###### Abstract  
This research examines and analyzes the measured electromagnetic characteristics of vegetal soil for Wireless Underground Sensor Networks applied to precision agriculture. For this, we used Wireless Underground Sensor Network (WUSN) technology, which consists of sensors that communicate through the soil to collect data on irrigation, such as temperature and humidity, for good plant growth. However, underground communication channels and signal transmission are required to travel through a dense and heterogeneous soil mixture. For the measurement results of the vegetal soil dielectric parameters, a precision domain sensing probe operating at 433 Mhz was used. Moreover, the different choices of capacitance, inductance, and varactor were included, with a reasonable estimation of the dielectric permittivity, ranging from 2 to 15, and an unlimited range of conductivities. Despite promising results in predicting the dielectric permittivities, several improvements were made to the mode for low permittivity values, and it was designed to accommodate a wide range of dielectric permittivities. probe; dielectric permittivity; Wireless Underground Sensor Network (WUSN); resonance; precision agriculture; Frequency Domain Reflectometry (FDR) +
Footnote †: journal: applied sciences  
0000-0001-5000-0000-00001-5000][PERSON]  
0000-0001-5000-0000-00001-5000-00001-50000-00001-50000-00001-50000-00001-50000-00001-50000-00001-50000-00001-50000-00001-50000-00001-50000-00001-500000-00001-50000-00001-50000-00001-50000-00001-50000-00001-500000-00001-500001-500000-00001-500001-5000001-500001-500001-500001-500001-500001-50 This technology offers numerous advantages, such as ease of deployment, timely data collection, reliability, coverage density, communication techniques, and underground wireless networking, leading to potential applications in precision agriculture [7; 8]. The flexibility of their interface makes WUSNs ideal candidates for providing efficient and economically viable solutions in precision agriculture. Despite their potential advantages, several significant challenges remain, with regard to improving the performance of underground networks. The WUSN [9; 10] was the main element of this research. Depending on the data required for precision agriculture, various types of sensors can be envisaged, such as humidity, temperature, salinity, and pH sensors. These sensors are deployed in a network of equidistant nodes at depths of up to 70 cm. Further research was needed, to ensure their accuracy for different soil types and to evaluate their performance under subsoil moisture and pressure conditions. An intelligent communication system needed to be implemented, to route the data collected by the various sensors to the base station responsible for aggregating all the data. In this network, communication occurs by using multi-hop methods, where a node can transmit its data to neighboring nodes. Thus, the communication protocol had to seek the optimal path between the concerned node and the base station while considering the nodes to be used to optimize energy consumption at each node. To minimize the network's cost, communication between the various nodes would be wireless, using the underground as the communication channel instead of air. Different soil types had to be characterized, to determine the best frequencies to minimize attenuation. Additionally, a study of the propagation of electromagnetic waves in the subsoil had to be conducted, accounting for the scattering of waves from buried objects that may be present along the path between the nodes. Finally, particular importance needed to be attached to bidirectional communication between the sink node(s) and the base station on the surface. Due to the subsurface/air interface, reflections occur at this boundary, further reducing communication quality.