Total carbon organic carbon and organic matter

Total Carbon, Organic Carbon, and Organic Matter

The transformations of nitrogenous compounds by soil bacteria have beenstudied for over a century. In terms of the global fluxes between aerial and terrestrial-aquatic systems, the simplified nitrogen cycle can be envisioned as a triangle where the only biologically reversible reaction occurs between ammonium and nitrate. The reverse reactions of dinitrogen fixation or denitrification by biological means do not occur in nature. Hence, the reductive process of denitrification, defined as the reduction of nitrate or nitrite to gaseous nitrogen (usually N2), is intimately associated with the oxidative process of nitrification.

Biochemical Ecology of Nitrification and Denitrification

The sustainable management of fertilizer and manure P to minimize freshwater eutrophication requires identification of soil P levels that exceed crop P requirements and have the potential for P enrichment of runoff. Although several states have established such P levels, insufficient data are available to theoretically justify them. Thus, this study investigates the relationship between the concentrations of P in runoff and in soil. Surface samples (0-10 cm) of 10 Oklahoma soils were packed in 0.15 m 2 boxes, incubated for 7 d with poultry litter (0-20 Mg ha -1 ) to obtain a range in Mehlich-3 P contents (7-360 mg kg -1 ), and received five 30-min rainfalls applied at 1-d intervals. The concentration of dissolved, bioavailable, and particulate P in runoff was related (r 2 > 0.90 ; P < 0.1) to the Mehlich-3 P content of surface soil (0-1 cm), with regression slopes ranging from 2.0 to 7.2, increasing as soil P sorption maxima increased (r 2 = 0.93). Two soils of 200 mg kg -1 Mehlich-3 P supported a dissolved P concentration in runoff of 280 μg L -1 (San Saba clay ; fine, montmorillonitic, thermic Udic Pellustert) and 1360 μg L -1 (Stigler silt loam ; fine, mixed, thermic Aquic Paleudalf). Thus, relationships between runoff and soil P will have to be soil specific for use in management recommendations. A single linear relationship described the dependence of dissolved (r 2 = 0.86) and bioavailable P (r 2 = 0.85) on soil P sorption saturation. The added complexity of the P saturation approach may limit its application ; however, the approach integrates the effect of soil type with soil P content to better estimate the potential for P loss in runoff than soil P alone.

Dependence of runoff phosphorus on extractable soil phosphorus

Preface. Symbols. Abbreviations. Atomic weights. Soils in pond aquaculture. Physical, chemical, and mineralogical properties of soils. Soil nutrients. Exchange of dissolved substances between soil and water. Soil organic matter, anaerobic respiration and oxidation-reduction. Sediment. Relationships to aquatic animal production. Pond bottom management. Pond bottom soil analyses.

Bottom soils, sediment, and pond aquaculture

Total nitrogen analysis in water, soil and plant material with persulphate oxidation

THE DICHROMATE-WET COMBUSTION DETERMINATION OF SOIL ORGANIC MATTER INVOLVES A TITRATION OF THE EXCESSIVE DICHROMATE. A POTENTIOMETRIC TITRATION IS PROPOSED. THIS MODIFICATION ENABLES A FAST AND ACCURATE END POINT DETERMINATION. MOREOVER, THE METHOD CAN BE EASILY ADAPTED FOR AUTOMATIC TITRATIONS.

Potentiometric Determination of Soil Organic Matter

It is indicated here that organic macro molecules in the soil are aggregated due to bonds, presumably hydrogen bonds, formed in the presence of water. When the soil is dried, this structure is broken and the stability of the organic matter decreases. This process is not an instantaneous process and apparently some relaxation period is needed for a complete dispersion of the organic matrix. An appreciable fraction of the organic molecules is hindered, even from contact with the solution in the aggregated structure, as indicated by the lower acidity in the wet soil. This steric hinderence seems to be one of the important factors contributing to the stability of humic compounds.

Ariella Raveh

Papers

Total nitrogen analysis in water, soil and plant material with persulphate oxidation

Potentiometric Determination of Soil Organic Matter

The effect of drying on the colloidal properties and stability of humic compounds

The effect of drying on the colloidal properties and stability of

A method for the evaluation of conditions in a fish pond sediment