Ames, Iowa — A study by Iowa State University looked at the effects of soil disturbance and early restoration practices in Dakota access pipeline construction, and found significant soil compaction and crops in the right of way within five years The gradual recovery of production.  

Dakota Access Pipeline (DAPL) funded research aimed at investigating the impact of underground pipelines on farmland construction. The pipeline transports crude oil from North Dakota to Patoka, Illinois, over 1,172 miles in length, and approximately 347 miles through South Dakota and Iowa. The main objective of the study was to assess the degree of soil and crop disturbance in the approximately 150-foot right of way caused by land clearing, topsoil removal and soil mixing, pipeline trenching and backfilling during construction.

Researchers also want to evaluate the effectiveness of the national restoration requirements and DAPL agricultural mitigation plans designed to minimize the impact on farmland. Iowa's public utility regulations require pipeline projects to remove the topsoil and deep plow the exposed subsoil before replacing the topsoil. Researchers are continuing to study the benefits of these practices, which can be expensive.

After installing pipelines on farmland, this field study to quantify soil properties and restoration is limited in the corn-soybean region of the United States.  

"Our research results show that extensive soil disturbances caused by construction activities have adverse effects on the physical properties of the soil. These effects come from the mixing of topsoil and subsoil, and soil compaction caused by heavy machinery," said Mehari Tekeste, assistant professor of agricultural and biological systems engineering. Say. Director of Iowa Soil Machinery Dynamics Laboratory and project leader.

Tekeste worked with a team including: Mark Hanna, a retired Iowa Extension Agricultural Engineer; Robert Horton, Charles F. Curtiss, Outstanding Agricultural and Life Sciences Agronomy Professor; and Elnaz Ebrahimi, agricultural and biological systems engineering research scientist.

After the completion of the local pipeline construction in 2016, researchers began to study the impact of construction and reclamation on the pipeline passing through a short section of the Iowa State Research Farm near Ames, Iowa. They monitored soil characteristics, such as bulk density and chemical properties, at different depths in three areas within the right of way and adjacent undisturbed farmland. In 2017 and 2018, they analyzed the yield data of corn and soybean plots planted on the reclaimed land under the pipeline right of passage under two farming systems (no-tillage and conventional farming), and compared the yield of crops in undisturbed fields. With similar soil. A peer-reviewed article in the journal "Soil Use and Management" summarized their early results.

"In general, in the first two years, we found that construction caused severe subsoil compaction, disrupting the physical structure of the soil, thereby hindering root growth and reducing water infiltration in the right of way," the chief soil physics of the project Home Horton said. They also found changes in available soil moisture and nutrients.

Although the compaction phenomenon caused by heavy equipment is still obvious after two years of construction, deep ploughing treatment has certain advantages in relieving compaction.

The research team found that compared with undisturbed fields, crop yields in the right of way were reduced by an average of 25% and corn by an average of 15% during the first and second crop seasons.  

"However, we have already begun to see soybean-corn rotation re-established in the right of way and yields gradually recovered," Ebrahimi said. "In addition, our farming comparison results show that the use of no-tillage technology in the right-of-way area has slightly increased corn production, especially under adverse weather conditions in 2020."

Researchers are completing the analysis of the project in subsequent years. At this point, all they can say is that compaction and yield are beginning to recover very slowly. Ebrahimi used the Agricultural Production System Simulator (APSIM) to simulate the impact of soil compaction on crop yields over time. Publications on her results are under review.

"We hope to continue this research—especially to collect more years of corn data—and use it to provide recommendations for best management practices to more effectively reduce the impact of future pipeline installations on crop yields," Tekeste said.

Mehari Tekeste, Agriculture and Biosystems Engineering, 515-292-2464, mtekeste@iastate.edu Ann Y. Robinson, Agriculture and Life Science Communication, 515-294-3066, ayr@iastate.edu

Researchers on the pipeline research team are (from left) Mark Hanna, Mehari Tekeste, Elnaz Ebrahimi and Robert Horton. The photo was taken by Whitney Baxter of Iowa State University. 

Scenes during the construction of the access pipeline in Dakota. The photo was taken by Mehari Tekeste, Iowa State University. 

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