Study On Soil Carbon Sequestration And Emission Mitigation Under Different Fertilization

Rice was the main food crop in the world, meanwhile, paddy soil was one of the importantsources of methane emission, based on the above two points, the paddy ecosystem had become theglobal focus of attention. Fertilization was a major management measures during paddy cultivationprocess, long-term fertilization effect on C content and storage of topsoil and methane and nituousoxide were recognized, meanwhile, fertilization had influence on the soil fertility and rice yield, whilethe soil carbon sequestration had extremely important significance on greenhouse gas emissionreduction. In order to respond to the climate change effectively and guarantee the sustainability ofagricultural production, exploring the effective measures that reducing greenhouse emission andguaranteeing the normal food production was necessary.The increased CH₄and N₂O emission from paddies after organic fertilizer return should beregarded as an important greenhouse gas leakage. Therefore, when analysis soil C sequestration and Cemission mitigation, obtain the effect of altogether wins with fertility betterment, yield increase andemission reduction, the soil carbon sequestration and the offset of the mitigation benefits need to beconsidered. To study the effect of different fertilization treatrnent on the organic carbon accumulation,the seasonal variation of CH₄and N₂O emission, the effete of physieal and chemical propertychanges result from different fertilization on methane emission, contribution of CH₄,N₂O emissionon GWP and the offset of the mitigation benefits under different fertilizing systems (includingCK,NPK1, NPK1+BIS(straw burned in situ), NPK2+S(staw), NPK2+MD(mushroom digestion),NPK3+CD(cow dung) and NPK3+BD(biogas digestion)) carbon density in plough layer, methane andnituous oxide emission fluxes from the double-cropping paddy field in Hunan red soil were monitored,methane and nituous oxide emission fluxes were monitored by using the method of static chamber-gaschromatographic technique. Finally the optimal fertilizer management measure was recommended.The results showed that:1. CH₄and N₂O emission observation(1)Fertilizer applying increased the emissions of CH₄. Straw burned in situ reduce CH₄by28.3%. When total N input amount was equal, adoption of mushroom digestion and biogas digestionreduced CH₄emissions by26.1%～61.5%compared with staw and cow dung. Ploughing under dryconditions and draining during the winter period reduced CH₄emissions effectively.(2)CH₄emissions has closed relationship with air temperature and C/N of organic fertilizer.There was a significant positive correlation between CH₄emission and organic carbon mass fractionand C/N, a low negative correlation between CH₄emission and NH₄⁺-N and NO₃^-N concentration.(3)N₂O emission in late rice period was occupied sizeable share. Chemical fertilizer treatmentincreased N₂O emission compared with chemical fertilizer combinated with organic fertilizertreatments. Straw burned in situ reduce N₂O emission by85.0%. Adoption of cow dung reduced N₂Oemission by80%compared with mushroom. There was not exited a trade-off relationship between CH₄and N₂O emission during early and late rice period but winter season.(4)There was a low positive correlation between N₂O emission and soil total nitrogen, asignificant positive correlation between N₂O emission and NH₄⁺-N concentration.2. C sequestration and C emission mitigation(1)Biogas digestion and rice straw combinated with chemical fertilizer treatments had goodeffect on carbon sequestraton. The carbon sequestration capacity of chemical fertilizer was small,while Straw burned in situ reduced soil carbon storage.(2)The total greenhouse warming potential and emission intensity (CO2e/t grain yield) ofbiogas digestion combinated with chemical fertilizer treatments was the strongest, secondly for ricestraw treatment,3. The best choiceBiogas digestion had the most effective capacity of C sequestration and C emission mitigation,which increase carbon density from54.7%～91.7%, increased yield from6.9%～13,7%and reduceCH₄and N₂O emission fromï¹£19.4%～153.3%, was considered as the best choice.