Abstract
To reveal the impact of soil moisture distributions on nitrous oxide (N2O) emissions from wet soils irrigated by sub-surface drip irrigation (SDI) with different surface soil wetting proportions, pot experiments were conducted, with surface irrigation (SI) as a control. Results indicated that irrigation triggered N2O pulsing effect in all SDI treatments, yet N2O values reduced with the decrease of surface soil wetting proportions of SDI irrigated soils, and the occurrence times were lagged. The peak N2O fluxes and the corresponding soil water filled pore space (WFPS), as well as the coefficients of determination (R2) of the exponential function between N2O fluxes and soil WFPS, decreased with the reduction of surface soil wetting proportions with SDI treatment, and from the central sub-region to the periphery sub-region. The pulse period contributed most to the reduction of N2O emissions in SDI compared to SI treatments and should be a key period for N2O emission mitigation. Over the whole experimental period, the area-weighted average cumulative N2O fluxes from SDI treatments were 82.3–157.3 mg N2O m−2 lower than those from SI treatment, with periphery sub-regions of R3 and R4 (radius of 19–27 cm and 28–36 cm from the emitter horizontally) contributing to more than 75.8% of the total N2O emission mitigation. These results suggest that reducing surface soil wetting proportions or the increments of topsoil WFPS for SDI irrigated soils is a promising strategy for N2O emission reduction.
Highlights
Nitrous oxide (N2 O) is one of the most important atmospheric trace gases, with a global warming potential 298 times that of carbon dioxide over a 100-year scale [1,2,3]
N2 O emissions from surface drip irrigation (SDI) irrigated soils with different surface soil wetting proportions were investigated in the present research
Results indicated that surface soil wetting patterns caused by SDI significantly affected soil N2 O emissions
Summary
Nitrous oxide (N2 O) is one of the most important atmospheric trace gases, with a global warming potential 298 times that of carbon dioxide over a 100-year scale [1,2,3]. The differences in soil moisture distribution might lead to changes in soil-related factors (such as soil aeration, the transformation of nitrogen, the distribution of soil NH4 + and NO3 − , and soil microbial community composition), and in the production and emission of N2 O [15,16] It has been suggested in the literature that SDI might be a promising water management practice for mitigating soil N2 O emissions [11,17,18]. For SDI, the soil wetting pattern will vary greatly due to the depth the emitter is set at or differences in the irrigation water volumes [20,21], which might lead to differences in the distribution of soil moisture, and N2 O emissions. The objectives were to quantify N2 O emissions from SDI irrigated soils under different surface soil wetting patterns, and to reveal the differences in N2 O emission responses to soil moisture among SDI wetting patterns
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