Development And Research Of Real-time Soil Moisture Sensor System On Line Scale

Contradiction growing between continuous developments of urban forestry and greening the city water shortage, monitoring root zone soil moisture of landscaping plants such as trees that distribution difference to achieve variable precision irrigation has enormous social and economic benefits. Traditional monitoring tools can be divided into point measurement and surface measurement with its measurement range, the paper designs a line measurement of soil moisture sensing system, which uses only one soil moisture sensor can measure soil water on line regional scale, and the accuracy can match point measurement, superior surface measurement, while measuring range is greater than point measurement, with much lower cost.Soil moisture sensor based on frequency domain oscillometry was developed firstly and then the sensing system which has STM32 cored controller and main structure with "U" shaped PVC tube, both ends of it is a stepper motor, drag the soil moisture sensor in horizontal PVC tube movement. The results of laboratory environment sensor performance testings showed that system has good response to moisture change, can be practical applicated in the wild. Then the system and six BD-Ⅲ soil moisture sensors were installed in the wild environment, buried depth of 30cm, and in the field a radio station Vantage Pro 2 automatic weather stations was set up. The results of wild environment showed that the measuring accuracy of system were capable of comparable to BD-III soil moisture sensor. Soil moisture at a depth of 30cm in the absence of rainfall or watering was remained stable in the short term. Sensing system was able to detect soil moisture changes due to rainfall or irrigation, while its data reflects the lag of soil and Darcy’s Law.In summary, the line regional scale soil moisture sensing system has good accuracy, stability and reliability, can actually be used in the plant root zone soil moisture monitoring and other soil moisture measurement related fields, providing an effective mean for accurate variable irrigation.