Eighteen soybean genotypes, six each from Maturity Groups (MG) V, VI, and VII were planted in four-row (6 m long and 0.9 m wide) experimental plots in a randomized complete block, with four replications, under field conditions using standard cultural practices. The objective was to determine seed yield efficiency (SYE), phytomass accumulation and leaf area index (LAI) development and other physiological and morphological traits and their relationships to yield. Significant differences were found in most of the parameters studied.