Submitted to: Proceedings of the Central Plains Irrigation Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/21/2014
Publication Date: N/A
Interpretive Summary: Infrared thermometers are commonly used as a tool to measure crop canopy temperature and aid in irrigation scheduling. Scientists from ARS (Bushland, Texas) have combined a network of wireless infrared thermometers with a commercial variable rate irrigation system to build prescription maps. The maps were built using data from crop canopy temperature and manual measurements of soil water content. Three irrigation rates were applied. The rates for the automatic plots were based on crop water stress index thresholds. Those for manual irrigated plots were based on soil water measurements. Results showed that yield and water use efficiency between automatic and manual plots were not significantly different at the higher irrigation levels. However, more research is needed to control irrigations at the lower deficit level.
Technical Abstract: Ground-based infrared thermometry has been used as a tool to provide a non-invasive method to detect crop water stress and schedule irrigations. However, studies are limited on the use of infrared thermometry for irrigation scheduling with variable rate irrigation (VRI) systems. This study describes preliminary results of a wireless network of infrared thermometers integrated with a commercial VRI system to build dynamic prescription maps, and automatically control site-specific irrigation scheduling for cotton. A center pivot field was divided into manual and automatic- irrigation scheduling treatment plots. Measured lint yield, crop water use, crop water use efficiency, and irrigation water use efficiency were compared between the two irrigation-scheduling methods at three irrigation treatment levels (75%, 50%, and 25% of replenishment of crop water use to field capacity). Lint yields were not significantly different between the manual (0.181 kg m**2 and 0.146 kg m**2) and automatic (0.182 kg m**2 and 0.164 kg m**2) treatment plots at the 75% and 50% irrigation treatment levels, respectively. However, twice the amount of irrigations were applied to the automatic control plots at the 25% irrigation treatment level, resulting in yields that were 53% greater than the manual 25% treatment plots. These preliminary results demonstrate that it is plausible to use a plant feedback system based on infrared thermometry to control a VRI system to achieve site-specific irrigation scheduling for cotton at higher treatment levels. However, maintaining deficit irrigation at a low level (25% replenishment of crop water use to field capacity) will require future research.