Fractional Integrated Stomatal Opening to Control Water Stress in the Field
1991
Fiscus, Edwin L. | Mahbub-Ul Alam, A. N. M. | Hirasawa, Tadashi
The usefulness of totally automated irrigation control systems is well established. Mass-flow porometers can be used as the sensing and feedback elements to implement such a system for the experimental control of water stress in the field. This study was conducted to determine if consistent relationships could be established between the mass-flow readings and other water-related physiological parameters. A range of stress conditions were imposed on plots of corn (Zea mays L.) by the system during the 1986 and 1987 field seasons in Greeley, CO. Midday leaf xylem water potential, leaf diffusive conductance, and year-end grain yields were measure during both years. In 1987, additional measurements were made of the infrared canopy temperature for calculating the Crop Water Stress Index (CWSI), and individual kernel weights and numbers, to determine the components of the grain yield predictions observed in 1986. Reductions in the number of kernels produced per unit land area were associated with stress-induced delays of silking relative to pollen shed. Additional yield reductions in some treatments were attributable to reduced weight per kernel. Significant correlations were found between the mass-flow sensors and grain yield and CWSI. The relationship between grain yield and stomatal conductance was consistent over both years, suggesting that the cumulative mean conductance may be useful as a yield predictor. Contribution of USDA-ARS, Great Plains Systems Res. 1701 Center Ave., Fort Collins, CO 80526.
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