Different pipe burial depths associated with subsurface drip irrigation significantly affected soil gas emissions

Abstract Efforts are needed to reduce soil greenhouse gas emissions from irrigated croplands. Thus, in this study, patterns of soil carbon dioxide (CO2) and nitrous oxide (N2O) emissions in the root zone of tomato plants grown under subsurface drip irrigation (SDI) involving different pipe burial depths were studied, with surface drip irrigation (DI) used as a control (CK). The soil CO2and N2O emission curves under DI and SDI with pipe burial depths of 10 and 20 cm tended to be similar. In contrast, SDI with a pipe depth of 30 cm resulted in peak CO2and N2O emissions occurring at different times. The different pipe burial depths led to significantly different spatial distributions of soil water‐filled pore space, which indirectly affected root–soil interactions and soil gas emissions through direct effects on total tomato root fork numbers and microbial community composition. The SDI treatments involving 10‐ and 20‐cm pipe burial depths increased the number of root forks to 1.85 and 2.77 times that in the DI treatment, respectively, and increased the Shannon index of the fungal community by 11.9 and 7.29% compared with that in the DI treatment, respectively. The SDI treatment involving the 30‐cm pipe burial depth resulted in 2.22 times the number of root forks compared with that in the DI treatment; however, the Shannon index of the fungal community decreased by 13.6% compared with that in the DI treatment. As a result, the total soil CO2emissions and total soil N2O emissions in the SDI treatment involving the 10‐cm pipe burial depth were 1.37 and 2.03 times those in the DI treatment, and those in the SDI treatment involving the 20‐cm pipe burial depth were 1.33 and 2.17 times those in the DI treatment, respectively. In the SDI treatment involving the 30‐cm pipe burial depth, the total amount of soil CO2emissions was similar to that in the DI treatment; however, the total amount of soil N2O emissions was 28.98% lower than that in the DI treatment. Therefore, soil gas emissions can be reduced by increasing the burial depth of irrigation pipes. These results provide insights into the control of soil gas emissions in agroecosystems.