The Effect of Environment and Nutrients on Hydroponic Lettuce Yield, Quality, and Phytonutrients

A study was conducted with green and red-leaf lettuce cultivars grown in a deep-water culture production system. Plants were seeded in rockwool and germinated under greenhouse conditions at 25/20 °C (day/night) for 21 days before transplanting. The experimental design was a randomized complete block with a 2 × 3 factorial arrangement of cultivar and nutrient treatments that consisted of six replications. Treatments consisted of two lettuce genotypes, (1) green (Winter Density) and (2) red (Rhazes), and three nutrient treatments containing electroconductivity (EC) levels of (1) 1.0; (2) 2.0; and (3) 4.0 mS·cm−1. After 50 days, plants were harvested, processed, and analyzed to determine marketable yield, biomass, plant height, stem diameter, phenolics, and elemental nutrient concentrations. An interaction between growing season and lettuce cultivar was the predominant factor influencing yield, biomass, and quality. Nutrient solution EC treatment significantly affected biomass and water content. EC treatments significantly impacted concentrations of 3-O-glucoside and uptake of phosphorous, potassium, iron, boron, zinc, and molybdenum. Effects of growing season and cultivar on leafy lettuce yield and quality were more pronounced than the effect of nutrient solution EC treatment. Thus, greenhouse production of green and red-leaf lettuce cultivars in the south-eastern United States should be conducted in the spring and fall growing seasons with elevated nutrient solution EC of ≈4.0 mS·cm−1 to maximize yield and quality

Effects of Elevated Temperature and Potassium on Biomass and Quality of Dark Red ‘Lollo Rosso’ Lettuce

Lettuce is an economically important crop for small and medium-sized growers. When grown in adverse environmental conditions, lettuce is vulnerable to a deterioration of yield and quality. Research concerning the impact of elevated potassium (K) levels on leafy vegetables, such as lettuce, is lacking. Therefore, seeds of dark-red ‘Lollo’ lettuce were germinated under greenhouse conditions at 25/20 °C (day/night). Plants were transferred into 11-L containers and placed into growth chambers at 25 and 33 °C. Plants were grown with K treatments of 117.3 (control), 234.6 (2×), 469.2 (4×), and 4) 938.4 (8×) mg·L−1. Increasing K treatments resulted in a negative quadratic response on lettuce dry mass and generated 14% more leaf calcium at 234.6 mg·L−1. An increase in temperature from 25 to 33 °C increased leaf dry matter and biomass by 40% and 43%, respectively. Leaf water content increased by 3% as temperature increased. Plants grown at 33 °C had greater quercetin glycosides compared to plants grown at 25 °C. The results from this study suggest that temperature is a stronger regulatory factor than increasing K in the determination of lettuce yield and quality. Increasing K concentration to 234.6 mg·L−1 results in greater concentrations of leaf minerals without compromising plant yield

Nitrogen Fertigation Rate and Foliar Urea Spray Affect Plant Growth, Nitrogen, and Carbohydrate Compositions of Encore Azalea ‘Chiffon’ Grown in Alternative Containers

The objective of this study was to investigate the plant vegetative growth, flower production, nitrogen (N) concentration, and carbohydrate compositions of Encore® azalea ‘Chiffon’ when fertigated with five N rates—0, 5, 10, 15, and 20 mM N—and grown in two types of containers, a black plastic and a biodegradable container, during one growing season. Foliar urea of 3% was applied to half of the plants in late fall to investigate its effect on plant N and carbohydrate concentrations. The paper biocontainers resulted in superior plant growth, increased plant size, dry weights, root length and surface area compared with the plastic containers with N rates of 10, 15, and 20 mM. The paper biocontainers also increased N uptake and carbohydrate concentrations mainly by increasing plant biomass. High N rates of 10 to 20 mM combined with urea spray and biocontainers generally resulted in the highest plant N concentrations. Foliar urea application in late fall tended to increase plant N concentration but decreased carbohydrates, including starch, glucose, fructose, and sucrose, to varying degrees, likely due to increased N assimilation. Fall foliar urea spray can be effective in improving the N status of azalea plants without affecting plant biomass

Lettuce Biomass Accumulation and Phytonutrient Concentrations Are Influenced by Genotype, N Application Rate and Location

The purpose of this research is to determine how increasing levels of nitrogen (N) fertilizers, locations, and cultivars affected yields, biomass accumulation, and polyphenol concentrations in lettuce. This study is carried out at the North Mississippi Research and Extension Center (NMREC) and Northwest Washington Research and Extension Center (NWREC). The experiment is a randomized complete block design arranged in a 2 × 2 × 4 factorial with 4 replications. Treatments include two cos (romaine) lettuce cultivars, ‘Salvius’ and ‘Thurinus’. N treatments include 42, 63, 105 and 189 kg·ha−1. ‘Salvius’ has greater fresh mass (FM) and dry mass (DM), and a smaller DM:FM ratio when compared to ‘Thurinus’. The NWREC location has higher lettuce FM and DM. Quercetin-3-glucoside (Q-3-G) increases with increasing N concentrations. There are interactions between locations and lettuce cultivars for chlorogenic acid, Q-3-G, and quercetin/luteolin glucuronide (QL-G). There is increased chlorogenic acid content in ‘Salvius’ at the NMREC and increased concentrations of Q-3-G and QL-G in ‘Thurinus’ compared to the NWREC location. ‘Thurinus’ has significantly more chicoric acid and quercetin-malonyl-glucoside (QM-G) than ‘Salvius’. Lettuce at the NWREC has significantly more chicoric acid and cyanidin-3-glucoside (C-3-G). Lettuce at the NWREC has greater yields and biomass accumulation. Lettuce at the NWREC also has greater amounts of flavonoids and anthocyanins. ‘Salvius’ has greater amounts of phenolic acids and ‘Thurinus’ has greater amounts of flavonoids and anthocyanins

Feasibility of developing a portable driver performance data acquisition system for human factors research: Technical tasks. Volume 1

A two-phase, multi-year research program entitled ``development of a portable driver performance data acquisition system for human factors research`` was recently completed. The primary objective of the project was to develop a portable data acquisition system for crash avoidance research (DASCAR) that will allow drive performance data to be collected using a large variety of vehicle types and that would be capable of being installed on a given vehicle type within a relatively short-time frame. During phase 1 a feasibility study for designing and fabricating DASCAR was conducted. In phase 2 of the research DASCAR was actually developed and validated. This technical memorandum documents the results from the feasibility study. It is subdivided into three volumes. Volume one (this report) addresses the last five items in the phase 1 research and the first issue in the second phase of the project. Volumes two and three present the related appendices, and the design specifications developed for DASCAR respectively. The six tasks were oriented toward: identifying parameters and measures; identifying analysis tools and methods; identifying measurement techniques and state-of-the-art hardware and software; developing design requirements and specifications; determining the cost of one or more copies of the proposed data acquisition system; and designing a development plan and constructing DASCAR. This report also covers: the background to the program; the requirements for the project; micro camera testing; heat load calculations for the DASCAR instrumentation package in automobile trunks; phase 2 of the research; the DASCAR hardware and software delivered to the National Highway Traffic Safety Administration; and crash avoidance problems that can be addressed by DASCAR