The effects of planting date and row spacing on determinate and indeterminate soybean sister lines

Stephen Lee Robinson, Purdue University

Abstract

Planting date and row spacing frequently affect determinate ($dt\sb1$ $dt\sb1$) and indeterminate ($Dt\sb1$ $Dt\sb1$) soybean strains differently. The objective of this study was to determine if the $Dt\sb1$ and $dt\sb1$ genes in closely related genetic backgrounds responded similarly to planting date and row spacing. Thirty-eight determinate lines and their corresponding indeterminate sister lines were randomly selected from six populations. These lines were planted with two determinate and two indeterminate check cultivars in a split-split plot design at West Lafayette, Indiana. Days to flowering, maturity, reproductive period, plant height, lodging, seed size and seed yield were measured in 1985 and 1986. Determinate lines flowered earlier, matured earlier, had longer reproductive periods, were shorter, lodged less, had larger seed, and yielded less than their indeterminate sister lines. Simple correlations indicated that, except for yield, the determinate lines performed in a similar manner to their indeterminate sister lines. Early planted lines required a greater number of days to flower, matured earlier, had a longer reproductive period, were taller, lodged more, and yielded more than late planted lines. Seed size was not significantly different between early and late planting dates. Planting date x growth type interactions were highly significant for all characters studied. Growth type had a greater effect on plant height, lodging, seed size and yield than did planting date, while planting date had a greater effect on days to R1, maturity, and length of the reproductive period than did growth type. Lines planted in narrow rows were taller, lodged more, yielded more, and had smaller seed than did lines planted in wide rows. Row spacing x growth type interactions were significant for days to first flower, lodging, and seed size. The lack of a significant row spacing x growth type interaction for yield indicated that both determinate and indeterminate lines produced higher seed yields at the narrow than at the wide row spacings.

Degree

Ph.D.

Advisors

Wilcox, Purdue University.

Subject Area

Agronomy

COinS