Intergenotypic Competition between Late-Planted Determinate and Indeterminate Soybean
- J. D. Sutton and
- D. B. Weaver
Studies of several crop plants including soybean, Glycine max (L.) Merr., have indicated a seed-yield advantage for certain genotype mixtures over the weighted mean of the component genotypes grown in pure stand. This 2-yr field study was designed to evaluate the performance of late-planted soybean mixtures consisting of determinate (‘Braxton’, ‘Foster’, and ‘Gordon’)/indeterminate (G84- 9010, G84-9043, and G82-8611) genotype combinations, and to examine the nature of competition between the two growth-habit types. Soybean genotypes differing in plant height and relative maturity were chosen to comprise the determinate/indeterminate genotype combinations. The two-component mixtures were planted at Tallas-see, AL in alternating 0.61-m rows and in seed ratios of 0:1, 1:3, 1:1, 3:1, and 1:0. No significant differences in mean seed yield were observed among mixtures and pure stands. A significant quadratic regression component was observed in yield of all genotypic combinations that included G84-9010 and G84-9043, each indicating undercompensation (yield less than the weighted mean of the components grown in pure stand). Combinations involving G82-8611 had no significant regression components, and were the most diverse in both height and maturity. Lack of overcompensation effects may have been related to a small range in diversity of days to maturity between the genotypes comprising each mixture (2-7 d) as well as the general competitive ability of each genotype. Soybean planted in alternating rows tended to yield higher than 1:1 mixtures. We concluded that the nature of competition between determinate/indeterminate genotype pairs when planted late is dependent on the competitive ability of the genotypes in the pair, and is likely to be undercompensatory.
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