Construction of pipelines to transport natural gas often result in disturbances to soil not conducive to re-establishing plants in these environments, which then leaves soil susceptible to erosion. Additionally, these disturbed soils may also suffer from compaction thus reducing pore space and the infiltration of water. These problems often require landowners or construction entities to reseed right-of-ways (ROW) multiple times.

This study was conducted at the Williston Research Extension Center at the heart of the Bakken oil-extraction region of North Dakota. This study examined how various preparation methods impacted several soil and plant parameters. Our study examined land imprinting, straw pinning, hydromulching, and the combination of hydromulching with land imprinting, all on 2% and 5% slopes. Rain simulations were conducted so that plant establishment, bulk density, sediment load in runoff, total runoff, and water infiltration could be quantified.

Study Objectives:

The end goal of this study is to determine which treatment would offer the best site-preparation method for the two slopes investigated in this study. While this study does not occur on an active- or post-construction site, it will be able to help understand the potential of these treatments to aid plant establishment.

Site Preparation Techniques:

In 2020 the site was cropped to barley and in the fall 2020, to reduce the concentration of straw on the soil surface, the site was tilled multiple times. All plots were then broadcast seeded with oats and a native seed mix of cool and warm-season grasses. Once seeded, the following treatments were imposed at two landscape positions, three replications each: land imprinting, straw pinning, hydromulching, and the combination of hydromulching with land imprinting.

Land Imprinting

Land imprinting is most often used in arid, desert environments. However, land imprinting has not been previously used in the study region. Imprinting is used to create small impressions across the landscape and depending on the imprinter, these imprints can range in size from a few inches to about the size of a standard sheet of paper. They are commonly V-shaped so that water collects at the bottom of the imprint, thus concentrating water, so that these microenvironments assist seed germination and reduce erosion.

Hydromulching

In the study region, hydromulch may be used to help maintain seed-soil contact, conserve soil water, and reduce erosion, especially in areas with drastic topographic relief. Hydromulch is commonly cellulose based and is mixed with water in a tank and subsequently sprayed across the desired area. In addition, hydromulch does provide an immediate source of moisture for seeds to germinate and it can conserve water by reducing evaporation.

Straw-pinning

The use of straw on ROWs is another frequently used method to reduce erosion and conserve soil water. Straw is first blown across the target area and then pinned into the soil surface with disc-type rollers so that the straw stands up on its end, much like post-harvest wheat or barley residue.

Current Progress:

Rain Simulations

Rain simulations were conducted on each of the four treatments plus a control on two landscape positions. These simulations were carried out for a duration of 30 minutes each, simulating a 1 in 25-year rain event. Plots were set up in September of 2020, with simulations being carried out within two weeks.

Results:

After completion of the rain simulations, we concluded that there was no difference between the two landscape positions, and thus analyzed results accordingly. Results indicate that hydromulch in both situations had significantly more runoff, but less sediment load in water runoff. Imprinting also had significantly less total runoff than any treatment, with one trial not producing any runoff as the impressions filled with water. Straw pinning also greatly reduced runoff when compared to the hydromulch trials. Lastly, bulk density remained unchanged between treatments.

Considerations:

The fall of 2020 and subsequent spring of 2021 have been highly unusual for western North Dakota. There has been very little rainfall to date and the area received very little snowfall, with no snow cover being present the entirety of winter. This lack of snow cover left sites susceptible to wind erosion, with the area seeing gusts of over 100mph. Imprints have leveled out more than expected, which was initially a concern of partnering entities. Moving forward, an additional round of rain simulations will be conducted in the summer of 2021. We hope to also evaluate plant establishment as the summer continues.

Conference Presentations:

     Lardy, J., T. DeSutter, M. Meehan, N. Derby, K. Horsager, A. Daigh. 2021. An Examination of Pipeline Site-Preparation Methods for Improving Plant Establishment. Presented at the 2021 Manitoba Soil Science Society Annual General Meeting, 4-5 February, Winnipeg, Manitoba (virtually)