Impacts of irrigation methods on greenhouse gas emissions/absorptions from vegetable soils

Recently, N2O, CO2, and CH4 have been gaining attention as major greenhouse gases (GHGs) that contribute to global warming. Agricultural water-saving irrigation technology has become more and more important and is widely applied to the arid areas. These influences have important and strategic significances for reducing greenhouse effects. However, there is limit information regarding the influence of irrigation methods on soil gases emissions. We investigated the effect of mulched drip irrigation (MDI), drip filtration irrigation (DFI), and conventional irrigation (CK) on N2O, CO2, CH4 emissions, affecting factors and their correlations in a greenhouse soil. Observations were performed from April to August in 2015 on the entire tomato growth season. We monitored the flux of GHG emissions by the static chamber-gas chromatograph method under three irrigation conditions: mulched drip irrigation (MDI), drip filtration irrigation (DFI), and conventional irrigation (CK). To investigate the effects of affecting factors on soil GHG emissions, we also measured soil temperature (5 cm), soil moisture, and air temperature. Compared with the cumulative emission of GHGs (N2O and CH4 calculation in the form of CO2), we created the concept of the ratio of yield and gas (crop yield and soil accumulated GHG emissions). Tomato yield of MDI and DFI is significantly higher than CK. Soil moisture is the main factor affecting N2O emissions and CH4 exchange during the tomato-growing season. N2O emission fluxes have an extremely significant correlation with water-filled pore space (WFPS) at suitable temperatures. CO2 emissions demonstrated a significant correlation with environment temperature (soil and air). CO2 emissions gradually increased and had seasonal variations with rising temperatures and plant growth in each irrigation method. CH4 exchange fluxes showed a significant correlation with WFPS. MDI obtains high yields, is cost-efficient, conserves water, and produces the least amount of integrated GHGs. It helps to mitigate global warming and it would be the best irrigation method.