Partial wetting irrigation resulted in non-uniformly low nitrous oxide emissions from soil

Abstract

Partial wetting irrigation influences soil moisture distribution, which potentially changes soil nitrous oxide (N2O) emission. Incubation experiments were conducted to reveal the impact of non-uniform moisture distribution on soil N2O emissions under subsurface-drip-irrigation (SDI), with surface-irrigation (SI) as a control. Results indicated that soil N2O emission from different subregions of SDI soil varied synchronized to soil moisture. The wetting-drying process in different soil subregions under SDI incurred pulse N2O emissions unexceptionally, but the pulse magnitudes and timing of the occurrence varied among subregions. The pulse N2O emission magnitudes positively correlated to the match degree of soil moisture to the optimal soil moisture level for peak N2O emissions. The soil water-filled-porosity WFPS ranges for peak N2O fluxes, the determine coefficient of the exponential functions between N2O flux and soil WFPS and its average slopes, decreased gradually from the central to periphery SDI soil subregions. Both peak and cumulative N2O fluxes were much lower from the periphery subregions than from central subregions. On the whole, SDI reduced the cumulative N2O emissions by 77.3–86.7% compared to SI, with periphery suberegions of R3 and R4 contributing for more than 76%. The partial wetting SDI irrigation can significantly reduce soil N2O emissions and is a promising strategy for soil N2O emission mitigation. Further research should be conducted on how to design SDI properly to balance the soil moisture uniformity/efficiency and soil N2O emission reduction.