Soil Health Indicators in Areas Affected by Pipeline Installation

View the project final report

Commodities

Practices

• Natural Resources/Environment: Soil reclamation
• Soil Management: organic matter, soil analysis, soil chemistry, soil microbiology, soil physics, soil quality/health

Soil Health Indicators in Areas Affected by Pipeline Installation
In the US, approximately 2.5 million km of hazardous liquid pipelines and natural gas mains have been installed (PHMSA, 2021). Assuming a mean width for a pipeline’s right of way (ROW) of 30 m, affected areas represent approximately 7.5 million hectares. The installation of the Dakota Access Pipeline (DAPL) in 2016 created a cross-section of disturbed soil from northwest to southeast Iowa. Since that time, farmers have observed lower crop yields along the path of the pipeline and have implemented a variety of management practices to address that issue. This situation creates a unique opportunity to study the effect of pipeline installation on soil health indicators. To date, studies conducted on the effects of pipeline installation on
individual fields have observed that soil bulk density and pH tend to be increased, corresponding to a decrease in total porosity, water holding capacity, and organic carbon (Naeth et al., 1987; Soon et al., 2000; Yu et al., 2009; Antille et al., 2014; Tekeste et al., 2018). In the present study, previous work is expanded upon by stratifying soil samples by soil landscape position, management practice, and disturbed versus undisturbed areas. The pipeline path was divided into three parts: pile area, trench area, and traffic area. Samples collected every 30 cm to a depth of 90 cm were measured for nitrate, organic matter, available phosphorous, exchangeable potassium, magnesium, calcium and hydrogen, pH, buffer index, cation exchange capacity (CEC), percentage of base saturation of cation elements and texture. For hydrologic properties, one ring of 34.210 cm3 was taken every 30 cm to construct the water retention curves at 0.1, 0.3, 1.0, 3.0, and 15.0 BAR. Among the different soil health indicators studied, physical properties, especially bulk density, and as a consequence, total porosity and available water for plants were the ones most affected by DAPL six years after installation. The reduction in available water for plants in the best-case scenario produces a yield reduction of around 12%, but in the worst-case scenario, where bulk density values surpass values of 1.5 g cm-3, yield reductions due to limitations in available water for plants was 22%. 

Particularly for Iowa, farmers whose fields were crossed by DAPL, after its installation in 2016 have experienced yield reductions. To remediate that, they have implemented a variety of management practices to address that issue, ranging from cover crops, deep ripping tillage to address compaction, additional passes of normal tillage applying four passes instead of two passes, while others are considering the increase in tyle density. But these are measurement practices applied without knowing what the underlying causes may be. One significant challenge in researching soil disturbance within pipeline ROW areas is the restricted availability of direct field-scale measurements for soil variables (Ebrahimi et al. 2022). Moreover, to date, the vast majority of studies have focused on particular fields without considering different soil types, hillslope positions, and parent materials. Hence, this study
addresses the following research question: Are there differences in soil health indicators between disturbed vs undisturbed areas six years after DAPL installation?

A unique dataset will be assembled of soil health indicators across a range of soil forming conditions and known time of disturbance. The learning outcome will be to answer farmers’ questions about what soil health indicators may be affected in the pipeline's path that is causing a yield reduction. Based on this, as an action outcome, farmers will have the information to decide based on the findings of this project which soil health indicator is affected, allowing them to switch from their current random treatments - ranging from cover crops to deep ripping tillage - to better informed and targeted practices. The benefit to farmers will be a reduction in their current, desperate mitigation strategies and the ability to strategically address the problem of decreased crop yields.