A stimulus response model for characterizing cotton yields as a function of water deficits /
| Main Author: | |
|---|---|
| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1988.
|
| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | The Stress Day Index model, as originally proposed by Hiler and Clark (1971), has been used as an irrigation scheduling tool. The two components of the model are the crop susceptibility factor (CS) and the stress day factor (SD). The model assumes a constant susceptibility factor within each crop growth stage. However, Hiler and Clark (1971) recognized that the value of the CS factor is dependent on both the degree and duration of the water deficit. A stimulus-response model was developed in this study in which the crop susceptibility factor (CS*) was no longer dependent on the degree and duration of the water deficit. To characterize SD, the model utilizes an integrated value over time of the chosen indicator of plant water stress. During 1987, a field study utilizing nonweighing lysimeters was performed with cotton (Gossypium hirsutum L. cv. Stoneville 825) during the peak flower growth stage to test the proposed stim ulus-response model. Three water deficit treatments, each with a different target value of SD, plus a control (SD=0.0) treatment were utilized during the peak flower growth stage. SD was determined by integrating a normalized stress value (S) over time. Both dawn leaf water potential and available soil water were utilized to characterize the normalized stress value (S). The water deficit treatments were initiated on the same day and were not watered again until the plants in the lysimeter reached their target SD value. The imposed water deficits decreased the cotton lint and seed yields with the amount of yield reduction increasing with the level of water deficit. The cotton variety used in this study (Stoneville 825) is a nondeterminate variety and substantial regrowth occurred following the water deficit period. The amount of regrowth was directly related to the imposed SD; i.e. the lysimeters with the largest target value of SD had the most regrowth. CS values for the stress day index model were determined from the lint yields and found to be significantly different for the three water deficit treatments. This supports the statement made by Hiler and Clark (1971) that the value of CS depends on the degree and duration of the water deficit. CS* values from the stim ulus-response model were also evaluated using the dawn leaf water potential stress factor and the available soil water stress factor... |
|---|---|
| Item Description: | Typescript (photocopy). Vita. "Major subject: Agricultural Engineering." |
| Physical Description: | xvi, 187 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |