Effect of Potassium and C/N Ratios on Conversion of NH4^+ in Soils
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...
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Published in | Pedosphere Vol. 18; no. 4; pp. 539 - 544 |
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Main Author | |
Format | Journal Article |
Language | English |
Published |
2008
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Subjects | |
Online Access | Get full text |
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Summary: | 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. |
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Bibliography: | clay minerals, fixed NH4^+, N mineralization, organic C, potassium S15 32-1315/P |
ISSN: | 1002-0160 2210-5107 |