CWSI and Stomatal Resistance of Cotton and Soybeansby Melvin E. Keener, Standard Oil Co, Cleveland, OH, USA,
Bronson Gardner, Standard Oil Co, Cleveland, OH, USA,
Document Type: Proceeding Paper
Part of: Irrigation Systems for the 21st Century
Abstract: A new instrument, Scheduler(TRADEMARK), has been developed to measure the onset and duration of plant water stress. This device consists of a sensor package (containing an infrared thermometer, a solar radiation sensor, a capacitance type relative humidity sensor and a thermistor) connected to a dedicated microprocessor. Proprietary algorithms for each crop in the microprocessor use measurements from the sensors to calculate an 'Idso type' crop water stress index. A field experiment was designed to test the Scheduler against an independent method of measuring plant water stress, stomatal resistance. Two crops were used, cotton and soybeans, as well as two irrigation treatments. A farmer's field was used near Steele, Missouri. The crop water stress indices and the lower surface stomatal resistance showed similar patterns for both cotton and soybeans, but the soybeans had slightly higher resistances at the same crop water stress index than did cotton. This indicates that the algorithms in the Scheduler are accurately characterizing the stress in both crops, but that the calibration of the cotton or soybean index may have small errors.
Subject Headings: Crops | Load and resistance factor design | Solar radiation | Scheduling | Probe instruments | Humidity | Algorithms | North America | Missouri | United States
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