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United States Department of Agriculture

Agricultural Research Service

Research Project: CONSERVATION EFFECTS ASSESSMENT FOR THE ST. JOSEPH RIVER WATERSHED

Location: National Soil Erosion Research Lab

Title: Evolution of Pedostructure Parameters Under Tillage Practices

Authors
item Mallory, J -
item Mohtar, R -
item Schultz, D -
item Heathman, Gary

Submitted to: ASABE Annual International Meeting
Publication Type: Abstract Only
Publication Acceptance Date: January 10, 2009
Publication Date: June 21, 2009
Citation: Mallory, J., Mohtar, R.H., Schultz, D.G., Heathman, G.C. 2009. Evolution of Pedostructure Parameters Under Tillage Practices. American Society of Agricultural and Biological Engineering Annual International Meeting, June 21-24, 2009, Reno, Nevada. CD ROM.

Interpretive Summary: As water supplies across the globe continue to dwindle in the face of the growing uses for population, industry, and agriculture, improved methods of soil-water modeling are needed to protect water resources still available. The pedostructure concept is a new paradigm of soil-water modeling that predicts soil-water behavior using physically-based equations based upon soil structure. Fifteen unique pedostructure parameters are extracted using a soil’s continuously measured shrinkage, potential, conductivity, and swelling curves. The purpose of this work is to determine an accurate means of estimating the physically-based parameters of the pedostructure concept using common soil information and discover how land use affects these parameters. By understanding and accounting for the physical processes that occur between the water, air, and soil solids at the soil aggregate scale, the pedostructure concept is more able to accurately model the soil-water medium as well as scaling behaviors and processes between various spatial levels. Future work includes incorporating discontinuous soil features, such as cracks, into the pedostructure model.

Technical Abstract: The pedostructure (PS) concept is a physically-based method of soil characterization that defines a soil based on its structure and the relationship between structure and soil water behavior. There are 15 unique pedostructure parameters that define the macropore and micropore soil water behavior for an individual soil. These fifteen parameters are extracted in the laboratory from the continuously measured shrinkage, swelling, potential, and conductivity curves of undisturbed soil cores. Up to this point, there has been little work on how these parameters evolve, especially under different land management schemes, and if the pedostructure concept will accurately capture differences in soil water behavior due to land management differences. We believe PS parameters related to macro-porosity will exhibit substantial changes between tillage schemes, while those PS parameters related to micro-porosity will not exhibit significant differences between tillage practices. In addition, the pedostructure-based soil water model (KamelR) will accurately capture the changes in water holding capacity properties due to tillage. Two subwatersheds were monitored near the town of Waterloo, IN. They consisted of primarily one soil type and one tillage type, a Glynwood silt loam (fine, illitic, mesic, Aquic Hapludalfs) under no-till and a Blount silt loam (fine, illitic, mesic, Aeric Epiaqualfs) under moldboard ploughing. Each soil and tillage type was characterized by the pedostructure concept using the methodology described by Salahat (2006). Time-domain reflectometry (TDR) hydraprobes measuring volumetric water content were installed at 2, 8, 16, and 24 inch depths at each subwatershed outlet. Using the measured Pedostructure parameters and climatic data taken from weather stations at each subwatershed as inputs, the dynamic soil moisture profile was modeled using KamelR over a one week period and compared to the measurements taken by the TDR hydraprobes.

Last Modified: 9/23/2014
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