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

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 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.

ÉTUDE COMPARATIVE DE L'AGRÉGATION ET DE LA MATIÈRE ORGANIQUE ASSOCIÉE AUX FRACTIONS GRANULOMÉTRIQUES DE SEPT SOLS SOUS CULTURE DE MAÏS OU EN PRAIRIE

1990 ◽  
Vol 70 (3) ◽  
pp. 395-402 ◽  
Author(s):  
J. ELUSTONDO ◽  
M. R. LAVERDIÈRE ◽  
D. A. ANGERS ◽  
A. N'DAYEGAMIYE
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Size Fraction ◽  
Cropping System ◽  
Clay Content ◽  
Size Fractions ◽  
Particle Size Fractions ◽  
Carbon And Nitrogen ◽  
Water Stable Aggregates ◽  
Continuous Corn

Water-stable aggregation and organic matter associated with particle-size fractions were compared for seven pairs of soils that were either under meadow or continuous corn cropping for more than 5 yr. Soils that have remained under meadow contained 25 and 29% more carbon and nitrogen than those under continuous corn. Carbon contents of the sand- and silt-size fractions were also 61 and 15% higher, respectively, under meadow than under continuous corn. The cropping system had no significant effect on the carbon and nitrogen contents of the clay-size fractions. The amount of water-stable aggregates (> 1 mm) was on average 34% higher in soils under meadow than in soils under corn cropping. Significant correlations were found between water-stable aggregates and total C (r = 0.77) and C in sand-size fraction (r = 0.79). The results also indicate that the beneficial effect of meadow over continuous corn on soil aggregation increases as soil clay content increases. Key words: Aggregation, organic matter, particle-size fractions, corn, meadow

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