The Evolution Characteristics And Turnover Mechanisms Of Soil Organic Carbon Under Long-term Fertilization In Grey Desert Soil In Xinjiang Province

Soil organic carbon (SOC) is not only one of the important index for soil fertility, but also has aclose relationship with global climate change, therefore it is becoming to the hot topic for scienceresearchers.For the purpose to show the effect of agricultural management on the soil fertility in GreyDesert soil, clarify the SOC dynamics and turnover mechanisms under different fertilization. Weselected five to nine treatments in the Grey Desert soil long-term experimental site in Xinjiang province,include no fertilization(Control), nitrogen(N), nitrogen plus phosphorus(NP), nitrogen plus phosphorusplus potassium(NPK),NPK plus manure(NPKM),1.5time NPKM. NPK plus straw(NPKS),Manure (M),straw(S). We analyzed of SOC dynamics and its storage, the time decrepency under different carbonfraction, the seasonal dynamics of soil microorganism biomass carbon (SMBC), and combined withDNDC model to predicted the dynamics of SOC in the future30years, and estimated the SOCsequestration. The main results followed:(1) The dynamics of SOC demonstrated that the SOC continue increased in NPKM, hNPKM, andNPKS plots, and the increments were0.004g/kg~0.626g/kg per year. The SOC and the annual C inputhad significantly positive relationship (P＜0.05).While the SOC decreased0.056g/kg~0.024g/kg peryear in CK, NP, and NPK plots. The SOC storage rate change was small during the whole experimentalperiod in inorganic fertilizer and/or straw return plots, while it was higher during1990-1994than thatduring1995-2013in plots with manure. Compared to initial year, the SOC storage increase ranged from32.1%to152.7%in the same plot. The SOC storage was decreased as1.35tC/hm2å'Œ10.0tC/hm2in CKand NP compared with NPKS. This might caused by the declined bulk density in NPKS plot.Meanwhile, the slight SOC increase resulted to the decrease of SOC storage in NPKS had therelationship with the special climate condition and straw return style and time in Xinjiang.(2) The results of fraction of SOC in surface layer (0-20cm) and sub-layer (20-40cm) showed thatcompared with CK, the content of active carbon pool (AC), slow carbon pool (SC), and refractorycarbon pool (RC) was increased in all fertilization plots except N only plot. The increase rate rangedfrom15.7%to300.86%. Compared with the fallow plot, the three SOC pools all increased in plots withmanure; the AC and RC pool decreased while SC increased in NP plot; the AC pool increased while RCand SC decreased in NPK and NPKS plots. These results indicated that the fertilization and crop speciesinfluenced the SOC pool and change. SMBC/SOC (microbial quotient qSMBC) of Grey desert range is0.3%~2.8%, less than the southern paddy field (3.4%~4.9%) or red (2.5%~4.3%).(3) Cultivation and field test results show that carbon flux of grey desrt soil have three stage:quick release, slow and stability. The respiration reate of Manure treatement is significantly higher thanNPK or NPKS. the respiration rate was0.497mol/m2s in M plot.First order kinetics equation areadopted to simulate the cumulative emission of CO2–C. The result showed that organic fertilizer(NPKM, hNPKM) significantly increased the soil respiration rate, its potential to release a quantity to4.37mg/kg,8.65mg/kg, and CK and NPK to release a quantity to1.81mg/kg,3.70mg/kg. Gray desertsoil soil respiration rate and soil are negatively related5cm ground tempurature (P <0.05).(4)We validated the DNDC model in Grey Desert soil, it was suitable for SOC dynamics under all the plots except NPKM and hNPKM, which overestimated. The M value ranged from1.49g/kg~4.04g/kg. The SOC prediction during2010to2040showed that the SOC sequestration potential was-1.5tC/hm2~-0.75tC/hm2ranged from CK and plots without N, this indicated that it was C source underthese plots. The SOC sequestration potential ranged from0.19tC/hm2to2.41tC/hm2under plots with N,and it was2.37tC/hm2~83.71tC/hm2in plots with organic material application.Generally, this study based on the Grey Desert soil, analyzed the SOC evolution, the fraction, theSMBC change and soil respiration. Fertilization significantly affected the SMBC and caused thediscrepancy of soil respiration. The model simulation indicated that chemical fertilizer only was hard tomaintain SOC, while the additional straw return play an important role to maintain soil fertility, manureapplication can improve SOC in short time. The study provided a management option for mitigation andC sequestration in Grey Desert soil in Xinjiang province.