ARS | Publication request: Irrigation system management assisted by thermal imagery and spatial statistics

Submitted to: World Congress of the International Commission of Agriculture and Biosystems Engineering
Publication Type: Proceedings
Publication Acceptance Date: April 12, 2010
Publication Date: June 16, 2010
Citation: Thomson, S.J., Ouellet-Plamondon, C.M., Defauw, S.L., Huang, Y., Fisher, D.K., Hanks, J.E., English, P.J. 2010. Irrigation system management assisted by thermal imagery and spatial statistics. World Congress of the International Commission of Agriculture and Biosystems Engineering. Quebec City Canada, June 13-17, 2010. Paper no. CSBE101126.pdf, 13 pp.

Interpretive Summary: Irrigation system management involves scheduling water application and diagnosing system components and irrigation structures that leak water. Irrigation of crops depends on providing water at the right time and in the right amounts. Irrigation timing is a challenge because it is not always obvious when the crop is stressed enough to require water. Water applied too early can be wasteful, but water applied too late may have detrimental effects on crop yield and quality, thereby decreasing its value. In theory, an imaging system flown in aircraft that “takes the temperature” of the crop canopy can be used to determine areas of a field that require water. Warmer canopies signify higher crop water stress, and thermal information could be used to signal when irrigation is required. Spatial statistics shows relationships between many variables in space and, in this case, can be used to identify areas in a field that consistently promote crop water stress. A review of some issues with thermal imaging is presented, along with an example using spatial statistics. Examples for detecting leakage from irrigation systems are also presented, along with description of a new variable-rate center pivot irrigation system that can utilize spatial irrigation scheduling criteria.

Technical Abstract: Thermal imaging has the potential to assist with many aspects of irrigation management including scheduling water application, detecting leaky irrigation canals, and gauging the overall effectiveness of water distribution networks used in furrow irrigation. Many challenges exist for the use of thermal imagery to accurately determine the timing of irrigation based on crop water status. These challenges include proper accounting for variations in solar radiation and wind on a spatiotemporal basis, delineating canopy-air temperature difference (CATD) under periods of low vapour- pressure deficit, and accounting for altitude effects on canopy temperature represented at the camera. At the Crop Production Systems Research Unit of the USDA-ARS in Stoneville, MS (USA), information from thermal imagery obtained with agricultural aircraft are being used along with ground-based readings of soil moisture status and canopy temperature in an attempt to develop consistent criteria for scheduling irrigation. A review of some issues with thermal imaging is presented, along with a proposed approach using spatial statistics that can enhance the value of thermal imagery for detecting water-stressed field areas. Thermal imagery has been used to identify plant canopy temperature differences related to crop water/heat stress. In addition, we have applied spatial statistics to help to delineate areas of the field with high potential for crop water stress. Thirdly, we illustrate the utility of thermal imagery for detecting leakage from irrigation canals and poly-pipe furrow irrigation systems. Lastly, operational characteristics of a new variable-rate center pivot irrigation system that can utilize spatial irrigation scheduling criteria are described.