1999 Fiscal Year Final Research Report Summary
Dynamics of Clay Fixed Potassium of Rhizosphere Soil Eco-System of Grasslands
| Project/Area Number |
10460031
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Plant nutrition/Soil science
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| Research Institution | Tokyo University of Agriculture & Technology |
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Principal Investigator |
SUZUKI Sohzoh Tokyo University of Agriculture and Technology, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (30137898)
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| Co-Investigator(Kenkyū-buntansha) |
TANAKA Haruo Tokyo University of Agriculture and Technology, Faculty of Agriculture, Assistant Professor, 農学部, 助手 (20236615)
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| Project Period (FY) |
1998 – 1999
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| Keywords | rhizosphere / potassium ion / vermiculite / clay minerals / root exudates / organic acied |
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| Research Abstract |
1. PURPOSE : It was found that the potassium fixed by clays in the rhizos-phere soil in a grassland was removed more easily than that of in the non-rhizosphere soil. It is supposed that the relationships was caused by the actions of organic acids exudated from the grasses. We investigated that 1) Identification and determination of rganic acids exdated from grass roots. 2) Measuring of basal spacings of potassium interlayered vermiculite reacted with organic acids identified from the grass root exudates.
2. RESULTS : 1) The basal spacing of potassium interlayered vermiculite was 1.0nm. It expanded to 1.4nm after treatment with grass roots and the reaction increased with the numbers of grass roots. 2) There were many known and unknown organic acids in the exudates of root tips. The known ones were identified as maleic, citric, tartaric, malonic, malic, succinic, lactic, acetic and propionic acids. 3) The contents of the root-exudated organic acids were different by the conditions of potassium and light, and the sites of exudation were different accoding to the varieties of organic acids. 4) The basal spacing of potassium interlayered vermiculite expanded to 1.3nm after treatment with the identified known organic acids which pH were less than 4. The contents of potassium in the solution of organic acids began to increase exponentially with decrease of pH value from 4.
3. CONCLUSION : It was clarified that there were many organic acids in the grass root exudates and they act on the less available potassium which was held in a fixed state in the interlayers of vermiculite to remove to the soil solution as an available potassium.
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