Path Analyses of Population Density Effects on Short‐Season Soybean Yield

Abstract

Yield component analysis provides a framework for identifying potentially useful traits for yield improvement. Consideration of how population density affects other yield components has not been addressed specifically for short‐season soybean [Glycine max (L.) Merr.] production. We assessed the direct and indirect contributions of population density for short‐season soybean yield and its components over a wide range of population densities (6–134 plants m−2) using path‐coefficient analysis. Data were from field tests conducted in 1997, 1998, and 1999 at Keiser, AR. Although population density had a large inverse association with pods plant−1, the large direct effect of population density on yield was greater than its negative indirect effect via pods plant−1. The direct effects of pod number plant−1 and seeds pod−1 on yield were positive, whereas mass seed−1 had a negligible effect. Pods fertile‐node−1 differed between cultivars, and it was reduced by increasing population density. For early sowing, the contribution of population density to yield was less because pods m−2 could be achieved at low population densities by a large number of fertile‐nodes plant−1 and pods fertile‐node−1. In contrast, at late sowing, the decreased potential for fertile‐nodes plant−1 was compensated by increasing plant population density. In short seasons, maximizing nodes m−2 and pods m−2 can be achieved by high population densities and early canopy closure, rather than the conventional system of larger plants with greater numbers of pods plant−1 and pods fertile‐node−1