Urban expansion is a threat to agricultural land. As cities increase in size and residential areas are being built on arable land, a new solution to growing food in urban area needs to be considered. Shipping container farms are designed to grow a high number of plants in a small area. These farms are programmable to fit the environmental parameters that are optimal for each type of crop. In this experiment, ‘Toscano’ kale was grown inside the farm and harvested weekly for one year to simulate farm production. The average day/night temperature in the farm was 22.8C and 15.6C with a photoperiod of 20 hours. Sole sourced lighting was supplied by light emitting diodes with an 80:20 red:blue ratio and an intensity of 100 mol . m -2. s -1 for a daily light integral of 7.2 mol . d -1 . Electrical energy use of the farm was collected on three categories of energy usage: Lighting, HVAC, and all Other Energy usage. Seeds were sown four weeks prior to transplant. Plants were transplanted weekly into vertical channels and harvested 12 weeks after sowing. This experiment was a complete block design with block nested in time. Yield data was collected at time of harvest, including plant number, fresh mass, dry mass, plant height, canopy area, and leaf number. The mean number of plants per replication was 320. The mean fresh mass per plant by block was 43.34g, 48.84g, 53.17g, 59.15g, 57.88g, and 53.29g, respectively, while mean dry mass was 3.31g, 3.66g, 3.94g, 4.42g, 4.3g, and 4.08g, respectively. Daily mean lighting and other energy consumption exhibited no variation across all 48 harvests. Daily mean HVAC energy consumption varied based on outdoor environmental conditions, with increased usage during summer months and a maximum of 33.53 kWh/day. Overall, fluctuations across mean fresh mass needs to be investigated further as the optimal harvest date for this farm may occur prior to 12 weeks, for both plant yield and energy consumption levels.
At the last ASHS annual conference, I, Satitmunnaithum et al., (2023), presented our study on the effect of blue and white LED light ratio on red leaf lettuce, however, the effect of blue LED on red coloration during its growth is still unclear. Thus, at this year’s conference, we aim to clarify the mechanisms of red coloration under blue LED based on anthocyanin biosynthesis gene analysis and its content in vertical farming condition to stabilize its production for high market demand. To elucidate the effect of blue LED light on the red coloration of red leaf lettuce, green and red leaf lettuce (Lactuca sativa L.) were selected for this study. Both were hydroponically cultivated at the Advanced Plant Factory Research Center at Meiji University, Japan. The cultivation temperature was set at 22 ℃ with a humidity of 60%. Seeds were sown under white LED for 24 hours. Ten-day-old seedlings were transplanted to different light conditions: white LED and blue LED. The photoperiod was set for 16 hours. The nutrient solution was supplied at an EC of 1.6 mS/m^2 with a pH of 6.0 ± 0.5. Both light treatments had a PPFD of 100-120 µmol/m^2/s. After 20, 25, and 30 days of transplantation, lettuces were harvested. The red area on leaf lettuce, along with the total anthocyanin content and its precursors, as well as the expressions of anthocyanin biosynthesis-related genes such as ANS, CHS, bHLH, DFR, and HY5, were evaluated. Blue light shows a large red area on red leaf lettuce at most of the development stages resulting in a high red area percentage, while green leaf lettuce remained completely green in both light conditions. The interested genes were upregulated mostly in blue light irradiated red leaf lettuce which led to high total anthocyanin content. This can be assumed that blue LED light enhances anthocyanin synthesis in red leaf lettuce which can contribute to the stable production of red leaf lettuce in vertical farms.
