Effect of Ammonium, Potassium, and Sodium Cations and Phosphate, Nitrate, and Chloride Anions on Zinc Sorption and Lability in Selected Acid and Calcareous Soils

Abstract

Zinc availability and mobility in soils is controlled by its interaction with the soil matrix and amendments. Contradicting evidence has been reported for factors influencing Zn behavior in soils. This study was conducted to investigate the effect of common cations and anions on Zn sorption and lability characteristics. Zinc sorption isotherms were conducted on three acid and four calcareous soils in NH 4 + , K + , and Na + and H 2 PO 4 − , NO 3 − and Cl − backgrounds. Lability of the sorbed Zn was evaluated by DTPA following sorption. Calcareous soils exhibited greater Zn sorption than did acid soils. Predicted Langmuir maxima for Zn sorption differed among the various ionic backgrounds. A majority of the total sorbed Zn (60–96%) was recoverable in the labile fraction. Both NH 4 + and K + equally decreased Zn sorption, as opposed to Na + in acid and calcareous soils; however NH 4 + yielded 4 to 12% more of sorbed Zn into the labile pool than did K + in acid soils. Zinc sorption was enhanced by H 2 PO 4 − as opposed to Cl − or NO 3 − in acid soils, but it was decreased in three out of four calcareous soils. The effect of H 2 PO 4 − on the lability of the sorbed Zn in acid soils was similar to that of Cl − or NO 3 − , but in calcareous soils the phosphate held 10‐25% more of the sorbed Zn in the nonlabile pool. It was concluded that even in calcareous soils, total Zn sorption could be impacted by phosphate–Fe oxide interactions. Furthermore, the effect of background ions on the lability of sorbed Zn varied between acid and calcareous soils. These results have important implications on Zn management in relation to other nutrients.