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Potential mitigation of midwest grass-finished beef production emissions with soil carbon sequestration in the United States of America

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Beef production can be environmentally detrimental due in large part to associated enteric methane (CH4) production, which contributes to climate change. However, beef production in well-managed grazing systems can aid in soil carbon sequestration (SCS), which is often ignored when assessing beef production impacts on climate change. To estimate the carbon footprint and climate change mitigation potential of upper Midwest grass-finished beef production systems, we conducted a partial life cycle assessment (LCA) comparing two grazing management strategies: 1) a non-irrigated, lightly-stocked (1.0 AU/ha), high-density (100,000 kg LW/ha) system (MOB) and 2) an irrigated, heavily-stocked (2.5 AU/ha), low-density (30,000 kg LW/ha) system (IRG). In each system, April-born steers were weaned in November, winter-backgrounded for 6 months and grazed until their endpoint the following November, with average slaughter age of 19 months and a 295 kg hot carcass weight. As the basis for the LCA, we used two years of data from Lake City Research Center, Lake City, MI. We included greenhouse gas (GHG) emissions associated with enteric CH4, soil N2O and CH4 fluxes, alfalfa and mineral supplementation, and farm energy use. We also generated results from the LCA using the enteric emissions equations of the Intergovernmental Panel on Climate Change (IPCC). We evaluated a range of potential rates of soil carbon (C) loss or gain of up to 3 Mg C ha-1 yr-1. Enteric CH4 had the largest impact on total emissions, but this varied by grazing system. Enteric CH4 composed 62 and 66% of emissions for IRG and MOB, respectively, on a land basis. Both MOB and IRG were net GHG sources when SCS was not considered. Our partial LCA indicated that when SCS potential was included, each grazing strategy could be an overall sink. Sensitivity analyses indicated that soil in the MOB and IRG systems would need to sequester 1 and 2 Mg C ha-1 yr-1 for a net zero GHG footprint, respectively. IPCC model estimates for enteric CH4 were similar to field estimates for the MOB system, but were higher for the IRG system, suggesting that 0.62 Mg C ha-1 yr-1 greater SCS would be needed to offset the animal emissions in this case.
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Research Paper Future of Food: Journal on Food, Agriculture and Society
4 (3) Winter 2016
Potential mitigation of midwest grass-nished beef
production emissions with soil carbon sequestration in the
United States of America
Jason E. RowntREE*1, REbEcca Ryals2, MaRcia s. DElongE3, w. RichaRD tEaguE, MaRilia b. chiavEgato, PEtER byck6,7,
tong wang8 & sutiE Xu1
1 Department of Animal Science, Michigan State University
2 Department of Natural Resources and Environmental Management, University of Hawaii
3 Union of Concerned Scientists, Washington, DC
4 Department of Ecosystem Science and Management, Texas A & M University
5 Departmental de Zootecnia, Universida de de São Paulo
6 School of Sustainability, Arizona State University
7 Walter Cronkite School of Journalism and Mass Communications, Arizona State University
8 Department of Economics, South Dakota State University
* Corresponding author: rowntre1@msu.edu | Tel.: +1-517-974-9539
Data of the article
First received : 30 March 2016 | Last revision received : 28 November 2016
Accepted : 05 December 2016 | Published online : 23 December 2016
URN: nbn:de:hebis:34-2016111451469
Key words
Grass-nishing beef, GHG
emissions, Soil organic
carbon sequestration
Abstract
Beef production can be environmentally detrimental due in large part to associated enteric
methane (CH4) production, which contributes to climate change. However, beef production in
well-managed grazing systems can aid in soil carbon sequestration (SCS), which is often ignored
when assessing beef production impacts on climate change. To estimate the carbon footprint
and climate change mitigation potential of upper Midwest grass-finished beef production sys-
tems, we conducted a partial life cycle assessment (LCA) comparing two grazing management
strategies: 1) a non-irrigated, lightly-stocked (1.0 AU/ha), high-density (100,000 kg LW/ha) system
(MOB) and 2) an irrigated, heavily-stocked (2.5 AU/ha), low-density (30,000 kg LW/ha) system
(IRG). In each system, April-born steers were weaned in November, winter-backgrounded for 6
months and grazed until their endpoint the following November, with average slaughter age of
19 months and a 295 kg hot carcass weight. As the basis for the LCA, we used two years of data
from Lake City Research Center, Lake City, MI. We included greenhouse gas (GHG) emissions as-
sociated with enteric CH4, soil N2O and CH4 fluxes, alfalfa and mineral supplementation, and farm
energy use. We also generated results from the LCA using the enteric emissions equations of the
Intergovernmental Panel on Climate Change (IPCC). We evaluated a range of potential rates of
soil carbon (C) loss or gain of up to 3 Mg C ha-1 yr-1. Enteric CH4 had the largest impact on total
emissions, but this varied by grazing system. Enteric CH4 composed 62 and 66% of emissions for
IRG and MOB, respectively, on a land basis. Both MOB and IRG were net GHG sources when SCS
was not considered. Our partial LCA indicated that when SCS potential was included, each graz-
ing strategy could be an overall sink. Sensitivity analyses indicated that soil in the MOB and IRG
systems would need to sequester 1 and 2 Mg C ha-1 yr-1 for a net zero GHG footprint, respectively.
