Section 9
Chapter 8,356

Comparison of ammonium bicarbonate-DTPA, ammonium carbonate and ammonium oxalate to assess the availability of molybdenum in mine spoils and soils

Wang, L.; Reddy, K.J.; Munn, L.C.

Communications in Soil Science and Plant Analysis 25(5-6): 523-536


ISSN/ISBN: 0010-3624
DOI: 10.1080/00103629409369060
Accession: 008355659

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A variety of extractants has been used to assess the availability of molybdenum (Mo) in soils. Most of the extractants have been studied from a deficiency aspect rather than for soils with Mo toxicity, and none of them have been used to extract available Mo from mine spoils. The purpose of this study was to examine the potential of different chemical extractants for assessing the availability of Mo in mine spoils and soils. One mine spoil and three soils were treated with sodium molybdate and then subjected to wetting and drying cycles for two months. These spoil/soils were extracted with ammonium bicarbonate DTPA (AB-DTPA), ammonium carbonate, and ammonium oxalate solution for available Mo. Crested wheatgrass (Agropyron cristatum) and alfalfa (Medicago sativa) were grown in the spoil/soils in a greenhouse to determine plant uptake of Mo. Additionally, four mine spoils and six soils were extracted and analyzed for available Mo as mentioned above. The results obtained by these three extractants were highly correlated. It was found that ammonium oxalate extracts the greatest amount of Mo among the three extractants from spoil/soils since it dissolves some adsorbed Mo from Fe-oxide and Al-oxide. The changes in pH of spoil/soils did not have a significant effect on the amount of Mo extracted by any of these methods. The relationships between Mo uptake and Mo extracted by each method were all significant at 1% level. None of the extractants were clearly better or worse than the others. All three methods can be used to assess Mo availability, and potential toxicity from plant uptake of Mo from reclaimed spoils.

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