Growth and Yield Recovery of Soybean Following near-Plant Competition Removal at Different Growth Stages.

Soybean seeding rates have become a familiar topic in response to an increase in seed prices.   In order to maximize yield in Illinois, 247,000 harvested plants hectare^-1 are typically considered necessary.  Soybeans have a remarkable ability to regulate yield components in relation to population or competition.  Research was conducted in Illinois to examine yield variability, and yield compensation by population and intra-specific competition.  Two soybean cultivars (AG 3205, AG 3803) were compared at four initial seeding rates of 150,000; 300,000; 445,000; and 600,000 seeds hectare^-1.  Plants were either relieved of competition at four growth stages (V3; V6; R2; R4) to 52,000 plants hectare^-1, while similar sized cohorts remained in competition.  Plant heights, growth stages, and node counts were recorded at each growth stage for both the groups relieved of competition, and the group remaining in competition.  At maturity, yield components (pod count, seed count, seed mass) data were collected and analyzed.  Plants recovered by increasing total seed yield plant^-1 for all timings and initial population densities when densities were thinned (intra-specific competition reduced). Earlier timings compensated by increasing pods and seeds plant^-1 while seed mass contributed to yield compensation when plants were removed at R4.