RESUMO:Populações de milho (Zea mays L.) com características desejáveis e eficientes quanto ao uso de nutrientes são promissoras para uso em agricultura de baixo nível tecnológico. Assim, o presente trabalho foi realizado com o objetivo de estudar a variabilidade genética e identificar populações eficientes quanto ao uso do nitrogênio (N), visando à produção de óleo nos grãos. Neste sentido, foram realizados quatro ensaios de competição de populações de milho em Palmas, Tocantins, sendo dois ensaios na safra e dois na entressafra, sob condições de alto (150 kg ha -1 de N) e baixo N (0 kg ha -1 de N) em cobertura. O delineamento experimental utilizado em cada ensaio foi de blocos casualizados com três repetições e dez tratamentos. Foi determinada a eficiência do uso de N por meio da metodologia de Fischer e a divergência genética pelo método de agrupamento de otimização de Tocher, para o teor de óleo nos grãos. No estudo da divergência genética, cada ensaio representou uma variável distinta no modelo multivariado. Os ensaios de safra e entressafra, independentemente das doses de N, foram similares para o teor de óleo nos grãos. As populações POP 12 e POP 13 são potencialmente promissoras para produção de óleo e eficientes no uso do N.

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O presente trabalho foi realizado com o objetivo de identificar genótipos de milho, em cultivo sob alto e baixo nível tecnológico, para produção de óleo, em Palmas-TO. Os genótipos UFT 7, ORION, UFT 1, P29-M5 e P37-3 são recomendados para produtores que adotam baixo nível tecnológico. Os genótipos de milho P36-19, BR 205, AL BANDEIRANTE, AG 1051 e P28-2B, são indicados para produtores que utilizam alto nível tecnológico.

The genetic variability allows selection of superior genotypes and makes it possible to increase the frequency of favorable genes through appropriate selection methods that provide genetic mater ial's retrieval adapted to environmental conditions prevalent in the different producing regions. Thus, this work was performed with the goal of studying the genetic divergence of populations of open pollination of corn in the South of Pará State. To this end, two tests were made of corn genotypes competition, being the first to top P (100 kg ha-1 of P) and the second for low P (50 kg ha-1 of P). The study of genetic divergence was performed using together with the data from the two trials. The experimental design used in each trial was randomized with ten treatments (open-pollinated maize genotypes) and three repetitions. The characteristics studied were: plant Height, Ear height, the diameter of the Spike, Spike length, grain in the row numbers and productivity. In the study of genetic divergence was employed the Tocher optimization method. The importance of characters, was the Foundation of Singh. Three medium-sized groups were formed, which were in the same genotypes 08 groups, and two other genotypes (AG 1051 and AL BANDEIRANTE.), were in different groups. The characters presented more collaboration for the genetic divergence were productivity, plant height and ear height.

Aims: The research was carried out to evaluate the agronomic performance of corn cultivars in contrasting phosphorus environments in the state of Pará, Brazil. Study Design: The experimental design was randomized blocks with ten treatments and three replications. The treatments were composed of ten cultivars: AG 1051, AG 8088PRO2, BR 206, BRS 3046, PR 27D28, 2B655PW, AL BANDEIRANTE, ANHEMBI, CATIVERDE 02 and ORION Place and Duration of Study: In the 2017/18 crop, two competition trials of corn cultivars were carried out at Sítio Vitória, municipality of Santa Maria das Barreiras, state Pará, Brazil. Methodology: Two competition trials of corn (Zea mays L.) cultivars were carried out under contracting conditions of phosphorus: high P (100 kg ha-1 of P2O5) and low P (50 kg ha-1 of P2O5), using simple superphosphate (18% P2O5) as the source. The agronomic efficiency of phosphorus use was obtained by the difference between grain yield in both levels, divided by the difference between doses. The variables evaluated were: ear height, plant height, ear diameter, number of rows per year, number of grains per rows and grain yield. Results: The mean grain yield of the cultivars ranged from 5,446 kg ha-1 (low P) to 11,486 kg ha-1 (high P), and the means of all cultivars were higher in high P. The means agronomic efficiency ranged from 25.1 kg kg-1 (AL BANDEIRANTE) to 96.6 kg kg-1 (AG 1051). Conclusion: The highest phosphorus dose (100 kg ha-1 of P2O5) resulted in higher values in the variables studied. The cultivars that stood out the most, under high and low phosphorus, were AG 8088PRO2, AG 1051 and BRS 3046, the last two being agronomically efficient.