Wireless Sensor Network System for Real-Time Prescription Map Development to Improve Cotton Production in a Semi-Arid Region.

Variable rate irrigation (VRI) equipment enables site-specific control for delivery of required amounts of irrigation water to specific management zones within a field. Manually uploaded prescription maps provide geospatially referenced data to prescribing irrigation amounts for specific management zones. This set of instructions is uploaded to the center pivot irrigation system control panel. While changes based on visual observations, and remote sensing can be made to prescription maps during the growing season, the acquisition and manual uploading of updated data can be expensive and time consuming. In this study, a wireless sensor network system of infrared thermometers mounted on a center pivot and a plant feedback algorithm (integrated crop water stress index) were used to build dynamic prescription maps for a VRI sprinkler system irrigating cotton at three different levels (75%, 50%, and 25% replenishment of soil water depletion to field capacity). Prescription maps were built every two days throughout the 2012 growing season; and these maps guided automated irrigation. Results from this study indicated that mean lint yield from the plant feedback method using thresholds corresponding to the 75% (1824 kg ha^-1) and 50% (1641 kg ha^-1) irrigation levels were greater than yield from manual irrigated plots of the same irrigation treatment levels (1742 kg ha^-1 and 1460 kg ha^-1) using weekly neutron probe readings. The wireless sensor network system and algorithm used in this study provide one possible framework for establishing and integrating dynamic prescription maps to address within field spatial and temporal crop water stress with a VRI sprinkler system.