Predicting the hydraulic properties of compacted soils: model validation

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Ngo-Cong, Duc
Antille, Diogenes L.
van Genuchten, Martinus Th.
Baillie, Craig P.
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American Society of Agricultural and Biological Engineers
Tekeste, Mehari
Associate Professor
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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.

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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  • Department of Agricultural Engineering (1907–1990)

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This paper reports on the validation of two numerical approaches that were developed to determine the effect of compaction on the soil water retention curve (WRC). The proposed approaches satisfactorily expanded the applicability of the van Genuchten (1980) model. In Approach 1, an optimization problem was solved to enable the van Genuchten model parameters α and η to be estimated for a range of soil bulk densities, based on the WRC of the corresponding non-compacted soil and the estimated saturation, residual, and permanent wilting-point (-1500 kPa) water contents of the compacted soil. In Approach 2, the parameter η was assumed to be unaffected by changes in soil bulk density. Subsequently, the parameter α was determined using an equation especially developed by this study. Compared with measured data, Approach 2 yielded slightly better predictions of the WRC than Approach 1. However, both numerical approaches may be used with confidence in a wider range of scenarios than those presented in this study. Across all soils, our analyses showed that relatively small increments in soil bulk density, due to compaction, can result in significant reductions in the available water storage capacity (AWSC) of soils; the effect being dependent on soil type and the relative increase in soil bulk density. Mechanization systems that mitigate, or where possible avoid, soil damage due to compaction (coupled with management practices that reduce loss of soil organic carbon) are encouraged. Quantification of the benefits of compaction avoidance, in terms of improved infiltration, soil water retention and water-use efficiency, as well as better predictions of the hydrology of compacted soils, may be possible through the application of the models reported in this study.
This presentation is published as Ngo-Cong, Duc, Diogenes L. Antille, Martinus Th van Genuchten, Mehari Z. Tekeste, and Craig P. Baillie. "Predicting the hydraulic properties of compacted soils: model validation." In 2021 ASABE Annual International Virtual Meeting. American Society of Agricultural and Biological Engineers, 2021. ASABE meeting paper No. 2100008. St. Joseph, Michigan: ASABE. DOI: 10.13031/aim.202100008. Copyright 2021 American Society of Agricultural and Biological Engineers. Posted with permission.