- Agronomic: grass (misc. perennial), Legumes, Birdsfoot trefoil, Sainfoin
- Animals: bovine
- Animal Products: meat
- Animal Production: feed/forage, grazing management, pasture fertility
- Crop Production: nutrient cycling, nutrient management
- Education and Training: decision support system, demonstration, display, workshop
- Farm Business Management: whole farm planning
- Production Systems: agroecosystems, integrated crop and livestock systems
- Soil Management: nutrient mineralization, soil analysis, soil chemistry
- Sustainable Communities: local and regional food systems, public participation
Beef production is at a crossroads in terms of environmental and economic sustainability. Recently, grass-fed beef has gained popularity with consumers who are concerned about the environmental impact of beef production and animal welfare. However, feedlot-finished beef has been shown to have lower rates of greenhouse gas emissions than pasture-finished beef. Here, we proposed using tannin- and saponin-containing legume forages to lower greenhouse gas (GHG) emissions and improve soil nitrogen (N) retention in pasture-finished beef systems. These forages are known for reducing methane production in cows, reducing leachable N-inputs, reducing the need for further N-additions, improving animal rate of gain, and preserving natural grassland ecosystem services. However, it was still unclear how tannins and saponins function in the soil. Previous work has shown that tannins reduce mineralization rates, although it is unclear whether this is a function of tannin structure or concentration. Saponins are another secondary plant compound which have been observed to have a similar function to tannins in the soil. To discriminate the effect of tannin or saponin source and concentration on soil N-cycling, we conducted an in vitro incubation study using varied doses of condensed tannins extracted from Lotus corniculatus (birdsfoot trefoil) and Onobrychis viciifolia (sainfoin), and saponins from Medicago sativa (alfalfa) as opposed to commonly studied commercially-available varieties, to monitor rates of N-mineralization, volatilization, and GHG production in pasture soil. Incorporating the influence of N-cycling on soil GHG emissions required a whole-farm environmental sustainability assessment. Holos is a comprehensive and user friendly GHG accounting software which uses a whole-farm approach to assess beef production environmental and economic sustainability. Holos is designed for use in Canada, restricting its adoption in the U.S. We collaborated with Agriculture and Agri-Food Canada to extend Holos’ geographic range and characteristics to include Utah for easier adaptation throughout the Intermountain West. We trained local producers and researchers to use Holos through workshops, poster presentations, talks, and a fact sheet. These activities facilitated Holos’ use, giving producers the ability to understand how management changes affect environmental and economic sustainability and giving researchers new tools to model on-farm emissions. Through our research, we found that tannins from birdsfoot trefoil were able to reduce soil soluble total N yields, N mineralization, and nitrification in a dose-dependent manner with no notable effects on C cycling. We also found that switching from grass to legume forages decreased the net GHG emissions from the finishing stage of pasture-based beef production operations by reducing fertilizer and fuel use. Based on our educational and outreach activities, all participants indicated a change in their knowledge, attitudes, and skills, as well as an intention to change their practices in the future. A majority of participants also indicated that they anticipated using knowledge from the workshop in future new and existing educational programs.
- Extract tannins from fecal samples produced by cows that have grazed on birdsfoot trefoil (BFT) and sainfoin (SFN) tannin-containing legumes to determine a baseline tannin concentration that we would expect to see in the field in April 2018. We will also extract tannins from the leaves of BFT and SFN plants, and saponins from the leaves of ALF plants in April 2018. The tannins and saponins extracted from these leaves will be added to the soils during the incubation study and used as assay standards.
- Perform a 84-day soil incubation study with varying concentrations of tannins extracted
from BFT and SFN leaves, and a single concentration of saponins extracted from ALF leaves (May-June 2018).
- Determine concentrations of NH4+, NO3–, and NH3 at the start and end of the incubation, and throughout the study on the same days as headspace sampling (May-June 2018). These data will be used to calculate rates of N mineralization.
- Determine concentrations of soluble total N, total C, and organic C in soil samples at the start and end of the incubation study (May-June 2018) as an approximation of secondary compound complexation in soils. Soils will also be assayed for autoclaved citrate extractable protein (ACE protein) prior to KCl extraction at the start and end of the incubation to determine the amount of protein substrate available to be bound by tannins or saponins (May-June 2018). Soluble nutrient extractions and ACE protein assay trials will be performed prior to the incubation study.
- Determine concentrations of CO2 and N2O gases using gas chromatography throughout
the incubation to determine production rates of each gas as well as cumulative production (May-June 2018). Headspace samples will be collected on days 0, 2, 7, 14, 28, 42, 56, 70, and 84.
- Create Holos farm scenarios for feedlot-finished, and various pasture-finished (MBG,
BFT, SFN, ALF) beef production systems for Utah using climate and soil data from Utah sites where pasture-based beef production is or could be carried out, and quantify GHG
emissions for each scenario in units of CO2 equivalents (CO2-eq) (April-June 2018).
- Create an electronic fact sheet resource explaining the benefits of using models as an exploratory tool to understand how farm management changes affect net GHG emissions (March 2019).
- Host two half-day training sessions for regional producers and outreach personnel in
partnership with USU Extension to demonstrate the use of Holos software (April 2019).
- Evaluate how producers’ skills have changed with regard to Holos software abilities as
well as their understanding of how management changes influence farm sustainability
before and after the Holos training sessions (April 2019).