Pedosphere 23(1): 81--87, 2013
ISSN 1002-0160/CN 32-1315/P
©2013 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Effect of Fe/Al hydroxides on desorption of K+ and NH4+ from two soils and kaolinite |
WANG Yan-Ping1,2, XU Ren-Kou1 and LI Jiu-Yu1,2 |
1 State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China)
2 University of Chinese Academy of Sciences, Beijing 100049 (China) |
| ABSTRACT |
| Potassium (K) and nitrogen (N) are essential nutrients for plants. Adsorption and desorption in soils affect K+ and NH4+ availabilities to plants and can be affected by the interaction between the electrical double layers on oppositely charged particles because the interaction can decrease the surface charge density of the particles by neutralization of positive and negative charges. We studied the effect of iron (Fe)/aluminum (Al) hydroxides on desorption of K+ and NH4+ from soils and kaolinite and proposed desorption mechanisms based on the overlapping of diffuse layers between negatively charged soils and mineral particles and the positively charged Fe/Al hydroxide particles. Our results indicated that the overlapping of diffuse layers of electrical double layers between positively charged Fe/Al hydroxides, as amorphous Al(OH)3 or Fe(OH)3, and negatively charged surfaces from an Ultisol, an Alfisol, and a kaolinite standard caused the effective negative surface charge density on the soils and kaolinite to become less negative. Thus the adsorption affinity of these negatively charged surfaces for K+ and NH4+ declined as a result of the incorporation of the Fe/Al hydroxides. Consequently, the release of exchangeable K+ and NH4+ from the surfaces of the soils and kaolinite increased with the amount of the Fe/Al hydroxides added. The greater the positive charge on the surfaces of Fe/Al hydroxides, the stronger was the interactive effect between the hydroxides and soils or kaolinite, and thus the more release of K+ and NH4+. A decrease in pH led to increased positive surface charge on the Fe/Al hydroxides and enhanced interactive effects between the hydroxides and soils/kaolinite. As a result, more K+ and NH4+ were desorbed from the soils and kaolinite. This study suggests that the interaction between oppositely charged particles of variable charge soils can enhance the mobility of K+ and NH4+ in the soils and thus increase their leaching loss. |
| Key Words: amorphous Al(OH)3, amorphous Fe(OH)3, electrical double layer, surface charge, variable charge soil |
| Citation: Wang, Y. P., Xu, R. K. and Li, J. Y. 2013. Effect of Fe/Al hydroxides on desorption of K+ and NH4+ from two soils and kaolinite. Pedosphere. 23(1): 81-87. |
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