Study On The Decision Support System Of Variable Rate Irrigation Based On Component GIS

The deficit in water source day by day and the increasing with water consumption year after year in agriculture in our country, it leads to the contradiction with water in all the country. So it's necessary to apply to the technology of water saving. The practice of producing in agriculture proves that sprinkling irrigation is a good method for water saving. At present, there are many sprinkling irrigation methods. But the parallel moving sprinkling and stationary sprinkling irrigation are applied more, and these two methods are researched in the paper. The soil water content is one of important index to control the irrigation amount for crop. There is great difference of the soil water content in different region. The amount of irrigation of the crop in different region in the different bearing period is distinct. Thus variable rate irrigation is one of the effective measures to save water according to the soil water content.The irrigation prescription map is the significant precondition for variable rate irrigation. With the foundation of the theory of variable rate irrigation and using the component geography information system, the irrigation prescription map is made in this article. The distributed map of soil water content can be made, through the interpolation, according as the real soil water content of different sampling site. This system can forecast soil water content of each grid using the forecast model of soil water. When decision making, whether or not irrigate can be decided by comparing the current soil water content with the light drought and heavy drought index of the crop. The amount of irrigation in each grid can be decided by the model of amount of irrigation. The only amount of irrigation can be made by the analysis of economy benefit according to the model of water consumption-yield and the optimization decision making, thus the irrigation prescription map can be made. Using this prescription, the control system of the sprinkling machine can be ordered to how to work. The fixed sprinkling irrigation system is also designed. The controller can control the on or off of the electromagnetic valve. Each valve controls one area. Controller can set the time for irrigation of each area, thus different amount of irrigation can be carried out in different area.This system is developed by Visual C++ 6.0 and MapObjects 2.0. This System can realize the input of the information, the making of the distributing map of soil water content, the query and analysis of space information and the making of the prescription map. Some assistant function is also implemented, such as the inverse distance weightedinterpolation and the transformation of the coordination. The module of extension is also worked out, for the sake of the expansion for system. This system has been put into use in the Xiaotangshan Precision Agriculture Demonstration Station and the effect of water saving is prominent. The extension and application of the system will provide a new approach for water saving.