Maximization of Water Productivity and Yield of Two Iceberg Lettuce Cultivars in Hydroponic Farming System Using Magnetically Treated Saline Water

Egypt has limited agricultural land, associated with the scarcity of irrigation water and rapid population growth. Hydroponic farming, seawater desalination and magnetic treatment are among the practical solutions for sustaining rapid population growth. In this regard, the main objective of the present research study was to design and construct a hierarchical engineering unit as a hydroponic farming system (soilless) to produce an iceberg lettuce crop using magnetically treated saline water. The treatments included four types of irrigation water: common irrigation water (IW1) with an electrical conductivity (EC) of 0.96 dS/m as a control treatment, magnetically treated common irrigation water (IW2) with an EC of 0.96 dS/m, saline water (IW3) with an EC of 4.56 dS/m and magnetically treated saline water (IW4) with an EC of 4.56 dS/m; three depletion ratios (DR) of field capacity (DR0 = 50%, DR1 = 60% and DR2 = 70%) and three slopes of hydroponic pipes (S1 = 0.0%, S2 = 0.025% and S3 = 0.075%). The results revealed that seawater contributed 7.15% to produce iceberg lettuce in the hydroponic system. The geometric parameter, the slope of the pipes, influenced the obtained luminous intensity by an average increase of 21% and 71% for S2 and S3, respectively, compared with the zero slope (horizontal pipes). Magnetization of irrigation water increased the total soluble solids (TSS) and enhanced the fresh weight and water productivity of both iceberg lettuce varieties used. The maximum percentages of TSS were 5.20% and 5.10% for lemur and iceberg 077, respectively, for the combination IW4DR2S2. The highest values of fresh weight and water productivity of 3.10 kg/m and 39.15 kg/m3 were recorded with the combinations IW3DR2S3 and IW4DR1S3, respectively, for lemur and iceberg lettuce. The percentages of these increases were 109.46% and 97.78%, respectively, when compared with the combination IW1DR0S1. The highest values of iceberg lettuce 077 fresh weight and water productivity were 2.93 kg/m and 36.15 kg/m3, respectively, which were recorded with the combination IW4DR1S3. The percentages of these increases were 112.32% and 120.56%, respectively, when compared with IW1DR0S1 (the control treatment).

Light Intensity Modulates the Accumulation of Carbohydrates, Antioxidant Enzymes and Production of Iceberg Lettuce under Tropical Conditions

High solar radiation in tropical regions can affect the development, physiology, and biochemistry of plants. Our aim with this research was to evaluate the biochemical responses and production of iceberg lettuce cultivars under environments with different shadings. An experiment under field conditions was installed in a 4 × 4 factorial scheme. Four cultivars of iceberg lettuce (Great Lakes, Winslow, Delicia, and Balsamo) and four environments with different shadings (three types of shading screens: red, ChromatiNet®, and black; and treatment under the full sun) were evaluated. Forty-five days after transplanting, the plants were harvested, and the biomass was weighed to obtain the fresh consumable part (FCP) and the biochemical parameters: total soluble sugar (TSS), reducing sugar (RS), and the activity of SOD, CAT, and POD. We found that shading modulates biochemical and productive responses of iceberg lettuce, and the main microclimatic factor related to these responses was solar radiation. We observed a negative correlation between RS and FCP. The solar radiation between 16 and 18 MJ·m−2·day−1, observed in the environments with a black screen and ChromatiNet®, promoted the highest activity of the SOD enzyme and average levels of TSS and RS, providing higher FCP of the cultivars Delícia and Balsamo in high temperatures period.

Development and production of iceberg lettuce irrigated with magnetically treated water

Irrigated agriculture has become a concern, given the scarcity of freshwater. To reduce its water consumption, new techniques and technologies have been proposed. Based on this, the objective of this work was to evaluate the influence of different soil water tensions at initiation of irrigation with magnetically treated water, on ‘iceberg’ lettuce Lucy Brown (Lactuca Sativa L.) development and production. The experiment was conducted in a greenhouse, using a completely randomized factorial design, to evaluate two water types (magnetically treated water – MW and ordinary water – OW) and four soil water tensions at initiation of irrigation (T1 – 15 kPa, T2 – 25 kPa, T3 – 40 kPa and T4 – 70 kPa), with three replicates. Tensiometers were used to estimate soil water tension. The evaluated parameters were: aerial part fresh and dry total mass; commercial head fresh and dry mass, root fresh and dry mass; stem fresh and dry mass; stem length and diameter; percentage of leaves with tip burn, total and commercial yield; water use efficiency related to total and commercial yield; plant exposed area; and dry matter content. Despite achieving greater water use efficiency, the magnetic treatment may have hindered the removal of water from the soil by the crop, especially at increased soil water tension at initiation of irrigation.

