Grazing
A major opportunity for reducing emissions in agriculture is feed reduction. A major opportunity for carbon sequestration is ecological grazing.
Analysis
Source
Biochar-manure has a higher C sequestration potential than regular manure.
Pasture had a higher rate of SOC sequestration than reduced tillage cropping (1.2 vs 0.28 Mg C ha–1 year–1, 0–0.3 m); and organic amendments had higher rates of SOC sequestration than without (1.14 vs 0.78 Mg C ha–1 year–1, 0–0.3 m).
Life-cycle analyses suggest that the novel plant-based meat alternatives have an environmental footprint that may be lower than beef finished in feedlots, but higher than beef raised on well-managed pastures. In this review, the nutritional and ecological impacts of eating plant-based meat alternatives vs. animal meats are covered.
At drier locations facing adverse climate change in Australia, a transition towards a greater emphasis on livestock versus cropping production could be beneficial when assessed against multiple criteria of farm profit, downside financial risk, and environmental damage.
70 per cent of agricultural land is used to grow feed crops for animals or for grazing. Nearly 30% of total food value of global crop production is lost by “processing” it through inefficient livestock systems.
Due to the overwhelming dependence of agriculture on external energy sources, dominated by fossil fuels, reaching energy neutrality is extremely challenging. Our results highlight that the major opportunity to reach energy neutrality in agriculture is in feed reduction”
Grazing exclusion was associated with dramatically less overall belowground allocation of SOC, with lower root biomass, fine root exudates, and microbial biomass. Concurrently, grazed pasture contained greater total SOC, and a larger fraction of SOC that originated from plant tissue deposition, suggesting that higher root litter deposition under grazing promotes greater SOC.
Some graziers are able to be profitable whilst maintaining and enhancing the biodiversity on their properties and suggests that they have a set of management capabilities, different to other producers that creates these outcomes. This study presents case study data that is probably the best we have in terms of link between specific grazing practices and ecological function outcomes in Australian grassy woodland context.
Ogilvy et al. (2018)
The response magnitude and directions of belowground C- and N-related variables largely depend on grazing intensities.
Incorporating periods of rest into grazing regimes improves ground cover and animal production per hectare and that these benefits are more pronounced with increases in the length of time land is rested for. This extended rest also improves biomass production and weight gain compared to continuous grazing systems. Based on these meta‐analyses, we recommend that future research considers the duration of rest compared to graze time in comparisons of grazing systems.
Areas managed for conservation and under rotational forms of commercial grazing management generally had greater floristic richness and diversity than continuously grazed areas (results varying with season (spring/autumn) and soil type (clay/sandy-loam).
Removing grazing pressure may lead to lower soil carbon stocks in native pastures over time. The cell grazing treatment had total carbon stock of 32·9 Mg C ha−1 (SE = 1·8) in the 0–0·30 m soil layer, which was a significant increase (p < 0·05) relative to the ungrazed treatment at 25·6 Mg C ha−1 but not statistically greater than the tactical treatment at 29·5 Mg C ha−1. Combination of factors contributed to a greater stock of soil carbon under grazed pastures e.g plant shoot/root allocation, root growth and root turnover with defoliation under grazing, lower plant productivity where grazing is excluded because of shading and nutrient tie‐up.
Grazed grasslands generally accumulate SOC more rapidly than undefoliated grasslands. Low or moderate stocking rates favor SOC accumulation relative to high stocking rates, especially in lower-rainfall environments. But short-term SOC accumulation rates observed after conversion of cropland to perennial grassland do not continue indefinitely. Managing grazing to increase uniformity of excreta deposition increases efficiency of nutrient cycling. Other benefits:
Methane: More digestible forages defoliated at optimal maturity may decrease CH4 emitted per unit of feed consumed or per unit of animal product.
Nitrogen: Substituting legumes for N fertilizer and reducing livestock N excretion through diet manipulation reduce N2O emissions.
Pollination: Species-rich grasslands with flower-rich legumes and forbs increase foraging opportunities for pollinators.
Total soil P, N and C was significantly higher in soils sampled in the season following a grazing event, irrespective of grazing intensity or duration. Grazing’s role in nutrient cycling means it is an important driver of native plant diversity. (No significant differences in soil nutrients or bulk density were detected between different grazing treatments, likely due to the importance of total grazing pressure i.e. from all exotic and native herbivores and the level of environmental variation between sites).
On-farm beef production and emissions data are combined with 4-year soil C analysis.
Feedlot production produces lower emissions than adaptive multi-paddock grazing.
Adaptive multi-paddock grazing can sequester large amounts of soil C.
Emissions from the grazing system were offset completely by soil C sequestration.
Soil C sequestration from well-managed grazing may help to mitigate climate change.
