The simulated environmental impact of incorporating white clover into pasture-based dairy production systems

Abstract

White clover (WC) offers an alternative source of nitrogen (N) for pasture-based systems. Substituting energy-and carbon-intensive synthetic N fertilizers with N derived from biological fixation by WC has been highlighted as a promising environmental mitigation strategy through the omission of emissions, pollutants, and energy usage during the production and application of synthetic fertilizer. Therefore, the objective was to investigate the effect of the inclusion of WC in perennial ryegrass (PRG) swards on the environmental impact of pasture-based dairy systems. Cradle-to-farm gate life cycle assessment of 3 pasture-based dairy systems were conducted: (1) a PRG-WC sward receiving 150 kg of N/ha per year (CL150), (2) a PRG-WC sward receiving 250 kg of N/ha per year (CL250), and (3) a PRG-only sward receiving 250 kg of N/ha per year (GR250). A dairy environmental model was updated with country-specific N excretion equations and recently developed N 2 O, NH 3 , and NO 3 − emission factors. The environmental impact categories assessed were global warming potential, nonrenewable energy, acidification potential, and eutrophication potential (marine and freshwater). Impact categories were expressed using 2 functional units: per hectare and per metric tonne of fat-and protein-corrected milk. The GR250 system had the lowest milk production and highest global warming potential, nonrenewable energy, and acidification potential per tonne of fat-and protein-corrected milk for all systems. The CL250 system produced the most milk and had the highest environmental impact across all categories when expressed on an area basis. It also had the highest marine eutrophication potential for both functional units. The impact category freshwater eutrophication potential did not differ across the 3 systems. The CL150 system had the lowest environmental impact across all categories and functional units. This life cycle assessment study demonstrates that the substitution of synthetic N fertilizer with atmospheric N fixed by WC has potential to reduce the environmental impact of intensive pasture-based dairy systems in temperate regions, not only through improvement in animal performance but also through the reduction in total emissions and pollutants contributing to the environmental indicators assessed.

Life cycle assessment of pasture-based dairy production systems: Current and future performance

“…Using the same methodology, Herron et al ( 2021) calculated an AP of 5.76 to 6.21 mol c H + -eq/ton of FPCM for 3 pasture-based research systems in Ireland. Both Herron et al (2021) and the current study identify NH 3 as the dominant acidifying pollutant from pasture-based systems, with manure management and synthetic fertilizer application being key emission sources. The adoption of available technologies (i.e., low-emission slurry spreading and protected urea) and improving grassland and manure management in the target systems contributed to the mitigation of NH 3 emissions and thus AP.…”

“…Life Cycle Inventory. Life cycle inventory analysis was conducted using the LCA model described in Herron et al (2021). Animal performance, forage production, and manure management data were used to populate the model.…”

“…The low FEP is attributed to the current study importing less P onto the farm through inputs, P fertilizer application rate, and variation in life cycle inventory methodology. Using a similar methodology, Herron et al (2021) reported lower FEP per kilogram of FPCM for research-based pasture systems, due to superior milk production and grassland management, and lower concentrate feed supplementation.…”

“…Life cycle assessment (LCA) is an internationally recognized methodology used to determine the environmental impact of all stages embodied in the life of a product, service, or process (ISO, 2006a,b). Agricultural research has adopted LCA to determine the environmental impact of different products (Famiglietti et al, 2019) and production systems (Cederberg and Mattsson, 2000;Ledgard et al, 2009;O'Brien et al, 2012), and to assess the effects of management practices (Schils et al, 2005;Chobtang et al, 2017;Herron et al, 2021). Agricultural LCA studies often take a holistic view of an agricultural system up to the point in which the product leaves the farm gate, where all processes that occur on farm and those associated with the production of farm inputs are included.…”

Solutions to enteric methane abatement in Ireland

“…There are a number of other ERA-GAS-funded projects including SeaSolutions, a Teagasc co-ordinated project which aims to determine the potential of seaweeds to reduce enteric CH 4 emissions from sheep, beef and dairy cattle, METHlab which focuses on the use of lactic acid bacteria as an approach to reduce CH 4 emissions from ruminant livestock and GrassToGas which aims to identify individual animal, feed and environmental attributes associated with feed and water intake efficiency for pasture-based sheep production systems using portable accumulation chambers (Image 1). Herron et al, 2021). Thus, investigating how different sward compositions impact CH 4 emissions/emissions intensity from grazing livestock is certainly an avenue worth further investigation.…”