IPCC model estimates for enteric CH4 were similar to field estimates for the MOB system, but
were higher for the IRG system, suggesting that 0.62 Mg C ha-1 yr-1 greater SCS would be needed
to offset the animal emissions in this case.
Citation (APA):
Rowntree, J. E., Ryals, R., DeLonge, M.S., Teague, W.R., Chiavegato, M.B., Byck, P., Wang,T., Xu, S. (2016). Potential mitigation of midwest grass-nished
beef production emissions with soil carbon sequestration in the United States of America.
Future of Food: Journal on Food, Agriculture and Socie-
ty
, 4(3), 31 -38.
31
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32 UniKassel & VDW, Germany- December 2016
Future of Food: Journal on Food, Agriculture
and Society, 4 (3)
Introduction
There is a growing concern about beef productions
impact on the environment, including contributions to
climate change. However, beef production systems are
variable, ranging broadly from intensive confined feed-
lots to diverse grazing systems. As a result, these sys-
tems contribute differently to climate change through
mechanisms such as animal impacts, off-farm inputs,
and land management. Identifying opportunities to re-
duce climate impacts requires a systematic approach
that considers the larger agroecosystem. This need for
a systems approach has become increasingly urgent,
particularly in light of the fact that one outcome of the
United Nations Conference on Climate Change (COP21)
was a call for greater adoption of regenerative agricul-
tural practices. Specifically, this call includes the “4/1000
Initiative: Soils for Food Security and Climate” and the
Life Beef Carbon Initiative, which recommends greater
adoption of grazing systems that sequester C and re-
duce net GHG emissions from beef production.
Life cycle assessments (LCAs) are important tools that
have been applied to evaluate the costs and benefits of
beef production systems with respect to the environ-
ment and climate change. While LCAs can be insightful,
the outputs are highly sensitive to the methodologies
and boundaries used to develop the analysis. Many ex-
isting beef LCAs have concluded that grazing systems
have a bigger climate footprint than more intensive,
confined systems due to reduced meat yield per unit
land and increased enteric methane (CH4) associated
with greater ruminal fiber digestion (Eshel, Shepon, Ma-
kov, & Milo, 2014; Ripple et al., 2014; Capper, 2012). How-
ever, these assessments have generally not accounted
for the important influence that land management and
soil dynamics can have on the outcome.
Soil is an important pool of C that is sensitive to land
management and can cumulatively have a significant
impact on climate change. Recently, Teague et al. (2016)
indicated agriculturally induced global soil erosion esti-
mates at 1.86 Gt C yr-1, resulting in an annual 0.5 ppm
atmospheric CO2 increase. Because soils can be either a
source or sink of C depending on management practic-
es, soil C is a potentially important component of beef
LCAs (Teague et al., 2016). Soil C has often been unac-
counted for in LCAs (Stackhouse-Lawson, Rotz, Oltjen, &
Mitloehner, 2012; Capper & Bauman, 2013), but has been
found to have a large impact on net GHG footprints
when explicitly included (Liebig, Gross, Kronberg, & Phil-
lips, 2010; Wang, Teague, Park, & Bevers, 2015) or at least
considered (Pelletier, Pirog, & Rasmussen, 2010; Lupo,
Clay, Benning, & Stone, 2013). The availability of experi-
mental data on soil C and GHG effects of grazing systems
has been an obstacle in filling this critical gap in LCAs.
