QUANTITATIVE DESCRIPTION OF PLANT DENSITY EFFECTS ON BRANCHING AND LIGHT INTERCEPTION IN SOYBEAN

Abstract

The objective of this study was to quantify the effects of plant population density (PPD) on branching, light interception, and vegetative stages of soybean (Glycine max L.). A field study was conducted in Maryland, USA on a Beltsville silt loam soil (Fine-loamy mixed mesic Typic Fragiudult). The planting dates were 20 July 1992 and 14 June 1993. There were 10 plant densities that varied from 10 to 59 plants m^<-2>. Significant differences in plant heights among the different plant population densities were found in 1993 but not in 1992. The vegetative stage progression rates and number of branches were significantly related to PPD in both years. The internodal lengths increased with increase in PPD. Fewer branches were produced in 1992 than in 1993 at the lower PPD\u27s and the number of branches were similar at the highest PPD\u27s. The low PPD plants in 1992 did not have time to grow large enough canopy to capture all available light. We fit a logistic equation to the change in branch number with time. The maximum number of branches per plant as a function of PPD was described by a gaussian type equation. The fitted parameters and equations described the addition of branches