Sowing date is one of the most important factors affecting soybean yielding potential. The main aim of this research work was to evaluate the effects of delayed sowings on soybean (Glycine max (L.) Merril) cultivar agronomic traits and seed yields. Experimental trials were carried out during the 1998/1999 and 1999/2000 growing seasons, using three sowing dates (November 15th, January 15th; and February 15th) and five soybean cultivars with different seed maturation periods (BRS-132: very early; BRS-133: early; BR-16: early; BRS-134: intermediate and FT-Estrela: late). A randomized complete block design, with three replications, was set up for each sowing date, the November sowing date considered as the reference. The following agronomic traits were scored: number of days from sowing to seedling emergence, full blooming and seed maturation; first pod insertion height; plant height and degree of laid-down plants as well as the seed parameters overall seed yields, number of pods per plant and mass of thousand seeds. The strong seed yield reductions in delayed sowings for all soybean cultivars (not talking into their flowering and/or seed maturation periods), in both growing seasons, regardless the seed maturation periods of soybean cultivars, as compared to the usual growing season (November), as well as other agronomic traits, clearly indicate the unfeasibility of delayed sowings at the region of Maringá, Paraná State, Brazil.
soybean; seeds; sowing date; yield
