Patterns of Reproductive Abscission, Seed Yield, and Yield Components in Soybean1

Abstract

Field studies were conducted in 1981 and 1982 to determine patterns of flowering and reproductive abscission for nodes on the main stem of soybean [Glycine max (L.) Merr.] and to relate these patterns to seed yield components at nodes in various levels of the canopy. ‘Evans,’ an indeterminate, Maturity Group 0 cultivar was used. Individual flowers were tagged at anthesis and monitored through abscission or pod maturity. Date of anthesis and date of flower or pod abscission were recorded. Percent abscission was calculated on a per node basis. Number of mature pods, seeds/pod, and seed weight/pod were recorded for each main stem node. Data are reported as averages over nodes within four sections of the stem, each of which included approximately one‐fourth of the flowering nodes. Seed weight/node and seed weight/section were significantly greater in the middle two sections than in the top or bottom sections in both years. Pods at nodes in the middle two sections accounted for at least 75% of the main stem yield. Flowers produced per node generally varied only slightly among the sections, so percent abscission was the main determinant of pods/node. Pods/node varied as much as 300% among sections, whereas individual seed weight varied less than 35%. The primary cause of differences in number of pods/node and therefore in productivity of nodes in various stem sections was differential flower and pod abscission.