Response of Soil N2O Emissions to Soil Microbe and Enzyme Activities with Aeration at Two Irrigation Levels in Greenhouse Tomato (Lycopersicon esculentum Mill.) Fields

Abstract

Aerated irrigation is proven to increase soil N2O emissions; however, the mechanisms of N2O release are still unknown. A field experiment for two consecutive greenhouse tomato-growing seasons, from August 2016 to July 2017, was carried out to examine (1) the differences of aeration and irrigation on soil N2O emissions with a static chamber GC technique, and on soil physical and biotic parameters, and (2) the response of soil N2O emissions to soil physical and biotic parameters. Two irrigation levels were included: 60% (low irrigation) and 100% (high irrigation) of the full irrigation amount. Each irrigation level contained aeration and control, totaling four treatments. During the two growing seasons, soil N2O emissions with aeration were 4.5% higher than the control (p > 0.05). Soil N2O emissions under the high irrigation were 13.8% greater than under the low irrigation, and the difference was significant in 2017 (p < 0.05). Aeration and irrigation had positive effects on the mean soil nitrifier abundance and mean soil urease activity, and the impact of irrigation on urease was significant in 2016 (p = 0.001). In addition, aeration negatively influenced the mean soil denitrifier abundance, while irrigation positively influenced the mean soil denitrifier abundance. Regression analysis showed that the soil water-filled pore space, temperature, and denitrifier abundance were primary factors influencing soil N2O fluxes. This study provides a further understanding of the processes affecting soil N2O emissions and N dynamics, which may assist in developing mitigation strategies to reduce N2O emissions.