Response at different growth stages of soybean to deficit irrigation condition

Abstract

An attempt was made to assess the effect of deficit irrigation on yield components at individual growth stages of soybean [Glycine max (L.) Merrill]. The deficit irrigation treatments were 0 - 25, 25 - 50, 50 - 75 and 75 - 100% of total available water (TAW). Evapotranspiration was dominated in order by: Flowering > pod formation > development > maturity stage. Water stress coefficient (K_s) or ETa/ETm at Flowering and Pod formation stages were too strong to be tolerated due to the effect of high evapotranspiraton rates. Both water use efficiency (WUE) and yield efficiency (YE) was also very sensitive under water stress conditions at flowering and pod formation stages. Available water deficit level lower than 50 - 75 % (D₃) throughout the different growth stages of soybean was good enough for calculating the yield response factor (K_y = 0.87), and both WUE and YE was higher at 50 - 75 % of TAW (D3) than the full irrigation (D₁). It may be concluded that deficit irrigation was effective (K_y < 1) for economy of water usage under water deficit lower than 50 - 75 % of TAW (D₃). It reveals from the results that to get a good yield of soybean under limited supply of irrigation water it is better to avoid moisture stress at the reproductive stage (flowering and pod formation) of the crop.

Bangladesh J. Sci. Res. 27(2): 165-174, December-2014