Influence of Defoliation and Depodding on Quality of Soybeans

Abstract

The influence of 4 levels of depodding at 4 levels of defoliation on quality of soybeans was evaluated at each of 5 stages of plant growth by measuring seed size, number of pods per plant at harvest, oil content, protein content, and seed germination. The overall trend was for defoliation to decrease and depodding to increase seed size. Significant regression equations were developed expressing seed size as a function of defoliation and depodding. An increase in defoliation during growth stages R6, R7, and R8 decreased number of pods per plant at harvest, but defoliation at R9 and R10 did not significantly affect number of pods. Depodding at R6 did not affect the number of pods at harvest because plants were able to compensate, but thereafter, depodding significantly reduced the number of pods per plant. A highly significant multiple correlation coefficient was obtained between yield, seed size, and number of pods per plant. In general, depodding at all growth stages decreased oil content; defoliation had no significant effect except with complete depodding during R6 to R9. Defoliation at any growth stage did not affect protein content by more than 6%; in contrast, depodding at all growth stages increased protein. The correlation was strong between oil and protein content and was independent of growth stage. The main effect of defoliation on germination was that complete defoliation significantly reduced germination at growth stages R7 and R8. Depodding significantly affected germination only at growth stages R8 and R9.