Estimation of Available Zinc in Soils from Yield-of-Zinc Curves
1956
Nearpass, D. C.
The native soil zinc that is equally as available to plants as is a standard source of zinc supplied as fertilizer, may be estimated from yield-of-zinc curves if the total zinc in the aerial portions of the plants is related to the available zinc supply in a soil, and the amount of available native soil zinc is unaffected by the addition of fertilizer zinc. A logarithmic relationship between zinc in the substrate and zinc in the aerial portions of plants was found when plants were grown in ion exchange resin-sand-nutrient cultures. From 88 to 95% of the variation was accounted for by the logarithmic regression equation. When plants were grown in soils, the yield-of-zinc curves obtained were also curvilinear and could be described by logarithmic or parabolic equations. The estimated available native soil zinc values found by solving the logarithmic regression equations were significantly correlated, r being +0.800, with the zinc contents of the control plants. On the other hand, available zinc by parabolic fit and dithizone extractable zinc were also significantly correlated, with a correlation coefficient of +0.847. In further experiments, the soil zinc values found from the yield-of-zinc curves obtained by growing millet, were less than those found from the yield-of-zinc curves obtained by growing oat and tomato plants.
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