The influence of soil moisture transfer on building heat loss via the ground

The paper presents the results of field studies on the movement of moisture and salts during freezing of Prairie soils. It is shown that large fluxes of water can migrate to the freezing front and move upward into the frozen soil above. The fluxes are largest in light-textured soils (e.g., silt loam) having a water table at shallow depth. However, substantial amounts of soil moisture may also move in silty clay, silty clay loam, and clay soils under dryland farming provided there is sufficient water present to support capillary flow.The dynamics of soil moisture transfer under natural conditions as a result of freezing involves movement of water in both vapor and liquid phases. In the shallow surface layer of soil, to a depth of 300–400 mm, vapor flow predominates; in the depth below, water usually moves primarily as a liquid. It is demonstrated that the accumulation of ice with time increases because of the downward movement of the freezing front and the upward movement of water into the frozen soil above. In a silt loam with large fluxes, the ice content of the frozen zone rapidly reaches a level (80–85% pore saturation) where measurable migration ceases. Conversely, in a silty clay the movement of moisture into the frozen soil is observed to continue throughout most of the freezing period, and the ice content reaches 93% pore saturation. The greater movement in the finer grained soil is attributed to a higher freezing-point depression, a larger number of capillary pores, and a higher concentration of soluble salts in the liquid films.A close association is observed between changes in the ice content and electrical conductivity of a silt loam after freezing. In a silty clay the agreement is less clear, probably the result of the exchange of ions between the migrating liquid water and the clay particles. Maximum amounts of exchangeable ions moving into a 1 m depth of soil by the freezing action are estimated to be 11.9 t/ha in a silt loam and 15.7 t/ha in a silty clay loam.Data showing the redistribution of water and salts during thawing are also presented and discussed.

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Використання нечіткої логіки для автоматизації функціонування зрошувальних систем

Вісник Полтавської державної аграрної академії ◽

10.31210/visnyk2018.02.25 ◽

2018 ◽

pp. 153-157

Author(s):

Л. І. Лєві

Keyword(s):

Fuzzy Logic ◽

Soil Moisture ◽

Moisture Content ◽

Moisture Transfer ◽

Control Object ◽

Climatic Conditions ◽

Agricultural Crops ◽

Weather Factors ◽

Rational Use ◽

Moisture Management

Розглянуто підхід до автоматизації процесу керування зрошувальними системами із застосуванням нечіткої логіки. Потужність та інтуїтивна простота нечіткої логіки як методології вирішення проблем гарантує її успішне застосування в системах контролю та аналізу інформації. При цьому відбувається підключення людської інтуїції та досвіду оператора. Запропонований підхід дозволяє підвищити точність керування вологістю ґрунту, забезпечити отримання планових врожаїв сільськогосподарських культур, економити водні та енергетичні ресурси за рахунок їх раціонального використання. The highest yield of agricultural crops is achieved with the optimal amount of moisture, nutrition, heat, air and light. In this case, the necessary water regime for agricultural crops is created by the appropriate irrigation regime, which establishes the norms, timing and number of irrigation, depending on the biological characteristics of crops, natural and economic conditions. In determining the flow of water to irrigation take into account water consumption or total evaporation, which depends on climatic conditions, the amount of thermal energy that enters the surface, soil moisture, species and yield of the crop. Therefore, the issues of adaptation and self-studying of automated systems for controlling soil moisture in the conditions of the action of random weather factors, changes in the characteristics of the control object, improving the accuracy of control due to the operational consideration of the perturbations of the object, ensuring the receipt of planned yields of agricultural crops for the rational use of energy and water resources. In addition, modern water management systems for crops should not only provide sufficient management accuracy, but also forecast the need for plants in water for a certain period, minimize energy and water costs without loss of crop, be reliable and easy to operate, provide the operator with complete and timely information the value of all parameters and the state of the control system. A comprehensive solution to these problems is possible only through the development of modern technical means of automation, new mathematical models of moisture transfer in the unsaturated zone of soil and methods of managing moisture content of agricultural crops. Thus, the development of methods for automated management of moisture content of agricultural crops, taking into account perturbations, is an actual scientific and practical task. To solve these problems, the approach to automating the management of irrigation systems with the use of fuzzy logic is considered. The power and intuitive simplicity of fuzzy logic as a solution to problems ensures its successful application in information monitoring and analysis systems. At the same time there is a connection of human intuition and operator experience. The offered approach allows to improve the accuracy of soil moisture management, to ensure that planned crops are harvested, and to save water and energy resources at the expense of their rational use.

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