Soil Health Indicators in Areas Affected by Pipeline Installation

Progress report for GNC21-319

Project Type: Graduate Student
Funds awarded in 2021: $14,964.00
Projected End Date: 09/01/2023
Grant Recipient: Iowa State University
Region: North Central
State: Iowa
Graduate Student:
Faculty Advisor:
Dr. Bradley Miller
Iowa State University
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Project Information


Soil Health Indicators in Areas Affected by Pipeline Installation
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 soil health and resiliency across a spectrum of soil types and management practices. The implications of measuring soil health on disturbed and adjacent undisturbed soil across this spectrum are far reaching. In the US, approximately 517,000 km of natural gas pipelines has been installed and another 6,200 km will be constructed in the coming years (Olson & Doherty, 2012). To date, studies conducted on the effects of pipeline installation on individual fields have observed that soil bulk density and pH tends to be increased while soil organic carbon (SOC) tends to be decreased (Naeth & Bailey, 1987; Soon et al., 2000; Yu et al., 2010; Antille et al., 2016; Tekeste et al., 2019). The proposed study will expand on previous work by stratifying soil samples by soil parent material, landscape position, management practice, and disturbed versus undisturbed areas. Samples collected every 30 cm to a depth of 90 cm will be 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, texture, and microbial activity. To estimate the plant available water (field capacity – permanent wilting point), one ring of 5 cm height will be taken every 30 cm to run in ceramic plates and pressure chambers. Results from the sampling will be used with a machine learning algorithm and remote sensing to produce maps of evaluated soil properties, illustrating the broader impact beyond the fields sampled. As a learning outcome, farmers will be informed on the current distribution of soil properties in relation to the pipeline in their fields and the potential underlying causes to their decreased crop yields. Once they have a better understanding of their soil issues, they will be better able to target their management practices to help their soil recover. The evaluation plan will include a survey evaluating farmers’ level of comfort with the results and rate of adoption for specific management practices to improve the soil in their fields.

Project Objectives:

A unique dataset will be assembled of soil health indicators across a range of soil forming conditions and known time of disturbance. That dataset will be leveraged with geospatial technologies to produce a regional map illustrating the broader landscape effect of the pipeline on soil properties. The learning outcome will be to answer farmers’ questions about changes that may have occurred to the soil along the pipeline’s path and the effectiveness of the management practices they have implemented. As an action outcome, farmers will have the tools 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.


Click linked name(s) to expand/collapse or show everyone's info
  • Dr. Robert Horton (Educator and Researcher)
  • Dr. Marshall McDaniel (Educator and Researcher)


Materials and methods:

The hypothesis of this project is that soil health indicators capacity to recover their original condition after six years pipeline was installed will vary by parent material, landscape position, and management practices. Based on this, we defined the goal of creating a unique dataset of soil health indicators that covers the requirements to test our hypothesis. For this, two Iowa Physiographic Macro-Regions with distinctive characteristics were selected (Des Moines Lobe, and Southern Iowa Drift Plain). A questionnaire was designed to send to farmers affected by the installation of DAPL (Dakota Access Pipeline) in these two regions. To see the questionnaire access through the following link: 

However, the efforts of trying to get farmers involved using the questionnaire were not successful. For this reason, an alternative method was applied. Farmers were contacted via phone to arrange a meeting with them on their farm where we explained the project, and we filled the questionnaire together with them. This process was more successful and done individually with each of the 14 farmers involved in the projects in the Des Moines Lobe and Southern Iowa Drift Plain.  

The first round of interviews was completed in fall 2021 for farmers in the Des Moines Lobe, and the second round was completed in fall 2022 in the Southern Iowa Drift Plain. After each round of interviews was completed, we georeferenced each of the fields involved in the project. With the georeferenced data, we design the field samples collection along the DAPL path, stratifying locations by soil parent material, landscape position, management practices, and disturbed vs undisturbed areas. Once this information was set to each of the farms, sampling points were uploaded to the GPS before going to the field.  

Besides the coordination with farmers, by law we also needed to coordinate with DAPL because we took samples over the pipeline. To complete this process, we needed to register to Iowa One Call and upload one ticket per field where we specify field location, sampling depth, purpose of the sampling, among other information (Fig. 1). Once the tickets were approved, a representative person from DAPL contacted us and together with farmers we coordinated the visit to take samples on the different farms. The representative person of DAPL was present on each of the fields with a scanner that identifies the exact location of the pipeline, which helped us to be more precise by taking the samples from the exact place we planned (Fig.2). 

