| Summary: | 碩士 === 國立臺灣大學 === 農業化學研究所 === 93 === Effects of current four cropping systems, including paddy-paddy, paddy-upland, upland-paddy, and upland-upland on emissions of greenhouse gases (CO2, CH4, N2O) from agricultural soils in northern Taiwan were examined by a closed chamber method. The results showed that the total emissions of the three greenhouse gases (expressed as total CO2 equivalent) for the four cropping systems (paddy-paddy, paddy-upland, upland-paddy, upland-upland) were 20,707, 8,486, 13,324, and 7,399 kg C ha-1 y-1, respectively. The mitigation potential of total greenhouse gases emissions could range from 1,087 to 13,308 kg C ha-1 y-1, with a mean value of 7,460 kg C ha-1 y-1. The results of forward stepwise regression analysis showed that the significant contributing factors to CO2 fluxes in the decreasing order were bulk density (BD), and soil temperature (Ts) for paddy-paddy cropping system; were air temperature (Ta), pH, organic mater content (OM), and inorganic nitrogen content (IN) for paddy-upland cropping system; were Ta, BD, electronic conductivity (EC), and water filled pores spaces (WFPS) for upland-paddy system; and were BD, nitrate content (NO3-), Ts, and EC for upland-upland system (P＜0.05). The significant contributing factors to CH4 fluxes in the decreasing order were BD, Ts, IN, water content (WC), and EC for paddy-paddy cropping system; were IN, Ts, pH, and WC for paddy-upland cropping system; were Ts, and total nitrogen content (TN) for upland-paddy system; and were ammonium content (NH4+), WC, and IN for upland-upland system (P＜0.05). The significant contributing factors to N2O fluxes in the decreasing order were BD, NO3-, and Ts for paddy-paddy cropping system; were Ta, WC, WFPS, and IN for paddy-upland cropping system; were Ta, OM, BD, EC, and WFPS for upland-paddy system; and were BD, and NO3- for upland-upland system (P＜0.05).
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