Data/hora: 14/06/2024 03:37:26

Biblioteca(s): 	Embrapa Instrumentação.	
Data corrente: 	28/04/2003	
Data da última atualização: 	28/04/2003	
Autoria: 	BAYER, C.; MIELNICZUK, J.; MARTIN-NETO, L.; ERNANI, P. R.	
Afiliação: 	UFRGS, Departamento de Solos, Porto Alegre, RS; Embrapa Instrumentação Agropecuária, São Carlos, SP; UFSC, Departamento de Solos, Lages, SC.	
Título: 	Stocks and humidification degree of organic matter fractions as affected by no-tillage on a subtropical soil.	
Ano de publicação: 	2002	
Fonte/Imprenta: 	Plant and Soil, Hague, v. 238, p. 133-140, 2002.	
Idioma: 	Inglês	
Conteúdo: 	Assessment of particulata (>53-mi) and mineral-associated (<53-mi) soil organic matter (SOM) fractions is a useful approach to understand the dynamic of organic matter in soils. This study aimed to compare the long-term (9-yr) effects of no-tillage (NT) and conventional tillage (CT) on C and N stocks in the two above mentioned organic fractions in a Brazilian Acrisol. The degree of SOM humification, which has been associated with the concentration  of semiquinone-type free radicals ("spin") determined by electron spin resonance (ESR), was also evaluated. Soil under no-tillage had 7.55 Mg ha-1 (25%0 more C and 741 kg ha-1 (29%) more Ne than conventionally tilled soil in the 0-175-mm depth. Both particulate and mineral-associated SOM increased in the no-tilled soil. The incrase of C and N stocks in the mineral-associated SOM accounted for 75% and 91% of the difference in total soil C and N stocks between NT and CT, respectively. Averaged across tillage systems, C and N stocks were respectively 4.6 and 16.8 times higher in the mineal-associated SOM than in particulate SOM. The higher C and N stocks were associated with greater recalcitrance of mineral-associated SOM to biological decomposition, resultin, probably, from its interaction with variable charge minerals. This is corroborated by a positive relationship between concentrations of C and iron oxides and kaolinite in the 53-20, 20-2 and <2-mi particle size classes, of the 0-25-mm soil layer. The degree of SOM humification, assessed by ESR, decreased in both the 53-20 and 20-2-mi fractions under NT. However, it was unaffected by tillage in the <2-mi fraction, which mormally presented the lowest "spin" concentration. Since quality as well as quantity of SOM improved in the no-tillage soil, adoption of this system is highly recommended for amelioration of degraded tropical and sutropical solis.	
Palavras-Chave: 	Clima subtropical; Electron spin resonance; Grau de humificação; Particulate soil organic matter; Subtropical climate.	
Thesagro: 	Matéria Orgânica; Solo.	
Thesaurus Nal: 	no-tillage.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Instrumentação (CNPDIA)	
Exemplares: 	CNPDIA - (7456-1) - UPC - SP - -- - PROCI-02.00009 -  - 02.00009 - DIS