Soil temperature detection based on acoustic method and improved Wyllie model

Soil temperature is one of the important environmental factors for the underground parts of plants. It is important to detect soil temperature in agricultural production. Acoustic waves serve as effective carriers of soil information, providing a reliable means to detect soil physical properties. In order to detect the temperature of sandy loam soil based on acoustic technology, this study extends the application of Wyllie model to the temperature measurement of sandy loam soil. The relationship between soil temperature and acoustic velocity is explored. A model of soil moisture content-soil temperature-acoustic velocity (MTV) for temperature measurement in sandy loam soil is proposed by extending the temperature-velocity of sound relationship with the introduction of a variable empirical coefficient related to soil moisture beta(theta). In order to determine the parameters of proposed model, a pulsed acoustic velocity detection system was built in this paper. The influence of temperature on the acoustic velocity in sandy loam soil was analyzed through experiments. Based on the experimental results, the key parameters of the MTV model are refined. Finally, a validation experiment was carried out on sandy loam soil. The maximum estimation error of soil temperature based on the MTV model for sandy loam soil temperature estimation is 8.55 %. The results indicate that the MTV model proposed in this study can be used for temperature estimation in sandy loam soil, providing a theoretical basis for the development of acoustic soil physical information detection sensors.