## 2 Materials and Methods
### Sensor Nodes  
From the hardware/software point of view, there are two types of nodes: type A and type B, with different subtypes according to the sensors connected to them. The electronics of nodes A and B are housed inside a 120 \(\times\) 120 \(\times\) 90 mm IP65 box (G279C, Gainta AEK GmbH--Electrical Enclosures, Frankfurt, Germany). The power supply system consists of a 3.7 V, 3000 mAh Li-ion rechargeable battery, charged by an 80 \(\times\) 80 mm solar panel (5 V, 0.8 W). Figure 2 shows pictures of both types of node installed in the field. Table 2 shows the 25 nodes installed in the plot (see Figure 1), detailing, for each of them, the type it belongs to, the replicate, the irrigation treatment it is monitoring and the sensors connected to it. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Sensor**} & **Measured** & \multirow{2}{*}{**Output**} & \multirow{2}{*}{**Range**} & \multirow{2}{*}{**Resolution**} & \multirow{2}{*}{**Accuracy**} & **Supply** & **Current** \\  & **Data** & & & & & **Voltage Range** & **Consumption** \\ \hline \(10\)HS 1  & Soil moisture & 0.3–1.25 V & 0-57\% VWC & Not applicable & \(\pm\)3\% VWC & 3–15 VDC & 15 mA \\ \hline \multirow{3}{*}{MPS-6 1  & Soil matric potential and temperature & SDI-12 & \(-\)9 to & 0.1 kPa & \(\pm\)10\% (from -9 to -100 kPa) & \\  & & & \(-\)40 to +60 \({}^{\circ}\)C & 0.1 \({}^{\circ}\)C & \(-\)100 kPa) & 6–15 VDC & 10 mA \\ \hline \multirow{3}{*}{LVDT DF2.5 2  & Displacement sensor & & & & & \\  & & & & (analog sensor) & & 10–24 VDC & 10 mA \\ \hline \multirow{3}{*}{VP-4 1  & Relative humidity, temperature, vapor pressure & & 0 to 100\% RH & 0.1\% RH & \(\pm\)2 to -8\% & \\  & & & & & from \(\pm\)0.3 to -65 VDC & 5 mA \\  & & & \(-\)40 to 80 \({}^{\circ}\)C & 0.1 \({}^{\circ}\)C & \(\pm\)0.4 \({}^{\circ}\)C & & \\  & & & & & from \(\pm\)0.03 to -65 VDC & 5 mA \\  & & & & 0 to 47 kPa & 0.001 kPa & \(\pm\)0.03 to -65 V & \\  & & & & & & & \\  & & & 50 to 110 kPa & 0.01 kPa & \(\pm\)0.4 kPa & & \\ \hline \multirow{3}{*}{IR120  & Leaf temperature & 20 mV per \({}^{\circ}\)C (difference from sensor body) & \(-\)25 to +60 \({}^{\circ}\)C (analog sensor) & Not applicable \(\pm\)0.2 \({}^{\circ}\)C & \(-\)2.5 V or or -40 mA +400 mV & \\  & & & & & & (Theristor) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Overview of the sensors used in the plot. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Node** & **Node Type** & **Replicate** &
\begin{tabular}{c} **Irrigation** \\ **Treatment** \\ \end{tabular} & **Sensors** \\ \hline
1 & B1 & 1 & Control & 2 10 HS, 2 MPS-6, 1 VP-4 and 1 IR120 \\  
3 & 2 & RDI45 & 1 1R120 \\
25 & B3 & 2 & Control & 1 1R120 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Description of the deployed nodes. Figure 2: Pictures of type-A (left) and type-B (right) nodes. The hardware of the type A node (see Figure 3) is based on a wireless datalogger designed by our research group for PA applications (MEWiN MainBoard) [20]. For the signal conditioning from the sensors, an interface board (SensorBoard A) has been designed, connected to the first one by means of expansion connectors. An ESP8266 microcontroller (Esspressif Systems Co. LTD., Shanghai, China) with WiFi communication capability is also plugged to the SensorBoard A. The SensorBoard A consists of four DC/DC voltage converters (12, 10, 5 and \(-\)5 V), required to supply the sensors and to guarantee the operation of the different interfaces on the board: one for SDI12 sensors, another for radial dendrometers and one for analogue sensors (0-3 V). Finally, the board includes a circuit for the management of the rechargeable battery that supplies the power to the node. The type B Node is similar to type A, but it is based on the use of a Wipy 3.0 (Pycom(r), London, UK) (see Figure 4).