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Intelligent Drip Irrigation Control System for Greenhouse Based on Penman-Monteith Equation

Author: HanLiNa
Tutor: WangXiao
School: Nanjing Agricultural College
Course: Detection Technology and Automation
Keywords: Penman-Monteith equation Intelligent drip irrigation Greenhouse Single-chip microcomputer Venturi Injector
CLC: S275.6
Type: Master's thesis
Year: 2013
Downloads: 3
Quote: 0
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Abstract


As the typical representative of water-saving agriculture, drip irrigation has been widely used in the greenhouse production. Evapotranspiration information is an important index to control drip irrigation which is not only good for improving the intelligent level of greenhouse water-saving irrigation, but also good for crop growing, so as to improve crop yield and quality.This study designed a set of intelligent drip irrigation control system for greenhouse, which used single-chip microcomputer as the core controller, Penman-Monteith equation as the decision model of system irrigation amount. The system used the measured temperature, humidity and net radiation values as the inputs of Penman-Monteith equation, and then single-chip microcomputer program was used to calculate the crop evapotranspiration, so as to set the appropriate duration of irrigation. Environmental information and crop evapotranspiration were fed back to the computer control system. The greenhouse experiment demonstrated this means was convenient and reliable and could be applied in precise irrigation in the greenhouse canopy. The main content of this paper was as follows:1. The drip irrigation control system was designed and studied generally according to the characteristics of drip irrigation technology. The single-chip microcomputer hardware system was set up. The core of the system was STC89C58single-chip microcomputer, and was composed of LCD display module, information collection module and A/D conversion module. Temperature and humidity sensor and net radiation sensor collected temperature, humidity and net radiation signal in the greenhouse, then the signal converted into corresponding digital signal through A/D was transferred to the single-chip microcomputer. The system employed Penman-Monteith equation for the calculation of crop evapotranspiration. The single-chip microcomputer program was used to convert crop evapotranspiration into the duration of drip irrigation, controlling the electromagnetic valve through the driver circuit so as to control irrigation.2. According to the analysis of requirement, this study confirmed the total design scheme of the PC software which used Visual Basic as the development tool and Microsoft Access as the development tool of the database. According to the main function of the PC software, it was divided into three main modules:Real-time detection area, Data management area and Drip irrigation control area. The system realized the digicom between PC and single-chip microcomputer in serial digicom. According to actual needs, a communication agreement was set up. The MSComm control in Visual Basic was used and the relevant program was designed to realize the communication function.3. The relationship between temperature, humidity, net radiation and crop evapotranspiration was set up. Crop evapotranspiration was determined by meteorological factors. And then the irrigation decision was made. Three kinds of drip irrigation method were set up. Timing drip irrigation was setting drip irrigation time and duration according to crop growth conditions, weather conditions and practical experience. Automatic drip irrigation was a scientific irrigation which used Penman-Monteith equation to calculate crop evapotranspiration according to the collected environmental parameters. Semi-automatic drip irrigation was that avoiding special period not suitable for crop irrigation, crop evapotranspiration was calculated without watering. And then additive amount was distributed to the other time.4. The performance experiment of this drip irrigation system was conducted in the greenhouse. Firstly, the study finished the experiment of the same crop in different growth phases that are initial flowering period and resulting period of cucumbers. The contrast experiment between the crop actual evapotranspiration and the system irrigation amount was finished. The results showed that both of them had basically the same trend and the curve relevance achieved to R2=0.9587. The study also completed the experiment between different crops that are cucumbers and tomatoes. The curve relevance of tomatoes achieved to R2=0.8868. This proved the reliability of this system between different crops. These results showed that this drip irrigation control system could be applied in actual production in the greenhouse.5. In order to study the characteristics of this system which spread liquid fertilizer through drip irrigation, water and fertilizer distribution experiment of Venturi Injector was conducted. According to analyze the results, the relationships of fertilization concentration changing with time were concluded. This provided the basis in theory and practical foundation for Venturi Injector applying in this system. The results showed that the relative errors between fertilization concentration of every drip arrow and average fertilization concentration of all the drip arrows in every minute changed with time. The average relative error was less than10percent after6minutes, and reduced to0.74percent in the tenth minute.

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CLC: > Agricultural Sciences > Agricultural Engineering > Irrigation and water conservancy > Irrigation technology > Drip irrigation
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