COMPARATIVE AMOUNTS OF ZINC EXTRACTED FROM SOILS BY A CHEMICAL SOLVENT AND BY PLANTS

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Abstract
The amt. of Zn found in many spp. of plants in their natural habitat is compared with the amt. extracted from the same or similar soils by a simple chemical extractant, which is 0.5 M KCl plus acetic acid to make the soln. about pH 3. The process is simple and short compared with the time and effort required to grow and analyze the plants grown in sand with Zn-free nutrients to which is added 10 gms. of the soil mixed with 1,000 gms. of Zn-free sand. A novel, all-glass-tubing apparatus automatically returns the solvent to the top of the sand after the soln. has passed through the sand culture to a receiver. The plants extract much more Zn than does the chemical solvent. The amts. of Zn extracted by the 2 methods, though quite different in amt., are similar but parallel. High Zn in a soil is indicated by either method, and both indicate low Zn. Therefore, the short chemical method may be used instead of the method of extracting the Zn by growing plants in the soil. The chemical method supplies a simple, quick method for classifying soils as to available Zn.