Establishing a plant availability test for Ba, Cu, Mn and Zn from calcareous soil from Malta using wheat as an indicator plant

Abstract

Phytoavailabilty of metals to plants depends on several factors and although several extraction procedures are established, there is no indication as to which is the best extractant. Four soil extraction procedures with ammonium bi-carbonate diethylene triamine pentacetic acid (AB-DTPA), DTPA- triethanolamine, calcium chloride (CaCh) and ammonium acetate (NH40Ac) were carried out to establish the best extraction method for phytoavailabilty of Ba, Cu, Zn and Mn in Maltese soils. A pot experiment with wheat was also carried out to establish which extraction procedure shows the best relationship with shoot accumulation by the plant. Ammonium bicarbonate-DTP A overall extracted the highest concentrations of metals from the soils used, DTPA-TEA also extracted significant concentrations of metals from the soils but extracted less than ammonium bicarbonate-DTP A. Calcium chloride extracted either very small concentrations or nothing at all, suggesting that it might not be the ideal extractant for Maltese soils. Ammonium acetate extracted only Ba in significant concentrations while the concentrations of the other elements were either minimal or beyond detectable limits. Overall ammonium bicarbonate-DTP A was the best extractant of metals in Maltese soils amongst those studied. However there was either no statistically significant relationship between the metal concentration extracted and plant uptake, or the relationship was very minimal.