-Soybean is cultivated in the wide range of environments of Paraná State. Selection for genotypes of high and predictable yields with wide adaptability are main targets of the breeding programs for this region. The adaptability and stability of 30 soybean cultivars of three different maturity groups (early, semi-early and medium maturity) with a focus on grain yield were evaluated in the

ResumoNum experimento de campo em Cambe, PR (23º16'45" S, 51º16'45" W e 650 m) com o cultivar de soja BRS 133, foram aplicados 20 tratamentos em parcelas sub-sub-divididas, com quatro repetições em delineamento de blocos casualizados. Os tratamentos foram combinados, potássio no momento da calagem -CALPOT (0,0 e 2,35 t.ha ). The basic cation equilibrium in the soil helped to maximize this effect.