Nitrogen and sulfur effects on leaf lettuce quality

Nitrogen*sulfur fertilizer combinations and growing season effects on senso ry quality/acceptability and color of hydroponically grown greenhouse lettu ce cultivar, "Grand Rapids': were studied. Lettuce samples were evaluated u sing an attribute rating scale for appearance, color, texture, flavor, bitt erness and overall acceptability; actual leaf color was measured with a chr omameter. Initially, 20 N*S treatment combinations were tested. Then based on specific sensory responses, eight N*S treatment combinations were select ed for further study in the Winter and in the Spring. Univariate ANOVA show ed that in both studies significant (P < 0.05) color and texture difference s were found Generally, plants receiving the highest treatment level (240 m g/L) of nitrogen were greener (sensory) and darker and duller (chromameter) than the other samples. Spring samples receiving 30 and 60 mg/L N were per ceived as having firmer texture. Between seasons, it was found that lettuce grown in the Spring was perceived as being greener and having a softer tex ture than lettuce grown in the Winter. Principal component (factor) analysi s revealed three factors accounting for between 79 to 81% of the variance i n the data. Factor loadings varied depending on the season grown.