Sowing date changes phenological development, plastochron index, and grain yield of soybeans under Cerrado conditions1

The sowing date is a crop management practice that affects soybean development and grain yield, and is directly related to the genotype and cycle type. Our objective was to evaluate phenological development as a function of photoperiodic responses, plastrochron index, and grain yield in three soybean cultivars with different growth cycles sown on three sowing dates. The study was conducted in Selvíria, Mato Grosso do Sul State, Brazil, using a split-plot design with the main plots arranged in blocks with four replications. The main plots included three sowing dates, 15 days apart, beginning on November 15, and the subplots were composed of three cultivars: BMX Turbo RR (extra-early cycle), BMX Potência RR (early cycle), and TMG 1180 RR (medium cycle). Delayed sowing increased the plastochron index and reduced the growth cycle duration, plant height, node number of the main stem, and pod number per plant. We found that cultivars with longer cycles were more suitable for delayed sowing, had improved vegetative and reproductive development, and had higher grain yields than those with shorter periods. The second sowing date was most suitable for soybean cultivation in this region.