Irrigation Control System For Greenhouse Matrix Cultivation Based On Chlorophyll Fluorescence

Irrigation control is the water management for crop growth and development.Most of the traditional irrigation control techniques achieve irrigation control by inferring the crop moisture information from the soil water content and environmental parameters,rather than considering the water requirements of the crop itself.Chlorophyll fluorescence detection technology can detect crop photosynthesis rapidly and non-destructively,characterize the status of crop water stress,understand crop water requirements with a deeper level.Under the premise of ensuring the normal growth of plants,developing a timely and appropriate greenhouse matrix cultivation irrigation control system based on chlorophyll fluorescence can improve efficiency of water use.The main contents and conclusions are as follows:（1）Exploring the effect of water stress on chlorophyll fluorescence parameters of lettuceThe ways of exploring the effects of different irrigation treatments on the chlorophyll fluorescence parameters of lettuce are as follows:Firstly,the chlorophyll fluorescence distribution of different positions of lettuce was analyzed by canopy photosynthetic measurement experiment,and the measurement point of chlorophyll fluorescence parameters of lettuce was determined to be 1-2 cm away from the leaf edge.This program designed and developed a matrix water stress test system to explore chlorophyll fluorescence parameters of lettuce in day-to-day changes,daily changes,and daily changes in different moments by different treatment of substrate water content lower limit water stress.The results show that the chlorophyll fluorescence parametersand₈)′can reflect the water stress status of the lettuce.The chlorophyll fluorescence parametersand₈)′are significantly correlated with meteorological parameters of solar radiation and air temperature and humidity.However,the daily variation ofhas a law of stability change to judge the status of crop water stress at a specific time.The water stress condition of lettuce can be judged byat 9 o’clock through the sensitivity analysis of the daily variation ofat different times.（2）The Studying of Irrigation control strategy based on chlorophyll fluorescenceThrough the gradual drought test of substrate cultivation and the analysis of the response characteristics ofto the water content of the substrate,the regression equation of the chlorophyll fluorescence parameterand the matrix water content was established by Logistic equation,and the goodness of fit² is 0.979.A chlorophyll fluorescence-based matrix irrigation control strategy was established by combining chlorophyll fluorescence with matrix water content response model,matrix water content detection technology and meteorological-based evapotranspiration prediction.Combining the prediction of greenhouse environmental parameters based on historical meteorological and greenhouse environmental parameters with the improved Penman-Monteith formula to establish irrigation prediction model.（3）Development of Greenhouse Irrigation Control System Based on Chlorophyll FluorescenceAccording to the design requirements of the irrigation system,development of a greenhouse chlorophyll fluorescence greenhouse irrigation control system based on the Internet of Things architecture.The design and selection of hardware such as sensors for monitoring chlorophyll fluorescence,air temperature and humidity,illuminance,soil moisture,and irrigation control systems and intelligent gateways were carried out;The system communication method based on SDI-12 and MODBUS was built,and the system perception layer,transmission layer and application layer software were developed.The embedded field,computer and mobile phone WeChat small program human-computer interaction application was constructed,in order to realize real-time data monitoring and irrigation remote control decisions of greenhouse irrigation control system based on chlorophyll fluorescence.A experiment verification was conducted on the irrigation control strategy through field trials.The results showed that the chlorophyll fluorescence-based irrigation control method achieved a water saving rate of 23.5%and a water use efficiency of 18.1 kg/m^3 compared with the traditional substrate water content-based irrigation control method.