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| Influence of slope positions on the composition and phosphorus content variation in colloidal particles of citrus orchard red soil |
| Received:March 05, 2024 |
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| KeyWord:citrus orchard red soil;variation of slope position;colloidal phosphorus;mineral composition;organic-inorganic cementing material |
| Author Name | Affiliation | E-mail | | LIU Zhuoling | School of Ecology and Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, China | | | WANG Yanling | School of Ecology and Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, China | ylwang@nuist.edu.cn | | ZHANG Jiamin | School of Ecology and Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, China | | | LI Huan | School of Ecology and Applied Meteorology, Nanjing University of Information Science and Technology, Nanjing 210044, China | | | GAO Lei | State Key Laboratory of Soil and Sustainable Agricultural Development, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China | |
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| Abstract: |
| In order to clarify the effect of slope position change on the composition of colloidal particles and the content of colloidal phosphorus in red soil. In this study, based on Stoke's law, the "water disperse-siphoning method" was used to obtain soil particle sizes of < 0.1, 0.1-< 0.45, 0.45-< 1 μm and 1-5 μm colloidal particles, in citrus orchard at the flat top, top, middle and bottom of the slope of the Sunjia typical red soil watershed in Yingtan, Jiangxi Province. The distribution ratio of colloidal particles, organic matter（OM）, amorphous iron oxide（Feo）, amorphous alumina（Alo）and the content of colloidal phosphorus（Pcoll）in red soil of citrus orchard were compared and analyzed. Taking the red soil of citrus orchard on the flat top of slope as an example, the micromorphology and element enrichment characteristics of colloidal particles of various sizes were observed by means of emission scanning electron microsoopy, and X-ray energy spectrometer（SEM-EDS）and X-ray diffractometer（XRD）. The constituent minerals and relative proportions of colloidal particles of each size were determined. The results showed that the distribution ratio of 1-5, 0.45-<1, 0.1-<0.45 μm colloidal particles was 20.1%-24.8%, 4.1% - 6.1%, 0.2% - 0.6% in citrus orchard red soil at different slope positions, respectively. With the decrease of slope position, the distribution proportion of 1-5 μm colloidal particles increased first and then decreased, while that of 0.45 -<1 μm and 0.1 -<0.45 μm colloidal particles showed a trend of reduced-increased-decrease. As the decrease of citrus orchard slope position, the proportion of OM and Alo in colloidal particles increased first and then decreased and the proportion of OM in the middle and top slopes was the lowest and the highest, while the proportion of Alo in the flat top and top slopes was the lowest and the highest, respectively. The proportion of Feo in the top and middle slopes was the lowest and the highest, respectively. With the decrease of colloidal particle size, the proportion of OM and Feo in each colloidal particle size showed a trend of first decreasing and then increasing, while the proportion of Alo showed a trend of first increasing and then decreasing. The Pcoll content of citrus orchard red soil at different slopes ranged from 0.66 g·kg-1 to 1.57 g·kg-1, and showed a trend of decreasing and then increasing with decreasing slope, and the Pcoll content of each grain in the middle of the slope was the lowest, and that at the bottom of the slope was the highest. Pcoll content was higher the smaller the colloidal particle size. According to SEM-EDS, the binding degree of 0.1-<0.45 μm colloidal particles in the red soil of the citrus orchard at the flat top of the slope is the best and the particles are compact and clustered, the binding degree of <0.1 μm colloidal particles is the worst and the particles are dispersed, while the 1-5 μm and 0.45- <1 μm colloidal particles are scattered and dispersed, and the binding degree is similar. Phosphorus （P）is mainly enriched on the surface of colloidal particles of 1-5 μm and 0.1- <0.45 μm, and iron（Fe）is mainly enriched on the surface of colloidal particles of <0.1 μm. The colloidal particles of each grade are mainly composed of kaolinite and halloysite. Results of the correlation analysis showed that total carbon, total nitrogen, total phosphorus, OM and Alo had significant effects only on colloidal phosphorus of 0.1- < 0.45 μm colloidal particles contents in the red soil of citrus orchard. |
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