Soybean Yield and Yield Components in Two Planting Patterns

Soybean [Glycine max (L.) Merr.] plant density for maximum yield in Japan is usually from 16 to 25 plants m−2. The objective of this study was to compare yield and yield components, especially node number between square- and zigzag- (an equilateral triangle-planting pattern or plants in the row offset from each other) planting patterns within a range of plant populations (16, 20 and 25 plants m−2). Field experiments with cultivar Enrei (Maturity Group VII) were conducted in the field at Niigata University on a loamy sand soil in 1991, 1992 and 1993. Yield increased as density decreased in 1991 and as density increased in 1992 and 1993. This result seemed to be due to adverse weather conditions during seed filling in 1991. Yield tended to be higher in zigzag- than in square-planting patterns except at 20 plants m−2. Seed number m−2 due to increased yield was highly correlated with branch node number. The yield increase was caused by an increase in total node number, especially branch node number m−2 (about 60 % contribution at 16 plants m−2 and about 40 % contribution at 25 plants m−2).