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Avaliacao de alguns processos do ciclo do azoto em solos Portugueses, designadamente atraves do marcador 15N

By Corina Luisa Videira de Abreu Fernandes Carranca

Abstract

It is necessary to obtain more detailed information on the processes involved in the N cycle of the soil-plant system. Thus, the fixing ability of several legumes was quantified and the N balance on Winter wheat, at Elves (Portugal) was evaluated, using "1"5#NU# isotope. Fababeans presented the highest fixing capacity (53 - 90% N derived from the fertilizer N dfa), even without inoculation, and under drought stress. Chickpea also showed a high fixing rate (44-80% N dfa), but total N_2 fixed was low (20 Kg N ha"-"1). Symbiosis with peas was depressed by water deficit and by Mo deficiency. Under favourable conditions, fixation rate reached 88%. Soybeans and green showed low fixation rates, probably due to inefficient rhizobium strains and/or inadequate plant genotypes. Sub clover mixed with non-legumes fixed 50% of its N in the above ground plant material, but no significant N transfer was observed to the non-legumes. The fertilizer use efficiency by Winter wheat was 19% - 44%. The fertilizer N recovered in the soil varied from 15% to 66%. Unaccounted N reached a maximum value of 55% of the applied N. Leaching of NO_3_- was the main loss, but denitrification and volatilization also occurredAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1200 Lisboa / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga

Topics: 02C - Agricultural engineering, LEGUMES, N BALANCE, 15N TECHNIQUES, TRITICUM AESTIVUM L. CV. TEJO, SYMBIOTIC N2 FIXATION CAPACITY
Year: 1996
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Provided by: OpenGrey Repository
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