Data/hora: 02/06/2024 01:15:35

Biblioteca(s): 	Embrapa Instrumentação.	
Data corrente: 	25/04/2003	
Data da última atualização: 	25/04/2003	
Autoria: 	BAYER, C.; MARTIN-NETO, L.; MIELNICZUK, J.; SAAB, S. da C. MILORI, D. M. P.; BAGNATO, V. S.	
Afiliação: 	UFRGS-Departamento de Solos, Porto Alegre, RS; Embrapa Instrumentação Agropecuária, São Carlos, SP; UEPG-Departamento de Física, Ponta Grossa, PR; USP-Instituto de Física, São Carlos, SP.	
Título: 	Tillage and cropping system effects on soil humic acid characteristics as determined by electron spin resonance and fluorescence spectroscopies.	
Ano de publicação: 	2002	
Fonte/Imprenta: 	Geoderma, Amsterdam, v. 105, p. 81-92, 2002.	
Idioma: 	Inglês	
Conteúdo: 	long-term (- and 9-year) effects were evaluated of two tillage regimes (conventional tillage:  CT; and no-tillage: NT) and two cropping systems (oat/maize: O/M; and oat + vetch / maize + cowpea: O + V/M+C) on characteristics of humic acids (HAs) from surface layer (0 to 25 mm) of subtropical Brazilian Paleudult soil. Generally, soil HA samples from conservation management systems with no soil disturbance (NT) and high crop residue addition (O+V/M+C) showed lowest humification degree, as demonstrated by lowest concentration of semiquinone-type free radicals, determined by electron spin resonance (ESR_, and lowest total fluorescence (TF), which is proportional to area under fluorescence spectrum; however, cropping systems had less effect than tillage regimes on two spectroscopic parameters. Since all HA samples presented a maximum fluorescence emission peak around 518nm, when excited with blue light, we believe that differences in the fluorescence intensity could be attributed to concentration of similar condensed aromatic moiety. This assumption was consistent with strong correlation with stable semiquinone-type free radicals (r=0.84, P<0.01), which are believed to be stabilized in humic substances by condensed aromatic structures. The results showed positive effects of conservation management in evaluating management system quality.	
Palavras-Chave: 	Aromatic groups; Brazilian soils; Espectroscopia; Fluorescência; Humidade; Humification degree; Semiquinone free radicals.	
Thesagro: 	Matéria Orgânica; Solo.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Instrumentação (CNPDIA)	
Exemplares: 	CNPDIA - (7448-1) - UPC - SP - -- - PROCI-02.00001 -  - 2002.00001 - DIS