Simulation Of Soil Organic Carbon Dynamics In Oasis Farmland In Arid Regions

Farmland soils have the double functions of source and sink of CO2, which are more active in theglobal carbon pool compared with natural soils. Farmland soils can adjust its carbon pool in a short timescale,although in serious human disturbance. For the prediction and estimation of farmland soil organiccarbon (SOC), model research is a better approach. Among many estimating farmland soil organic carbonmodel, the Denitrification and Decomposition (DNDC) model, with accurate simulation and simpleparameter input, is widely used. Using the DNDC model and data from Xinjiang gray desert soil fertilityand fertilizer efficiency long-term monitoring experimental station, we achieved the simulation, checkedthe related parameter sensitivity analysis and expanded the model to Xinjiang Manas farmland for dynamicsimulation and spatial distribution of SOC The following results:Firstly, HNPKM treatment processed the highest CO2release rate that’s0.55mg/kg/h. The second wasthe NPKM treatment at0.43mg/kg/h. Although organic manure and chemical fertilizer NPK can improveSOC content, they also stimulate CO2emission rate, and CK treatment had the slowest CO2-C release rateat0.35mg/kg/h. The reason was that the easy decomposition of SOC content, the difficult decompositionof SOC for soil microbial starting to break down. Decomposition rate and the release of CO2intensitygradually reduced.Secondly,(1) the DNDC model can well simulate different fertilization conditions dynamics of SOC, thecorrelation between simulation results and measured results was significant (P <0.01) and (2) The next30years forecast results showed that organic manure and NPK fertilizer (NPKM) will be37.13%higher thanin2010, SOC content in straw with NPK fertilizer will increase by8.81%. Continuous application of NPKfertilizer stability for the SOC content, showing that the balance of fertilizers can only make the root cropcarbon returned to the mineralization of organic carbon balance, the SOC in no fertilizer (CK) felled by4.76%, in without N fertilizer (PK) felled by4.64%, and in fertilization of N fertilizer increased by2.25%.The SOC in NK fertilizer and NP fertilizer treatment increased by1.50%and1.50%respectively. thecontent of SOC in nitrogen treatment (N, NP, NK, NPK) remain stable or small growth in the next30years,which suggeasting that nitrogen would be still the primary factor affecting the carbon balance.Finally, the DNDC model of Manas county farmland SOC prediction and ArcGIS spatial interpolation,on SOC and soil carbon density to do further research.The results showed that:(1) The SOC contentpredicted by the model in2041would increase by0.71-2.61g/kg, comparing with that in2011, soil carbondensity would increase by0.36-0.59kg/m2, NPK fertilizer and organic material (straw) could increase SOCcontent.(2) High farmland soil carbon density area of Manas county in2011mainly distributed in thecounty surrounding, other areas for low, present group shape distribution. But through the model simulationof soil carbon density and fertilizer application last year (2011-2041) analyzeing, according to therelationship between Manas county farmland, the soil carbon density in2041increased by0.012-0.021kg/m2per year.(3) In the next30years, Manas farmland could sequestrate soil carbon with the maximumrate of207kg/hm2/yr, and the minimum rate was121kg/hm2/yr, averaging at164kg/hm2/yr.