Sensitivity of Southern Peas to Plant Water Deficit at Three Growth Stages1

Abstract

AbstractResponse of southern peas (Vigna sinensis L. Endl. var. Burgundy) to different levels of water deficit at three different stages of growth was measured in a greenhouse. In each stage, plants were stressed to three levels of leaf water potential: — 14 bars, — 21 bars, and —28 bars. Crop susceptibility factors (fractional reductions in yield compared to a nonstressed treatment) were determined for each stage of growth and level of plant water deficit. The flowering period was found to be the most sensitive stage, regardless of deficit level. The pod development stage was found to be least sensitive to level of deficit. A water deficit of — 28 bars, however, caused a yield reduction of greater than 50% for all growth stages. Stress‐day index values were calculated and related to crop yield. The use of the stress‐day index concept in irrigation scheduling is discussed. Leaf water potential varied linearly with soil water potential between 0 and — 15 bars. Leaf diffusion resistance became high and transpiration was negligible after the leaf water potential reached — 10 to — 12 bars; the corresponding soil water potential was — 5 bars. Water‐use efficiencies were highest for the nonstressed treatment and the treatment with the low deficit level during the first stage.