Nanoemulsified carvacrol as a novel washing treatment reduces Escherichia coli O157:H7 on spinach and lettuce

Fresh produce continues to be the main source of foodborne illness outbreaks in the United States implicating bacterial pathogens such as Escherichia coli O157:H7 (EHEC). The efficacy of nanoemulsified carvacrol (NCR) as a washing treatment in reducing EHEC on fresh produce was investigated. Fresh baby spinach, Romaine lettuce, and Iceberg lettuce leaves (2.5 cm diameter cores) were spot-inoculated with a five-strain cocktail of nalidixic acid resistant EHEC at ~ 6 log CFU/cm 2 . After air-drying for 1 h, 20 pieces of each inoculated produce leaves were immersed in water-based treatment solutions (200 ml/group), including water alone, 25 or 50 ppm free chlorine, and 0.25% or 0.75% NCR for 2 minutes. Inoculated produce leaves without any treatment served as baseline. Produce leaves were stored at 10°C and surviving EHEC populations were enumerated on days 0, 2, 7 and 14. The viability of EHEC following NCR treatments on the fresh produce was visualized under fluorescence microscope. NCR treatment at 0.75% immediately reduced EHEC populations on Iceberg lettuce by 1.3 log CFU/cm 2 as compared to the produce treated with water alone (P<0.05). Antimicrobial activity of NCR against EHEC was comparable to chlorine treatments on day 0 for all produce (P>0.05). After 14-days of storage at 10°C, populations of EHEC on 0.75% NCR treated Romaine lettuce were reduced by 2.3 log CFU/cm 2 as compared to the recovery from 50 ppm chlorine treated samples (P<0.05). Microscopic images revealed that EHEC cells were observed to be clustered on the baseline samples, indicating the development of cell aggregation, as compared to the scattered cells seen on NCR-treated leaf surfaces. Treatments with NCR did not significantly affect the color on the fresh produce leaves during the 14 days of storage at 10°C. Results of this study support the potential use of NCR as a water soluble natural antimicrobial wash treatment for controlling EHEC on fresh produce.

Rising levels of antioxidative phyllobilins in stored agricultural produce and their impact on consumer acceptance

Consumers often throw away faded greens, because taste and appearance are less appealing compared to fresh ones. We report here a family of antioxidants, the phyllobilins, which increase during storage in iceberg lettuce and cucumber. We show that informing consumers about rising levels of phyllobilins leads to a longer willingness to consume faded lettuce and to an improved health and safety perception.

Effect of Light-Emitting Diodes (LEDs) on Some Physical and Bioactive Compounds of ‘Iceberg’ Lettuce (Lactuca Sativa L.)

The use of light-emitting diodes (LEDs) is a recent concerned application in the indoor crop system of the modern plant production. In our research, we evaluated the influence of four monochromic LED lights including 100% White (W), Yellow (Y), Red (R) and Blue (B) in comparison to solar lightening condition (GR) as a control. In this regard, some morphological characteristics and biochemical content of the common outdoor ‘Iceberg’ lettuce (Lactuca sativa L.) was measured. The results show that leaf length, leaf area and total head weight were significantly greater in the plants grown under B LED, while all the other physical parameters were significantly higher in the plants grown under GR environmental conditions. On the other hand, chlorophyll (Chl), carotenoids (Car), and nitrate content were also influenced by different light treatments. Plants grown under LED light treatment resulted in significantly higher chlorophyll content compared to the control. However, significantly greater carotenoid content was in the plants grown under GR condition. The highest total chlorophyll content was recorded under B and R LED, whereas the lowest was in the GR condition. The lowest nitrate content in the blade and petiole was recorded in the plants grown under Y LED, while the highest nitrate content was recorded in the GR. Based on our result, it is possible to grow and improve some quality parameters of common outdoor ‘iceberg’ lettuce under LED where the solar light is limited or unavailable. Thus, plants performed better under GR light conditions than monochromic LEDs; however, some LED lights could improve some quality parameters and biochemical contents in the ‘iceberg’ lettuce variety.

Nitrate content of spring leafy vegetables from different outlets

The issue of nitrate contamination has become increasingly acute, with the awareness of their toxicity on the human body and the identification of increasing sources of contamination. Human intervention in the natural nitrogen cycle has serious repercussions that are manifested by its accumulation at one or more levels. The use of fertilizers in agriculture is crucial to ensure food security, but their unreasonable use causes accumulations of nitrogen in the form of nitrate ions in plants, and from here they reach human intake, over a certain amount becoming harmful. The aim of this paper is to quantify the amount of nitrates present in certain vegetables intensively consumed during spring, sources of food which if does not conform with the current recommendations of EFSA and EU, can become major factors of risk to public health. The studied material consists of 5 types of vegetables products intensively consumed in spring: lettuce (Lactuca sativa), curly lettuce (or Lollo - Lactuca sativa var Crispa), Iceberg lettuce (Lactuca sativa lime Iceberg), spinach (Spinacia oleracea) and wild garlic (Allium ursinum). The samples were collected from different commercial locations (outlets): hypermarkets (H), open markets (OM), street trade (ST) and house gate trade (HGT). The highest nitrate concentrations were found in lettuce in ST (4306 mg kg-1) and HGT (4175.5 mg kg-1), in Lollo salad in ST (4306.5 mg kg-1) and HGT (4602.75 mg kg-1) and spinach in OM (3469.25 mg kg-1). The study findings suggest that ST and HGT are commercial points that may constitute a danger to public health, the ADI value exceedingly even by 107.21% in the case of Lollo salad purchased from HGT. The issue calls for more drastic controls by the authorities.