Densidade de semeadura e níveis de nitrogênio no rendimento e sanidade de milho safrinha em Dois Vizinhos - Paraná

Abstract

Brazilian corn crop is grown along spring-summer and autumn-winter seasons. Nowadays, the prohibition of soybean cultivation as a second summer crop associated with good prices of these commodities (season 2015/2016), has stimulated corn growth at the 2nd summer crop at southwestern Paraná. However, it is known that there are a number of factors that can affect corn production, such as seeding rate and fertilization levels, factors able to be managed by the farmer and therefore dependent of studies to assess the best arrangement between these factors. In this context, this study evaluated corn plants grown in off-season, as plant architecture and yield components, conducted under four plant densities (45, 55, 65, and 75 thousand seed ha-1) and four nitrogen levels (0, 50, 100 and 150 kg N ha-1) applied in sidedress. Corn stem diameter, ear height and plant height increased as nitrogen rates increased, although, there was no significant effect on yield. Regarding to the seeding rate, its increase reduced the basal stem diameter, number of ears per plant, number of kernels per row, yield per plant, weight of thousand grain and increased the percentage of small ears, lodging and plants without ears, however, the greatest initial and final stand of plants resulted in a higher number of ears per area and yield per hectare. It was noticed that the longer the duration of exposure in the field, the higher the values of sprouted grains, presence of fungi in grains and cob. The percentage of plant losses, plants with more than one spike and number of rows per ear showed no statistical differences. Corn grown as a second summer crop at Dois Vizinhos – PR shows good yield potential, but with high contamination of fungi from genera Aspergillus spp., Fusarium spp, e Penicillium spp.