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Carrot nutrition : the influence of varying levels of nitrogen, phosphorus and potassium on the yield and food value of Daucus carota (L.), variety Red Core Chantenay Hughes, Robert William

Abstract

In a vegetable nutrition experiment, fertilizers were applied in such a way as to make possible a study of the effects of three levels each of nitrogen, phosphorus, and potassium on the yield and food value of carrots. The levels of each nutrient applied were: nitrogen 50, 100, and 150 pounds; phosphoric acid 100, 200, and 300 pounds; and potash 50, 100, and 150 pounds per acre. The experiment was arranged in a 3 X 3 X 3 design with second order interactions confounded with blocks. Under the conditions of the experiment it was found that applications of nitrogen caused a very highly significant, positive, linear response for root yield; that applications of phosphorus had no primary effect on yield; and that applications of potassium caused a highly significant, positive, linear and quadratic response for root yield. Nitrogen applications caused a very highly significant, positive, linear trend for crude protein content, and a negative trend of similar significance for crude ash content. No effect was observed on dry weight, total available carbohydrate or total carotenoid contents. Phosphorus applications had no primary effect on those food value factors assayed. Potassium applications caused a significant, negative, linear trend for dry weight, and a highly significant, positive, linear trend and a significant, positive, quadratic trend for ash content. No primary effect was observed on total available carbohydrate, crude protein, or total carotenoid contents. Five significant interactions were found. These were: quadratic phosphorus X linear potassium, for total yield; linear nitrogen X linear phosphorus and linear phosphorus X quadratic potassium, for total available carbohydrates; quadratic phosphorus X quadratic potassium, for crude protein; and quadratic nitrogen X linear phosphorus for crude ash content. The experimental design adopted, and the statistical analysis used, proved satisfactory for the evaluation of primary and second order interaction effects. Significance of pairs of adjusted means for root yield, calculated as a part of the statistical analysis, has been summarized by means of the tri-cyclograph.

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