Among air pollutants, particulate matter (PM) has been identified as a major cause of environmental pollutants due to the advancement of industrial development and the generation of smaller particles. Particulate matter, in particular, is defined only by the size of particles and thus is not enough to study its composition yet. However, edible crops grown in contaminated atmospheres can be contaminated with heavy metals contained in particulate matter in the atmosphere, which can seriously damage food safety. In this study, we investigated the influence of the accumulation of particulate matter on leafy vegetables cultivated at areas with different levels of PM in atmosphere. Four districts of Gyeongsangnam-do were chosen to conduct this experiment: outdoor spaces of three respectively located in industrial, near-highway, and rural areas were considered, and research plant growth chambers at Gyeongsang National University were used as the control. After 3 weeks of cultivation in those conditions, the results showed that Pb in milligrams per kilogram of fresh weight (FW) was 0.383 in Chrysanthemum coronarium and 0.427 in Spinacia oleracea that were grown near the highway, which exceeded the 0.3 mg kg −1 FW standard set by the Republic of Korea, EU, and CODEX. However, when those vegetables were sufficiently washed with tap water, it was confirmed that the heavy metal content fell into the safety standard range.
As the risk of open-field cultivation increases with climate change, some analysts say that the day when ordinary vegetables will be produced at home is not far away. Moreover, due to the recent coronavirus outbreak, outdoor activities are becoming difficult, leisure activities that can be done at home have become more necessary, and the demand for home gardening has increased. This study was conducted to improve the technology for hydroponics at home. We experimented with whether the harvest time can be hastened or delayed by environmentally controlling the growing season, and what conditions are appropriate. Experiments were conducted with leafy vegetables (Lactuca sativa L. ‘Oak-leaf’ and Lactuca sativa L. var. longifolia, or romaine) that can easily be grown in a closed plant cultivator in which the external air can circulate, and the temperature/photoperiod can be controlled. Two settings for the temperature (25/18 °C and 20/15 °C; day/night) and three settings for the photoperiod (10, 14, and 18 hours; day/night) were employed. It took a total of four weeks from sowing to harvest, and the appropriate harvest time was predicted from the yield. As a result, although there was a difference depending on the vegetable variety, a temperature setting of 25/18 °C and a photoperiod of 14 hours were the most suitable for hastened growth, and a 20/15 °C temperature and 18 hours of photoperiod were suitable for the delayed growth.
Ssamchoo is recently attracting attention as a household hydroponic vegetable in Korea. It has a refreshing texture and a rich content of vitamins and fiber. Ssamchoo with a wide leaf area is suitable for traditional ssam or vegetable wraps, as well as a vegetable for salads; thus, it can be used in a variety of dishes. However, Ssamchoo plants responds sensitively to the nutrient solution, and it is often difficult to secure sufficient leaf area and robust growth using a commercial nutrient solution for leafy vegetables. This study consisted of three experiments conducted to develop the nutrient solution for Ssamchoo grown in a newly developed home hydroponic cultivation system using light-emitting diodes as the sole source of light. In the first experiment, growth and development of Ssamchoo in a representative commercial nutrient solution, Peters Professional (20-20-20, The Scotts Co., Marysville, OH, USA), was compared with laboratory-prepared nutrient solutions, GNU1 and GNU2. As a result, the Ssamchoo grown in Peters Professional had a high NH4+ content in the tissue, leaf yellowing, darkened root color, and suppressed root hair development. In addition, adverse effects of ammonium such as low fresh weight and shorter shoot length were observed. In the second experiment, Peters Professional was excluded, and the ratio of NO3− to NH4+ in the GNU1 and GNU2 nutrient solutions was set to four levels each (100:0, 83.3:16.7, 66.7:33.3, and 50:50). As a result, the fresh weights of 83.3:16.7 and 66.7:33.3 were the greatest, and the leaf color was a healthy green. However, at 100:0 and 50:50 NO3−/NH4+ ratios, the fresh weight was low, and leaf yellowing, tip burn, and leaf burn appeared. The nutrient solution with a 83.3:16.7 NO3−- to-NH4+ ratio, which gave the greatest fresh weight in the second experiment, was chosen as the control, while the solution with a 50:50 NO3−/NH4+ ratio with a lower nitrate content among the two unfavorable treatments was selected as a treatment group for the next experiment. In the third experiment, NH4+ was partially replaced with urea to make four different ratios of NO3− to NH4+ to urea (83:17:0, 50:50:0, 50:25:25, and 50:0:50) in combination with two levels of Si (0 and 10.7 mmol·L−1 Si). The greatest fresh weight was obtained in the treatment in which the NO3−/NH4+/urea ratio was 50:25:25. In particular, when Si was added to the solution, there was no decrease in the number of leaves, and plants with the greatest fresh weight, chlorophyll content, and leaf area were obtained. The number of leaves and leaf area are important indicators of high productivity since the Ssamchoo is used in ssam dishes. It can be concluded that a solution with a NO3−/NH4+/urea ratio of 50:25:25 and supplemented with 10.7 mmol·L−1 Si is the most suitable nutrient solution for growing Ssamchoo in the home hydroponic system developed.
The development of various types of plant factories is central to improving agriculture. In one form, it is expanding from the existing commercial plant factories to home cultivation systems or cultivators. The plant cultivation system grafted into the living space for people produces differences in the growth of the plant depending on the lifestyle (cooling and heating, residence time, number of residents, etc.) of the resident. In this study, identical home cultivation systems that automatically adjust environmental conditions (temperature, photoperiod, light, and nutrient solution supply) other than the carbon dioxide level were set in an office and warehouse. The study confirmed how plant growth can differ depending on the amount of carbon dioxide generated by humans occupying the space. In addition, it was confirmed whether the growth of plants can be further promoted depending on the external air exchange speed by a ventilation fan even if the indoor carbon dioxide concentration is the same. Due to the nature of the cultivation system that controls the temperature, the type and speed of the fan were set to minimize heat loss in the cultivator. The airspeed from ventilation fans attached to the indoor cultivation systems of an office and warehouse was adjusted to one of three levels (0.7, 1.0, or 1.3 m·s−1). In this study with two species, Ssamchoo and Romaine, it was confirmed that the office space was significantly advantageous for the growth of Ssamchoo, especially in terms of the fresh weight, root activity, and chlorophyll content. Romaine also had a significantly higher fresh weight when grown in the office. Shoot length, leaf length, and leaf width were longer, and there were more leaves. When comparing the relative yield based on an airspeed of 1.0 m·s−1, the yield increased up to 156.9% more in the office than in the warehouse. The fan airspeed had an important influence on Ssamchoo. The higher the fan airspeed, the greater the yield, root activity, and chlorophyll. However, fan airspeed had no consistent effect on the growth tendencies of Romaine. In conclusion, carbon dioxide produced by humans occupying the space is a significant source of carbon dioxide for plants grown in the home cultivation system, although both the speed of the ventilation fan that can promote growth without heat loss and delayed growth caused by the photorespiration in a carbon dioxide-limited situation require additional experiments.
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