Parcelamento e largura da faixa de aplicação da uréia na recuperação do nitrogênio pela planta de milho Splitting and width of strip urea applications and the recovery of nitrogen by maize plants

Com o objetivo de estudar o parcelamento e a largura da faixa de aplicação como meios para aumentar a recuperação pelo milho do nitrogênio da uréia aplicada em superfície, foi conduzido no ano agrícola 93/94, em um Latossolo Vermelho Escuro, em condições de campo, um experimento delineado em blocos ao acaso, com cinco repetições. Sete tratamentos foram utilizados: testemunha (sem N em cobertura); aplicação de N parcelada (50 kg ha-1 de N aos 38 dias após semeadura - d.a.s e 50 kg ha-1 de N aos 60 d.a.s.) para faixas de 10, 20 e 40 cm; aplicação de N (100 kg ha-1 de N aos 38 d.a.s.) para faixas de 10 e 40 cm e, aplicação de N parcelada (50 kg de N/ha aos 38 d.a.s. e 50 kg ha-1 de N aos 60 d.a.s.) para faixa de 20 cm de largura, neste caso, uréia granulada. A aplicação de uréia parcelada em cobertura, em faixas de 10, 20 e 40 cm de largura, não afetaram a massa de matéria seca, o conteúdo, a quantidade e a recuperação do N pela planta de milho. A recuperação de N pela planta de milho foi maior para a aplicação de 220 kg ha-1 de uréia em uma única aplicação em faixas de 10cm de largura em relação a de 40 cm. O parcelamento da uréia aumentou os valores de massa seca, conteúdo, quantidade e recuperação do N na planta de milho em relação a aplicação em uma única vez.<br>In order to evaluate the nitrogen recovery by maize, following a surface application of urea, a trial was carried out during 1993/94 under field conditions, on a dark red latosol (oxisol). A randomized complete block statistical design was used, with seven treatments and five replications. The seven treatments were: control (no N); three split N applications (50 kg N ha-1 urea at 38 and 60 days after sowing) using 10, 20 or 40 cm width strips; two single N applications (100 kg N ha-1 urea at 38 days after sowing) using 10 or 40 cm width strips; and split N applications (50 kg N ha-1 urea at 38 and 60 days after sowing) using a 20 cm width strip (granular urea). The top dressing that was applied at two growth stages in 10, 20 or 40 cm width strips did not affect dry matter production, content, amount and recovery of N in the corn plant. Only when one urea application was made, the recovery of N from the corn plant was larger for the 10 cm of width in relation to 40 cm. The split application increased significantly dry matter production, content, amount and recovery of N in the corn plant in one single application

Food Habits of the Harpy Eagle, a Top Predator from the Amazonian Rainforest Canopy

The Harpy Eagle (Harpia harpyja), the heaviest and the most powerful bird of prey in the canopy of the Neotropical rainforests, is critically endangered in some parts of its range, mainly due to hunting pressure and habitat loss by deforestation. In this study, we found that the diet of five breeding pairs of Harpy Eagles in the central Amazonian rainforest over three years was dominated by two species of sloths (Bradypus variegatus and Choloepus didactylus) in terms of number of individuals and biomass consumed. Twelve other species, including primates, rodents, carnivores, and birds, also contributed to the Harpy Eagle diet in central Amazonia; there was no evidence of Harpy Eagle predation on livestock or domestic animals. Throughout the Harpy Eagle's entire range, 69 prey species have been documented, indicating that it can use a wide range of food resources. However, in our study, there was an evident diet specialization, resulting in a niche breadth which was relatively low (Bsta = 0.171). Conservation of Harpy Eagles should include protection of nesting trees, territories, and prey species to maintain the variability and availability of resources and its ecological functions throughout its geographic range. © The Raptor Research Foundation, Inc