Low natural light and high heating costs limit northern winter greenhouse production. Technology advancements now offer opportunities to improve delivery of light to and within crop canopies. The greenhouse tomato cultivars Bigdena and Beorange were chosen to evaluate high pressure sodium irradiance with LED interlighting. Plants were grown in a high-wire drip irrigation system using dutch (bato) buckets (17.7 L volume) filled with a 50/50 mixture of perlite and a peatlite medium (Pro-Mix BX). The containers were placed in alternating rows across a drainpipe. Seeds were sown on 8 Sep and two seedlings were transplanted into each container 38 d later (17 Oct). Day temperature was 22 ± 2°C and reduced to 18 ± 2°C during the night. Lower leaves were removed as fruit ripened and the study was terminated at a plant height of ~250 cm (128 d from transplanting). The photoperiod was 18-h. In addition to overhead 400-W HPS lighting, LED fixtures designed for placement within the canopy were evaluated (GE current Arize® Integral). Two horizontal LED bars were positioned 30 cm (12 inches) apart with the upper bar adjusted within 30 cm of the top of the plants throughout the study. The integral lighting provided a spectrum with blue (peak 450 nm) and red (peak 660 nm) wavelengths in a 12:88 ratio. The perpendicular horizontal distance from the LED bars to the plant stems was 30 to 35 cm. The intensity (400-700 nm) measured at the plant stems horizontally from the LEDs averaged 195 ± 30 µmol m-2s-1. Overhead HPS provided ~130 ± 20 µmol m-2s-1, 100 cm below the fixtures. Seasonally short days and low sun angles limited natural light during the study. The first ripe tomatoes were harvested 62 d from transplanting (18 Dec). Interlighting resulted in higher plant yields with 6.3 ± 0.82 kg for Bigdena and 4.9 ± 0.67 kg for Beorange. In comparison, 4.1 ± 0.37 kg (Bigdena) or 3.4 ± 0.80 kg (Beorange) was recorded for plants receiving only HPS lighting. Five or six additional tomatoes were harvested with interlighting for Bigdena (25 ± 2.0 versus 19 ± 1.8) and Beorange (22 ± 2.5 versus 17 ± 1.9). Average tomato size increased from 217 ± 11.9 g to 250 ± 19.3 g (Bigdena) or from 199 ± 36.1 g to 227 ± 20.2 g (Beorange) with interlighting.
Introduction: Preliminary studies have shown that ultraviolet treatment is able to reduce microbial contamination in the nutrient water of hydroponic systems. However, it is not known how these ultraviolet treatments may impact nutrient water chemistry or crop growth and yield. Purpose: The objective of this study is to examine the impact of an ultraviolet light treatment on romaine lettuce growth parameters and nutrient levels in the treated hydroponic water. Methods: Commercially-available DWC (Deep Water Culture) hydroponic systems were used to grow romaine lettuce (Latticua lettuceia var. Sparx) in a two-part nutrient solution (Hydro-Gro Leafy and calcium nitrate). The electrical conductivity (EC) was maintained between 1.6 and 1.8 mS/cm during the study. The nutrient solution was treated with a UV-C device (MiniPure MIN-1; 500ml capacity) emitting peak irradiance at 254nm at flow rates of 0, 3 and 6 L/min. Water samples were collected before and after each treatment and the experiment will be repeated twice for a total of three times. Twice weekly during the six-week growth period, parameters including plant height, SPAD value, and chlorophyll fluorescence were measured. At the end of the production, fresh weight and dry weight of each plant sample were measured. Results: Low and high UV doses resulted in 1.17 and 1.36 log reductions of Escherichia coli in hydroponic nutrient water. Preliminary findings for the effect of UV light on the concentration of nutrients (NPK) yielded no significant difference in the nutrient level. The study is underway for assessing the effect on the lettuce growth parameters and therefore we are not reporting any results on the crop growth parameters. Significance: UV light technology at optimized dosage levels has the potential to improve the safety of hydroponic systems with minimal effect on the plant growth and nutrient water.
This study explored the effects of low root-zone temperature (LT) and UV radiation (UV) alone and combined on changes in growth, transcription, and gene expression related to secondary metabolite in Nicotidana benthamiana. The plants were grown in a controlled environment (25/20°C, 16/8 h [light/dark], 70% relative humidity, 1,000 µmol·mol−1 CO2 with photosynthetic photon flux densities of 100 and 200 µmol·m−2·s−1 for 10 and 18 d, respectively). Twenty-eight days after sowing, the seedlings were treated with LT (15°C), 0.3 W·m−2 of UV radiation, and a combined treatment with LT and UV (LT*UV) for 3 d. Results found that the treatment with UV alone decreased the quantum efficiency of photosystem II by approximately 1.5 times, and most growth characteristics decreased under the UV (approximately 1.5 times) and LT*UV treatments. Combined treatment with LT*UV significantly inhibited the growth characteristics and photosynthetic rates compared to those under the single LT and UV treatments. In particular, the transcriptome levels of phenylpropanoid and flavonoid biosynthesis were the most significantly affected by LT*UV. This suggests the potential of using LT treatment in hydroponic systems and UV radiation to control the synthesis of health-promoting compounds of secondary metabolites in greenhouses and controlled-environment agricultural facilities.
