Studies On Soil Carbon Pool And Carbon Cycle Under Different Residue Management And Fertilizer Application In Farmland Ecosystem Of Oasis

Soil organic pool is important for maintaining soil quality and mitigate climate change.Human activity greatly influences the SOC pool and carbon cycle process in farmland.The Xinjiang is the largest arid area in China,and Oasis Agriculture play an important role in economy development.But Oasis farmland soil organic carbon is poor,which r estrict the sustainable development of agriculture in arid region.Therefore,the paper from the change of soil organic pool,field experiment was conducted to reveal the regulation mechanisms of agricultural management practices included two residue management practices [residue incorporation(S)and residue removal(NS)] and four fertilizer treatments [no fertilizer(CK),organic manure(OM),chemical fertilizer(NPK),chemical fertilizer plus organic manure(NPK+OM)] on soil organic carbon and global carbon cycle in an oasis cotton field.Below are the main results in this thesis.1.Effect of different agricultural management practices on the dynamic changes of soil organic carbon were studied.The results showed that fertilization and residue incorporation significantly increased SOC pool,soil organic carbon(SOC),labile carbon (LBC),microbial biomass carbon(MBC),water-soluble organic carbon(WSOC),hot water-soluble organic carbon(HWSOC)and carbon management index(CMI).The SOC pool was increased by 20.6% by residue incorporation.compared to residue removing.SOC pools were increased by 7.8%,29.5% and 37.7% in NPK,OM and NPK+OM treatments compared to CK,respectively.The contents of SOC,LBC,MBC,WSOC and HWSOC under different fertilization treatments were shown as NPK+OM>OM>NPK>CK.There was a significant correlation between CMI and SOC,LBC,MBC,WSOC,HWSOC and SOC pool.Therefore,we concluded that CMI is an important index for evaluating the effect of agricultural management practices on soil quality 2.Effect of different agricultural management practices on the dynamic changes of soilrespiration were studied.The results showed that soil respiration rate has a significant seasonal characteristic under different agricultural management practices.Soil respiration rate reached a peak in mid-July and then reduced to the minimum in January-February.The residue incorporation significantly increased soil respiration.The soil respiration rate under different fertilization treatments were shown as NPK+OM>OM>NPK>CK.Under the residue × fertilizer interaction,the S-NPK+OM treatment had the highest soilrespiration rate.There was a significant correlation between soil respiration and soil temperature.By contrast,there was no significant correlation between soil respiration and soil moisture.3.Effect of different agricultural management practices on the canopy apparent photosynthesis,photosynthesis product accumulation and seed cotton yield were studied.The results showed that cotton canopy apparent photosynthesis reached a maximum during the full flower stage and then gradually declined.Residue incorporation treatment had no significantly affected cotton canopy apparent photosynthesis,but fertilizer treatment significantly increased canopy apparent photosynthesis.The canopy apparent photosynthesis under different fertilization treatments were shown as NPK+OM>OM>NPK>CK.The NPK+OM treatment had 55.70-58.98%,30.96-32.44%,13.05-14.93% more canopy apparent photosynthesis,respectively,than CK,OM,NPK.The photosynthesis product accumulation and seed cotton yield decreased in the same order as canopy apparent photosynthesis.The NPK+OM treatment had 19.05-24.95%,7.57-10.25%,3.01-3.73% more yield,respectively,than CK,OM,NPK.4.Effect of different agricultural management practices on the soil carbon sequestration and correlation between agricultural management and carbon cycle were studied.The results showed that residue incorporation and fertilizer significantly increased soil C input and CO2 emission.But only S-NPK+OM and S-OM were C sinks,other treatment were C sources.It should be noted that soil carbon balance was-1.1 t C ha-1 under present agricultural management(S-NPK)in Xinjiang.This meant that a minimum of 1.1 t C ha-1 yr-1 must be added to the soil to offset C losses and maintain the soil C pool.Hence,the combination of residue incorporation and inorganic fertilizer plus organic manure application is a strategy to achieve food security and mitigate climate change by improving soil C sequestration in arid regions.