CROP, LIGHT INTENSITY, SOIL pH, AND MINOR ELEMENT EFFECTS ON THE YIELD AND VITAMIN CONTENT OF TURNIP GREENS

Abstract

It is well recognized that factors affecting the vitamin content of plants usually cause composition changes of considerable nutritional importance. Most previous investigations of these effects have considered a single factor rather than studying several factors simultaneously.Harmer and Sherman (9) and Hester (20) have indicated that low ascorbic acid content of certain plants is associated with a deficiency o r low availability of manganese in the soil. I n these instances, applications of manganese increased the ascorbic acid content of plants. Gum, Brown, and Burrell ( 4 ) , Lyon and Beeson (11,22), and Lyon, Beeson, and Ellis (?3), report either no effect, or slight but inconclusive effects, on the ascorbic acid content of certain plants when minor element application was made in amounts ranging from deficient t o toxic concentrations.Probably the largest and most consistent increases in the ascorbic acid content of plants have been caused by increases in light intensity, a phenomenon reported by Aberg (Z), Hammer, Lyon, and Hamner ( 6 ) , Bernstein (2), Hamner and Parks (8), and Somers, Kelly, and Hamner (22). The influence of fertilizers on the ascorbic acid content of turnip greens has been studied by workers of the Southern Cooperative Group at several locations in the South. Reports on these studies have been made by Reder, Ascham, and Eheart ( l a ) , Reder et al. (15), and Sheets et al. (28). Although the fertilizer treatments produced no consistent effects, increases in the ascorbic acid content of the greens occurred at locations having high light intensities prior to harvest.Work by Bernstein, Hamner, and Parks ( 2 ) and Hamner and Maynard (7) showed that increases in the carotene content of turnip greens and tomatoes respectively were obtained with increased light intensity. Gustaveson (5) found that increasing light intensity caused proportional increases in the thiamine content of tomatoes, potatoes, beans, peas, and New Zealand spinach; and consistent but less pronounced increases in the riboflavin content of these vegetables. Excellent literature reviews on the effect of environment on the chemical composition of plants have been prepared by Somers and Beeson (20) and Richardson et al. (16).Recognizing the limitations of single-factor experiments for obtaining information of this type, an experiment was initiated in 1950 at Blacksburg, Virginia, in which the effect of crops, soil pH, light intensity, and minor elements, and their interactions, on the nutritive value and yieId of turnip greens, were studied simultaneously.