Path analyses of population density effects on short-season soybean yield

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 contributioms of population density fur 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 held 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 if 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) acid 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).