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Suggested Citation:"DISCUSSION." National Research Council. 1953. Composition of Corn in the United States, 1946-1947. Washington, DC: The National Academies Press. doi: 10.17226/18444.
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8 COMPOSITION OF CORN IN THE UNITED STATES small and often did not agree in sign. Of 434 correlation coefficients computed for the two years, only 34 equalled or exceeded 0.5. It may therefore be concluded from this investigation that the correlations between nutrients are not very useful, and a knowledge of the composi- tion of corn with respect to a few nutrients does not aid materially in assessing its composition hi other nutrients. Thus, in feeding practice one must either use average data from tables to apply to a given lot of corn or, if greater pre- cision is desired, determine the nutrient content for that lot. From the standpoint of sampling, it appears that each nutrient should be con- sidered independently. The negative correlations of nitrogen-free extract with protein, fat, and ash would be ex- pected because the former is determined by subtracting these three nutrients and fiber from the total dry matter. No attempt is made to explain the other correlations shown. The rela- tively large number of nutrients with which fluorine and carotene are appreciably corre- lated should be noted. The more significant correlation results which, after being averaged for the two years, equaled or exceeded 0.3 are presented in Table VI. This figure was selected because correla- tions of this size or less mean that 9 per cent or less of the variance in one factor is associ- ated with variance in the other factor. The simple coefficients of correlation between all nutrients are given in Table VII. DISCUSSION The observation of the feed industry that the protein content of corn declined appreci- ably in the years prior to 1946 seems to have been verified by this study. Morrison (4) gives the mean protein content of No. 2 corn as 9.4 per cent. In contrast, a value of 8.7 per cent was obtained in the 1946 survey, and one of 9.1 per cent in the 1947 survey. Barley and De Turk (3) concluded that "the decline in protein reported by the feed industry is not due to inherently low protein hybrids" and that "the decrease in corn protein is be- lieved to be caused by both a decreased soil nitrogen at regular rates of planting and by an increased rate of planting on soils relatively k>w in nitrogen." These views were not contra- dicted by the results of the present work. At least, the heavier corn producing areas tended to yield corn of low protein content, and varie- tal differences in protein content accounted for a very small portion of the variance. Nothing conclusive on these points is offered by the present studies, however, because their design did not permit arriving at such conclusions. Regional, state, and varietal differences were appreciable and statistically significant for some nutrients. For most of the nutrients, however, it appears that these factors per sc have little to do with the nutrient content of commercial corn. To account for the major variability in nutrient composition of corn, one must look to other factors. Soil type and local- ized climatic effects are indicated, with atten- tion directed particularly to some of the things, such as the micronutrient element content, which might vary within a given soil type. Other factors of possible importance are those associated with cultural practices such as fer- tilization. These factors seem especially worth consideration for those minerals and vitamins which have high coefficients of variation. In surveys designed to inquire into the causes of locational variations in composition, it appears that special emphasis would have to be placed on the above local factors in allocating samples, and intense sampling rates would have to be employed. Controlled experiments would pos- sibly be helpful. The change in protein content of corn through the years indicates the desirability of periodic checks on nutritive composition of feeds on a national scale. New varieties of crops and greater use of fertilizers, particularly the micronutrient elements, permit the production of many crops under new and different ecologi- cal conditions. Thus, different soil and climatic factors combined with the new varieties may

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Composition of Corn in the United States, 1946-1947 Get This Book
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At the first meeting of the Committee on Feed Composition on August 15 and 16, 1946, a plan was initiated to study the chemical composition of the 1946 corn crop in the United States. This study was later extended to include the 1947 crop. Corn was selected because a large percentage of the total production is used for feeding, and more corn is fed to livestock in the United States than any other grain. Furthermore, evidence was presented indicating that the percentage of protein in corn had decreased over a period of years. Composition of Corn in the United States, 1946-1947 determines the validity of, and possible reasons for, this alleged diminution.

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