Response of Soybeans to Overseeding Followed by Plant Thinning at Various Growth Stages
1977
Boerma, H. R.
Accurate field plot technique is an important factor in soybean [Glycine max (L.) Merr.] experimentation. The practice of overseeding followed by plant thinning has become a common practice for many experiments involving the estimation of physiological parameters, and for some experiments designed to measure seed yield. In most cases the results of these experiments are extended to the general field situation. The purpose of the present study was to determine the growth stage at which thinning of overseeded plots must be accomplished to provide similar results to direct seeding at the desired population rate. Three soybean cultivars, in maturity groups VI, VII, and VIII, were overseeded at 53 viable seeds/m in rows spaced 0.96 m apart and different plots were thinned to 23 plants /m for 8 consecutive weeks following emergence. The experiment also included a control which was seeded at 26 viable seeds/m and obtained a plant population of 23 plants/m. The results indicated that the week of thinning had a significant effect on seed yield, nodes/ plant, and branches/plant. Seed yield and nodes/plant decreased at thinnings after the V4 growth stage (2 weeks after emergence) and branches/plant at thinnings at the V5 growth stage (3 weeks after emergence). The cultivar × thinning week interaction across years was nonsignificant for all characteristics. There was a significant year × week of thinning interaction for plant height at maturity and lodging. To obtain the same seed yield and general plant characteristics expected from seeding at the desired population rate, overseeded plots should be thinned prior to the V5 growth stage.
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