Sandy Soil Microaggregates: Rethinking Our Understanding of Hydraulic Function

Journal Article · Sun Jan 01 04:00:00 EST 2017 · Vadose Zone Journal

DOI:https://doi.org/10.2136/vzj2017.05.0090· OSTI ID:1410115

Paradiś, Ashley; Brueck, Christopher; Meisenheimer, Douglas; Wanzek, Thomas; Dragila, Maria Ines

This study investigated the peculiar structure of microaggregates in coarse sandy soils that exhibit only external porosity and investigated their control on soil hydrology. The microstructure underpins a hydrologic existence that differs from finer textured soils where aggregates have internal porosity. Understanding the impact of these microaggregates on soil hydrology will permit improved agricultural irrigation management and estimates associated with ecosystem capacity and resiliency. Microstructure was investigated using a digital microscope, and aspects of the structure were quantified by sedimentation and computed microtomography. Sandy soil microaggregates were observed to be comprised of a solid sand-grain core that is coated with fines, presumably cemented by organic media. This microstructure leads to three distinct water pools during drainage: capillary water, followed by thick films (1–20 μm) enveloping the outer surfaces of the crusted microaggregates, followed by adsorbed thin films (<1 μm). The characteristics of the thick films were investigated using an analytical model. These films may provide as much as 10 to 40% saturation in the range of plant-available water. Using lubrication theory, it was predicted that thick film drainage follows a power law function with an exponent of 2. Thick films may also have a role in the geochemical evolution of soils and in ecosystem function because they provide contiguous water and gas phases at relatively high moisture contents. And, because the rough outer crust of these microaggregates can provide good niches for microbial activity, biofilm physics will dominate thick film processes, and consequently hydrologic, biologic, and geochemical functions for coarse sandy soils.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: USDA
• OSTI ID: 1410115
• Journal Information: Vadose Zone Journal, Journal Name: Vadose Zone Journal Journal Issue: 9 Vol. 16; ISSN 1539-1663
• Publisher: Soil Science Society of America
• Country of Publication: United States
• Language: ENGLISH

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54 ENVIRONMENTAL SCIENCES