Management of nitrogen fertilization on agronomic and nutritional characteristics in second crop corn

Fertilization management, mainly nitrogen, is one of the factors that most directly affect corn grain yield. Nitrogen dynamics in the soil is quite complex and its main source currently used in corn production, the urea, undergo intense losses in its conventional form, mainly by volatilization and leaching. Thus, the aim of this study was to assess the effect of forms, sources, and times of nitrogen application on the second crop corn. The experiment was conducted in 2016 in the Fundação Chapadão, Chapadão do Sul, MS, Brazil. The sources conventional urea, polymer-coated urea, and foliar N (8 treatments) were used as follows: control (without N addition), conventional urea (single in V3 and split in V3 and V6), polymer-coated urea (single in V3 and split in V3 and V6), conventional urea + foliar N (conventional urea in V6 and foliar in pre-flowering), polymer-coated urea + foliar N (polymer-coated urea in V6 and foliar in pre-flowering), and foliar N (split in V6 and pre-flowering). The variables stem diameter, ear index, ear length, number of grains per row, number of rows per ear, plant height, first ear height, leaf chlorophyll index, leaf N index, leaf values of Ca, Mg, Fe, Zn, Mn, and Cu, 100-grain weight, and grain yield were assessed. Nitrogen application in the form of conventional urea, polymer-coated urea, and foliar N (single or split) for second crop corn does not result in distinct benefits for the crop. Thus, attention should be paid to the commercialization of the product, which has prices established according to nitrogen forms, but without result, for example, in grain yield, which in fact will compose the producer income. The applied nitrogen form and mode of application were positive only to increase the contents of Ca, Mg, Zn, and Mn in the leaves of second crop corn. Ca was favored by the use of conventional urea and split conventional urea, Mg and Mn were only benefited by foliar N application, and Zn was benefited by the use of conventional urea, split conventional urea, conventional urea + foliar N, and polymer-coated urea+foliar N.