Prairie enhancement of cool-season grass stands
Can roadsides dominated by cool-season grasses be enhanced by direct seeding and frequent first year mowing? This simplified management technique would reduce costs associated with weed control and site preparation, increase simplicity in equipment and skill requirements, add flexibility in planting options, and improve pollinator/monarch habitat and water quality in roadsides at comparatively low cost.
We established three research sites testing native plant establishment with and without mowing in three different Iowa counties (Benton, Linn, Fayette) consisting of experiment plots paired with demonstration plantings. We used a diverse prairie seed mix with 71 species and standardized seeding rates for milkweed species. We conducted site-preparation by mowing and removing the duff layer in April 2017, then seeded using a no-till drill in late April. We conducted establishment mowing every three weeks from June 1- August 30.
Based on our first year of data:
- Most prairie species established poorly when seeded (no-till drilled) into established stands of non-native grasses
- Milkweed seedlings emerged at sufficient densities to create monarch habitat (> 0.6 plants/m2) with minimal site preparation (duff removal only) and no follow-up management, but it is still unknown whether that translates to adult milkweed establishment
- First year mowing does not reduce competition enough for sufficient native seedling establishment- initial herbicide is likely necessary
Building Multifunctional, Cost-effective Prairies
Many conservation programs are highly specified in their restoration objectives, and program design (enhance pollinators or halt surface erosion for example) may focus entirely on optimizing one ecological metric at the expense of others. Can multifunctional seed mixes be designed to meet many objectives at once, or is continuing single objective optimization the most effective conservation strategy? What is the most cost-effective way to do it?
We established a randomized complete block experiment testing seed mix designs (grass to forb seeding rate ratios, site customization) with and without mowing in northeastern Iowa. We assessed an economy grass mix ($130/ac, 21 spp., 3:1 grass-to-forb seeding ratio), a diversity mix ($291/ac, 71 spp., 1:1 grass-to-forb), and the pollinator mix ($368/ac, 38 spp., 1:3 grass-to-forb). We conducted site-preparation by disking and cultivating the site and seeded using a no-till drill in late April. We conducted establishment mowing three times during the first year (2015), but did no other management afterwards.
Based on two years of data:
- Diverse, site-appropriate seed mixes (1:1 grass to forbs) established well and supported pollinator forage plants while remaining cost effective
- Pollinator seed mixes (1:3 grass to forbs) supported pollinator forage plants but established poorly and were not cost-effective
- Grass dominated seed mixes (3:1 grass to forbs) were cost-effective but supported very few pollinator forage plants
- Frequent first year mowing greatly increased native plant establishment and cost-effectiveness for all seed mixes