Light Interception Accrual in Soybean as Affected by Seeding Rate and Latitude.

With the increasing cost of soybean [Glycine max (L.) Merr.] seed, sowing the minimum plant population that results in optimal yield is critical for maximizing producer’s profits.   The objective of this research was to develop a model for predicting the optimum planting density for any given latitude in the USA.  To accomplish this objective, collaborators in six states (MN, IA, MI, AR, KY, LA) covering latitudes from ~30° to ~48° initiated a three year experiment in 2009 to evaluate six soybean population densities from 61,750 to 679,250 plants per hectare.  At all locations fraction of light intercepted was measured weekly from V1 through R6.  In addition, biomass accumulation will be determined at the R5 stage of growth and grain yield will be measured at harvest maturity.  In this paper we report how population density affects the amount of cumulative light intercepted and R5 biomass yield across multiple latitudes.