Data/hora: 24/06/2024 13:34:49

Biblioteca(s): 	Embrapa Agrobiologia.	
Data corrente: 	18/07/2005	
Data da última atualização: 	18/07/2005	
Autoria: 	CAMPILLO, R.; URQUIAGA, S.; UNDURRAGA, P.; PINO, I.; BODDEY, R. M.	
Título: 	Strategies to optimise biological nitrogen fixation in legume/grass pastures in the southern region of Chile.	
Ano de publicação: 	2005	
Fonte/Imprenta: 	Plant and Soil, Dordrecht, v. 273, p. 57-67, 2005.	
Idioma: 	Inglês	
Conteúdo: 	Pastures in southern Chile are composed of forage grasses and associated legumes. Apart from native grass species, in many areas perennial ryegrass (lolium perenne L.) and white clover (Trifolium repens L. ) have been introduced. It is thought that most of the N in these is derived from the symbiosis between rhizobium bacteria and the clover. However, various factors can limit the biological nitrogen fixation (BNF) potentia. Soils of chiloé (southern Chile) are derived from volcanic ash (Andisols), and show high acidity and phosphorus (P) retention capacity and there is often a low avalibility of exchangeable cations and, somential by nodulated legumes. An experiment was carried out on an Andisol of Chiloé, on a permanent pasture, to evaluate the influence of these fertility factores grass and legume productivity and on the BNF contribution to white clover. Treatments included two rates of lime (0 and 4 Mg há-1) and eight fertilisation treatments: 1. Complete (macronutrients in Kg há-1 : N-50, P2O5-180,  K2O-100, MgO-70, S-50, and micronutrients); six other treatments with complete fertilisation but, respectively, without N, P, K, Mg, S and micronutrients, and a control without fertiliser application. The experiment was conducted over 2 years and soil fertility parameters, grass and clover biomass production were evaluated and the BNF contribution to the clover was estimated using 15n isotope dilution technique. Potassium was found to be the most limiting element for dry matter production, especially for the clover. Liming increased soil pH values and Ca and Mg contents, strongly reduced Al saturation and increased dry matter production. The proportional contribution of BNF to the white clover was high, reaching 80% of total N accumulated by the plants and not significantly affected by addition of lime or fertiliser. However, the accumulation of dry matter and total N, and the total N derived from BNF by the clover were over three times higher in the complete fertilisation treatments tan in the control in both years and in the limed and unlimed treatments. The results of this study indicate that pasture productivity can be improved by liming and fertilisation which favour growth of the legume and ryegrass to the detriment of the native grasses. The increased in the proportion of ryegrass and clover should result in improved quality of the available forage, and in the case of the clover, stimulates and increase in the N contribution from BNF thus dispensing with the need for N fertiliser.	
Palavras-Chave: 	Biological nitrogen fixation; BNF; FBN; Fertilização; Fertilization; Fixação biológica de nitrogênio; Lime; White clover.	
Thesagro: 	Limão; Lolium Perenne; Trevo Branco; Trifolium Repens.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Agrobiologia (CNPAB)	
Exemplares: 	CNPAB - (32655-1) - UPC - SP - -- -  -  - 0022859 - DIS