Water and heat stress: the effect on the growth and yield of maize and the impacts on irrigation water

The onset of water stress and the determination of heat stress on maize were studied using a ground-based remote sensing technique. The experiments were conducted at the University of Wyoming Research and Extension Center located in Powell, WY during the 2012 growing season on fields subjected to sub-surface drip irrigation (SDI), on-surface drip irrigation (ODI), and sprinkler (SPR) irrigation methods. In all three experiments the crop was subjected to three irrigation strategies, including 1.00ETc, 0.75ETc and 0.50ETc. Throughout the growing season the canopy temperature was monitored with infrared thermometers (IRTs) and the environmental variables were monitored with an automated weather station that was located on site. The IRTs were set to automatically retrieve and transmit the data to a dedicated computer using data loggers and radio transmitters/receivers. The soil moisture was monitored weekly with a neutron probe to a depth of 1 m. Plant samples for growth analysis were obtained regularly, and phenology observations were recorded bi-weekly. Photosynthesis was obtained in all treatments within each experiment using an infrared gas analyzer. Compared to the ODI and the SPR fields, water and heat stress had less effect on maize grown at the SDI field. Reduction on net photosynthesis was as little as 5.91 percent at the 0.75ET treatment of the SDI to as much as 65 percent at the 0.50ET treatment of the SPR. A functional relationship between the average crop water stress index (CWSI) and grain yield, was found. The use of IRTs for conditions in the semi-arid and arid regions of