Preliminary Study On The Relationship Between The Formation Of Short-Range-Ordered Minerals In Soils And Microorganism

According to the survey,in the existing cultivated land in China,approximately 70%of the soils is middle-and-low-yielding soils in the existing cultivated land in China.Excessive use of fertilizers is one of the reason of land degradation.Now,about 40%cultivated land is degraded in China.The effective ways in preventing land degradation are increasing soil organic matter content and thus improving soil fertility.To date,the accumulation and turnover mechanism of soil organic matter are still unclear.The turnover and accumulation mechanism of soil organic matter are critical to guide reasonable measures to promote soil organic carbon.Globally,reactive iron(mainly short-range-ordered minerals,SRO minerals)can protect about 20%organic carbon in soil or sediments.However,it is still unclear in how to affect short-range-ordered minerals in soils by agricultural regimes.By microcosm experiments,this paper aims to investigate the critical role of arbuscular mycorrhizal fungi(AMF),root and strawsin promoting soil short-range ordered mineral.Moreover,combined incubation experiments with high resolution transmission electron microscopy(HRTEM)and synchrotron radiation-based fourier transform infrared(SR-FTIR),this paper examines the biological and chemical formation mechanism of short-range-ordered.The main results of this paper are listed as follows.1)AM fungi,root activity and straw amendment had a significant influence in shoot biomass and root biomass in different treatments.In sand experiments,straw could markedly increase shoot biomsaa.Change of soil of pH was dependent on soil type,indicating that AM could affect soil pH by assimilating ammonium nitrogen and nitrate nitrogen.Clay experiments has the highest of TC,TN and C/N ratio,suggesting that AM fungi,root activity and straw had a better influence in the increment of TC and TN in clay than that in sand.A significant difference in the accumulation of soil DOC was observed.2)No significant correlation was built between OC and dissolved minerals in soils.However,short-range-ordered iron,reactive iron and organic associated iron were significantly correlated with DOC.Synchrotron radiation-based fourier transform infrared(SR-FTIR)showed the distribution of elements(C,N,Fe,Al,Si)on the surface of AMF,implying that AMF,root and carbon(i.e.,straw)may be involved in the formation of SRO minerals.3)Fungi-mineral incubation experiment showed that after 48h cultivation of kaolinite and magnetite with Z5,large amounts of nano-scale minerals with a size of 3-5nm appearred in both solution and mycelium.Meanwhile,organic acids were produced during the cultivation experments,which decreased the solution’s pH and thus the formation of nanominerals.Low molecular weight acidic metabolites produced by fungi could destory mineral crystal lattice and promoted the formation of nanomineral.In summary,organic amendments can promote the formation of short-range-ordered minerals in soil,which will furthe effectively promote carbon perservation in soil.In addition,fungi play an important role in the formation of short-range-ordered minerals.