The Effect Of Different Fertilization On Red Soil Aggregate Stability And Hierarchy Structure

Aggregate is the basic unit of soil structure, like the cells of an organism. Aggregate stability is an important property of maintaining soil aggregate structure and function, and it has important ecological significance in the fields of cultivated land quality, soil and water conservation and biological diversity. Different fertilization methods on soil cementing material contents, speciation and transformation have greater impact, the existing research mostly concentrated in the cementing material and aggregate stability, the correlation between; for different fertilization under aggregate stability of quantitative research and aggregate level structure reports is still not much, also mechanism of cementing material in the aggregates of various particle size fractions to be clear.Therefore, this paper uesd aggregates as the research object from Hunan Qiyang Red Soil Experimental Station under long-term different fertilization, using ultrasonic excitation and the laser diffraction particle size analysis technology, combined with selective dissolution cementation material, quantitaty define the stability of aggregates under different fertilization by the dispersive energy, revealed aggregate breakage in the process of particle size variation, showed the difference of aggregate hierarchical structure and the main function of the cementing material in the aggregate size and cemented form be clear. The main research contents and conclusions are as follows:(1) Different fertilization mainly affect the ultrasonic energy dispersion of large aggregates, which makes the ultrasonic dispersion energy of micro aggregates increased. The stability of red soil aggregate structure was evaluated by ultrasonic dispersion energy, and the stability of the soil aggregate structure under different fertilization methods was NPKM > M > NPK > CK. The ultrasonic energy dispersive energy of large aggregates is higher than that of micro aggregates, which is related to the structure of the aggregates.(2) After long-term fertilization of soil aggregates in 53~250 obtained M size fraction are reflected in the hierarchical structure, but under different fertilization modes aggregate level structure form differences: m and NPKM aggregates release speed is greater than the rate of dispersion, so 53~250 obtained m particle level quality percentage showed curve first increased and then decreased; and under CK and NPK, aggregate release rate less than dispersion rate, so 53~250 obtained M size mass percentage showed gradual decline curve. The manifestation of the hierarchical structure of the aggregate implies the relationship between the cohesion of the internal micro aggregates and the bond strength of the cementing material in the micro aggregates. The fertilization of micro aggregates do not have hierarchical structure, direct release powder, clay under ultrasonic excitation.(3) CK and NPK under non crystalline iron of high aggregate stability with greater contribution, and m and NPKM humus under the high aggregate stability with greater contribution; humus in the fertilization of micro aggregate structure stability plays a dominant role. CK and NPK with amorphous iron cementation dominated, and m and NPKM humus and iron oxide together cementation; in 53~250 obtained M size fraction, m and NPKM humus of cementation is dominant, and CK and NPK humus and amorphous iron also play the cementation; in 2~53 obtained M size fraction, CK and NPK cementing material in the humus dominated, and m and NPKM cementing material may extracellular polysaccharide or glomus and cementing material.(4) Fertilization increased the aggregate organically complexed and amorphous iron oxide content of Shi organic fertilizer and organic inorganic fertilizer applied in promoting the complexation reaction of soil organic matter and Fe and Al oxides, and organic and inorganic fertilizer to promote soil aggregate and soil organic matter humification process. correlation analysis showed that the organic matter contributed to the red soil macroaggregates formation and for 250~2000 obtained m aggregates formed with larger; mineral bound state of organic matter and organic complex ferric oxide and ultrasonic dispersion energy showed a highly significant positive related, indicating that complexation of humus and minerals, and iron oxides is cemented soil.