South Africa is currently the largest producer and exporter of macadamia nuts in the world and the Limpopo Province is the third largest producer amongst the country’s nine Provinces. This explains the overall higher agricultural annual income amongst both small-scale and large-scale macadamia nut farmers recorded in the study. Results from the study reveal that income from HVCs facilitates the purchase of staple food products and provide a mechanism for meeting long term food security goals at both household and national levels. The study focuses on land out of the four drivers of production i.e. land, labour, capital and enterprise, and highlights how aspects of the land resource drive the two farming systems in South Africa and the pathway of agricultural enterprise. Results have emphasized the importance of land as a driver of production for sustainable agriculture. There is great potential for ensuring a positive future for South African farming systems and consequently food security in the sustainable production of HVCs. According to Ba in order for African countries to commercialise their agricultural sectors sustainably there is need for farmers to adopt a stable, productive agricultural resource base. This requires a targeted investments in such as into the cultivation of HVCs amongst small-scale farmers which will prove highly beneficial.Conventional soil-based agriculture has been resource-intensive. According to the United Nations, 70% of global water use is consumed by agriculture. Moreover, the global population is predicted to increase to a projected 11.2 billion nearing 2100. The increasing population represents a requirement for an increase in food production capacity in the face of declining arable land per capita. However, the increasing trends of world populations trends are not evenly spread and tend to be concentrated in urban areas. According to the United Nations, more than half the world’s citizens live in urban areas, which is projected to be more than 60% by 2030. Therefore, relying solely on conventional soil-based agriculture poses stresses to food security. There are many critical issues related to conventional agriculture: water, air, and soil pollution, soil salinization, desertification, climate change-induced droughts, extreme variation in temperatures, extreme variation in solar radiation, and pests.
With more frequent and extreme weather patterns, climate change will continue to increase pressures on world agricultural productivity. By FAO estimates, around 33% of global farmland is degraded to some extent, if not higher. The decrease in productivity of arable land in the face of increasing demand for food is another challenge confronting food production. Another concurrent problem in industrialized countries is the common phenomenon of food retailers underserving socioeconomically disadvantaged areas. These areas are identified as food deserts, vertical farming racks defined as urban areas with lower accessibility to fresh foods. Lower income, lower education, and lower health levels are the commonly occurring characteristics of food deserts. Neighborhoods in the vicinity of food deserts tend to have higher adverse health outcomes, mortality, and morbidity. Socioeconomically disadvantaged families tend to have children that are more than likely to develop obesity and diabetes, which together account for $395 billion in medical costs and lost productivity annually. As of 2018, 11% of the population in the US faced food insecurity. There is a need to make nutritious food sources readily available to residents of such areas. Agricultural growth in controlled environments is increasingly used to increase crop productivity and make produce accessible without traveling long food miles. These setups can be referred to as a controlled environment with artificial lighting or plant factories with artificial lighting, among many others. Controlled Environment Agriculture can refer to urban farms that use soilless systems such as hydroponics, aeroponics, or aquaponics. CEAL/PFAL setups can serve as an excellent solution for feeding future cities. Plant factories serve as closed plant production systems with lower interaction with the outside environment. Agriculture needs to focus on reducing natural resource losses, decreasing environmental pollution, and increasing crop returns using innovative technologies. In addition, the agricultural industry needs to increase its productivity to meet market commitments of high-quality produce. The Yang laboratory at the University of Connecticut first introduced the concept of GREENBOX farming as a new system for urban agriculture. The concept presented an overall idea of growing food crops in standard grow boxes in urban structures, with optimal environmental controls that have been greatly improved with the advancement in LED lighting, environmental sensors, and information technology. The GREENBOX technology was specifically designed to be used in urban warehouse conditions , generally defined with a lower degree of environmental controls, high ceilings, and minimal lighting conditions. Urban warehouse spaces have the distinct advantage of minimal requirements of retrofitting or modification to be ready for GREENBOX crop production. Growing food crops in such settings can effectively use urban spaces, produce different species to be harvested at different times, reduce food transport distances, harvest produce just before they are purchased/consumed, and quickly adopt the new industrial technologies to reduce operational costs.
