Lookup NU author(s): Dr Jan Dolfing
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Leaching of phosphorus (P) can be a serious problem in P-enriched sandy soils. Techniques that decrease the P content of such soils have been proposed as possible remediation methods. In this study, we determined the effect of P removal from two P-rich sandy soils on extractability of soil P in a laboratory experiment. We created soil samples in increasing stages of P depletion by using a sink method, which consists of a dialysis membrane tube filled with hydrous Fe-(hydr)oxide (DMT-HFO). Total amounts of P removed were relatively small compared with the high initial ammonium-oxalate extractable P contents. However, amounts of water and CaCl2 extractable P in the depleted soil samples decreased by 57 to 80%, on average, for both soils. On the other hand, the ammonium-oxalate-based P saturation index decreased by only 11%. Apparently, labile P forms were readily removed, which means that depletion by the DMT-HFO was selective. Our results suggest that remediation methods that remove a small but selective amount of P from soil may cause a significant decrease of the soil potential to release dissolved P. We also used our results to evaluate the suitability of the DMT-HFO to act as an infinite sink for P. For that, the desorption results were described with a simple kinetic Langmuir equation. Errors of k(d) (desorption constant) and Q(0) (amount of P initially adsorbed) were calculated. Although the model fit was good for both soils (r(2)=0.98*** and 0.99***), errors in Q(0) and k(d) were large. Therefore, the DMT-HFO method could not be used to determine the desorption constants of our soils. Values of k(d) and Q(0) obtained by this method should not be used in modeling studies.
Author(s): Koopmans GF, van der Zeeuw ME, Chardon WJ, Dolfing J
Publication type: Article
Publication status: Published
Journal: Soil Science
Print publication date: 01/07/2001
ISSN (print): 0038-075X
ISSN (electronic): 1538-9243
Notes: Times Cited: 3
Cited Reference Count: 34
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