New methods for the determination of the availability of nitrogen and phosphorus to plants
1935
Emmert, E.M.
It was assumed that the nutrients found in the lower conducting tissues of the plant are a close approximation of the materials the plant is able to obtain from the soil, whereas the nutrients found in apical tissues would be such as had not been utilized or elaborated in the process of growth. Inasmuch as the nutrients derived by a growing plant from the soil must enter in solution through the stem, it seems reasonable that the concentration of a given nutrient in the conducting tissue of the stem should be directly proportional to the available supply of that nutrient from the soil. A measure of the content of nutrients in this conducting tissue, therefore, may be a better measure of the ability of the soil in which the plant is growing to supply nutrients than a chemical test of the soil itself. It seems probable, also, that an optimum content of nutrients in this kind of tissue should exist for the various stages of growth of each kind of crop regardless of the kind of soil in which the crop is growing. The work reported in this paper was done to test this hypothesis. The results are favorable and seem to justify thorough investigation of the question.
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