Research has been conducted to analyze the energy and water use of the GREENBOX system using dynamic simulation models for lettuce crop production, in comparison with conventional greenhouses. The simulation study indicated that the GREENBOX used less water than greenhouses over both summer and winter seasons, and the energy use efficiency of the GREENBOX was lower in the summer and higher in the winter compared to a greenhouse. Since 2019, The Yang Laboratory has initiated a systematic experimental study on the technical and financial feasibilities of the GREENBOX technology. The overall objective of this paper was to demonstrate the GREENBOX as a sustainable and alternative avenue for vegetable crop production in urban settings. We studied the growing environments and productivity of lettuce growth in two protocol GREENBOX units and carried out a parallel growth cycle in an experimental greenhouse for reference and comparison. Using descriptive statistics, we aimed to present the observations on the environmental and biomass patterns in lettuce crop output. We also intend to discuss the overall implications of GREENBOX technology in urban horticulture.We carried out the experiments in the headspace of the greenhouse and greenhouse bays in the Agricultural Biotechnology Lab at the University of Connecticut at Storrs, Connecticut, United States of America. Connecticut’s climate is temperate, characterized by cold, snowy winters and warm, humid summers. The defining characteristics of Connecticut weather are large temperature ranges , precipitation equally distributed amongst seasons, and considerable variation in weather over a short time. The headspace is a semicircular section building with 40 m diameter and approximately 400 m2 . The Greenhouse Bay 8 dimensions are 7.62 × 9.14 m, and Bay 6 dimensions are 3.96 × 7.62 m.Thus, the headspace’s ambient conditions are similar to a warehouse environment. The similarities lie in that they are large volume spaces with high ceilings and have sparse windows and lighting. Greenhouse Bays 8 and 6 are connected to water and power, and have shade curtains and supplemental lighting to modulate controlled environments that sustain crop growth along with ventilation through fans and vents.The grow tents with dimensions of 1.5 × 1.5 × 2.1 m consisted of an exterior canvas covering were meant to serve as the exterior of the prototype GREENBOX. The interior of these grow tents is comprised of diamond reflective walls to serve as insulation. An LED light source was installed in each GREENBOX to facilitate photosynthesis. The lighting elements were four feet long, provided white light of 40,000 K color temperature, vertical rack system and had a rated diode life of 50,000 hours. The lighting element was positioned one meter above the plant canopy. Modulating the use of fans and vents maintained the ambient growing conditions inside the GREENBOX by a forced ventilation system.
Greenhouse Bay 8 is equipped with 1000-watt metal halide HID bulbs, and Bay 6 is equipped with Infinity LED Linear Fixtures in the form of overhead lighting for light control placed one meter above the crop canopy. Greenhouse Bays 8 and 6 are heated by hot water in fin tubes . Passive ridge vents or three exhaust fans are used for cooling. Both bays are controlled by the Argus Titan greenhouse control system . The controlled environmental parameters included light intensity, light duration, air temperature, and air moisture content. We used environmental controllers to monitor the environment outside the GREENBOX units and inside the greenhouse. The other environmental controller was used to monitor and regulate the inside environment conditions in the GREENBOX. The sensors were positioned 0.15 m above the plant canopy in the GREENBOX and greenhouse. For growing crops in the GREENBOX and greenhouse, we use hydroponics as means of soilless cultivation. Compared to conventional soil-based growth, hydroponic growth isolates the plant from the soil, thereby preventing exposure to disease, salinity, and drainage issues, along with a rapid turnaround time on crops. The hydroponic nutrient film technique channels were placed on a 0.91 × 0.91 m tray stand . The NFT channels were 0.10 × 0.05 × 1.2 m with holes for plants, spaced for inserting transplants 15.24 cm apart. We placed the NFT channels 7.62 cm apart to keep a distance of 15.24 cm between plants, forming a 4 × 6 matrix in each GREENBOX and two panels of 4 × 6 in the greenhouse bays. We monitored the pH and the electrical conductivity of the nutrient solution using a portable pH/EC meter . The piped nutrient delivery system consisted of a reservoir with submersible pumps to facilitate nutrient delivery. Reviewed reports have indicated that when grown in a soilless system, lettuce has a high yield and quality. Pelleted Rex lettuce seeds were chosen for the crop for offered advantages such as lettuce include having a maximum height of thirty centimeters and having a growth cycle between ten to thirty days. As a preventative measure, we used bio-controls on our crops during the growth cycles in both growing locations. Environmental variables including light intensity , temperature , and relative humidity were collected using iPonic controllers that log data instantaneously every minute and are accessible via the cloud. The environmentaldata collected by the iPonic sensors had a precision of 0.1 W/m2 for light, 0.1˚C for temperature, and 1% for relative humidity. We harvested lettuce on the thirtieth day from the day of the transplant from the GREENBOX and greenhouse. We randomly selected two lettuce plants from both growing locations every three days for destructive sampling to obtain the wet and dry weights . To obtain the wet weight, we pulled apart the roots and any growing medium attached to the plant before weighing the lettuce immediately after harvest.
The wet weight indicates the amount of biomass accumulated in the crop resulting from evapotranspiration. We blotted the plant gently with a soft paper towel to remove any free surface moisture and weighed the plants immediately after harvest. Finally, we obtained the lettuce’s dry weight by drying the leaves in a forced air convection oven . We derived the productivity of both growing locations using the wet weight values at harvest to determine the total biomass output in kilograms per square meter of growing area. Lighting was represented by DLI by using instantaneously measured light data and converted to cumulative light accumulated per day. Temperature and humidity were processed to 15-minute averages using data from the iPonic environmental controllers. We used descriptive statistics to characterize the environmental data of DLI, temperature, and relative humidity, which were plotted to 15-minute averages over a thirty-day growing period for the summer and winter. We detailed their average values, along with their standard deviations except for light . We report dry weight, wet weight, and productivity of lettuce crops in GREENBOX and greenhouse over summer and winter at harvest .The descriptive statistics of the environmental variables are summarized in Table 1, and the dynamic variations of these variables are shown in Figure 2 for both growing locations. The mean DLI in GREENBOX ranged between 32.48 – 36.70 mol/m2·d over the two growing cycles . It was purposely set higher than the recommended minimum DLI of 6.5 – 9.7 mol/m2·d.