Agronomy and Horticulture Department
Date of this Version
Current agricultural systems focused on production of few commodities are facing production, economic, and environmental challenges. To address these challenges, Integrated Crop Livestock Systems (ICLS) have emerged through three primary methods 1) perennial grasslands for grazing and/or hay production, 2) crop residue grazing, and 3) cover crop grazing. To evaluate potential of ICLS mitigating current challenges, a field scale model ICLS was developed in 2015. The ICLS includes 4-ha each of ‘Newell’ smooth bromegrass (Bromus inermis L.), ‘Liberty’ switchgrass (Panicum virgatum L.), and ‘Shawnee’ switchgrass. The ICLS also included 8-ha of continuous corn (Zea mays L.). In 2016, only hay was harvested from perennial grasslands and in 2017, 2018, and 2019 the perennial grasslands were grazed. Following grazing, the switchgrass varieties were harvested for residual biomass production post-senescence. Continuous corn included residue removal treatments with and without a cover crop. This thesis reports results from three studies. To evaluate the response of cool-season annual grass cover crops to defoliation, a greenhouse study, in conjunction with a replicated field experiment, was conducted in 2018-2019 and 2019-2020. Results showed small grains used as cover crops had decreased survivability and biomass production when defoliated during early plant establishment. Production data from the ICLS was used to construct enterprise budgets to evaluate system profitability on marginally productive cropland. The ICLS was not consistently more profitable than continuous corn production. However, baling hay only and removing grazing from the ICLS was more profitable than continuous corn production. To evaluate ICLS as a mitigation strategy for soil GHG emissions, soil N2O and CH4 were measured during each growing season in the perennial grasslands and continuous corn. Results suggested that 1) grazing perennial grasslands did not consistently impact soil GHG emissions, 2) crop residue and cover crop management may impact soil N2O emissions, and 3) continuous corn production resulted in greater soil N2O emissions than perennial grasslands due to higher application amounts of synthetic N fertilizer. The results from this research can provide options for producers implementing ICLS and insight for further development of ICLS for Eastern NE that meet production, economic, and environmental challenges.
Advisors: Daren Redfearn and Rob Mitchell
Agricultural Science Commons, Agriculture Commons, Agronomy and Crop Sciences Commons, Botany Commons, Horticulture Commons, Other Plant Sciences Commons, Plant Biology Commons
A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agronomy, Under the Supervision of Professors Daren Redfearn and Rob Mitchell. Lincoln, Nebraska: July, 2020.
Copyright 2020 Elizabeth K. Christenson