The effects of different spectral compositions of light-emitting diode (LED) sources and fertilizer containing biologically active silicon (Si) in the nutrient solution on morphological and physiological plant response were studied. Qualitative indicators and the productivity of plants of a red-leaved and a green-leaved lettuce were estimated. Lettuce was grown applying low-volume hydroponics in closed artificial agroecosystems. The positive effect of Si fertilizer used as a microadditive in the nutrient solution on the freshly harvested biomass was established on the thirtieth day of vegetation under LEDs. Increase in productivity of the red-leaved lettuce for freshly harvested biomass was 26.6%, while for the green-leaved lettuce no loss of dry matter was observed. However, being grown under sodium lamps, a negative impact of Si fertilizer on productivity of both types of plants was observed: the amount of harvested biomass decreased by 22.6% and 30.3% for the green- and red-leaved lettuces, respectively. The effect of using Si fertilizer dramatically changed during the total growing period: up to the fifteenth day of cultivation, a sharp inhibition of the growth of both types of lettuce was observed; then, by the thirtieth day of LED lighting, Si fertilizer showed a stress-protective effect and had a positive influence on the plants. However, by the period of ripening there was no effect of using the fertilizer. Therefore, we can conclude that the use of Si fertilizers is preferable only when LED irradiation is applied throughout the active plant growth period.

City farming is a modern area of agriculture. It is currently becoming more and more promising due to the growing proportion of the population living in large cities. The successful development of city farms largely depends on the improvement of its technical systems and modular devices, in which a microclimate is created that ensures the rapid growth of crops without the use of plant protection chemicals. The modern devices for growing plants in an urban environment are discussed in the papers. The authors consider some factors infl uencing the growth of plants under the conditions of an intensive cultivation system, the main of them including: technological, plant parameters, ambient temperature, air humidity, and lighting. To ensure the necessary microclimate conditions within the agrotechnical requirements for various crops in industrial and personal city farms, modern means and methods of automatic control and management are should be installed. To ensure microclimate conditions within the agrotechnical requirements for each crop, it is necessary to separately develop a cultivation technology in a city farm with the introduction of special implements for cultivation based on design analysis. To ensure the technological improvement of city farming systems, it is necessary to develop and improve systems for automatic irrigation, application of fertilizers and growth regulators, monitoring the functional state of plants online, harvesting and controlling its quality. An important area for the development is the modular designing of such devices, which will signifi cantly reduce the amount of design work and shorten the design time, increase the quality and reliability of equipment due to the preliminary development of unifi ed units and their manufacturing technology. When organizing the serial production of modules, the terms of assembly work, the cost of manufacturing machines and lines will be reduced, which will signifi cantly reduce the cost of equipment. The authors conclude that the formation of modular-designed technical systems, balanced in terms of the component composition and productivity of specifi c elements of technological blocks will ensure the maximum effi ciency of the production of demanded types of plant products in an urban environment.

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