- 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 propose using tannin-containing legume forages to lower greenhouse gas (GHG)
emissions and improve 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 is still unclear how tannins 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. To discriminate the effect of tannin source and
concentration on soil N-cycling, we propose an in vitro incubation study using varied doses of
condensed tannins from Lotus corniculatus (birdsfoot trefoil) and Onobrychis viciifolia
(sainfoin), 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 will require 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 currently designed for use in Canada, restricting its adoption in the U.S.
We propose to extend Holos’ geographic range and characteristics to include Utah for easier
adaptation throughout the Intermountain West. By training local producers and extension staff to
use Holos, we will facilitate its use while giving producers the ability to understand how
management changes affect environmental and economic sustainability.
Project objectives from proposal:
1. Extract tannins from fecal samples produced by cows that have grazed on BFT and 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 in April 2018. The tannins extracted from these leaves will be
added to the soils during the incubation study and used as assay standards.
2. Perform a 48-day soil incubation study with varying concentrations of tannins extracted
from BFT and SFN leaves (May-June 2018).
3. Determine concentrations of NH4
, 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.
4. Assay tannins in soil samples at the start and end of the incubation study (May-June
2018) to monitor tannin availability in soils. Soils will be assayed for Bradford reactive
soil protein (BRSP) prior to KCl extraction on each sampling date to determine the
amount of protein substrate available to be bound by tannins (May-June 2018). Soil
tannin extractions and BRSP assay trials will be performed prior to the incubation study
to determine the amounts of each substrate needed for successful assay.
5. 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, 3, 7, 14, 21, 28, 35, 42,
6. Create Holos farm scenarios for feedlot-finished, and various pasture-finished (MBG,
BFT, SFN) 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).
7. Create print and electronic resources explaining the effect of tannin-containing legume
forages on livestock health and soil nutrient cycling in Utah (March 2019).
8. 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).
9. Create an online video tutorial with partner researchers at Agriculture and Agri-Food
Canada where Holos was developed to demonstrate how to use Holos software and adjust
it for Utah soil and climate conditions (January 2019).
10. 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).