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SOIL FRACTIONATION STUDY

Topic of the Presentation is …

Soil organic carbon is of heterogeneity in components. The components are sensitive to agriculture management while the inert components play an important role in carbon fixation.

Soil Fractionation

1. The top sieve is gravel-set aside.

2. The second and sieves are sand.

3. The third sieve is silt.4. The bottom pan is clay.

Sieves of Soil Fractionation

There are three types of soil fractionation-

1. Physical fractionation

2. Chemical fractionation

3. Biological fractionation

Classification of soil fractionation

Physical fractionation is to separate the organic carbon into active and inert components based on the density, particle size and its spatial distribution. color, water retention, helps prevent shrinking and drying, combines with clay minerals, improves moisture-retaining properties, stabilizers structure, permits gas exchange.

Physical Fractionation

Chemical fractionation is to separate the organic carbon (OR) into various components based on the solubility, hydrolizability and chemical reactivity of organic carbon (OR) in a variety of extracting agents. chelation improves micronutrient availability, buffer action maintains uniform reaction in soil and increases cat ion exchange.

Chemical Fractionation

• In chemical fractionation the dissolved organic carbon (OR) is bio-available including organic acids, phenols and carbohydronates and acid hydrolyzed organic carbon can be divided into active and inert organic carbon. simulated enzymatic oxidation by using KMnO4 can separate organic into active and non-active carbon.

Ingredient of Chemical Fractionation

Biological fractionation is mineralization provides source of nutrients combines with xenobiotic influencing bioavailability and pesticide effectiveness. Biological fractionation can differentiate microbial biomass carbon and potential mineralizable carbon. under different farm land management practice. The chemical composition and pool capacity of soil organic carbon fractions will have different variations giving different effects of soil quality. To identify the qualitative or quantitative relationship between soil organic carbon components and carbon deposition. We should strengthen the standardization study of various fractionation methods explore the integrated application of different fractionation methods.

Biological Fractionation

• In order to investigate the role of SOM in soil structure, the processes by which soils maintain aggregation need to be identified. The work of Tisdall and Oades (1982) and Oades (1984) on soil binding agents has become the generally accepted theory of the bonding of many agricultural soils.

The Role of SOM in Soil Structure

• Density fractionation assumes that SOM can be separated into pools differing in structure and function. It has been used to separate the light fraction (LF) SOM isolated from whole soils by mild dispersion procedures as well as LF from size separates after thorough dispersion. The LF is considered to be decomposing plant and animal residues with a relatively high C:N ratio, a rapid turnover and a low specific density. The heavy fraction (HF) includes the organomineral complexes SOM which is more processed with a narrower C:N ratio and a slower turnover rate (Greenland and Ford 1964; Greenland 1965, 1971). Densities of - 2.0 and -1.6 g/cm3 are commonly used to separate light organomineral complexes.

Density fractionation

• Soil fractionation techniques have allowed much information to be gained on the location and dynamics of SOM and the effects of land use. In order to study the mechanisms involved in soil structure, the arrangement and functions of various bonding agents and the effects of management need to be known. Fractionation techniques which investigate these issues need to be developed. The fractionation techniques so far discussed do not appear appropriate for investigating soil structure dynamics.

Methods of Separation

• The term SOM encompasses organic residues in various stages of decay which are derived from plant, microbial and animal origin.

• SOM transformations depend on a complex interaction of the physical, chemical and biological processes within soils.

• A knowledge of these transformations is essential for an understanding of the structure, fertility and chemical reactivity of the soil and the impact of various management factors such as fertilizer, manure and residue additions.

• The chemical aspects of SOM and microbially mediated processes appear to be well understood (Christensen 1992) while physical soil fractionation and organomineral complexes have been studied less.

Common fractionation techniques

• Physical fractionation techniques have often relied on the breakdown of soil structure into its textural classes or density fractions in order to study SOM dynamics. This appears to be inappropriate for investigating how soil structure is maintained. The bonding agents responsible for structure have been well defined, although the effects of farming systems on them are not fully understood. Techniques which can rapidly assess the impacts of management on bonding agents and structure are required in order to develop sustainable farming systems.

Conclusions

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