Application note: A low cost microcontroller based system to monitor crop temperature and water status
A prototype system was developed and constructed for automating the measurement and recording of canopy soil and air temperature, and soil moisture status in cropped fields. The system consists of a microcontroller based circuit with solid state components for handling clock/calendar, sensor power, and data storage and retrieval functions. Sensors, including an analog soil moisture sensor, analog and digital temperature sensors, and a digital infrared thermometer, are widely available and inexpensive. The circuit board and sensor assemblies require approximately 4h to construct and test, and material costs totaled approximately US$84. Systems were built and tested during the 2009 growing season in a corn field to evaluate performance and suitability under local conditions. The sensors performed according to manufacturers' specifications, with accuracies of 0.4^oC, 1.4^oC, and 0.3^oC for air soil and canopy temperature measurements, respectively. Soil moisture sensors were calibrated and provided measurements within 2kPa of the manufacturer's values. Reliability of data collection and storage averaged 91% with most bad or missing data occurring during periods of inclement weather and electrostatic interference.