Adaptability and stability of soybean cultivars in five planting dates in the Rondonian Cerrado, Brazil

The objetive of this study was to evaluate the stability and adaptability o f soybean (Glycine mar (L.) Merrill) cultivars in five different planting d ates. The tests were composed by 21 cultivars outlined in a random blocks d esign, with three replicates, conduced in 1996/97 by Embrapa-Centro de Pesq uisa Agroflorestal de Rondonia, in a field of Vilhena, RO, Brazil. The used methods showed accordance between the achieved results, being the behavior of cultivars in different times of sowing represented by a linear model. T he coefficient of linear regression beta (11) did not show any significant difference of the unit by the t test for all the tested cultivars (P<0.05). The cultivars which presented significant regression deviation <sigma>(2)( d(i)) (P<0.05) were MT/BR-50 e EMBRAPA 31, R-2 = 58.56% e 74.43%, respectiv ely. The other cultivars did not present any significant regression deviati on.