Water-to-soil ratio

This type of extraction can be carried out in two different ways. A soil sample can be brought into the laboratory and extracted with relatively large amounts of water to try to determine its inorganic composition. The water-to-soil ratio can be either on a mass-to-mass basis or a volume-to-mass ratio. A one-to-one ratio is commonly used, although other ratios have been used. After a designated extraction time, with or without shaking, water is filtered from the soil and analyzed. A typical water extraction of soil is given in Procedure 11.1. 

The conductivity of a soil is precisely the specific conductivity at 25°C of a water extract obtained at a definite soil water ratio. The electrical conductivity is measure on an electrical conductivity bridge and is normally reported in mmhos cm k A fairly quantitative estimate of the soluble salt content of solutions extracted from the soils can be made from their electrical conductance. Soil extracts obtained using high water to soil ratios are as less accurate measure of the solute content of the soil since more salts may be removed than are ever present in the soil, at field moisture contents. Usually soil water ratio of 1 2.5 or 1.5 is used for routine measurement. Thus the soil water ratio employed must be specified with the analysis. 

Adsorption Study. The adsorption of the test compounds by the sandy loam soil (particle size less than 35 mesh) was determined by measuring the difference in the concentration of an aqueous solution of each chemical, before and after equilibration with soil. Four to five concentrations per chemical were tested and three replicate measurements were performed at each concentration. Water-to-soil ratios of 2 1 to 10 1 were employed in all experiments. The time required to reach equilibrium was determined separately for each chemical at one concentration and a specific water-to-soil ratio. 

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