Effects Of Fertilization On Hierarchical Aggregates Composition And Soil Organic Carbon Distribution From Black Soil

Soil organic carbon reserves has long been regarded as the important measure of soil fertility.On the one hand,soil organic carbon can provide fertility for growth and development of the crop;on the other hand,the greenhouse gases that in the atmosphere can be influenced,because of soil organic carbon.The purpose of enhancing the fixed and stability of soil organic carbon is to reduce CO2 emission,and increase soil fertility on the basis of the original soil,which promote the increase of the proportion of soil aggregate structure is one of the important means of commonly used to achieve this goal.Northeastern black soil is one of the biggest agricultural comprehensive production capacity soil,this type of soil is fertile under the condition of natural and the original organic carbon content is higher and soil aggregate structure is good.Compared with before,the physical and chemical properties of soil have been significant changed with the increasing of population,or the excessive reclamation and cultivation of farmland.Discuss different fertilization measures on black soil aggregate composition and distribution of organic carbon,to reveal the soil aggregate physical protection,chemical protection of soil organic carbon protection mechanism,the mechanism of soil carbon has important scientific significance.The study was conducted based on the long-term fertilization experiment,soil aggregates were grouped into >0.25 mm macroaggregates(Mac-A),0.25~0.053 mm free microaggregates(Fm)and <0.053 mm nonaggregated silt/clay(NA-silt / NA-clay)by water stable aggregate physical fractionation scheme;macroaggregates grading with multistage structure,it could be grouped into coarse particulate organic matter(cPOM),occluded microaggregates(mM),silt/clay(M-silt/M-clay).At the same time,m M and Fm were grouped into light fine POM,POM within heavy fraction,silt/clay occluded in microaggregates by water stable aggregate physical fractionation scheme combined with organic matter density fractionation.Explore the multistage aggregate structure on the physical and chemical protection mechanism of SOC after biochar,cow dung,corn stover into the soil by study effects of soil aggregate composition and organic carbon contribution in aggregates of black soil in different treatment including that the treatment without fertilizer(CK),chemical fertilizer(NPK)treatment,chemical fertilizer+biochar(NPK+biochar)treatment,chemical fertilize+cow dung(NPK+cow dung)treatment,chemical fertilize+corn stover(NPK+corn stover)treatment.The main results were as follows: 1.In the black soil water stable aggregate composition,soil mass proportion of >0.25 mm Mac-A was highest(53.36%~63.07%),grade for advantage,proportion of aggregate quality at all levels with the decrease of the aggregate particle size decreases.Compared with CK,mass proportion of the soil >0.25 mm Mac-A was increased significantly in NPK,NPK+biochar,NPK+cow dung and NPK+corn stover treatment,size in order:NPK+biochar,NPK+cow dung,NPK+straw>NPK>CK;0.25~0.053 mm Fm was reduced significantly than CK,and suggests that Fm under the effect of organic cementing material cementation form macroaggregates.2.Compared with CK,soil organic carbon(SOC)content was increased significantly in NPK+biochar,NPK+cow dung and NPK+corn stover treatment(increased by 23.64%,9.50% and 8.14%,respectively),size in order: NPK+biochar>NPK+cow dung>NPK + corn stover>NPK,CK.Application of biochar was is more advantageous to the accumulation of SOC.SOC storage of >0.25 mm Mac-A was increased significantly in NPK+biochar,NPK+cow dung and NPK+corn stover treatment,size in order: NPK+biochar>NPK+cow dung>NPK+corn stover>NPK,CK,relative contributions of total soil organic carbon was 62.52~68.34%.3.For >0.25 mm Mac-A composition,soil mass proportion of mM was highest(27.54~36.95%),M-silt was second(17.97~28.55%),M-clay and cPOM were lowest(4.63~6.81%,and 4.63~6.51%).Compared to CK treatment,mass proportion of mM and cPOM were improved significantly in NPK+biochar,NPK+cow dung and NPK+corn stover treatment(increased by 23.97~34.17% and 34.72~93.18%),increased SOC storage of mM,M-silt and cPOM(respectively increased by 1.33~1.41,1.18~1.20 and 1.41~3.07 times),application of chemical fertilizers with organic materials promoted the formation of mM and increase SOC storage of m M.4.For mM composition,mass proportion of silt associated with mM(mM-silt),clay associated with mM(mM-clay),POM associated with mM(mM-POM),fine POM of light fraction associated with mM(L-M(f)POM)were improved.Compared with other treatments,SOC storage of L-M(f)POM,mM-POM and mM-silt were improved significantly in NPK+biochar treatment.For Fm composition,compared with CK,SOC storage of fine POM of light fraction associated with Fm(L-F(f)POM)was improved and SOC storage of silt+clay associated with Fm(Fm-silt+clay)was reduced in NPK+biochar,NPK+cow dung,NPK +corn stover treatment;compared with CK,SOC storage of POM associated with Fm(Fm-POM)was improved.5.Compared with CK or NPK treatment,SOC content of the soil humic acid was improved significantly in NPK+biochar,NPK+cow dung,NPK+corn stover treatment,size in order: NPK+biochar,NPK+corn stover>NPK+cow dung>CK,NPK.And compared with other treatments,NPK+biochar treatment is conducive to the formation of humic acid,fulvic acid and humin.In conclusion,combined application of NPK chemical fertilizer with biochar,or cow dung,or corn stover improved SOC content of the black soil,promoted the formation of >0.25 mm macroaggregates,improve SOC storage of macroaggregates and coarse POC,SOC was mainly stored in macroaggregates,and macroaggregates plays an important role in fixed exogenous organic carbon such as biochar,cow dung,corn stover.Combined application of NPK chemical fertilizer with biochar,or cow dung,or corn stover is advantageous to formation of mM,included SOC storage and POC storage of mM,thus improve exogenous organic carbon such as biochar,cow dung,corn stover in the soil stability.Therefore,exogenous organic carbon such as biochar,cow dung,corn stover under the physical protection of macroaggregates and microaggregates,stability of SOC was improved,black soil C potential increased.Compared with NPK+cow dung,NPK+corn stover treatment,application of NPK chemical fertilizer with biochar was beneficial to the formation of soil humic substance,humic acid,fulvic acid and humin,add biochar into black soil was of great significance in immobility SOC and can improve soil quality.