THE ROLE OF COTRIC ACID AS A PHOSPHORUS MOBILIZATION MECHANISM IN HIGHLY P-FIXING SOILS
Exudation of low molecular weight carboxylates is an important phosphorus (P) acquisition strategy for plants in strongly P-fixing soils. The effect of citrate exudation on P availability was studied in five acid soils with a large organic matter content and a low available P pool. The amount of mol...
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| Autores principales: | , |
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| Lenguaje: | English |
| Publicado: |
Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción
2003
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| Materias: | |
| Acceso en línea: | http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-66432003000100009 |
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| Sumario: | Exudation of low molecular weight carboxylates is an important phosphorus (P) acquisition strategy for plants in strongly P-fixing soils. The effect of citrate exudation on P availability was studied in five acid soils with a large organic matter content and a low available P pool. The amount of molybdate reactive P extracted by citric acid 10 mM (0.1-2 mg kg-1) was larger than the molybdate reactive P (MRP) extracted by CaCl2 10-3 M (0.007-0.07 mg kg-1). Both extractants were adjusted to soil pH prior to extraction. Also, the total P content of citric acid extracts (2-44 mg kg-1) far exceeded the total P content of CaCl2 (0.2-1.5 mg kg-1). However, ratios of MRP to total dissolved P (TDP) remained constant. When citric acid was added to the CaCl2-extracts (the pH of citric acid being adjusted to the pH of CaCl2, and thus eliminating release of P through acidification) a significant pH increase was noted. Simultaneously, MRP increased significantly in all but one soil. This suggests that the P availability enhancing properties of citric acid are not only due to acidification of the plant rhizosphere, but also to its Al and Fe complexing capacity |
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