Influence of Simulated Early Lodging upon Soybean Seed Yield and its Components
1977
Woods, S. J. | Swearingin, M. L.
Early lodging of soybeans [Glycine max (L.) Merr.] in highly productive environments has been observed throughout the midwestern United States. It has been established that soybean seed yields are decreased when severe lodging occurs sometime prior to physiological maturity. The objective of this 2-year field study was to examine the effect of plant growth stage at the time of lodging on soybean seed yield and its primary components; pods per plant, seeds per pod, and seed size. The study was conducted at Tipton, Ind., in 1972 on a Crosby silt loam soil (member of the fine mixed mesic family of Aeric Ochraqualfs) and at Lafayette, Ind., in 1973 on a Chalmers silty clay loam soil (member of the fine loamy mixed mesic family of Typic Haplaquolls.) Two Group II soybean cultivars (‘Wells’ and ‘Corsoy’), representing distinct degrees of lodging resistance, were subjected to a simulated lodging treatment at 2-week intervals in the early reproductive growth stages. Controls were: a) plants supported by a 10 ✕ 10 cm plastic grid system, and b) no treatment or support which permited natural lodging to occur. Depending upon the time of simulated lodging, seed yields of both cultivars were reduced from 11 to 32% in 1972 and from 12 to 22% in 1973. The reproductive growth stage, R5, normally reached during the first 2 weeks of August in central Indiana, was found to be the most critical time for lodging to occur. Neither seeds per pod nor seed size was significantly reduced when lodging occurred at stage R5. The reduction in yield was due almost entirely to a reduced number of pods per plant, especially those on the central stem. When lodging occurred after flowering had commenced apical dominance was lost, resulting in lateral branches assuming central stem characteristics.
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