Pouvoir fixateur vis-à-vis des ions phosphate de sols tropicaux à argile 1:1

1992 ◽  
Vol 72 (2) ◽  
pp. 135-143 ◽  
Author(s):  
E. Frossard ◽  
M. Brossard ◽  
C. Feller ◽  
J. Rouiller
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Mineralogical Composition ◽  
Clay Soils ◽  
Exchange Method ◽  
Size Fractions ◽  
Particle Size Fractions ◽  
Particle Size Fractionation ◽  
Low Activity

This study was aimed to clarify the influence of secondary mineral constituents (iron and aluminium oxides, kaolinite) and organic matter on the determination of the phosphate-fixing capacity (PFIX) of well-drained low-activity clay soils. This study was done on soil samples (0–2 mm) and on their particle size fractions. The phosphate-fixing capacity, estimated by an isotopic exchange method, was highly related to the total iron content of the soils. The phosphate-fixing capacity of the particle size fractions was related to their mineralogical composition, and to the organisation of their constituents. H2O2 strongly increased the phosphate-fixing capacity of the soils and of their particle size fractions. Two hypotheses were proposed to explain this. Either H2O2 caused the formation in vitro of amorphous constituents with a high phosphate fixing capacity; or the destruction of organic matter by H2O2 caused the apparition of new surfaces previously masked by organo-mineral aggregation and/or caused the apparition on surfaces of fixation sites previously occupied by organic compounds. Key words: Phosphate-fixing capacity, low-activity clay soils, particle size fractionation, mineralogy, organic matter, H2O2 effect

scholarly journals Potassium status in different particle size fractions of some Finnish soils

1967 ◽  
Vol 39 (2) ◽  
pp. 45-56
Author(s):  
Armi Kaila
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Fine Sand ◽  
Clay Soils ◽  
Size Fractions ◽  
Particle Size Fractions

Samples of fine sand, silt and clay soils from the surface and the deeper layers were separated without destruction of organic matter into the following fractions: clay

Activité phosphatasique de quelques sols tropicaux à argile 1: 1. Répartition dans les fractions granulométriques

1994 ◽  
Vol 74 (2) ◽  
pp. 121-129 ◽  
Author(s):  
C. Feller ◽  
E. Frossard ◽  
M. Brassard
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Phosphatase Activity ◽  
Mineral Soil ◽  
Clay Fraction ◽  
Continuous Cultivation ◽  
Clay Soils ◽  
Size Fractionation ◽  
Particle Size Fractionation ◽  
Low Activity

The objectives of this work were: (i) to study the acid monophosphoesterase activity (pH 6.5) of the surface horizons of low-activity tropical clay soils (West Africa, West Indies, Brazil), cultivated or uncultivated, with widely different textures and organic matter (OM) contents, (ii) to measure the phosphatase activity (Pase) in the organic and organo-mineral soil fractions obtained by particle size fractionation. Pase was most significantly correlated to the soil OM content and to a lesser extent to the texture and total P content. Therefore, any modification in soil management resulting in important changes in soil OM contents, leads to important variations in phosphatase activity: Pase decreases after clearing of the native vegetation and continuous cultivation, Pase increase when grass-fallows or meadows succeed to annual cropping. The Pase of all the size fractions (20–2000 μm, 2–20 μm and 0–2 μm) was controled by their OM content. However, the "potential Pase" defined as the ratio Pase/C was higher in the 20- to 2000-μm and 0- to 2-μm fractions than in the 2–20 μm ones This is attributed to a higher Pase renewal by root restitutions in the plant debris fraction (20–2000 μm) and by microbial activity and microbial metabolites in the organo-clay fraction (0–2 μm). More than 50% of the soil total Pase was associated with fractions coarser than 2 μm. Most of the changes in Pase (75–100%) associated with the cultivation were ascribed to these fractions. This illustrate the probably important role of the fractions coarser than 2 μm in the phosphorus dynamics in these soils. Key words: Phosphomonoesterase, organic matter, particle size fractionation, low-activity tropical clay soils

scholarly journals Long term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. III. Distribution and kinetics of soil organic carbon in particle size fractions

Soil Research ◽  
1986 ◽  
Vol 24 (2) ◽  
pp. 293 ◽  
Author(s):  
RC Dalal ◽  
RJ Mayer
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Size Fraction ◽  
Organic C ◽  
Size Fractions ◽  
Particle Size Fractions ◽  
Clay Size Fraction ◽  
Sand Size

Distribution of soil organic carbon in sand-, silt- and clay-size fractions during cultivation for periods ranging from 20 to 70 years was studied in six major soils used for cereal cropping in southern Queensland. Particle-size fractions were obtained by dispersion in water using cation exchange resin, sieving and sedimentation. In the soils' virgin state no single particle-size fraction was found to be consistently enriched as compared to the whole soil in organic C in all six soils, although the largest proportion (48%) of organic C was in the clay-size fraction; silt and sand-size fractions contained remaining organic C in equal amounts. Upon cultivation, the amounts of organic C declined from all particle-size fractions in most soils, although the loss rates differed considerably among different fractions and from the whole soil. The proportion of the sand-size fraction declined rapidly (from 26% to 12% overall), whereas that of the clay-size fraction increased from 48% to 61% overall. The proportion of silt-size organic C was least affected by cultivation in most soils. It was inferred, therefore, that the sand-size organic matter is rapidly lost from soil, through mineralization as well as disintegration into silt-size and clay-size fractions, and that the clay fraction provides protection for the soil organic matter against microbial and enzymic degradation.

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