Quantifying water stress using crop water stress index in mahogany (Swietenia macrophylla King) seedlings

The present study was made to quantify water stress in mahogany (Swietenia macrophylla King) seedlings using crop water stress index (CWSI). Seedlings were provided with four different levels of irrigation as treatments - irrigation at irrigation water (IW)/evapotranspiration (ET) = 1, 0.6 and 0.3 at weekly intervals and a control with no irrigation (IW/ET = 0). Canopy air temperature difference (CATD) was recorded using an infrared thermometer. The non-water-stressed baseline (NWSB) was derived from CATD and vapour pressure deficit (VPD) in the well-watered treatment (irrigation at 1.0 IW/ET). The lower base-line equation for CATD was -0.25VPD - 2.9 and the upper baseline equation was -0.01VPD + 6.1. CWSI responded to irrigation events along the whole season and clearly detected mild water stress, suggesting extreme sensitivity to variations in plant water status. The present study reveals the potential of CWSI for early, non-destructive and less time-consuming estimation of water stress.