Study On Detecting System Of Crop Disease Stress With Acoustic Emission Technology

During the process of their growth, plants are usually subjected to various environmental stresses, including abnormal temperature, lack of moisture, adverse physical and chemical conditions of oil etc, especially the decrease of plants’growth and crop production caused by diseases stress becomes more and more serious. In our country, because of the crop variety, cultivation system, ecological environment changes as well as the more and more deterioration of crop growth environment, diseases have the tendency of becoming more and more serious, and due to the excessive use of pesticides cause product and environment pollution, which has great threat to our country’s food safety. The fundamental ways to solve the above problems are to vigorously develop the comprehensive and precise prevention and control of diseases, and to implement the automatic spraying of pesticides.In this topic, the American National Instruments (NI)’s virtual instrument software development platform LabWindows/CVI was used as the system’s development platform, the laws of occurrence and development for acoustic characteristics of diseases stress in crops were investigated by applying acoustic emission sensors to acquire the ultrasonic signals emitted by crops under diseases stress, and the study of relationship of factors between acoustic emission signals and plant disease conditions, other physiological parameters was further carried out by appropriately combining and considering other physiological indices and environmental factors, such as canopy transpiration amount, illumination, CO2concentration, temperature and humidity etc, so as to establish the dialog between man and plant.In this system, PCI-2acoustic emission board, R15probes, electronic balance, temperature, humidity, carbon dioxide concentration, illumination intensity sensors and PCI-8333data acquisition (DAQ) card were selected to construct hardware detection system, and virtual instrument technology was utilized to construct software system, the system for real-time acquisition and detection of information between the acoustic emission and diseases stress of crops was studied and developed, and the contrast experiment study was carried out in a greenhouse by taking a healthy tomato and a diseases stressed tomato crop as the objectives.The results show that there are a certain physiological cycle laws in the acoustic emission of healthy crop, generally the "double peak area" can appear; but distortion can occur in the acoustic emission of diseases stressed crop, a sharp increase of the acoustic emission frequency can suddenly take place at some time, immediately the crop begins to show disease symptoms, and acoustic emission signals lose the regularity; from the perspective of correlationship, there is a certain relevance between the acoustic emission frequency of plants and transpiration rate, temperature, humidity, CO2concentration, illumination intensity. The correlation coefficient of acoustic emission frequency and transpiration rate has certain volatility, and the volatility has a certain plant physiological significance, which can be regarded as an important index pertaining to acoustic emission.By taking these as the theoretical basis, to further determine the relationship between acoustic emission signals and disease degrees and physiological states of crops, and to investigate diseases forecasting and automatic spraying of pesticide variables of main crops, which will become a new approach for the physiological signal detection of crops as well as comprehensive and precise prevention and control of diseases.