Once in the field, on each selected location, the pipeline path was divided into three parts: pile area, trench area, and traffic area which should represent each of the areas during the construction (Fig.3). Samples were collected for each of those points and on the undisturbed area every 30cm (about 12 in) to a depth of 90cm (about 3 ft) on the different hillslope positions presented on the different fields (Fig. 3). Each sample is duplicated because one was used for chemical, physical, and biological analysis, while the other was taken as a bulk density ring for hydrological measurements. Examples of soil cores with their respective bulk density rings and examples of soil cores of the different areas are represented in Figs. 4 and 5.  

Next, we are going to describe what has been accomplished for each of the regions. For the Des Moines Lobe, field sampling was finished in fall 2021. A total of 192 samples were taken which corresponds to 16 transects times 4 points per transect times 3 depths per point. After field sampling was completed, all samples were dried, grinded, and sieved to 2mm (about 0.08 in). For evaluation of microbial activity, CO2 burst test (Haney et al., 2008) was completed in November 2022. Soil particle size distribution was completed in December 2022 using a laser diffractometer (Miller & Schaetzl, 2012) for particle sizes’ role in hydrologic characteristics and as an indicator of soil mixing. For hydrologic properties, one ring of 3 cm height was taken every 30 cm (Fig. 4) to construct the soil water retention curves until a matric potential of -15.0 bars, using a combination of ceramic plates and pressure chambers (Fig. 6). In this case, the pressures we are measuring for building the water retention curves are: -0.10, -0.33, -1.0, -3.0, and -15.0 bars. On each run, we can measure 36 rings at the same time, using a double ceramic plate per chamber. With this methodology we will assess porosity and relate the release of soil water under different suctions or matric potentials. Plant available water will be calculated as the difference between volumetric water content at field capacity (-0.10 bars) and permanent wilting point (-15.0 bars). On the other hand, bulk density was calculated once each run was completed. To do this, rings were oven dried at 105 Celsius degrees until constant weight. After this, bulk density was calculated using the following formula: (solid mass (gr) / total volume of soil (cm3), and total porosity was calculated as follows: [1 - (Bulk density / Real density)] * 100], assuming a real density of 2.65 g/cm3. For this region, hydrological measurements were completed in January 2023. By now, all samples are packed and ready to send to Midwest laboratories (Fig. 7) for the following analysis: nitrogen as nitrate, organic matter, available phosphorus (P1 Weak Bray and P2 Strong Bray), exchangeable potassium, magnesium, calcium and hydrogen, pH, buffer index, cation exchange capacity, and percent base saturation of cation element. These samples will be sent to chemical analysis next month once CO2 burst test results are checked in case, we need to repeat any measurement.  

For the Southern Iowa Drift Plain, field sampling was finished in fall 2022. A total of 276 samples were taken, which corresponds to 23 transects times 4 points per transect times 3 depths per point. As explained for the Des Moines Lobe, each sample also had a bulk density ring for hydrological measurements. After field sampling was completed, all samples were dried, and nowadays we are close to finishing the grinding process. Any lab analysis will be started before grinding is finished. Except for hydrological measurements, where samples were collected on bulk density rings. In this case, measurements started in January 2023 once Des Moines Lobe samples were finished. Right now, the first run of samples is on the -15.0 bars chamber which is the highest-pressure point.  

To see report with pictures, see attached document: SARE_first_report

Research results and discussion:

By now, as was previously mentioned we finished with field sampling and almost all lab analysis for the Des Moines Lobe region, and we are in the process of starting with Southern Iowa Drift Plain samples analysis. All results from lab analysis are stored in our lab server, and we are planning to start with data analysis in the coming month. But by now no data analysis has been performed yet. 

Participation Summary
14 Farmers participating in research

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

Because any data analysis have been performed yet, no educational and outreach have been completed. 

Project Outcomes

Knowledge Gained:

Because any data analysis have been done yet, we don't have any gained knowledge or outcome to include yet. But once we finish with the data analysis, a comprehensive set of materials for farmers along the DAPL will be developed, including a summary data and analysis of soil properties findings. Additionally, we will intend to publish our findings in a peer-reviewed journal. 

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.