Soil samples were collected from the areas surrounding Wuliangsuhai Lake in China. Dissolved organic matter （DOM） was extracted from the samples and characterized by fluorescence and UV-Vis spectra. Spectral propert...Soil samples were collected from the areas surrounding Wuliangsuhai Lake in China. Dissolved organic matter （DOM） was extracted from the samples and characterized by fluorescence and UV-Vis spectra. Spectral properties and humification degree of DOM were studied. The results indicated that both humic- and protein- like fluorophores were present in the DOM spectra, and the former was the dominant component. The analysis of humification （HIX） and r （A, C） indices revealed that the maximum humification degree in three agricultural soils （AAF, ASC, and ASW） was presented in the second soil layer （20-40 cm）. However, the humification degree of the two Halophytes soils （SSE and GKF） decreased with increasing depth. One index, I344/270, showed that humification degree increased gradually with an increasing proportion of humic-like acid. There was a significant positive correlation between humification degree （HIX） and aromaticity （SUVA254）, indicating that a higher aromaticity corresponded to a higher humification degree. Land use was an important factor responsible for the major difference of cation exchange capacity （CEC） in different soils, which led to a higher CEC value in the second soil layer for the three agricultural soils. CEC values and humification degree had the same trend for all five soils. The correlation analysis showed that there was a significant positive correlation between HIX and CEC,and a negative correlation between the r （A, C） index and CEC, indicating that humification degree increases gradually with increasing CEC values.展开更多
Humic materials make important contributions to soil organic carbon(C)and nitrogen(N)accumulation.However,information on the correlation between humic substances and the accumulation of soil aggregate-protected C and ...Humic materials make important contributions to soil organic carbon(C)and nitrogen(N)accumulation.However,information on the correlation between humic substances and the accumulation of soil aggregate-protected C and N in response to biochar application under tropical agroecosystems is limited.Therefore,a field trial was conducted to elucidate the effects of biochar on soil aggregate properties and humic materials and how these humic compounds affect aggregate-protected C and N in a humid tropical agroecosystem.The treatments included no-biochar control(CK),15 Mg biochar ha^(-1)(BC-15),30Mg biochar ha^(-1)(BC-30),and 30 Mg biochar ha^(-1)+phosphate fertilizer(BC-30+P).The treatments BC-30 and BC-30+P significantly increased the contents of humic materials(humic and fulvic acids)as compared to CK.There was a significant increase in the mean-weight diameter of soil aggregates by3-and 4-fold in BC-30 and BC-30+P,respectively.Similarly,BC-30 and BC-30+P led to significant increases in soil structural coefficient by 3-and 4-fold,re spectively,relative to CK.Significant increases in organic C and N accumulation were observed in the macroaggregates of the biochar-amended soils.Inverse relationships between the degree of polymerization and aggregate-protected C and N were observed,implying that low-molecular-weight aliphatic compounds favor organic C and N accumulation with biochar amendments.The important soil property that contributed to organic C and N accumulation in aggregates was fulvic acid content,which could be used as an early and sensitive indicator to notice early changes in aggregate-protected C and N accumulation in soils of the humid tropics.展开更多
基金Acknowledgements This work was financially supported by the National Social Science Fund （12CGLI 18）, the National Natural Science Foundation of China （Grant Nos. 41503110 and 51208020） and the Open Foundation of Jiangsu Key Laboratory for Biomass-based Energy and Enzyme Technology, Huaiyin Normal University （JSBEET1309）.
文摘Soil samples were collected from the areas surrounding Wuliangsuhai Lake in China. Dissolved organic matter （DOM） was extracted from the samples and characterized by fluorescence and UV-Vis spectra. Spectral properties and humification degree of DOM were studied. The results indicated that both humic- and protein- like fluorophores were present in the DOM spectra, and the former was the dominant component. The analysis of humification （HIX） and r （A, C） indices revealed that the maximum humification degree in three agricultural soils （AAF, ASC, and ASW） was presented in the second soil layer （20-40 cm）. However, the humification degree of the two Halophytes soils （SSE and GKF） decreased with increasing depth. One index, I344/270, showed that humification degree increased gradually with an increasing proportion of humic-like acid. There was a significant positive correlation between humification degree （HIX） and aromaticity （SUVA254）, indicating that a higher aromaticity corresponded to a higher humification degree. Land use was an important factor responsible for the major difference of cation exchange capacity （CEC） in different soils, which led to a higher CEC value in the second soil layer for the three agricultural soils. CEC values and humification degree had the same trend for all five soils. The correlation analysis showed that there was a significant positive correlation between HIX and CEC,and a negative correlation between the r （A, C） index and CEC, indicating that humification degree increases gradually with increasing CEC values.
基金one of the outcomes of a research conducted by Dr.Emmanuel Amoakwah at The Ohio State University,which was sponsored by the United States Department of Agriculture Leadership Enhancement in Agricultural Program via a grant to the University of California-Davis by the United States Agency for International Development,USAin part by the Ministry of Foreign Affairs of Denmark through the project“Green Cohesive Agricultural Resource Management,WEBSOC”(No.3-01AU)。
文摘Humic materials make important contributions to soil organic carbon(C)and nitrogen(N)accumulation.However,information on the correlation between humic substances and the accumulation of soil aggregate-protected C and N in response to biochar application under tropical agroecosystems is limited.Therefore,a field trial was conducted to elucidate the effects of biochar on soil aggregate properties and humic materials and how these humic compounds affect aggregate-protected C and N in a humid tropical agroecosystem.The treatments included no-biochar control(CK),15 Mg biochar ha^(-1)(BC-15),30Mg biochar ha^(-1)(BC-30),and 30 Mg biochar ha^(-1)+phosphate fertilizer(BC-30+P).The treatments BC-30 and BC-30+P significantly increased the contents of humic materials(humic and fulvic acids)as compared to CK.There was a significant increase in the mean-weight diameter of soil aggregates by3-and 4-fold in BC-30 and BC-30+P,respectively.Similarly,BC-30 and BC-30+P led to significant increases in soil structural coefficient by 3-and 4-fold,re spectively,relative to CK.Significant increases in organic C and N accumulation were observed in the macroaggregates of the biochar-amended soils.Inverse relationships between the degree of polymerization and aggregate-protected C and N were observed,implying that low-molecular-weight aliphatic compounds favor organic C and N accumulation with biochar amendments.The important soil property that contributed to organic C and N accumulation in aggregates was fulvic acid content,which could be used as an early and sensitive indicator to notice early changes in aggregate-protected C and N accumulation in soils of the humid tropics.
