Using surface solute transport properties measured by time domain reflectometry to predict subsurface leaching

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2004-01-01
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Gaur, Anju
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Robert Horton
James L. Baker
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Agricultural and Biosystems Engineering

Since 1905, the Department of Agricultural Engineering, now the Department of Agricultural and Biosystems Engineering (ABE), has been a leader in providing engineering solutions to agricultural problems in the United States and the world. The department’s original mission was to mechanize agriculture. That mission has evolved to encompass a global view of the entire food production system–the wise management of natural resources in the production, processing, storage, handling, and use of food fiber and other biological products.

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In 1905 Agricultural Engineering was recognized as a subdivision of the Department of Agronomy, and in 1907 it was recognized as a unique department. It was renamed the Department of Agricultural and Biosystems Engineering in 1990. The department merged with the Department of Industrial Education and Technology in 2004.

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1905–present

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  • Department of Agricultural Engineering (1907–1990)

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Agricultural and Biosystems Engineering
Abstract

Solute transport properties are required to evaluate the risk of contaminating ground water with agricultural chemicals under a wide variety of crop and soil management practices. Most solute transport measurement techniques are tedious and lead to extensive soil excavation. Two experiments were performed to evaluate whether surface transport properties determined by a non-destructive time domain reflectometry (TDR) technique could be used to accurately predict subsurface leaching. TDR probes installed in the surface 2-cm of soil were used to determine resident solute concentration from measured soil surface soil bulk electrical conductivity. Resident concentrations were analyzed with a one-dimensional (1-D) solute transport model in order to determine the surface solute transport properties. The surface measurements technique was first tested in a greenhouse soil. Surface dispersivities (1.02 cm) determined by the TDR method were similar to the 30-cm subsurface dispersivities (1.28 cm). The surface solute transport properties were used to predict the chemical concentration distributions within the 30-cm soil layer, and it was found that the centers of mass from predicted and observed subsurface chemical distributions were similar.;Further testing of the TDR technique was done in a strip-cropped tile-drained field. The plant-row and interrow zones significantly affected surface and soil profile (120-cm) dispersivities. The soil profile dispersivity (2.68 cm) was larger and more variable than the surface dispersivity (0.91 cm) indicating greater heterogeneity of flow within the soil profile than at the surface. The large soil profile dispersivity indicated that multidimensional flow and lateral spreading occurred in the soil profile. In order to evaluate solute transport in the soil profile, a 1-D convective lognormal transfer (CLT) function model and a 2-D model (CLT combined with exponential model) were used to make tile flux predictions. Surface transport properties combined with the 2-D model predicted the tile flux concentrations more accurately (root mean square error, RMSE = 0.023) than the 1-D CLT model (RMSE = 0.123). TDR is a promising tool for determining surface solute transport properties. In this field soil, surface solute transport properties can be combined with a 2-D solute transport model for accurate prediction of tile flux concentrations.

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Thu Jan 01 00:00:00 UTC 2004