INFORMATION SUPPORT AUTOMATION IRRIGATION IN THE GREENHOUSE

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INFORMATION SUPPORT AUTOMATION IRRIGATION IN THE GREENHOUSE

Journal Title: Machinery and Energetics - Year 2018, Vol 0, Issue 283

Abstract

Topicality. Plants, both in open and protected soils, use solar radiation, carbon dioxide from the atmosphere, water and nutrients for biomass production, the intensity of which is determined by the intensity of photosynthesis. The need for plants in water, which goes mainly to transpiration, is satisfied with absorption of its roots from the soil. In turn, water evaporation from the soil is also constantly occurring. The total evaporation, thus, determines the amount of water that is restored in the protected soil solely by watering. The cost of water and its preparation for irrigation make a considerable part in the total cost of growing products in greenhouses, but saving water, which does not lead to lower yields, is possible only with the correct definition of water regime of plants, that is, with proper programming watering. Analysis of recent research and publications. Programming the irrigation, thus, is a combination of technical procedures designed to predict and determine the time and duration of irrigation. Modern watering programming methods can be divided into applications for making information decisions in three groups: - based on the measurement of moisture content in the soil; - based on determining the water regime of plants; - based on measuring the parameters of the microclimate. The first group of methods is to maintain soil moisture between its two levels. Tensiometers, water absorbers, dynamic reflectometrers and environment scanning systems are used to measure the current soil moisture values. The first two of the above-mentioned measuring transducers are based on the measurement of the tensile strength of the fluid, i.e., the effort that must be made by the roots of the plants to remove moisture from the soil. These meters are widespread due to the low cost and simplicity of the installation, but the use of the indirect measurement method significantly reduces their accuracy, which also depends significantly on the type and temperature of the soil. Dynamic reflectometers, based on the principle of measuring the time of delay in electromagnetic pulse in the soil, despite their high accuracy, have not yet been widely disseminated outside the boundaries of research centers because of their high cost. Environmental scanning systems are a set of sensors located at different depths and attached to the data logger. However, the introduction of such systems in production is restrained by their high cost. Thus, for further broadening the implementation of irrigation programming methods based on the measurement of soil moisture, further improvement of the measuring transducers is necessary. However, we should not forget that the water regime of plants itself is determined not only by the moisture of the soil. Therefore, recent research is being carried out to develop irrigation programming methods based on the direct measurement of water regime of plants. These methods are based on measuring the diameter of the stem or vegetative organs at night and daytime, with the determination of the difference between these values, which is proportional to the volume of water evaporating by the plant during transpiration. An essential disadvantage of such methods is a noticeable difference in the value of transpiration for different species of plants and its dependence on the stage of development of the plant and its individual organs. Another type of water regime sensors are water flow sensors, allowing real-time measurements. The main disadvantage of such devices is their high cost and the need for a watering decision, taking into account the value of solar radiation and the size of the water vapor pressure deficiency. The general disadvantage of these devices is also the awkwardness of their application in production conditions, the difficulty in choosing representative plants and the number of installed sensors. All these problems significantly restrain the use of such sensors in real production. Such systems can be used mainly for the development or refinement of irrigation schedules in conditions of re-cultivation of one species of plants with the exact maintenance of microclimate parameters in the greenhouse. Purpose. Development of the system of automatic watering of plants, which allows to take into account the needs of plants in humidity and is suitable for use in production conditions. Methods. For the reasons outlined above, the most simple and available for use in the production environment is the programming of irrigation based on the parameters of the climate. These methods are based on the estimation of the parameters of the microclimate and the stage of development of plants (first of all, the value of leaf area and leaf index), which determine the need for water. To determine the need for water for greenhouses without soil, models of transpiration estimation for different types of plants have been developed. When cultivating plants in the soil on the recommendation of FAO with a sufficient degree of accuracy it is possible to determine the need for water (ie, total evaporation) to take the proportional amount of transpiration Ttr with the correction factor K defined for a particular structure with the possibility of clarifying the correction for the type of plants and stage development. Since in the buildings of protected soil the temperature is maintained with sufficiently high accuracy, the main disturbing factor, which mainly determines the amount of transpiration, is the magnitude of the flux of solar radiation. Large buildings due to the availability of sufficient volume of soil have a large accumulation capacity, so the need for irrigation water can be determined by the total amount of solar radiation entering the greenhouse, or by long-term meteorological data. Results In our measurements it was found that the value of transpiration can be determined by the empirical formula based on the measured total radiation in the greenhouse. Conclusion and perspectives. The use of programmable watering in protected soil structures, depending on the parameters of the microclimate, allows to reduce energy consumption and increase the adaptive tendency of plants to perturbing factors.

Authors and Affiliations

Л. Є. НИКИФОРОВА, М. О. СПОДОБА

Keywords

EP ID EP388561
DOI -
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