The purpose of this study is to develop a data-driven
partial LCA of upper Midwest grass-finishing beef pro-
duction systems. Our LCA explicitly considers soil C and
GHG dynamics and uses data from localized field exper-
iments. We employ a simple sensitivity analysis to eval-
uate the potential for soil carbon sequestration (SCS) to
offset emissions within grass-finished beef production
systems.
Materials and Methods
LCA components and boundaries
An LCA was constructed to determine net GHG impacts
of two different grazing management practices for beef
production in the upper Midwest, USA. Components of
Figure 1 : Grass-Finishing beef production phase
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Future of Food: Journal on Food, Agriculture
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the LCA include direct and indirect GHG emissions asso-
ciated with the grassland ecosystem, enteric emissions
from cattle, feed production and transportation, and on-
farm energy use. The model boundary was restricted to
the grass-finishing portion of the beef production cycle,
beginning at the time of weaning and ending at slaugh-
ter (Figure 1).
The model quantified the impacts of grazing manage-
ment practices on the net greenhouse gas emissions
(GHGnet) as:
GHGnet = GHGecosystem + GHGfeed + GHGenergy - GHGseq
where GHGecosystem represents biological greenhouse
gas emissions generated on the pasture. This parameter
includes enteric CH emissions from steers (> 1 year old)
and the difference in soil nitrous oxide (N2O) and CH4
emissions relative to an ungrazed control pasture. Emis-
sions associated with the mining, production, and trans-
portation of supplemental feed and minerals are repre-
sented as GHGfeed. Emissions generated from the use of
fossil fuels for on-farm technologies (i.e., irrigation) are
represented as GHGenergy. The change in soil carbon
is shown as GHGseq, where a positive value represents
sequestration (i.e., a sink). All model components are
expressed as GHG fluxes in CO2-equivalents using 100-
year global warming potentials (Intergovernmental Pan-
el on Climate Change, 2006). Positive values represent
a source of GHGs to the atmosphere, whereas negative
values represent a GHG sink. Metrics for comparison of
GHG impacts due to grazing practices were expressed
on a per steer and per area basis.
Study system
Data used for the LCA was derived from two years of on-
farm experiments conducted at the Lake City Research
Center in Lake City, Michigan. The experiments were
composed of grass-finishing beef production systems
that compared two different grazing management strat-
egies. The approaches were: 1) MOB: a non-irrigated,
high-density grazing system stocked at 1.0 animal units
(AU) ha-1 (100,000 kg live weight (LW) ha-1 d-1) and 2) IRG:
an irrigated, low-density grazing system stocked at 2.5
AU ha-1 (30,000 kg LW ha-1 d-1). An AU is considered
one 454 kg cow with or without calf. We define stocking
rate as the number of AUs assigned to the land base for
a given year, while stock density refers to the kg LW/ha
of animal weight assigned to a land base for 1 day. While
our LCA was driven by data specific to the Upper Mid-
west, the management characteristics of the IRG system
are similar to many grazing dairies and beef systems in
New Zealand, parts of Europe, Australia and the United
States. The IRG system is characterized by aggressive
plant defoliation with short (21-45 day) recoveries to
promote a highly vegetative sward. In contrast, MOB is
a grazing system characterized by high stock densities
with a lower stocking rate. The MOB system allows for
longer (> 60 day) plant recovery periods. As a result,
forage is typically more mature when compared to IRG
and has a higher fiber content when compared to other
rotational systems (Chiavegato, Powers, Carmichael, &
Rowntree, 2015b). In each grazing strategy, steers were
born in April, weaned in November, backgrounded on
high quality hay for 6 months, and grazed on pasture
until slaughter the following November, with an average
age at slaughter of 19 months and a 295 kg hot carcass
weight (HCW). Our life cycle model focuses on the peri-
od from weaning to slaughter (Figure 1).
