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Effect of various levels of nitrogen and sulfur on yield, color, ascorbic acid, and sensory attributes of hydroponically grown 'Grand Rapids' leaf lettuce
Abstract
The importance of nitrogen and sulfur as essential nutrients in the growth and development of plants is well documented. Nitrate concentration is an important criterion for food quality, and sulfur concentration affects the nutritive value and organoleptic properties of vegetables. Groundwater contamination due to nitrogen fertilizers is a major concern in agriculture. This research was done to determine if nitrogen supplied to lettuce could be reduced by addition of sulfur and what effect altering the nutrient balance would have on quality. The first series of experiments was designed to modify a hydroponic system for 'Grand Rapids' leaf lettuce production. The system was used to screen twenty-four nitrogen-sulfur combinations from which treatments for further experiments would be selected. The intent was also to determine if a reduction in the number of treatments per block using an incomplete factorial design would yield results equivalent to a complete factorial design. Eight treatment combinations were selected from the preliminary screening for further study. The purpose was to determine the effect of various levels of nitrogen and sulfur supplied on: fresh weight, dry weight, leaf nitrogen content, leaf sulfur content, ascorbic acid content, color, and sensory attributes of leaf lettuce. The incomplete design failed to yield results equivalent to the complete factorial design. Leaf nitrogen content increased as nitrogen supplied increased, but declined at 240 ppm nitrogen. Leaf sulfur content increased with increased application of sulfur and nitrogen. Nitrogen supplied affected color such that plants receiving 240 ppm nitrogen were a darker, duller green, and plants receiving 30 ppm nitrogen were a lighter, vivid yellow-green. Ascorbic acid content increased as nitrogen supplied increased. Sulfur had no detectable effect on ascorbic acid content. Differences in sensory evaluation were due to nitrogen and sulfur supplied. Sulfur and nitrogen supplied had similar effects on winter and spring grown lettuce, but the magnitude of difference was greater in the spring.
Subject Area
Plant propagation|Botany|Food science
Recommended Citation
McCluskey, Melinda McVey, "Effect of various levels of nitrogen and sulfur on yield, color, ascorbic acid, and sensory attributes of hydroponically grown 'Grand Rapids' leaf lettuce" (1994). ETD collection for University of Nebraska-Lincoln. AAI9507818.
https://digitalcommons.unl.edu/dissertations/AAI9507818