The Residual Effect of Zinc Applied to Soils
1964
Brown, A. L. | Krantz, B. A. | Martin, P. E.
Greenhouse tests with sweet corn were studied to measure the residual effect of soil applied Zn. Of the six soils, four had been shown to be Zn deficient by previous tests. Ten successive crops were grown in these soils to which had been applied, 0, 4, and 20 mg. Zn per 1,600 g. of soil. Dry weight yields showed that the 4-mg. Zn rate was adequate for 6 or 7 successive crops; the pots to which 20 mg. was added were not in the deficient range even after 10 crops. The two soils that were not deficient produced 10 crops without any deficiency symptoms developing or any growth response to the Zn applications. Dithizone-extractable soil Zn decreased gradually with cropping. When the values dropped below 0.55 ppm, there was a plant growth response to Zn. Alfalfa was found to obtain adequate Zn from soils which were inadequate for sweet corn.
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