U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska
Date of this Version
2015
Citation
Agricultural Water Management 156, 2015
Abstract
Infrared thermal radiometers (IRTs) are an affordable tool for researchers to monitor canopy tempera-ture. In this maize experiment, six treatments of regulated deficit irrigation levels were evaluated. Themain objective was to evaluate these six treatments in terms of six indices (three previously proposedand three introduced in this study) used to quantify water stress. Three are point-in-time indices whereone daily reading is assumed representative of the day (Crop Water Stress Index – CWSI, Degrees AboveNon-Stressed – DANS, Degrees Above Canopy Threshold – DACT) and three integrate the cumulativeimpact of water stress over time (Time Temperature Threshold – TTT, Integrated Degrees Above Non-Stressed – IDANS, Integrated Degrees Above Canopy Threshold – IDACT). Canopy temperature was highlycorrelated with leaf water potential (R^2= 0.895). To avoid potential bias, the lowest observation fromthe non-stressed treatment was chosen as the baseline for DANS and IDANS indices. Early afternoontemperatures showed the most divergence and thus this is the ideal time to obtain spot index values.Canopy temperatures and stress indices were responsive to evapotranspiration-based irrigation treat-ments. DANS and DACT were highly correlated with CWSI above the corn threshold 28◦C used in theTTT method, and all indices showed linear relationship with soil water deficit at high temperatures. Rec-ommendations are given to consider soils with high water-holding capacity when choosing a site fornon-stressed reference crops used in the DANS method. The DACT may be the most convenient index,as all it requires is a single canopy temperature measurement yet has strong relationships with otherindices and crop water measurements.
Comments
U.S. Government work