Brachytic Stem Trait, Row Spacing, and Plant Population Effects on Soybean Yield

Abstract

Brachytic stem (sb1sb1sb2sb2) of soybean [Glycine max (L.) Merr.] is characterized by shortened internodes, resulting in shorter, sturdier plants than normal stem types. Although studies have shown yield of brachytics to be less than normal types, this trait may have potential for higher yield in some environments. Little information is available on response of brachytics to planting pattern, particularly for duration of development stages or yield components. A field study was conducted to determine brachytic trait effects on yield, agronomic traits and yield components of four near‐isoline pairs, each consisting of one normal and one brachytic near‐isoline tested at plant populations of 51 and 26 plants m−2 and row spacings of 76 and 28 cm in four environments. Soil types were a Cahaba fine sandy loam (fine‐loamy, siliceous, thermic Typic Hapludults) and a Norfolk fine sandy loam (fine‐loamy, siliceous, thermic Typic Kandiudults). Normal types yielded more and responded to narrow rows; brachytics did not. Row spacing and plant population did not affect most other traits. Brachytics flowered later and had shorter reproductive period than normal types. Brachytic soybean produced more branch and mainstem nodes and greater seed mass and harvest index than normal types, but this was not enough to effect yield advantages over normal soybean. We concluded that plant growth and yield performance of the brachytic trait is influenced more by genetic background than other factors; however, under suitable conditions, brachytic soybean's production of larger seeds and more nodes indicates its potential for higher yields.