Factors Controlling the Extractability of Soil Zinc

Abstract

AbstractThe effect of total zinc, pH, and contents of clay and organic C on the extractability of soil Zn by Aspergillus niger, 0.1n HCl, dithizone, and 0.2m MgSO4 for 57 Wisconsin soils was evaluated by simple, partial, and multiple correlation.The relative amount of soil Zn extracted by the Zn tests was in the order A. niger > 0.1n HCl > dithizone > 0.2m MgSO4 extractable Zn. Simple, partial, and multiple correlation data indicated that the fungus extracts a fixed fraction of the total soil Zn. Consequently, total Zn and A. niger‐extractable Zn were of approximately equal importance in the prediction of Zn uptake by plants. Statistical interactions between clay and organic C content in relation to the amount of Zn extracted by 0.1n HCl were explained on the basis of organo‐clay complex formation. An increase in organic matter content at constant levels of clay increased the amount of Zn bound by the organo‐clay complex thereby resulting in increased extractability of soil Zn by 0.1n HCl. On the basis of correlation data and the greater extractability of Zn by 0.1n HCl than dithizone, it was concluded that much of the Zn extracted by 0.1n HCl over dithizone is not extractable by plants. It was shown that the amount of Zn extracted by 0.2m MgSO4 varied inversely with pH; clay and organic C contents had less effect on the relationship suggesting that 0.2m MgSO4 extracts only solution and readily exchangeable Zn.