Studies On Characteristic And Mechanisms Of CH₄and CO₂Emission In No-tillage And Straw Incorporation Paddy Field

Global greenhouse effect has become a main factor to restrict the economic development of all countries, harm human health and destroy ecological balance. CH4and CO2are the most important greenhouse gases. The paddy field is one of the main sources where CH4and CO2gas emitting from, so how to reduce the rice paddy greenhouse gas emissions has become the focus of current research. In this research we did two seasons of field experiment to study the relative mechanism between no-tillage and rice straw incorporation with CH4and CO2emission, in order to provide a theoretical basis for greenhouse gas emissions reduction from paddy field. The main results were shown as follows:1. Effect of no-tillage and straw incorporation on CH4emissions in paddy fieldIn early rice and second rice grow stage, CH4emissions were mainly concentrated from tillering stage to booting stage, which accounted for about90%of the total CH4cumulative emissions in the rice growth stage. No-tillage (NT) treatment decreased CH4emission flux in the peak period of CH4emission, compared to convention tillage (CT) treatment, in early rice and second rice grow stage NT treatment could decrease29.11%and23.14%of total CH4cumulative emissions in respectively; straw incorporation (SCT、 SNT) treatment could increase CH4emissions, and convention tillage with straw incorporation (SCT) treatment improving effect was best, but No-tillage with straw incorporation (SNT) treatment improving effect was not obvious.2. Effect of no-tillage and straw incorporation on CO2emissions in paddy fieldCO2emitting tendency in paddy field soil was similar to CH4emissions. In rice grow stage CO2emissions were mainly concentrated in tillering stage to booting stage. Compared to CT treatment, NT treatment decreased7.00%of the total cumulative CO2emissions; SCT and SNT treatment enhanced the role of soil CO2emissions, and SCT treatment raised the most obvious role, compared to SNT treatment it had increased in14.90%of total cumulative CO2emissions.3. Changes and the relationship with the emission of CH4and CO2of soil redox properties under the condition of no-tillage and rice straw incorporation.In early rice and second rice grow stage, NT treatment significantly decreased soil total amounts of reducing matter and active reducing matter content in0-5cm and5-20cm soil layer, SCT and SNT treatment significantly increased the total amounts of reducing matter and active reducing matter content at each soil layer. SCT treatment raised the most obvious role, SNT treatment increased the total amounts of reducing matter and active reducing matter content at0-5cm soil layer. With the statistical correlation analysis, in0-5cm、5-20cm、20-30cm soil layer both soil total amounts of reducing matter and active reducing matter content were extremely significant positive eorrelation with CH4flux and significant positive correlation with CO2flux. So we could make a conclusion that no-tillage treatment which reduced the amounts of soil reducing matter was one mechanism of CH4and CO2emissions reduction.4. Changes and the relationship with the emission of CH4and CO2of soil organic carbon under the condition of no-tillage and rice straw incorporation.NT treatment could increase organic carbon content in the0-5cm but decrease in the5-20cm and20-30cm soil layer, SCT and SNT treatment increased the content of soil organic carbon, and SCT treatment significantly increased organic carbon content in5-20cm and20-30cm soil layer, but SNT treatment only increased organic carbon content in0-5cm soil layer. With the statistical correlation analysis,5-20cm soil layer soil organic carbon content were significantly or extremely significantly positive correlative with CH4and CO2emission fluxes.5. Changes and the relationship with the emission of CH4and CO2of Soil Organic carbon components under the condition of no-tillage and rice straw incorporation.In early and second rice grow stage, NT treatment increased in0-5cm soil layer but reduced5-20cm and20-30cm soil layer soil label organic carbon(LOC), high label organic carbon (HLOC), middle label organic carbon (MLOC) and low label organic carbon (LLOC) content. SCT treatment increased LOC, HLOC、MLOC and LLOC content in0-5cm and5-20cm soil layer, NT and SNT treatment increased stable organic carbon (SOC) content in0-5cm soil layer. With the statistical correlation analysis, CH4and CO2emission flux were significantly or extremely significantly positive correlative with5-20cm and20-30cm soil layer soil LOC, HLOC and LLOC content and positive correlation with M LOC content; CH4and CO2emission flux were shown a negative correlation with0-5cm and20-30cm soil layer soil stable organic carbon (SOC). So we could make a conclusion that no-tillage treatment reduced activated carbon content in5-30cm soil layer was one mechanism of CH4and CO2emissions reduction.6. Changes and the relationship with the emission of CH4and CO2of soil microorganism under the condition of no-tillage and rice straw incorporation.In rice grow stage, NT treatment reduced and SCT and SNT treatments caused an increase in the quantity of bacteria, anaerobic bacteria and fungi at each soil layer. NT treatment increased in the quantity of actinomycetes in0-5cm soil layer but decreased the quantity actinomycetes in5-30cm soil layer. Contrary, SCT and SNT treatments increased in the quantity of actinomycetes in5-30cm soil layer.The quantity of bacteria, anaerobic bacteria, fungi and actinomycetes at each soil were signifieant or extremely signifieant positive correlative with CH4and CO2emission flux. So we could make a conclusion that no-tillage treatment which reduced CH4and CO2emissions was related to reduction of microorganism quantity in each soil layer on the whole.