Operational cost of producing lettuce (Lactuca sativa) during the winter in greenhouses is high in the northern regions of the United States due to the addition of supplemental lighting (SL) and heating. Crop productivity in greenhouses should increase to offset high operational costs and maintain profits. Factors including SL composition, heating efficiency, suitability of production systems (PS), and cultivar performance can affect crop productivity. Research-based information on optimizing the above environmental- and production-related factors is limited. This information is critical for growers to make informed decisions and increase profits during winter hydroponic production. We evaluated the interactive effects of SL composition, solution temperature, PS, and cultivar treatments on lettuce shoot dry weight (SDW, g·m−2) and shoot water content (SWC, %) in a greenhouse maintained at suboptimal air temperature (13.7 °C) using a split-plot design. There were three light treatments (sunlight without SL, sunlight + narrow-spectrum SL at nighttime, and sunlight + full-spectrum SL at nighttime), two solution temperature levels [heated (18.8 °C) and unheated (13.2 °C)], two hydroponic PS [constant flood technique (CFT) and nutrient film technique (NFT)], and eight cultivars included in the study. Results indicated that 1) a narrow-spectrum SL at nighttime in combination with heated solution resulted in maximum SDW of lettuce, 2) the SDW and SWC (major determinant of economic yield) increase between the heated and unheated solution temperature treatments was higher in the CFT than in the NFT, and 3) the positive effects of using heated solution were seen mainly in the green-color cultivars. Our research identified the optimal spectral composition of nighttime SL, tested the positive effects of alternate heating methods using heated solution on plant growth under suboptimal air temperature conditions, compared the suitability of two hydroponic PS for lettuce production, and quantified yield potential of several lettuce cultivars in hydroponic production during winter. Growers can use our research findings to make informed decisions about their investment and to maximize hydroponic lettuce productivity and profits during winter.
Alexander Miller, Petrus Langenhoven, and Krishna Nemali
Ariana Torres, Petrus Langenhoven, and Bridget K. Behe
The domestic market for melons, Cucumis melo L., has not been well characterized. The 2011 cantaloupe-related foodborne illness outbreak reduced melon production by 32%, and per capita consumption of cantaloupe and honeydew melons has not recovered. Our objective was to profile and characterize consumer segments of individuals who purchased melons in the 3 months before the survey. Responses from 1718 participants were analyzed by consumption volume and subjected to cluster analysis based on importance of melon attributes. Heavy and moderate consumers preferred local melons over imported. The top four melon attributes were flavor, freshness, ripeness, and sweetness. As consumption increased, consumers placed more importance for their diets. The heaviest consumption group accounted for 22% of the market, and consumed nearly three times the melon servings per month compared with the moderate consumer, and nearly 10 times the servings of the light consumption group. Cluster analysis produced three distinct clusters. Cluster 1 was the most promelon in attitudes and consumption, as well as general health interest, craving sweet food, food pleasure, and variety seeking in foods. The largest segment was cluster 3 and was the ideal group for future targeting of marketing and advertising campaigns for increasing the melon market share with their intermediate consumption and promelon attitudes. Last, members of cluster 2 consumed the lowest amount of melons, spent the least on melons, and traveled the fewest number of miles to purchase them, relative to the other two segments.