Micronutrient Cation Complexing in Soil Solution: II. Complexing of Zinc and Copper in Displaced Solution from Calcareous Soils

Authors:
  • JHJ. F. Hodgson
    J. F. Hodgson
  • WLW. L. Lindsay
    W. L. Lindsay
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Abstract
Zinc deficiencies are generally more widespread on calcareous soils than are Cu deficiencies. The concentration and the degree of complexing of Zn and Cu were measured in the soil solution of 20 calcareous soils from Colorado. The Zn levels in solution were generally less than 2 ppb with rarely more than 75% of the Zn being complexed. Copper levels generally ranged from 5 to 16 ppb in the soil solution with 98 to 99% of the Cu present as organic complexes. Thus, complexing increased the total Cu concentration in solution by a factor of about 100, whereas it increased the total Zn in solution by a factor of 4 or less. Compared to acid soils studied previously, soluble Zn levels were much lower and complexing of Cu was somewhat higher in calcareous soils.