[Effect of Irrigation Patterns on Soil CO₂ and N₂O Emissions from Winter Wheat Field in North China Plain]

The water-saving irrigation is the trend of modernized agriculture. This paper aimed to study the effect of water-saving irrigation on soil CO₂ and N₂O emissions. The field experiments were conducted under micro sprinkler irrigation of integrated water and fertilizer (MSI) and conventional flooding irrigation (FI) in winter wheat growth season in the west of North China Plain during 2013- 2014 using the static chamber method. This paper analyzed the seasonal variation of soil CO₂and N₂O emissions under MSI and FI, and then compared the soil CO₂ and N₂O emissions from treatments located in different vertical distance away from micro sprinkler pipe. Root exclusion was used to estimate the components of soil respiration and agricultural carbon sequestration intensity under MSI and FI in winter wheat field. The results indicated that: (1) The average soil CO₂ emissions under MSI and FI were 418.19 mg (m² · h)⁻¹ and 372.14 mg · (m² · h)⁻¹ respectively with no significant difference, and cumulative CO₂ emissions under MSI and FI were 2 150.6 g · m⁻² and 1 904.6 g · m⁻², respectively. (2) During returning green stage to harvest stage of winter wheat, the highest soil CO₂ cumulative emissions were found at the closest site to the micro sprinkler irrigated pipes under MSI. However, there were no significant differences among spatial treatments. (3) Under MSI and FI, soil heterotrophic respiration (C) was 468.49 g · m⁻² and 427.31 g · m⁻², and the net primary productivity (3) was 1988.21 g · m⁻² and 1770.54 g · m⁻²; the carbon sink (C) during winter wheat growing season was 1 519.72 g · m⁻² and 1 343.24 g · m⁻², respectively. (4) The average N₂O emissions under MSI and FI were 50.77 µg · (m² · h)⁻¹ and 28.81 µg · (m² · h)⁻¹ respectively with no significant difference. Cumulative N₂O emission under MSI and FI was 272.67 mg · m⁻² and 154.08 mg · m⁻², respectively. (5) During returning green stage to harvest stage of winter wheat, the farther the distance away from the micro sprinkler irrigated pipes, the smaller the soil N₂O emissions. Moreover, there were no significant differences among sptial treatment under MSI. Therefore, despite of the increase of soil CO₂and N₂O emissions, the intensity of carbon sink increased during the transformation from traditional flood irrigation to micro sprinkler irrigation in winter wheat fields.