Water Sensitive Periods during the Reproductive Growth Phase of Glycine max L. II Establishing Water Stress Sensitivity

Abstract

The water sensitivity of soybeans was determined on a day‐to‐day basis from the onset of flowering to physiological maturity by correlating daily leaf water potential values of 50 different soil water regimes with corresponding grain, vegetative and biomass yields. Days, and consecutive days forming periods, during which significant negative correlations were obtained were regarded as water sensitive periods during the reproductive growth phase of the soybean crop. Water deficits during flowering significantly inhibited vegetative and biomass production but inhibited grain yields only when occurring during early flowering. During pod elongation and seed development the sensitivity of the soybean plant to water stress was present but diminished in time with regard to vegetative and biomass yields. The effect on grain yields was restricted to pod elongation and to later seed development stages. Water stress affected grain yields to a far greater extent than vegetative growth during seed filling and physiological maturity.

Predicting Crop Yields with the Agricultural Reference Index for Drought

“…(), and de Bruyn et al. () observed that the most sensitive stages of this crop to water deficit are peak flowering and pod set. Brown et al.…”

“…The greatest effect of water deficit on economic yields has been reported to have been during flowering or anthesis because of reduction in grain numbers (Howell 1990). For soybean, Salter and Goode (1967), Hiler and Clark (1971), Hiler et al (1974), Doorenbos and Kassam (1979), Kpoghomou et al (1990), andde Bruyn et al (1995) observed that the most sensitive stages of this crop to water deficit are peak flowering and pod set. Brown et al (1985) found this crop to be most susceptible to drought around 100 DAP, with both weight and number of seed reduced.…”

“…Some researchers have also observed that a mild water stress stimulates flower production in cotton (Cothren 1999). Water stress during the pre-flowering period of cotton, which falls in the second month of the season (Grimes and El-Zik 1990), increases the number of flowers and bolls per plant and boll size in some cultivars causing increased yield (de Bruyn 1964, Singh 1975. With the negative value of the sensitivity coefficient for the second month for cotton (À0.10), the cotton yield model was also able to reflect the phenomenon of mild water stress increasing the yields of this crop.…”