ARS | Publication request: SPATIAL CANOPY TEMPERATURE MEASUREMENTS USING CENTER PIVOT MOUNTED IRTS

Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 16, 2000
Publication Date: N/A

Technical Abstract: Crop canopy temperature is useful as an indicator of plant water stress and possibly a good measurement to use as an irrigation schedule initiator. To help determine the feasibility of using canopy temperature to control irrigation events, 26 infrared thermometers (IRTs) were mounted along the main structure of a 3-tower, 137-m center pivot irrigation machine. The center pivot provided a platform to conduct spatial canopy temperature measurements over a 6-ha field that contained 12 different soil mapping units. The IRTs were mounted in pairs, for thirteen, 9.1-m segments along the center pivot. During the 1999 corn growing season, data were acquired on eight separate days during the grain fill period of an irrigation and nitrogen fertilizer rate experiment that consisted of 396 plots arranged in randomized blocks within the 12 soil mapping units. The IRT data were collected during a single pass of the center pivot, at mid-day during mostly sunny conditions. Data were collected and stored using a data logge and a PC mounted on the center pivot. Individual canopy temperature values were stored and later corrected using calibration values for each IRT. Data were then adjusted for temporal data slew caused by time-of-day effects. Measurement techniques, data adjustment algorithms, and sample data are reported. The quadratic relationship of adjusted canopy temperature and irrigation rate, for a day when the non-irrigated plots were under stress, indicates that approximately 65 to 95% of the variation across the 12 mapping units could be explained. For data acquired two days after a 41-mm rain, the relationship explained approximately 30 to 80% of the variation across the soil mapping units. Hence, there is a possibility of determining the relative soil water status using multiple, inexpensive IRTs.