Water Deficit Effects on Water Potential, Yield, and Water Use of Cowpeas1
- Peter Shouse,
- Samuel Dasberg,
- W. A. Jury and
- L. H. Stolzy2
Previous studies report conflicting results regarding the sensitivity of cowpeas to growth stage water deficits. Our 2-year field study was designed to monitor the effects of water deficit imposed at three growth stages on the yield and water use of cowpeas (Vigna ungiculata (L.) Walp.). Six irrigation treatments were used to impose the water deficit including a well watered control treatment (WWW) and five deficit treatments (DWW, WDW, WWD, DWD, WDD). Cowpeas were grown on a sandy loam soil (coarse-loamy, mixed thermic Haplic Durixeralf) on the experimental farm in Riverside, California.
The pre-dawn leaf water potential, as measured by the pressure bomb technique, was a better indicator of crop water stress than was the midday leaf water potential. The pre-dawn leaf water potential at any growth stage progressively decreased with time following cessation of irrigation, but completely recovered after soil water storage was recharged by irrigation or rain.
The most sensitive growth stages to drought were flowering and podfilling, with yield reduction from 35 to 69% depending on the timing and length of the drought treatment. A soil water deficit during the vegetative stage had the least effect on crop yield. This, coupled with decreased evaporation, resulted in a water-use efficiency which was greater than that of the control treatment, which was adequately watered throughout the season. The water-use efficiencies of the other stage deficit treatments were decreased below that of the control because of large decreases in crop yield.
Seed yield of cowpeas was found to be linearly related to an integrated water stress indicator based on the predawn measurement of leaf water potential.
We found that the relative dry matter yield was linearly related to crop transpiration as determined by the difference between a water balance measurement of ET and modeled evaporation (T = ET meas. - Emodeled).Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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