Light quality plays a crucial role in the growth and development of plants. In this study, we aimed to assess the effects of short-wavelength light on rose genotype '16401-N055’, which exhibits the flower color transitioning trait: the flowers change colors from yellow to pink in sunlight. Roses that exhibit this flower phenotype are termed transitioning-type roses. Specifically, we analyzed and compared the impact of six different light treatments [a sunlight control in open field and five spectral treatments created using light-emitting diodes (LEDs)] on various physiological and morphological characteristics. The five LED treatments included white light, blue light, UV-A white light, UV-B white light, and 80% blue 20% white light. Each treatment had two replications where one-year-old rose plants were the experimental unit. The total light intensity was maintained at 300-350 micromol m-2 s-1 for a photoperiod of 16 h light and 8 h darkness. The morphological traits measured included height, width, number of buds, number of flowers, and node density. The color scale parameters L* [luminance of the color ranging from 0 (black) to 100 (white)], a* [red (positive values) and green (negative values) color levels], and b* [yellow (positive values) and blue (negative values) color levels] were measured using a colorimeter. Additionally, the chlorophyll concentration index (CCI) was measured using a chlorophyll meter. Fully pigmented pink flowers were only observed in the UV-B white light treatment with an average L* value of 44.1 and a* value of 50.6. A slight pink hue was observed on the outer sections of petals in blue and blue white light treatments. The average L* and a* values of flowers in the blue treatment were 87.21 and 6.24, and in blue white treatment were 90.9 and 1.86, respectively. The flowers in the white UV-A treatment remained white with the highest average L* value of 92.4 and the lowest average a* value of -1.86. The CCI of plants under sunlight (23.5) was significantly lower than the plants treated with blue (34.4), and blue white (33.7) light. No significant differences in morphological traits were detected after two weeks. The plants will be monitored for longer periods and more data will be collected every two weeks for one month to document additional changes. The results obtained will provide additional information on morphological and floral changes in this genotype under different light treatments.
Inexpensive Arduino microcontrollers can be programmed to operate and log data from environmental sensors and operate other accessories such as irrigation solenoids. We describe our efforts to build a modified version of Arduino Uno systems previously developed at the University of Georgia, which operated analog moisture sensors and opened solenoid valves to drip emitters when moisture fell below user-defined thresholds. We attempted to 1) replace analog sensors with a bus of digital sensors that use the SDI-12 communication protocol, 2) include programming to parse digital output from two popular SDI-12 sensors (Decagon GS3 and Campbell Scientific 5TM), 3) use 12VDC solenoid valves that were less expensive and smaller (1/2”) than alternatives, and 4) overcome several challenges encountered in the construction and programming of the Arduino-based system. These included an approach to more easily manage the connection of numerous wires, the inclusion of a reversed diode at the solenoid terminals to prevent electrical interference from intermittently resetting the Arduino program, and the adoption of programming strategies to work around memory limitations that initially rendered our Arduino systems with digital sensors unreliable. We overcame these challenges to develop a robust, reliable, and easy-to-deploy Arduino-based environmental logger and automated drip-irrigation system that can operate numerous digital sensors. Sensor type and thresholds for volumetric water content are defined in a single location within the program, enabling the user to easily make minor adjustments to the system. We also included extensive line-by-line documentation of the source code. A list of the hardware used in this system is available. In 2023, eight of these systems operating 64 total sensors proved their reliability over a two-month experiment on the drought stress physiology of wetland shrubs. We conclude that this system is an effective solution for in-house sensor-automated irrigation with high customizability for end users.
Spinach (Spinacia oleracea) is a nutritionally and commercially significant crop grown in controlled environments; however, its seeds are difficult to germinate in soilless culture. Excess moisture in the root zone can inhibit germination and impede seedling establishment. To address this, we conducted an experiment with a randomized complete block design (three replications) to identify the optimal moisture content for spinach ‘Space’ germination. In each of 63 sealed containers, we placed 20 seeds on a double-layered paper towel pre-moistened with varying amounts of reverse-osmosis water. We quantified visible germination percentages daily in response to seven moisture indices [moisture mass ÷ (paper mass moisture mass)] ranging from 50% to 94% over an 11-day period. Air temperature and relative humidity were 22.12 ± 0.02 °C and 34.35% ± 8.80%, respectively. The optimal moisture index was 80%, which resulted in the highest cumulative visible germination percentage (92%, which is close to the labelled 93% on the seed package). Deviating from the optimal moisture index in either direction decreased the germination percentage to 0%–22% and delayed germination by up to 5 days. The response of the cumulative visible seed germination percentage to the moisture index followed a normal distribution. The daily new visible germination percentage peaked on day 3 under most moisture indices; it was 55% under the optimal moisture index and < 24% under the other moisture indices. In conclusion, a moisture index of 80% resulted in the highest germination percentage (92%) and the fastest germination time (2–5 days) in spinach ‘Space’, whereas lower or higher moisture indices caused poorer (0%–67%), delayed, and less uniform germination. Once transplanted, the spinach seeds germinated with this moistened-paper method under the optimal moisture index adapt and perform well in soilless substrates, including rockwool, which is notoriously difficult to germinate spinach seeds in.
