Study On Greenhouse Gas Emissions And Its Influencing Factors From The Maize-wheat Rotation Field

As a worldwide recognized environmental problem, Global Warming is caused by excessive emission of greenhouse gases, such as CO2, CH4and N2O. Agroecosystem is an important emission source of greenhouse gases and is greatly influenced by anthropological disturbance, which made it an important object to investigate Global Warming and climate change. In this study, the exchange fluxes of CO2, CH4and N2O from a wheat-maize crop rotation field during the whole growing seasons in Beijing area were investigated by static chamber-GC method. Greenhouse gases fluxes were measured from control plot, urea fertilization plot and nitrate fertilization plot during observation periods, and its influencing factors were also measured and discussed, such as soil temperature, pH, WFPS, NH4+-N and NO3--N concentration, organic carbon content and soil enzymes etc.This study showed N2O emissions from the wheat-maize rotation field showed significant unimodal diurnal variation and multimodal dynamic inter-annual variation, and the cumulative N2O emissions of maize growing season was higher than wheat growing season in fertilization plots. During the wheat-maize rotation cycle from2012to2013, the cumulative N2O emissions of control plot, urea fertilization plot and nitrate fertilization plot were1.11,3.84,7.77kg·N-hm-2, respectively. This suggested fertilization application significantly promoted soil N2O emissions and the promotion ability of urea was higher than nitrate fertilizer. In addition, irrigation was another important reason for N2O emissions during wheat growing season. During the observation,5cm soil temperature, NH4+-N concentrations, soil pH, organic carbon contents, catalase, invertase, urease and nitrite reductase significantly affected N2O fluxes, which were major influencing fators for N2O emissions.CO2emissions from the wheat-maize rotation field also showed significant seasonal variations and fertilization application significantly promoted soil CO2emissions, but there was no significant difference of CO2emissions between different N-fertilization applications. CO2emissions also closely related to crop growing situation. During the observation period, CO2fluxes were significantly positively correlated with5cm soil temperature, NH4+-N concentration, catalase, invertase and urease, which were major influencing factors for CO2emissions.During the observation period, soil from maize-wheat rotation field appeared to be a weak source of atmospheric CH4. CH4absorption fluxes varied greatly. Higher CH4absorption fluxes appeared from wheat sowing to soil freezing and from green up stage to maturation period in wheat growing season. The cumulative CH4absorption fluxes of maize growing seasons were less than that of wheat growing seasons. The accumulated absorption rates of CH4in the urea fertilization plot and nitrate fertilization plot during the wheat-maize rotation cycle from2012to2013reduced34.62%and27.88%, comparing with the control plot. This demonstrated the ability of urea to inhibit the absorption of CH4is higher than nitrate fertilizer. CH4fluxes were significantly negatively correlated with catalase.The total greenhouse gas global warming potential (GWP) from wheat-maize rotation field was mainly determined by CO2, and the value of CH4GWP could be approximated ignored. The net GWP of each maize growing season was positive, indicating the maize field was a source of atmospheric greenhouse gases. And the net GWP of the control plot was greater than that of the fertilization plot, thus fertilization reduced greenhouse gas warming capabilities to some extent.