Pedosphere 18(4): 539--544, 2008
ISSN 1002-0160/CN 32-1315/P
©2008 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Effect of potassium and C/N ratios on conversion of NH4+ in soils |
TANG Yan , WANG Xiao-Zhi, ZHAO Hai-Tao and FENG Ke |
| College of Environment Science and Engineering, Yangzhou University, Yangzhou 225009 (China) |
| ABSTRACT |
| Two soils, one consisting of 1:1 clay minerals at pH 4.5 and the other containing 2:1 clay minerals at pH 7.0, were used to estimate the conversion of added NH4+ under different C/N ratios (glucose as the C source) and the addition of potassium. Under lower C/N ratios (0:1 and 5:1), a large part of the added NH4+ in the acid soil was held in the forms of either exchangeable or water soluble NH4+ for a relatively long time and under higher C/N ratio (50:1), a large amount of the added NH4+ was directly immobilized by microorganisms. In the second soil containing appreciable 2:1 type clay minerals a large part of the added NH4+ at first quickly entered the interlayer of the minerals under both lower and higher C/N ratios. In second condition, however, owing to microbial assimilation stimulated by glucose the newly fixed NH4+ could be completely released in further incubation because of a large concentration gradient between external NH4+ and fixed NH4+ in the mineral interlayer caused by heterotrophic microorganisms, which imply the fixed NH4+ to be available to plants. The results also showed that if a large amount of K+ with carbon source together was added to soil, the higher K+ concentration of soil solution could impede the release of fixed NH4+, even if there was a lot of carbon source. |
| Key Words: clay minerals, fixed NH4+, N mineralization, organic C, potassium |
| Citation: Tang, Y., Wang, X. Z., Zhao, H. T. and Feng, K. 2008. Effect of potassium and C/N ratios on conversion of NH4+ in soils. Pedosphere. 18(4): 539-544. |
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