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Development of a Plant Response Feedback Irrigation Control System Based on Crop Water Stress Index and Evapotranspiration Modeling

Prenger, Jessica J.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1419601844

Abstract Details

2003, Master of Science, Ohio State University, Food, Agricultural and Biological Engineering.
A greenhouse irrigation control system directly linked to plant response and water status was developed. The control system used the crop water stress index (CWSI) to turn irrigation on/off and an evapotranspiration (ET) model to proportion water volume during irrigation. CWSI was based on infrared thermometry (IRT) measurement of plant canopy temperature. The ET model adjusted water loss rate for a drought stress crop. Since ET models were developed for unlimited water supply conditions, an adjustment to the water loss rate for stressed crops was used to provide a more accurate ET estimation for plants under drought stress. A closed loop CWSI feedback proportional control system was evaluated as a basis for plant water status management. The tests conducted focused on maintaining low water stress, while reducing runoff and waste to a minimum. A data acquisition and control system was established in a small research greenhouse at OARDC, Wooster, Ohio. Four CWSI methods were investigated using available growth chamber data (Kacira, 2000), and experiments in the research greenhouse. Two greenhouse experiments were completed in 2002, summer and fall to (1) study CWSI-IRT methods compared to weight based CWSI (CWSI-wt) measurements, and (2) test an ET adjustment with CWSI feedback compared to weight based ET measurements. Two more experiments were conducted to compare closed loop CWSI proportional irrigation control to two alternatives: open loop, closed loop CWSI feedback ON/OFF control Also, historical growth chamber data collected at Ohio State was used to test the ET adjustment proposed. Results of the CWSI testing showed some disparity between the CWSI-IRT to CWSI-wt. In growth chamber experiments, the correlation was r2 = 0.69 (Kacira et al., 2002). However, greenhouse experiment 1 showed correlations were r2=0.47. Low correlations were thought to be due to noise of the measured ET used to calculate CWSI-wt, as well as variability of temperature and light conditions in the greenhouse. Results of the ET adjustment with CWSI-IRT feedback showed significant improvement in the ET estimation. Analysis of eight growth chamber and greenhouse cases showed a more accurate ET estimate using the adjusted model with mean difference from measured ET closer to zero for seven of eight cases tested. The closed loop CWSI feedback proportional control was compared to open loop control, in the form of timed irrigation, and closed loop CWSI feedback using ON/OFF control. Two identical experiments using proportional control used 52 and 43% less water than the open loop irrigation that served as the control for each experiment with less than 50 mL/plant error between water used and water delivered. The ON/OFF feedback control used 103% of the amount for the control crop, while having greater than 100 mL/plant errors between the water amount required and that delivered. The improved performance of the proportional control was due to including information about the dynamic response of the plant system to changes in water supply and more accurate ET estimates. The proportional control system produced plants whose height, fresh weight, and dry weight were not significantly different (95% confidence interval) from a control crop (open loop irrigation control).
Peter P. Ling (Advisor)
Robert C. Hansen (Committee Member)
Harold M. Keener (Committee Member)
135 p.
Agricultural Engineering

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Citations

  • Prenger, J. J. (2003). Development of a Plant Response Feedback Irrigation Control System Based on Crop Water Stress Index and Evapotranspiration Modeling [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1419601844

    APA Style (7th edition)

  • Prenger, Jessica . Development of a Plant Response Feedback Irrigation Control System Based on Crop Water Stress Index and Evapotranspiration Modeling. 2003. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1419601844.

    MLA Style (8th edition)

  • Prenger, Jessica . "Development of a Plant Response Feedback Irrigation Control System Based on Crop Water Stress Index and Evapotranspiration Modeling." Master's thesis, Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1419601844

    Chicago Manual of Style (17th edition)

osu1419601844
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© 2003, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.