The Comparative Performance of Nutrient-Film Technique and Deep-Water Culture Method of Hydroponics for GREENBOX Technology

With the rising pressures on food security, GREENBOX technology was developed as an avenue for fresh leafy vegetable crop production in urban settings. GREENBOX units were designed to be thermally insulated and climate controlled, with an artificial lighting source that utilized soilless cultivation techniques. Previous studies conducted on GREENBOX technology used the Nutrient Film Technique (NFT);however, various hydroponic methods exist, such as the Deep-Water Culture (DWC) method being the most used. The APS Laboratory for Sustainable Food at Florida Gulf Coast University (FGCU) compared the crop growth performance between DWC and NFT systems using GREENBOX technology. The following study monitored environmental conditions and compared productivity and biomass data of Rex Butterhead Lettuce crops between DWC and NFT systems. We assembled two GREENBOX units using commercially available materials and the standard nutrient solution for fertigation. The crops grown in DWC and NFT were in a 4 × 6 configuration. The DWC and NFT systems were used to grow Lettuce Lactuca sativa “Rex Butterhead” over 30 days to full bloom from prepared plugs grown for 14 days. We collected environmental data including Photosynthetic Photon Flux Density (PPFD, μmol/m2∙s), Daily Light Integral (DLI, mol/ m2∙d), temperature (˚C), relative humidity (%), and Vapor Pressure Deficit (VPD, kPa). We collected lettuce crop growth data, which included wet weight (g), dry weight (g), leaf area (cm2), and chlorophyll concentration (μmol/m2). We derived data, including the Specific Leaf Area (SLA, cm2/g) and biomass productivity (kg/m2), from previously collected data. We used descriptive statistics to present the collected data. A paired t-test was performed to understand the differences in biomass and productivity parameters between the DWC and NFT-grown lettuce crops. Both the DWC and NFT-grown crops could grow lettuce crops to harvest weight at full bloom. Observed data demonstrated that the biomass parameters and productivity did not differ significantly between the two hydroponics techniques. Therefore, we believe both hydroponic methods may be similar in growth performance and may be used in future iterations of GREENBOX design and prove suitable for fresh vegetable crop production in urban settings.

The Assessment of Growth Performance of Brassica rapa var. chinensis ‘Li Ren Choi’, Spinacia oleracea ‘Auroch’, Eruca sativa ‘Astro’, and Brassica rapa var. japonica Using GREENBOX Technology

Obtaining nutritious food is becoming increasingly difficult due to the growing urban population and the degradation of soil, water, and air from mechanized and industrialized agricultural techniques. More than half the global population resides in urban areas, with not enough surrounding agricultural land to meet food requirements. Food traveling long distances, an average of 1020 miles, has resulted in increased food miles for the average food item in the United States of America, representing wasted resources. The novel GREENBOX technology was invented in response to increasing pressures on food security. Previous studies conducted on GREENBOX technology assessed the technical feasibility of utilizing Lettuce Lactuca sativa ‘Rex Butterhead’. We at the APS Laboratory for Sustainable Food at Florida Gulf Coast University assessed the technical feasibility of growing different leafy green vegetable crops. GREENBOX technology consists of thermally insulated climate-controlled enclosures, an artificial lighting source, a soilless cultivation method (hydroponics), and environmental control modules. We assembled two GREENBOX units to assess the environmental conditions and growth performance of Brassica rapa var. chinensis ‘Li Ren Choi’, Spinach Spinacia oleracea ‘Auroch’, Arugula Eruca sativa ‘Astro’, and Mizuna Brassica Brassica rapa var. japonica. Plugs were cultivated and then transplanted in a randomized manner to the nutrient film technique (NFT) channels, subsequently grown for 30 days to full bloom and ready for harvest. Fertigation was carried out using a standard concentration nutrient solution. Crops were arranged in twelve blocks of four species each. We collected environmental data including daily light integral (DLI, mol/m2∙d), temperature (˚C), relative humidity (%), and vapor pressure deficit (VPD, kPa). Collected biomass data included wet weight (g), dry weight (g), leaf area (cm2), and chlorophyll concentration (mg/cm2). We then derived the Specific Leaf Area (SLA, cm2/g). Descriptive statistics were utilized to understand the differences in biomass parameters between the four crops grown. We also compared the performance parameters of our crops with existing peer-reviewed literature and found it superior, if not comparable to commonly found industrial output. We determined that all crops grew to full bloom, demonstrating that GREENBOX technology may be used to grow a variety of different leafy green vegetable crops.

GREENBOX Horticulture, an Alternative Avenue of Urban Food Production

In response to the pressure on food security caused by rising global population and urbanization, the Yang Laboratory at the University of Connecticut has developed the so-called GREENBOX technology that allows crop growth in individual climate-controlled boxes in urban warehouse environments and other enclosed structures. A GREENBOX unit is a thermally insulated modular structure with LED artificial lighting, soilless (hydroponic) cultivation platform, and complete environmental controls. Multiple GREENBOX units can be integrated into a large production system at various scales. This study evaluated the applicability of the GREENBOX technology in the urban warehouse environment by studying the environmental parameters and productivity. We carried greenhouse growth simultaneously for reference. We grew Butterhead Rex lettuce (Lactuca sativa) over 30-day growing cycles in summer (July-August, 2020) and winter (December, 2020-January, 2021) in an experimental greenhouse and two protocol GREENBOX units located in the high ceiling headhouse of the experimental greenhouse at Storrs, Connecticut. We collected environmental data, including light, temperature, and relative humidity and crop growth data, including wet and dry biomass in the two production systems. Descriptive statistics were used to describe the environmental and biomass data. Results indicated that the GREENBOX could provide desired environmental conditions to sustain crop growth over summer and winter. The Daily Light Integral, controllable at the grower’s discretion, in the GREENBOX, ranged between 32.48 - 36.70 mol/m2·d at crop canopy height. The mean daily temperature and relative humidity in the GREENBOX fell within the optimal ranges of 17˚C - 29˚C and 40% - 60%, respectively. Regardless of seasons, lettuce crops were all healthy and grew to full size over the 30-day cycle. Measured productivity followed similar patterns, similar across both growing locations but higher over summer than winter for both systems. Our study indicated that the GREENBOX technology has a high potential in urban horticulture because it does not require arable land like greenhouses and can utilize existing urban structures for sustainable food production.