Many agricultural properties include areas of land that aren’t used for crop production, such as field edges, roadways, hedgerows, and rows between crop beds. These areas are often left bare and do not provide habitat for wildlife. In 2019, Scholls Valley Native Nursery, a family-owned business near Gales Creek, received a grant from Tualatin Soil and Water Conservation District. This grant allowed researchers to explore the use of native plants as groundcovers in non-crop areas to protect soils, support pollinators, and reduce the need to manage pesky weeds.
Nursey owners, George and Wendy Kral, explain that “standard agricultural practices in the Tualatin Valley maintain tens of thousands of acres in bare or mono-specific states in any given season.” Traditionally, farms in the Tualatin Valley utilize groundcovers, such as oats or red clover, to reduce erosion and maintain soil health in unseeded fields, but non-crop areas are kept “sterile and plant-free.” This practice, as well as the heavy use of pesticides and chemical fertilizers, increases water pollution and loss of plant and wildlife diversity, including pollinators, songbirds, and insects.
Over 100 native plant species were observed to determine their effectiveness as groundcover.
Researchers began with a pilot study to determine project cost as well as potential plant species. In 2020, they chose four groundcover mixes, including a total of 103 native species, to assess the positive effects of native ground-covering plants in different agricultural settings.
Planting sites were prepared by removing weeds and then planting native bulbs and seed mixes. Throughout the growing seasons, the cover crop species were monitored for their:
- ease in becoming established
- ability to provide ground coverage
- presence across seasons
- ability to support pollinators
- compatibility with crop systems (i.e., not competing with crops)
- level of invasiveness (i.e., moving into areas where they were not seeded)
Out of the 103 species tested, 76 were observed and measured during the growing seasons. Researchers recommended 40 of these species for planting in Tualatin Valley and Willamette Valley farms based on their ability to provide beneficial ground coverage and their adaptiveness to farmed areas. Relaxing “zero-tolerance policies” on various weeds was also recommended because these weeds increased plant cover and diversity while eliminating the cost of removing them.
Nectar-producing flower species were present in all seeded areas and there were no negative effects on field production from increasing ground cover. In fact, this study found that per-acre crop yields increased by 45% over the course of the study.
Native groundcover species benefit pollinator populations.
Pollinators, like bees, moths, and butterflies, rely on nectar-producing plants to survive, but pesticides and herbicides have greatly reduced the diversity and cover of these plants, thus reducing pollinator populations.
Observers from Oregon Bee Atlas noticed that the increase in plant diversity in the non-crop areas provided a direct benefit to pollinators. They recorded the frequency of visits for bees, beetles, butterflies, flies, and wasps. Overall, pollinator visitation was observed on 68 native species and 6 weed species in the study area.
Interested in learning more about this research?
Read the full findings report from Scholls Valley Native Nursery here: Findings and Recommendations: New Ground Covers for Ag
Grant funds are available for conservation research and projects.
This research project received funding from Tualatin SWCD’s Tualatin River Environmental Enhancement Grant, which provides between $5,000 and $100,000 for projects that promote conservation within the Tualatin River Watershed.