Utilization of thermal infrared thermometry for detection of water stress in spring barley

Abstract

Spring barley was irrigated using a line source sprinkler system to impose an irrigation gradient at Las Cruces, NM, U.S.A. Canopy temperature ( T c), air temperature ( T a), and vapor pressure deficit (VPD) were measured along with leaf water potential of the flag leaves during the pre- and post-heading growth stages at three moisture levels located 0, 8 and 14 m from the sprinkler line. Canopy and air temperature and VPD measurements were also taken during the senescence stage. Aboveground biomass, grain yield and 1000-grain weight were determined at the three moisture levels at the end of the growing season. Seasonal evapotranspiration was determined at each moisture level using the water balance method. The crop water stress index (CWSI) was determined as the relative position between an upper and a loswer baseline relating T c− T a to VPD. The baselines were different for the pre- and post-heading stages. During the senescence stage, no relationship existed between T c− T a and VPD for any moisture level, and the average T c− T a was 5.2°C with a coefficient of variation of 28%. The CWSI was significantly ( P≤0.05) related to measured evapotranspiration ( r 2=0.99), leaf water potantial ( r 2=0.75), aboveground biomass ( r 2=0.93), grain yield ( r 2=0.94) and 1000-grain weight ( r 2=0.97).