## 2 Methodology and System Specifications
### Methods and Equipment for Soil Measurements
The following bullets provide a brief description for these instruments:  
* The TEROS 10 and TEROS 12 sensors emit a 70 MHz signal, use the capacitance measuring method, and estimate the volumetric water content (VWC) and \(\epsilon_{\text{a}}\) of the soil sample that surrounds their needles. TEROS 12 measures also \(\sigma_{\text{b}}\) and temperature and has three stainless steel needles instead of the two of the TEROS 10. They both consist of an epoxy sensor body (for better installation even in hard soil conditions) and a ferrite core to prevent eddy currents and cable noise. They can be buried in fields for extended periods of time for long-term detection and they have a large volume of influence in VWC measurement sensitivity (1010 mL for TEROS 12 and 430 mL for TEROS 10) for more accurate results. The raw data collected by TEROS 10 and TEROS 12 are converted by the included calibration in the acquisition system into VWC and apparent dielectric permittivity. Their grade accuracy is \(\pm\)3% VWC, typical in mineral soils that have a solution EC \(<\) 8 dS/m. TEROS 10 has an analog output, while TEROS 12 has a digital interface that supports serial (DDI) or SDI-12 communication with other systems and is compatible with 3.3 V logic and is also 5 V tolerant. According to the manufacturer's instructions for TEROS 12, a voltage of 4 to 15 V DC should be supplied. The power consumption of TEROS 12 varies between 3.0 mA and 16.0 mA, with a typical value close to 3.6 mA. The nominal power consumption of TEROS 10 is 12.0 mA, while its supply voltage should be between 3.0 V and 15.0 V. The output of the TEROS 10 instrument varies from 1000 mV to 2.500 mV. The physical connection with the measuring circuit is achieved via a 3.5 mmstereo plug connector that both TEROS 10 and TEROS 12 devices have. According to the manufacturer, TEROS 12 needs up to 100 ms before starting performing a soil measurement, and when it finishes, it sends the measurement through the DDI serial protocol. After that, it enters the SDI-12 communication mode. To obtain another serial (DDI) signal, the sensor must be power-cycled, and special error indication values are also provided. * The 5 TE is a full-featured soil moisture sensor that operates at frequency \(f\) = 70 MHz and provides measurements of the \(\varepsilon_{\mathrm{a}}\), \(\sigma_{\mathrm{b}}\), and temperature. It determines VWC by measuring the dielectric constant of the media and also measures temperature (T) through an onboard thermistor and \(\sigma_{\mathrm{b}}\) using a stainless steel electrode array. The 5 TE device is 5 cm long and includes three prongs that are 5.2 cm long. The 5 TE device supports serial (DDI) or SDI-12 communication with other systems, which is compatible with the 3.3 V logic and also is 5 V tolerant. The timing sequence the 5 TE instrument follows in order to provide soil measurements via the simpler DDI protocol is similar to the one of the TEROS 12 unit, including power cycling. The temperature measurement range is \(-\)40 to 60 \({}^{\circ}\)C, and the bulk electrical conductivity measurement ranges from 0 to 23 dS\(\cdot\)m\({}^{-1}\). The accuracy for \(\varepsilon_{\mathrm{a}}\) is \(\pm\)1 from 1 to 40 (soil range), \(\pm\)15% from 40 to 80, for \(\sigma_{\mathrm{b}}\)\(\pm\)10% from 0 to 7 dS/m, and for T is \(\pm\)1 \({}^{\circ}\)C. According to its manual, the sensor's accuracy is \(\pm\)1% with soil-specific calibration and 3% with medium-specific calibration in soils that have a solution electrical conductivity EC \(<\) 10 dS/m. The 5 TE has an operating voltage between 3.6 V and 15 V, while its average consumption is 10 mA in measurement mode. The physical connection with the measuring circuit is achieved via a 3.5 mm stereo plug connector that the 5 TE instrument has. * The 10 HS sensor comes pre-calibrated to measure the soil dielectric permittivity, and the readings are provided directly in volumetric water content. It operates at a frequency of \(f\) = 70 MHz, which provides good accuracy even in high-salinity levels.