Effects of Single and Sequential Defoliations on Yield and Quality of Soybeans

A single defoliation of soybean plants at threshold levels for 5 growth stages (R3-40%, R4-19%,. R5-6%, R6-6%, R7-20%) did not significantly affect yield, seed size, or percent germination. Sequential defoliations at the same threshold values initiated at each of the same 5 growth stages significantly affected yield only at those defoliations intitiated at growth stage R3. Then, only the 2 heaviest defoliations caused significant yield reductions (R3-40% + R4-19% + R5-6% + R6-6% and R3-40% + R4-19% + R5-6% + R6-6% + R7-20%). Few of the sequential defoliations initiated at any of the 5 growth stages caused significant effects on seed size, % germination, % oil, % protein, and number of pods per plant at harvest.