By Allen Williams, Ph.D.
The problems of many current conventional grazing systems can be avoided by ecologically sensitive management of ruminants across the landscape. Wild ruminants, by the hundreds of millions, have existed for millennia on the North American landscape and are responsible for the tremendous fertility and soil carbon that amazed our ancestors as they moved across this continent. By implementing biomimicry and eco-mimicry in our grazing practices, emulating the way wild ruminants once roamed across this vast land, we can restore soil health and ecosystem health to a high state of function. We call this Adaptive Grazing.
Research Findings
Adaptive grazing management, using multi-paddock grazing strategies, has been shown to be superior to continuous grazing practices. It may be called several things: Adaptive Multi-Paddock grazing (AMP), Adaptive Stewardship Grazing (ASG), and regenerative grazing (RG). A long-term study conducted by Dr. Richard Teague at Texas A&M University verifies adaptive grazing improves vegetation, growth and recovery of vegetation, soil health parameters, soil carbon, and animal production relative to continuous grazing. The study measured impacts on pasture vegetation and soils achieved by grazers who adapted grazing management practices that allowed for flexibility in changing circumstances in order to achieve desirable outcomes (Teague, et.al., 2011).
At the ranch scale, adaptive grazing at higher stock densities provides the best outcomes in vegetation and animal performance. Additionally, it, is superior to continuous grazing in relation to conservation and restoration of resources, provision of ecosystem goods and services, and farm profitability.
The study by Teague differed significantly from prior grazing studies by researchers who examined multi-paddock grazing in relatively small areas, used set stock rotations, and did not manage adaptively. Teague’s study added the elements of real-world grazing conditions through whole-ranch grazing, high stock densities, and flexible management adapted to actual conditions.
The study showed significant improvements in soil aggregate stability, soil water infiltration rates, soil water holding capacity, vegetative biomass production, and plant recovery periods. Additionally, the soil fungi:bacteria ratio was significantly improved, indicating superior soil microbial functioning and mineral cycling.
Teague’s research has been critical to better understanding the benefits of adaptive grazing. More recent research has continued to validate these benefits. Research conducted by Martin et.al. (2014), Jakoby, et. al. (2014) and Teague, et. al. (2015) showed that ecological function and grazing profitability increased with an increase in the number of paddocks. However, these were temporary paddocks that facilitated adaptive management, not permanently constructed paddocks that would dictate more prescriptive management. The consensus from these trials was that:
- Short periods of grazing with adequate recovery gave the greatest profit and ecological function.
- Adjusting grazing management with changing conditions increases ecological function and profitability.
- Fixed management protocols reduced benefits.
- Profitability decreases if recovery is too short or too long.
- Stocking rates can be increased without damaging ecological function as number of paddocks is increased.
Antibiotic Use Affects Greenhouse Gas Emissions (GHG’s) and Microbiota
In a study published in 2016 (Hammer, et. al., Proc R. Soc. April 2016), it was revealed that routine antibiotic use in cattle has unintended consequences on micro- and macro-organisms in our ecosystems. Routine antibiotic use alters the gut microbiome of the ruminant which then alters microbial emissions of GHG’s. The result was increased methane fluxes from the manure of cattle due to alteration of the natural interactions between methanogenic archaea and bacteria in the cattle rumen and dung. The antibiotics not only changed the microbiota of the gut but also the microbiota of non-target organisms like dung beetles and other important soil insects. This created negative downstream effects on the microbiota of both the cattle manure and the dung beetles.
The results of this research are profoundly important because almost all prior research regarding methane emissions from livestock have been conducted using conventional systems as the model. This means heavy antibiotic use was routine in the systems measured. Results from regenerative models produces significantly different responses and alters the accepted “conventional science.”
Adaptive Grazing Lowers GHG’s
A study published in 2020 (Shrestha, et.al., Agronomy. 2020) found that adaptive grazing lowered GHG emissions by actually altering extracellular enzyme activity. Extracellular enzymes break down complex organic matter (i.e., lignified plant materials, cellulose, organic phosphates, etc.) into soluble sugars that can then be used for metabolism by other organisms.
The study compared adaptive grazed ranches to neighboring conventionally grazed ranches. The results showed that methane uptake was 1.5 times greater in the adaptively grazed soils compared to the conventionally grazed soils. The conclusion was that adaptive grazing has the potential to mitigate the impact of warmer soils on GHG emissions by consuming more methane than conventionally grazed lands.
Soil C and N are Enhanced
A study by Mosier, et.al. 2021 (J. Enviro. Man.) found that grassland soils are large reservoirs of soil carbon (C) but are at risk with cultivating these grasslands or through poor grazing management. Adaptive grazing increases soil C and other soil health parameters and lowers the risk of rising atmospheric CO2. The study showed that adaptive grazing enhances soil C ad soil nitrogen (N) stocks through mineral association in southeastern grazing lands.
The study found that adaptive grazing increases soil C stocks, with 13% more soil C on the adaptively grazed farms compared to the conventionally grazed. In addition, more of this soil C was shifted to persistent organic matter. This is a strong indicator of long-term carbon storage. There were also greater N stores on the adaptively grazed farms with an average of 9% more soil N. The researchers concluded that adaptive grazing can sequester and stabilize more C and N in agricultural soils.
An earlier study (Cong, et. al., J Ecology. 2014) found that soil C and N stocks are increased when plant species diversity is richer, even in the absence of legumes. Cong’s study showed that legumes can play a major role in N2-fixation but that many species of grasses, especially warm season grasses, can form associations with free-living N-fixing bacteria in the soil. The study demonstrated that both soil C and N stocks increased by 18% and 16%, respectively, in eight species mixes compared to monocultures of the same plant species. The increased soil C and N stocks produced a positive feedback on plant productivity through enhanced N mineralization, which, in turn, accelerate soil C and N storage.
Plant Species Diversity Matters
One final study that I will mention, found that as plant species diversity increases there are a multitude of benefits derived (Eisenhauer, et. al., Scientific Reports. 2017). Diversity increased the composition and functioning of the entire soil microbiome. Specifically, where there were more diverse stands of plant species, there was a significant increase in plant shoot biomass, root biomass, root exudate production, soil bacterial biomass and soil fungal biomass. The greatest increase came in the fungal biomass with a significantly improved fungi to bacteria ratio. The enhanced microbial biomass was principally due to the increased root-derived organic inputs.
Summary
The beneficial results of adaptive grazing continue to grow and are substantiated by real-life results and ongoing research findings. The increases in soil aggregate, water infiltration and retention, plant species and microbial species diversity, plant biomass production, and resilience to environmental stressors are significant. The additional benefits of reduced GHG emissions and improved ecosystems are hard to ignore. When you add the economic benefits, it starts to beg the question, “Why don’t all grazers implement adaptive grazing?” Why not, indeed.