Responses of rice and winter wheat to free-air CO2 enrichment (China FACE) at rice/wheat rotation system |
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Authors: | Hongliang Ma Jianguo Zhu Zubin Xie Gang Liu Qing Zeng Yong Han |
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Affiliation: | (1) Biogeochemistry and Ecology of Continental Environment, Laboratory UMR 7618, Ecole Normale Supérieure, Université Paris 6, CNRS, INRA, 46 rue d’Ulm, Paris, 75230, France;(2) Geology Laboratory, UMR 8538, Ecole Normale Supérieure, CNRS, 24 rue Lhomond, 75231 Paris Cedex 05, France |
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Abstract: | Potassium (K) availability influences many processes in cultivated and natural ecosystems. Several studies suggest that “non-exchangeable” K+ ions fixed in 2:1 clay mineral interlayers contribute to plant nutrition. Although depletion of these K+ ions could be observed by X-ray diffractometry, this technique has never been considered for the observation of short-term changes in illitic 2:1 clay minerals. We established in this study that new treatments of X-ray diffraction patterns allow quantification of short-term 2:1 clay mineral changes through K addition in solution and removal of interlayer K by Lolium multiflorum. Moreover, we obtained a significant relationship (r 2 = 0.95, P < 0.0001) between an indicator calculated from X-ray diffraction patterns and analyzed clay K content. X-ray diffraction should therefore be considered as an appropriate tool to follow qualitatively and quantitatively clay mineral modifications induced by soil K balance. Our results suggest that 2:1 clay minerals behave as a huge, renewable K reservoir whose theoretical capacity in fertile soils could exceed 3 t/ha. Beyond obvious agronomical implications, this new vision of soil K cycle raises ecological questions about plant inter specific competition and soil fertility. Finally, our study clearly shows that soil 2:1 clay minerals could react as quickly as a biological system. |
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Keywords: | Clay minerals Illite Interlayer potassium Potassium cycle Soil |
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