Respostas morfológicas e fisiológicas de cultivares de azevém a diferentes épocas de adubação nitrogenada para produção e qualidade de sementes

Abstract

Later fertilization can result in fewer vegetative tillers, but it can also result in better quality reproductive tillers. The objective of this study was to evaluate the effect of the season of nitrogen fertilization in cover, control (without application of N), vegetative (application of 60 kg/ha of N in the vegetative phase), differentiation (application of 60 kg/ha of N in the differentiation phase of the floral primordium - when there was intense elongation of internodes) and flowering (application of 60 kg/ha of N in the flowering phase - complete emission of the ear) in the production and quality of annual ryegrass seeds (Lolium multiflorum Lam. ) of the cultivars BRS Estações and BRS Integração. Structural and morphogenic characteristics were evaluated, such as number of senescent leaves, number of live leaves, number of expanding and fully expanded leaves, number of tillers, senescence (cm), plant height (cm), length of pseudo-stem (cm) , tillers length (cm), leaf length (cm), ear length (cm), number of spikelets per ear, number of flowers per spike, among others. In early spring, a single uniform cut was made. The plants were, on average, 51 cm and were lowered to 10 cm. Nitrogen fertilizations in cover performed during the reproductive period (floral differentiation and flowering) determine higher yield and high quality of seeds. The cultivar BRS Integração presented similar responses in terms of physiological quality of the seeds with fertilization carried out both in the period of floral differentiation and in the flowering period. However, the cultivar BRS Estações presented the best responses of physiological quality of the seed when fertilized during the flowering season. Nitrogen fertilization during the growing season resulted in greater losses of seed yield per crop and less investment in 3rd generation and aerial tillers. When nitrogen fertilization was performed during the reproductive period (floral differentiation and flowering), 3rd generation and aerial tillers produced seeds with high physiological quality.