Santiago A. Utsumi, PhD
Innovations for Sustainable
Farming & Ranching
Inspired by Nature, Driven by Science
Sustainable intensification of dairy through on-farm monitoring and decision management of GHG sources and sinks
Climate change along with population growth, hunger defeat, poverty alleviation, habitat regeneration, and community integration, is a defining challenge of the 21st century. From shifting weather patterns, to increasing risks for floods to devastating effects of droughts and heat waves on crops and farm animals, the impacts of climate change are becoming global in scope and unprecedented in scale. If solutions to revert drivers of climate change delay the issue will turn into a severe threat for humanity,
To contribute to the global sustainability of foods, habitats and communities, dairy must embrace the protection of Nature and the services Nature provides to people. We must embrace the social, economic and environmental dimensions of food systems, including hidden ecological benefits and services, and the likely synergies as well as trade-offs among cultural, environmental and societal services from agriculture,
A fundamental benchmark for dairy is to work towards a circular carbon economy. According to a recent report by FAO, global emission intensities of greenhouse gases (GHG) have declined by almost 11 percent over the period 2005-2015, with more efficiently managed and technified dairy regions ranging between 1.3 to 1.4 kg CO eq. kg of energy corrected milk (ECM), while dairy regions in most developing economies sat at 4.1 to 6.7 kg CO eq. per kg of ECM, The sustainable intensification of dairy must continue at pace, yet further commitments towards a lower-carbon future would be needed to meet global policy and mitigation agreements. To achieve this goal, both further reduction of emission intensities and increasing removals by alternative sinks, need to be addressed.
A long-term agriculture research (LTAR) project was established at the W.K. Kellogg Biological Station of Michigan State University in 2008. The mission was directed towards identifying and quantifying ways that ecological approaches for intensive grazing systems can reduce the GHG pressure of ruminant animal production, using grass-based robotic dairy systems as testing model. The enteric methane production by ruminants represents a substantial part of the GHG contributions, together with nitrous oxide emissions from N urine depositions on pastures and from manure management.
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Temperate grasslands are characterized by scale-dependent interrelationships and interactions between soil, plant, animal, and atmosphere components. As such, emergent synergies and trade-offs between ecosystem services of provision, support and regulation could rise at different temporal and spatial scales. Furthermore, we cannot assess those services by traditional plot experimentation alone; using this narrow spatial lens will certainly exclude scale-dependent effects, feed-backs and controls. The LTAR established a multiscaled patch to field, to farm experimental platform to test those effects. The fundamental hypothesis is that aggregating spatiotemporal effects of grazing in interaction with climate-related drivers (mainly precipitation and temperature) will trigger nonlinearities for potentially relevant regenerative processes (biodiversity retention, reduction of enteric methane and manure derived nitrous oxide, increase of SOM accrual, etc.) with implications on grassland production, grassland Global Warming Potential (GWP) and capacity of grassland for GWP mitigation (i.e. GWP/animal production ratio), as I have modeled hypothetically (left).
Above I share insights on the hypothetical aggregating and spatiotemporal effects of stocking rates and disturbances on animal production and the capacity for resiliency, adaptation and mitigation of grasslands. The vertical dash line represents the hypothetical disturbance level for maximum ecosystem adaptation and mitigation.
Reducing 'sources'
The customized design to quantify and monitor expired dairy cows' carbon gases (developed in collaboration with C-Lock Inc), individually and remotely, shows the degree to which scaled emissions from entire dairy herds can be properly quantified and managed. Across several experiments both, the fluxes of CH4 and CO2 were quantified with high repeatability (repeatability was over 75%) suggesting consistently a low variation for the NDIR gas sensors, instrumentation and methodology, but large variation associated to cows, dietary treatments and temporal diet effects.
Here I share plausible mitigation pathways according to a field work and structural equation modeling conduced by our lab assistant and former intern Lucinda Watt, in 2014, Lucy discovered two promising low-carbon pathways to further reduce the CH4 intensity of milk. The first is through continued improvements of milk production (left) such that fixed emission costs associated to the maintenance requirements of cows are diluted to the greatest extent possible. This appears to happen once dairy cows pass the mark of the 30 kg of milk production. The second pathway, is through further improvements of Net Feed Efficiency (or conversion of ME to NEL), as suggested by the marked vertical dispersion of CO2 and CH4 intensity fluxes for a same level of milk (left). Importantly here, is to recognize that a pathway that dilutes emissions by greater milk yield appears to be more effective to reduce the CH4 intensity compared to nutritional manipulations that seek reductions of enteric CH4 alone (right), yet both pathways, reducing enteric methane and increasing milk, can have synergistic effects on reducing the CH4 intensity of milk (right).
Increasing 'sinks'
The LTAR suggest today additional pathways that can be designed to minimize and even offset emissions through careful grazing prescriptions to either, sequester soil carbon, minimize pasture-derived emissions, or both. After 8 years of intensively replicated soil organic matter and soil carbon monitoring (32 grazed fields of 1 ha), we found that both, 'perenniality' and 'diversity' are among key drivers for regenerate soil processes and properties in transitions from intensive tillage systems of few homogeneously managed crops (mainly maize silage, soybeans and short rotation alfalfas) to a wider array of heterogeneously assembled plant communities (up to 8 species), both spatially and temporally,
The change over time for ecosystem health indicators, such as the rate change for SOM, was not different for the set of 'highly stocked (4 cow/ha) compared to the low stocked (2.5 cows/ha) fields (above), suggesting that the transition from annual cropping to diversified perennials outweighed the effects of stocking densities, if any. Furthermore, mending previously weakened links between intensive tillage systems, soil food webs, and biogeochemical processes, was link to a net accrual of over 2.1 t of SOM year or 1.2 t of carbon sequestration (30 cm of top soil) for the first years of transition, thereby suggesting an offset of 4.4 t of CO2 eq/ha/y or about 25% over a standardized IPCC Global Warming Potential (GWP) for the low stocking rate system (2.5 cows/ha at ECM of 8,800 kg/cow). Results from LTAR shows how simple biologically-based technologies, such as the prescribed grazing of diverse plant communities, can make pasture-based dairy management tenable, thereby fulfilling both environmental and economic objectives by making environmental outcomes economically viable and even advantageous. Despite the positive findings, future experimentation and modeling work would need to also address coming unknowns. First, whether soil carbon sequestration will level off with time, only a long-term soil monitoring agenda will tell. Second, as suggested recently there is a need to address differences on the atmospheric lifetime and radiative impacts of different dairy GHG, ruminant CH4 in particular. Methane is a GHG with a 10-year lifespan. Therefore the warming effect of the short-lived CH4 would be much lower than anticipated. Likewise, alternatives to the commonly used IPCC '100-year GWP index would be needed. One proposed approach is to use the GWP* index which considers deferentially the `warming-equivalents' of the short-live CH4. This alternative GWP* index may represent a more realistic measure to assess the warming effect of ruminant-based food systems.