Evaluation of Mehlich 3 reagent as a multielement extractant in mine soils

The usefulness of Mehlich 3 (M3) reagent was evaluated as a method to extra ct numerous elements from coalmine soils in As Pontes (Spain) showing a wid e range of physiochemical properties. Critical levels (deficiency and/or to xicity) were established for plant available elements extracted by this rea gent. The M3 method was compared to 1M NH,CI, Olsen, acid oxalate, and DTPA methods as extractants for exchangeable Ca, Mg and K, available P, non-cry stalline aluminium, and available heavy metals, respectively. The M3 method correlated significantly to NH,Cl for Ca, Mg and K (r = 0.76, 0.84 and 0.8 7, respectively), to Olsen P (r = 0.77) and to oxalate Al (r = 0.77). Signi ficant correlations were found between Fe, Cu, Zn and Cd extracted by M3 an d DTPA; for Mn, Ni, Co and Pb different relationship between methods were o btained for acid and alkaline samples, so that critical levels were establi shed for M3 metals as a function of soil pH. Copyright (C) 1999 John Wiley & Sons, Ltd.