield and global warming potential of soil N2O and CH4 emissions (GWP) increased as irrigation amount increasing. Compared with W1.0, W0.6 significantly decreased tomato yield by 17.0% and GWP by 22.9%, while the difference between the effects of W0.8 and W1.0 on these two parameters was not significant. Global warming potential per tomato yield presented an increase then a decrease as irrigation amount increasing (W0.8＞W1.0＞W0.6), but without stanificance. Irrigation water use efficiency (IWUE) showed a decrease with increasing irrigation amount. Compared with W1.0, IWUE under W0.6 and W0.8 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 ux and soil temperature when soil temperature was below or above 18 ℃. Irrigation increased tomato yield and soil greenhouse gas emissions, but decreased IWUE. Therefore, W0.8 was the best mode of irrigation management when synthetically considering tomato yield, IWUE, and greenhouse effect.