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United States Department of Agriculture

Agricultural Research Service

Title: Soil Pore Surface Properties in Managed Grasslands

Authors
item Hajnos, Meczislaw - POLISH ACAD OF SCI,POLAND
item Korsunskaia, Ludmila - PUSHCHINO ST UNIV,RUSSIA
item Pachepsky, Yakov

Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2000
Publication Date: June 1, 2000

Interpretive Summary: Properties of pore surfaces control adsorption and transport of water and chemicals in soils. Parameters are needed to recognize and monitor changes in pore surfaces caused by differences in soil management. We researched a possibility to use water vapor adsorption data to derive such parameters. Pore surface properties affect the adsorption in three ways. They control the total area available for an adsorbate, the availability of the surface as affected by the size of an adsorbate molecule, and the specific adsorption of particular adsorbates. Total area and size-dependent availability parameters were computed from the adsorption of water vapro in dry soil samples. Samples of Udic Argiboroll were taken at four plots where a long-term experiment on grassing arable land had been carried out for 12 years. The experiment had 2X2 design. Factors were 'harvest-no harvest' and 'fertilizer-no fertilizer'. Both fertilization and harvesting resulted in an increase of the total area, with the largest increase observed in soil that was fertilized but not harvested. The size-dependent availability parameters were not affected by treatments in the range of pore radii where the vapor condensation occurred so that the micropores became filled with water. These parameters were affected by the removal of carbohydrates known to be aggregate-binding agents in soils. The pore surface parameters present a promising set of values to use in land and soil quality indices, as well as in estimating the competitive adsorption of volatile organic compounds and water in soils as related to soil bioremediation and fate of fumigants.

Technical Abstract: Properties of pore surfaces control adsorption and transport of water and chemicals in soils. Parameters are needed to recognize and monitor changes in pore surfaces caused by differences in soil management. Data on gas adsorption in soils can be compressed into parameters characterizing (a) area available to a particular adsorbate, and (b) surface roughness or irregularity. Our objectives were to see (a) whether models of adsorption on fractal surfaces are applicable to water vapor adsorption in soils in the capillary condensation range, and (b) whether differences in long-term management of grasslands are reflected by soil pore surface properties. Water vapor adsorption was measured in Udic Argiboroll, samples of which were taken at four plots where a long-term experiment on grassing arable land had been carried out for 12 years. The experiment had 2X2 design. Factors were 'harvest-no harvest' and 'fertilizer-no fertilizer'. The hay was cut after over-seeding in harvested treatments every year. The total amount of nutrients of 60 kg per ha was applied annually. The monolayer adsorption capacity was estimated from the Brunauer-Emmett-Teller model. A fractal Frenkel-Halsey-Hill model of adsorption on a fractal surface and a thermodynamic adsorption model were applied in the range of relative pressures from 0.7 to 0.98 and provided good fit of data. Values of the surface fractal dimension Ds were in the range from 2.75 to 2.85. Removal of carbohydrates resulted in increase of Ds. Differences in management practices did not affect values of Ds in the scale range studied; whereas, the monolayer capacity was affected. Both fertilization and harvesting resulted in an increase of the monolayer capacity with the largest increase observed in soil that was fertilized but not harvested.

Last Modified: 9/10/2014