Soybean Yields as Influenced by Timing of ET Deficits

Abstract

ABSTRACT Seed yield responses for three soybean cultivars (maturity group 00, 0 and 1) were determined when ET deficits were imposed as moderate or severe (based on root zone water depletion and/or levels of leaf water potential in mid-afternoon) stress periods in the pre-bloom (before Rl), bloom to full seed (R1-R6) and after full seed stages (after R6). Seed yields were related to seasonal ET, relative seasonal ET, root zone available water at time of stress relief and minimum leaf water potentials at time of stress relief. Maximum yields were obtained when remaining available root zone water levels were maintained above 45-50%. Threshold leaf water potential at which seed yield began to decline was about 1.20 MPa. Seed yield production functions were linear with slopes ranging from 1.20 to 1.37 kg/m^. Slopes for relative yield vs relative ET functions ranged from 1.44 to 1.50.