Soil Moisture and Plant Canopy Temperature Sensing for Irrigation Application in Cotton

There is a need to provide technical tools to cotton producers for appropriate management of irrigation in the Mid-South region of the U.S.A wireless sensor network was deployed in a cotton field to monitor soil water status for irrigation. The network included two systems, a Decagon system and a microcontroller-based system. The Decagon system consisted of soil volumetric water-content sensors, wireless data loggers, and a central data station. Sensor data collected by each data logger were wirelessly transferred to and stored in the data station. The microcontroller-based system was designed to be a low-cost data logger for monitoring Watermark water-potential sensors. An infrared thermometer was used in the field to measure plant canopy temperature for evaluating its usefulness in detecting water stress in cotton under humid conditions. Soil water and plant canopy temperature data were collected during the 2011 cotton growing season. Results indicated that the soil water sensors were able to measure the soil water status, and the measurements recorded by the systems reflected general trends of soil water change during the growing season. Soil water content decreased at a higher rate in 15-cm and 30-cm depths than in 60-cm depth before 60 days after planting. A sharp decrease of soil water content in 60-cm depth was observed from 60 to 80 days after planting. Sensor measurements responded to effects of soil texture on available water capacity. Canopy temperature of non-irrigated plants is 2-4 C higher than that of the irrigated plants during peak time of day. Supplemental irrigation increased yield by 14.2 % in this study. System installation and maintenance procedures developed worked well in general. Some installation and operational issues were found and need to be resolved for wider field operation and user acceptance.