Document Type

Thesis - Open Access

Award Date

2020

Degree Name

Master of Science (MS)

Department

Agronomy, Horticulture, and Plant Science

First Advisor

David E. Clay

Keywords

Bulk density, Drainable porosity, Hydraulic Conductivity, Salinity Parameters, Subsurface Drainage

Abstract

World-wide, salinity and sodicity problems are increasing in coastal, irrigated and dryland agricultural systems. Traditional reclamation techniques for saline sodic soils include improving soil drainage by installing subsurface drainage, leaching with high quality water, and applying a source of calcium. However, due to differences in the soil parent material these traditional approach treatments were ineffective in removing sodium and other salts out of the soil profile of South Dakota. Understanding how the surface and subsurface soil characteristics and management interact to affect the sustainability of these systems is the first step in remediation. Each region and soil have a slightly different problems and require site-specific remediation techniques. The objectives of this study were to 1) evaluate the functionality of subsurface drainage to remove the salts out of the soil profile 2) investigate the impact of subsurface physical parameters on the effectiveness of tile drainage. The experimental field was separated into shoulder, back, and toe slope zone that had different soil characteristics. Within each zone, four undisturbed and four disturbed depth soil samples (7.5 cm x 120 cm) were collected in 2018 and 2019. Soil samples (7.5 cm x 7.5 cm) were collected from 0 to 7.5 cm , 50 to 57.5 cm , 82.5 to 90 cm , 92.5 to 100 cm, and 105 to 112.5 cm depths and were analyzed for soil electrical conductivity (EC), pH, Na+ concentration, soil particle size, available water at field capacity, drainable porosity, soil bulk density, and saturated hydraulic conductivity. From 2018 to 2019, there was a decrease for the ECe and Na+ in the surface soil due to the movement of low EC water through the soil. However, this decrease of soil ECe was associated with an increased in the subsoil dispersion risks. These findings suggest that the increased soil dispersion risks also could reduce the ability of subsurface drainage to remove excess salts. Moreover, other physical properties that are responsible for the effectiveness of tile drainage could be harmed. High bulk densities, low drainable porosities, and low saturated hydraulic conductivities will reduce the effectiveness of subsurface drainage were associated with back and toe slope soils. These results might be attributed to the low saturated hydraulic conductivity rates, low drainable porosity, and high bulk density in the subsurface soil depths. Our findings suggest that subsurface drainage is not recommended to remove the excess sodium and other salts for these soils.

Format

application/pdf

Number of Pages

44

Publisher

South Dakota State University

Rights

In Copyright - Educational Use Permitted
http://rightsstatements.org/vocab/InC-EDU/1.0/

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