Effect of plant density on soybean cultivars in two planting dates

Abstract

The objective of the present research was to study the effects of plant density and planting date on the behavior of three soybean cultivars. Four experiments were carried out under field conditions, on a Ultisol (Terra Roxa Estruturada), in Botucatu, São Paulo State, Brazil; two experiments were planted in November (11.23.82 and 11.23.83) and two in December (12.13.82 and 12.15.83). Three plant densities were studied: ten, 20 and 30 plants/m, in a row spacing of 0.6 m. The cultivars employed were 'IAC-Foscarin-31' (early maturity), 'IAC-8' (medium maturity) and 'IAC-9' (semi-late maturity). The plant density did not affect the duration of the development stages of plants but they were affected by planting date. In the lowest plant density were obtained the lowest plant height (in November sowing), the highest stem diameter, the highest pod number, the highest dry matter weight and the highest seed yield. The seed yield (kg/ha) of the experiments sowed in November was not affected by plant density, but in one experiment sowed in December, 'IAC-Foscarin-31' presented the lowest yield in the lowest plant density; in the other, 'IAC-9' presented the lowest yield in the highest plant density. 'IAC-Foscarin-31' showed a different behavior when compared to 'IAC-8' and 'IAC-9'.