Com objetivo de verificar o efeito da variação da época de plantio no comportamento da planta de milho (Zea mays, L.) Foram avaliadas ao longo de 11 diferentes épocas de plantio em 1984/85 e de 14 épocas em 1986/87, 6 e 10 genótipos respectivamente, em Cascavel e Palotina, cidades localizadas no oeste do Paraná. As conclusões principais foram: as melhores épocas de plantio do milho situam-se no intervalo entre 15/9 e 15/10; existe a possibilidade de se estenderem as épocas d e plantio até o início de marco em Palotina e até o início de fevereiro em Cascavel; a variabilidade genética pode ser explorada para se obterem genótipos adaptados ao plantio em janeiro/fevereiro; a altura da planta o número de dias do plantio do florescimento feminino e a produção são grandemente influenciados pela época de plantio; os híbridos duplos foram proporcionalmente mais sensíveis as variações ambientais decorrentes das diferentes épocas de plantio; sub-divisões no conjunto de épocas permitem reduzir a magnitude da interação genótipos x épocas; a interação genótipos x épocas foi mais importante do que a interação genótipos x locais

Trying to check the effects of planting period variations in corn (Zea mays, L.), it was evaluated during eleven different periods in 1984/85 and fourteen periods in 1986/87, 6 and 10 genotypes respectively, in Cascavel and Palotina which are located in the west of the state of Paraná. The genotypes included double cross hybrids, intervarietal cross hybrids and open pollinated varieties and were obtained some data from the following caracteristics: Grain production, stand, plant height, erect plants % in harvest time and cycle (female flowering). The main conclusions were: The best time for corn (Zea mays, L.) planting in the west of the state of Paraná is between September, 15th and october, 15th; There is the possibility to extend the period for planting until the beginning of March in Palotina and until the beginning of February in Cascavel (late planting); The genetic variability can be explored to obtain varieties adapted to January/February planting (late planting); Plant height, days number from planting to flowering and production were affected by the planting period; The short corn plants (br-2) were those which had the best performance in erect plant %; The double cross hybrids were more sentive to the environment changes caused by the different planting periods. The periods group for planting sub-division reduces the greatness of genotypes × periods of planting interaction; The genotypes × periods of planting interactions were more important than genotypes × locations interactions