Forage production and nitrogen use efficiency in afrincan liverseed grass ; Produção de forragem e eficiência no uso do nitrogênio em capim-corrente

The objective was to teste the effect of nitrogen (N) doses in the forage production, plant-part composition and structure of African liverseed grass (Urochloa mosambicensis) and to estimate the plant nitrogen use efficiency (NUE). The experimental design was in randomized block with six nitrogen doses 0, 25, 50, 75, 100 e 125 mg/dm3 and six replicates. The experiment was carried in greenhouse and the nutrients were applied in nutrient solution. There was N effect in all productive, morphological and structural characteristics studied in exception to leaves percentage. The N stimulated linearly the forage dry mass production (DMP), with an increase of 224.11% using 125 mg/dm³. There was also a positive effect of N in the number of tillers, which increased 82.60%. The number of inflorescences increased 712.29% with the maximum N application. Kd, estimated value that corresponds to the dose of N necessary to obtain half of the theoretical maximum production of MST (13,157.8 mg/vase) was 27.72 mg/dm3 of N. For this concentration, the NUE was of 40.5 mg of DMP for each mg of N Applied. The N increases linearly the total and leaves dry mass production, but it is associated to higher proportion of stems and inflorescences in the forage. The use of high nitrogen doses reduces the NUE and it is recommended to use 27.72 mg/dm³ and 23.03 mg/dm³ of N to optimizes the total and leaves mass of African liverseed grass, respectively. ; Objetivou-se testar o efeito de doses de nitrogênio (N) sobre a produção, composição morfológica, estrutura e eficiência no uso do N (EUN) em capim-corrente (Urochloa mosambicensis). Foi utilizado delineamento em blocos ao acaso com seis repetições e seis tratamentos referentes às doses de 0, 25, 50, 75, 100 e 125 mg/dm³ de N. O experimento foi conduzido em casa de vegetação e o N foi aplicado por solução nutritiva. Houve efeito significativo do N sobre as variáveis de produção, composição morfológica e características estruturais, exceto para porcentagem de folhas. As doses de N estimularam ...