Data/hora: 11/06/2024 23:01:01

Biblioteca(s): | Embrapa Pantanal.
Data corrente: | 03/09/1996
Data da última atualização: | 04/04/2017
Autoria: | GOLCHIN, A.; CLARKE, P.; OADES, J. M.; SKJEMSTAD, J. O.
Título: | The effects of cultivation on the composition of organic matter and structural stability of soils.
Ano de publicação: | 1995
Fonte/Imprenta: | Australian Journal of Soil Research, v.33, n.6, p.975-993, 1995.
Idioma: | Inglês
Conteúdo: | Soil samples were obtained from the surface horizons of five untilled sites and adjacent sites under short- and long-term cultivation. The soil samples were fractionated based on density and organic materials were concentrated in various fractions which enabled comparative chemical composition of the organic materials in cultivated and uncultivated sites by solid-state 13C CP/MAS NMR spectroscopy. Changes in the nature of organic carbon with cultivation were different soils and resulted from variations in the chemistry of carbon inputs to the soils and a greater extent of decomposition of organic materials in cultivated soils. Differences in the chemical composition of orghanic carbon between cultivated and uncultivated soils resided mostly in organic materials occluded within aggregates, whereas the chemistry of organic matter associated with clay particles showed only small changes. The results indicate a faster decomposition of O-alkyl C in the cultivated soils. Wet aggregate stability, mechanically dispersible clay and modulus of rupeture tests were used to assess the effects of cultivation on structural stability of soils. In four of five soils, the virgin sites and sites which had been under long-term pasture had a greater aggregate stability than cultivated sites. Neither total organic matter nor total O-alkyl C content was closely correlated with aggregate stability, suggesting that only a part of soil carbon or carbohydrate is involved in aggregate stability. The fractions of carbon and O-alkyl C present inn the form of particulate organic matter occluded within aggregates were better correlated with aggregate stability (r = 0.86** and 0.88** respectively). Cultivation was not the dominant factor influencing water-dispersible clay acroos the range of soil types used in this study. The amount of dispersible clay was a function of total clay content and the percentage of clay dispersed was controlled by factors such as clay mineralogy, CaCO3 and organic matter content of soils. The tendency of different soils for hard-setting and crusting as a result of structural collapse, was reflected in the modulus of rupture (MOR). The cultivated sites had significantly higher MOR than their non-tilled counterparts. The soils studied had different MOR due to differences in their physical and chemical properties.
Palavras-Chave: | Composicao; Composition; Cultivation; Cultivo; Dispersible clay; Estabilidade; Stability.
Thesagro: | Matéria Orgânica; Solo.
Thesaurus Nal: | organic matter; soil.
Categoria do assunto: | --
Registro original: | Embrapa Pantanal (CPAP)
Exemplares: | CPAP - (32907-1) - ADD - SP - PP - SP14969 -  - 14969 - DIS