Data/hora: 25/06/2024 00:13:09

Biblioteca(s): 	Embrapa Gado de Corte.	
Data corrente: 	16/06/2004	
Data da última atualização: 	16/06/2004	
Autoria: 	NAKAMURA, T.; KANNO, T.; OHWAKI, Y.; MIRANDA, C. H. B.; MACEDO, M. C. M.; FUKUDA, E.	
Afiliação: 	JIRCAS (Owashi, Japão).	
Título: 	Characterization of nitrogen utilization by tropical grasses in Brazilian savannas.	
Ano de publicação: 	2003	
Fonte/Imprenta: 	In: SUENAGA, K.; OSHIBE, A.; TANIGUHI, T. (Ed.). Development of sustainable agro-pastoral systems in the subtropical zone of Brazil. Tsukuba: JIRCAS, 2004.	
Páginas: 	p. 25-28.	
Série: 	(JIRCAS. Working Report, 36). 	
Idioma: 	Inglês	
Notas: 	CNPGC. Proceedings of the Workshop on the results and prospects of comprehensive studies on the development of sustainable agro-pastoral systems in the subtropical zone of Brazil, 2003. 
	
Conteúdo: 	Brachiaria species are widely cultivated in the Brazilian savanna (Cerrados). The  poor nitrogen (N) fertility of soils is one of the limiting factors of grass production in this area. Thus, the mechanism of absorption and utilization in these grasses are needed to be celar under N-limiting condition. In this research, we compared  the characteristics of N utilization inBrachiaria brizantha  (BB), B decumbens (BD), and B. humidicola (BR), which are widely cultivated in this area.  Firstly, in the pot experiment, BB, BD, and BH were grown under 3 levels of N, equivalent  to ) (ON), 50 (IN), and 150 (2N) kg N ha, with N as ammonium sulfate. The dry mater production of these  3 varieties, as affected by  N nutrition, was then compared. The dry mass quickly decreased with reduction of applied N level in BB and BD. In BH, however, the reduction  was smaller than  those of the other 2 grasses specially when N was not applied. These data suggest that BH was more adapted to limited-N conditions than the other 2 grasses. In the ON treatment, especially N absorption in plant was higher in BH than in the other 2 grasses. Scondly, the  contribution ratio of fixed N  from air in plant (%Ndfa) of Brachiaria species was also estimated in N-limiting condition in field. The estimated contibution ratio of N fixation was  1-29% and this ratio of BH was lower than that of BD and BB. Thus, contribution ratio of soil-N would be higher  in BH tan in other 2 grasses. Thirdly. Michaelis-mentens kinetic analysis was conducted to evaluate physiological traits of roots to N. In the nitrato uptake experiment, the value of Km was lower in BH than in the other 2 grasses. This result could indicate that, as BH has higher affinity for nitrate uptake, due to its low km, it may maintain a higher N uptake rate in  N-limiting condition. Therefore, it could be considered that the smaller reduction of dry mass of BH in low-N conditions is due to  high-N absorption rate in its roots. 	
Palavras-Chave: 	Brasil; Brazilian savannas; Marandu.	
Thesagro: 	Brachiaria Brizantha; Brachiaria Decumbens; Brachiaria Humidicola; Cerrado; Fertilizante Nitrogenado; Nitrogênio; Pastagem.	
Thesaurus Nal: 	Brazil; nitrogen; pastures.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Gado de Corte (CNPGC)	
Exemplares: 	CNPGC - (10498-1) - UPC - PL - -- - 630 - S944d -  - DIS