Effect of Drought Stress at Different Growth Stage on Yield and Root Characteristics of Soybean

In order to investigate the effects of drought stress on yield and root characteristics in soybean,pot-experiments were carried out in Shenyang,Liaodou18 was chosen as the tested variety,and 3 water supply levels were included in terms of soil water content controlled at vegetative stage(V2-R1),flowering and podding stage(R1-R5) and pod filling stage(R5-R7),respectively.The negative effect of soil drought(W1) at different stages on soybean yield showed in the order: R5-R7 R1-R5 V2-R1.Drought stress(W1) decreased soybean yield mainly through reducing pod number per plant,and mild drought(W2) caused lower yield decreasing than drought(W1).Both root length ratio and root surface area ratio were primarily fine root(root diameter,d =0-1.0 mm),accounting for 90% and 60%,respectively.Soybean root volume ratio was mainly thick root(d 4.5mm),accounting for more than 48% of total root volume.When water controlled at R1-R5 and R5-R7,the length and surface area allocation ratio of fine root(d = 0-1.0 mm) exceeded that of V2-R1.Soil drought reduced root length,root surface area and root volume allocation proportion of thick root(d 4.5 mm).The root biomass density increased with the advance of growthprocess,while drought stress reduced root biomass density.