Perennial Turfgrass Cover Crops in Maize Production Systems
Cost and time are the primary barriers preventing farmers from adopting cover crops in Iowa. Despite winter rye being able to reduce nitrate loss by nearly 50 percent, the cover crop is sometimes correlated with a yield loss in the following corn crop when terminated too close to the time of corn planting. However, terminating winter rye early to avoid yield loss in corn limits how much nitrate the cover crop can sequester. These challenges reduce the benefits and cost-effectiveness of cover crops.
Perennial grasses utilized as living ground cover could potentially overcome barriers experienced with annual cover crops. Ideally, a perennial cover crop would grow actively during the autumn and spring but become inactive during the summer when corn and soybeans experience the most growth, reducing competition with the main crop. Active growth of perennial grasses in autumn would increase nutrient accumulation that otherwise would have been lost through leaching or runoff. Previous research with cool-season grasses indicate that a Kentucky bluegrass cover crop grown concurrently with conventionally managed corn can produce comparable yields to a control with no cover crop. Current research corroborates these findings and suggests that Sandberg bluegrass cover crops can perform similarly.
In addition to their advantages over annual cover crops, perennial grass cover crops can restore valuable ecosystem services such as increased water infiltration, reduced soil erosion and decreased nitrogen and phosphorus losses to the environment. Researchers propose to evaluate the economic and environmental impacts of these relatively new perennial cover crop systems. The team will use suitable cool-season grass candidates identified through current research efforts, with a focus on investigating their above and below-ground nutrient dynamics and ability to reduce nonpoint nutrient pollution.
Three replications of 15 selected varieties of Kentucky bluegrass and Sandberg bluegrass will be planted into field plots along with a no-grass control at the Sorenson Farm near Ames, Iowa. Following successful establishment of grass plots, corn will be planted into tilled strips of grass at conventional rates and spacing. Growth of both grass and corn will be measured biweekly, with corn yield collected at the end of the field season. Soil testing and leaf tissue sample analyses for N and P concentrations will be conducted on a biweekly basis and data analyzed. At the end of the project, findings will be shared in an extension publication and at relevant conferences.
This project aims to investigate the above- and below-ground nutrient dynamics and the potential of using perennial ground cover (PGC) to reduce nonpoint nitrogen and phosphorus pollution. Two cool-season perennial grass species, Kentucky bluegrass (Poa pratensis) and bulbous bluegrass (Poa bulbosa), a species with a distinct and extended summer dormancy, are grown as PGC in otherwise conventionally grown corn. A field trial was established at the Sorenson Research Farm near Boone, Sept. 7, 2019. The experiment consists of 12 treatments with four replications. Each treatment is either a single cultivar of Kentucky bluegrass or bulbous bluegrass (PB 55), or a 2-cultivar Kentucky bluegrass blend. The control is non-grass plot with bare soil. The selected Kentucky bluegrass cultivars represent the diversity present in available commercial cultivars. Seeding rate for Kentucky bluegrass was approximately 2 lbs. per 1000 square feet while the seeding rate for bulbous bluegrass was 14 lbs. per 1000 square feet. Plots are 20 feet by 22.5 feet.
Preliminary observation indicated that uniform germination has taken place for all treatments except for the plots seeded to two Kentucky bluegrass cultivars (Geronimo and Blue Ghost), which had poor stand establishment and late germination. Soil samples used to establish baseline nutrient concentrations were collected shortly after grass seeding. For each replication, three sets of soil cores were taken at the 0-15 cm and 15-30 cm depth. The cores from each depth were combined and sent to AgSource Laboratories in Ellsworth, Iowa, for analysis.
Outreach this period included 2 presentations.