(1) Increasing pasture legume content and soil fertility can consistently benefit farm production and environmental indicators, (2) management interventions that target direct management of ground cover have the greatest potential to reduce soil erosion rates, (3) management during critical periods of naturally high soil erodibility and wind/water erosivity can substantially increase or decrease erosion risk; the timing of management interventions is therefore critical, and (4) grazing management to balance use of crop residues and pasture biomass is required to avoid developing hot spots of erosion and soil degradation.
Regenerative grazing enables spontaneous/natural emergence and growth of paddock trees across the landscape - restoring our grassy woodlands (and more carbon).
Light grazing and grassland restoration has potential to improve soil health and resilience through an increase in SOC and microbial community responses related to nutrient cycling.
    Grassland soils accumulated 18% greater SOC and 13% greater total N than cropland soils in the 0–80 cm profile. Microbial community size in the surface 0–20 cm was 90% greater, and enzyme activities were 131–155% greater in the grasslands than in the croplands.
    Within grasslands, cattle grazing increased microbial community size by approximately 42%, which was mainly due to greater fatty acid methyl esters (FAME) markers for gram-positive bacteria (51%) and Actinobacteria (73%).
    Grazed cropland had 95% more β‑glucosaminidase activity than ungrazed croplands.
The impacts of livestock production are highly variable depending on the region of production and feed regime (extensive or intensive) [18]. Pasture-based systems have a potentially beneficial role [19] as they contribute to faster and more balanced nutrient recycling in ecosystems [20], use marginal land unsuitable for crops [21], and legume-based pastures are a biological source of nitrogen for soils and protein for livestock [22]. LCAs need to fully account for these benefits.
Everything is also interconnected: soil carbon impacts water retention which impacts plant growth. Plant growth, in turn, impacts transpiration with water vapor impacting OH formation and availability, and thus methane oxidation. So carbon, hydrologic and methane cycles are all interconnected with system interactions. Due to these interactions, a reductive approach looking at these cycles independently doesn’t provide a full understanding of what actually is occurring with greenhouse gases in the atmosphere. The role of ag practices that increase OH radicals in atmosphere that then neutralise methane is an important process that needs to be considered in life cycle assessment of livestock systems. **This is not peer reviewed but it is a very comprehensive review article that cites literature that needs to be followed up**
We found that antibiotic treatment restructured microbiota in dung beetles, which harboured a microbial community distinct from those in the dung they were consuming. The antibiotic effect on beetle microbiota was not associated with smaller size or lower numbers. Unexpectedly, antibiotic treatment raised methane fluxes from dung, possibly by altering the interactions between methanogenic archaea and bacteria in rumen and dung environments. Our findings that antibiotics restructure dung beetle microbiota and modify greenhouse gas emissions from dung indicate that antibiotic treatment may have unintended, cascading ecological effects that extend beyond the target animal.
New estimation of C3-C4 diet composition of domestic ruminants (cattle, buffaloes, goats and sheep), a revised estimation of yearly enteric CH4 emissions, and a new estimation for the evolution of its δ13C during the period 1961–2012. Compared to previous estimates, our results suggest a larger contribution of ruminants’ enteric emissions to the increasing trend in global methane emissions between 2000 and 2012, and also a larger contribution to the observed decrease in the δ13C of atmospheric methane.
Australia has the highest rate of mammal extinction in the world. Resettlement of indigenous communities resulted in the spread of invasive species, the absence of human-set fires, and a general cascade in the interconnected food web that led to the largest mammalian extinction event ever recorded. In this case, the absence of direct human activity on the landscape may be the cause of the extinctions, according to a Penn State anthropologist.
In a region of extensive soil degradation in the southeastern United States, we evaluated soil C accumulation for 3 years across a 7-year chronosequence of three farms converted to management-intensive grazing. Here we show that these farms accumulated C at 8.0 Mg ha−1 yr−1, increasing cation exchange and water holding capacity by 95% and 34%, respectively. Thus, within a decade of management-intensive grazing practices soil C levels returned to those of native forest soils, and likely decreased fertilizer and irrigation demands.
Regenerative agriculture is being used by a small number of innovative farmers in Australia and elsewhere, using a range of holistic methods that work with the land and climate, such as short duration time of controlled grazing with long rest periods for the paddock and higher proportions of aboveground biomass, to improve soil health and farm profitability. This paper uses a delta life cycle assessment, focusing only on the differences between regenerative and conventional production systems to assess the potential impact of regenerative agriculture on a full range of midpoint impact categories and end-point areas of protection for an extensive sheep system in Australia. We assess the potential improvement to the water, carbon, and biodiversity footprints of sheep production, and find that regenerative agriculture has the potential to improve environmental performance compared with current industrial agricultural practices. In particular, there seems to be considerable potential to offset a significant proportion of the on-farm climate change impacts through a combination of biosequestration in soils and aboveground biomass and using harvested biomass to offset fossil fuel use. The assessment highlights the need for additional data to confirm the findings and the potential contribution that regenerative agriculture can make to sustainability of ruminant livestock production.
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