Título en español.

Abstract

At present there is available no method of soil analysis which provides the information required to estimate with enough precision the quantities of the various nutrients that must be added to a soil to ensure maximum profit to the farmer. Although the results of certain field experiments make possible the estimation of the optimum rate of fertilization required for the commercial production of a crop, it is necessary to wait until the experiment is harvested, and its results are interpreted to carry out this estimation. The information provided by experiments performed with indicator plants prior to the time of fertilization of the commercial crops is as unreliable as that provided by the chemical analysis of the soil. The author has found a mathematical equation that can be used with a high degree of precision to represent the relationship between the content of a nutrient by the plant tissue at a certain stage of its growth cycle and the relative yield of the plant of which the tissue is analyzed. By using this mathematical equation jointly with a relation between the available nutrient content of the soil and the yield of the crop grown in that soil, it is possible to estimate also, with a high degree of precision, the quantities of the different fertilizer elements that should be added to the commercial crop so that the farmer may obtain a maximum profit.

Additional Evidence on the Applicability of the New Fertilizer-Yield Relation

“…All these calculations were performed by using a Japanese abacus, the columns of which were identified according to a scheme devised by the author markedly to simplify its use and reduce the time and effort needed to record the figures needed and the results of the calculations. To reduce also the labor of computation, a table was prepared indicating the values of B(X -C) 2 for all values of B from 1 to 70 and all values of C from 1 to 120. By placing the decimal point where required, the values of B{X -C) 2 for decimal fractions of a unit of both B and C were easily estimated.…”

“…To reduce also the labor of computation, a table was prepared indicating the values of B(X -C) 2 for all values of B from 1 to 70 and all values of C from 1 to 120. By placing the decimal point where required, the values of B{X -C) 2 for decimal fractions of a unit of both B and C were easily estimated.…”

“…P per acre. 2 Y ~ observed mean yield in tons of cane per care. 3 Y' = mean yield in tons of cane per acre estimated with the fitted equation.…”

“…The variously proposed concepts, of course, have been advanced by the various workers as results of the studies of the nutrient-crop yield data technical Consultant, Agricultural Experiment Station, University of Puerto Rico, Río Piedras, P.R. 2 Italic numbers in parentheses refer to Literature Cited pp. 119-20.…”