Rangeland restoration often fails because native plants do not have enough water to germinate, experience overwhelming competition from non-native annuals, or both.
Creating a rough, pothole-like soil surface improves soil moisture and reduces competition from annual non-native plants (Johnston and Chapman 2014). Rough soil surfaces trap seeds in areas where soil moisture is high, and aggressive invasives are often less competitive in high-moisture environments.
The goal of this project was to extend these research results to larger scales. To make the rough surface efficiently, CPW partnered with WPX Energy to develop a new piece of machinery, dubbed a ‘pothole seeder’. In 2012, we used the seeder over about 7 acres at Horsethief State Wildlife area which were heavily invaded by cheatgrass. Combined with a light application of imazapic herbicide, this treatment worked well to establish native grasses, flowers, and shrubs at the site.
About half of the area also received a super-absorbent polymer treatment. Super-absorbent polymers swell when wet then slowly release moisture over time, reducing water stress in plants. Although we saw an initial benefit of super-absorbent polymer on seedling establishment, no long-term benefit of super-absorbent polymer was observed.
In 2018, CPW property technicians Ivan Archer and Derek Lovoi created a second pothole seeder. The newer pothole seeder combines seed boxes from a Truax rangeland seed drill with large notched discs which make the pothole pattern. The new potholer was tested at Escalante State Wildlife Area and works well.
The 2012 pothole seeder (top) and the 2018 pothole seeder (bottom)
The rough soil surface pattern produced by the 2018 pothole seeder at a test site in Escalante State Wildlife Area.