Labile pool and selective distribution of zinc in soils

Summary

The labile pool of zinc in alkaline soils was determined by the application of isotopic dilution principle under laboratory and greenhouse conditions using corn and wheat as experimental crops. Simultaneously, the selective distribution of⁶⁵Zn isotope between the solid and solution phases in 0.1M CaCl₂ was determined. The labile pool-selective distribution coefficient diagrams were used for delineating the soils into different categories of Zn availability. The variations of the parameters of zinc availability were related to the physical and chemical properties of the soils. The results indicated that the plants and the DTPA extractant removed forms of zinc that may not undergo isotopic exchange in indifferent electrolytes. The values of labile pool obtained by the laboratory and greenhouse methods were highly correlated. The selective distribution coefficient was related to the organic matter and clay contents of the soils (R=0.78). A comparison of the values of labile pool of zinc measured with corn and wheat crops indicated that the two crops differ appreciably in affecting the isotopic dilution of⁶⁵Zn in their root zone. The results indicate that the greenhouse method of determining the labile pool of zinc may be used as a reference procedure for calibrating soil test methods that extract amounts of Zn equal or proportional to that removed by growing plants in alkaline soils. The DTPA procedure of determining the available Zn in such soils meets the requirements of a satisfactory soil test method. re]19760726