Fig 1.
EC-5 sensor calibration for our specific soilless substrate.
Volumetric water content (VWC) as a function of EC-5 sensor output voltage (mV). Individual replicates of voltage readings are plotted for each VWC. The sensor output voltage for the first three VWC were identical for both replications.
Fig 2.
Automation system used for precision irrigation.
Universal power supply signals designated by 24V, 12V, 5V, GND (ground), or Vin (Voltage in). Specific modules follow annotation for data logger ports (C ports: I/O control ports for 5VDC; SE ports: Single-ended communication ports for sensor signal data; Vx ports: Excitation variable voltage supply of 0–2.5V); Multiplexer (RES: Voltage supplied >3.5V sets active mode; CLK: Used to cycle through measurements of sensors; COM: Measurement terminals for ODD High (H), Low (L) and EVEN H, L for signal lead communication between sensors attached to multiplexer and data logger; Sensors: Individual excite, GND, and signal terminals for each sensor attached to the multiplexer); Microcontroller (Analog ports: Measures voltage signal from data logger of 0-5V to coordinate activation of irrigation signals to relay driver) Relay Drivers (Uses 5V signal inputs from microcontroller to activate 24V irrigation valves corresponding to respective sensor data).
Fig 3.
Irrigation system connections between data logger, multiplexer, microcontroller and 16 channel switch.
Fig 4.
Arrangement and position of different components of the irrigation system.
A) Solenoids and tubing; B) hose ring, EC-5 sensor and emitters.
Fig 5.
Changes in volumetric water content (VWC) over time using four sorghum genotypes subjected to three final VWC levels (0.10, 0.20 and 0.30 m3 m-3) after ten days of dry-down.
Each point represents a daily VWC average. Bars indicate standard deviation.
Table 1.
Average dry matter per plant at the start (DMi) and last day (DMf) of water treatments, growth per plant (PG), irrigated water volume (IWV), and water use efficiency (WUE) in four sorghum genotypes.
Table 2.
Correlation coefficients between all variables evaluated to determine the efficacy of the irrigation system to control the dry-down process and final VWC.