Ecosystem greenhouse gas emissions
Ecosystem GHG emissions included enteric CH and
soil NO and CH fluxes measured at the experimental
site from 2012-13 (Chiavegato, Rowntree, Carmichael, &
Powers, 2015a, Chiavegato et al., 2015b). Emissions were
measured in spring (April/May; Period 1) and late sum-
mer (August/Sept; Period 2) for 2 years. These time pe-
riods were considered to be representative of seasonal
fluxes and were scaled by the numbers of days in each
season. For the base case scenario, soil emissions during
winter months are assumed to be negligible.
Enteric emissions were derived from on-site data from
cow-calf pairs with a mean weight of 555 kg (SE= 20 kg)
using a standard SF tracer gas technique (Johnson, Huy-
ler, Westberg, Lamb, & Zimmerman, 1994). Sampling was
conducted twice daily over 7 days in Periods 1 and 2 in
2012 and 2013. During each sampling period, cattle were
also dosed with chromic oxide to determine dry matter
intake (DMI). There was no management effect on DMI
as cows consumed 2.6 and 2.8% of their body weight
daily during the collection periods for MOB and IRG, re-
spectively. There were no differences between years or
treatments for enteric CH, with emissions ranging from
195 to 249 g CH4 d-1. We used a metabolic body weight
conversion of 0.85 to convert emissions from a mature
cow (555 kg) to a growing steer (454 kg). For both sys-
tems, we estimated winter CH emissions to be 120 g L-1
d-1 on high quality hay, based Stewart et al. (2014). We
also compared our data to enteric CH calculations using
the Tier 1 Methodology of the Intergovernmental Panel
on Climate Change (IPCC):
DayEmit = [GEI XYm ] / [55.65 MJ/kg CH]
where:
DayEmit = emission factor (kg CH head-1 day-1)
GEI = gross energy intake (MJ head-1 day-1)
Ym = CH4 conversion rate, which is the fraction of gross
Eq. 1
Eq. 2
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energy in
feed converted to CH (%)
To complete the IPCC equation, site-specific mean GEI
forage values (Chiavegato et al., 2015a) and the recom-
mended Ym of 6.5% (Mangino, Peterson, & Jacobs, 2003)
were used.
Soil GHG emissions data used for the base case scenario
is detailed in Chiavegato et al. (2015b). Briefly, soil N2O
and CH₄ emissions were measured via the static flux
chamber method and analyzed by gas chromatography.
A 14 day post-graze collection period in both periods in
2012 and 2013 was used.
Greenhouse gas emissions from protein and mineral sup-
plements
The grazed pastures and supplemented feed were pri-
marily alfalfa (Medicago sativa L.). For the supplemental
feed GHG assessment, we used the Farm Energy Analysis
Tool (FEAT ) (Camargo et al., 2013). Assumptions involved
in FEAT indicate a three-year lifespan for the alfalfa, with
an energy use of 9000 MJ input ha-1 y-1 and energy pro-
duction efficiency of 25 MJ output per MJ input (Camar-
go, Ryan, & Richard, 2013). No differences in supplement
consumption were used between the different grazing
systems. The on-farm supplemental feed consumption
per animal for the production cycle was 2044 kg. Half
of the alfalfa was produced on site, while the other half
was brought on farm from an average distance of 24 km.
In each case, a yield of 7490 kg ha-1 y-1 was used based
on USDA harvest estimates (USDA, 2015). All associated
transportation GHG emissions were estimated using die-
sel heavy-duty truck data from the EPA (2008).
Mineral supplement calculations were based on a dai-
ly intake of 77 g head-1 across each grazing treatment
(Buskirk, 2002). Mineral associated emissions were esti-
mated based on Lupo, Clay, Benning, and Stone (2013).
This involves the mining and processing components of
NaCl, CaCO and CaHPO production, along with trans-
port and delivery to the farm.
On-farm energy use
Any associated energy used for alfalfa production and
subsequent feeding is accounted for in the feed compo-
nent. Supplemental irrigation was used in IRG (K-Line Ir-
rigation, St. Joseph, MI) with a goal of providing 2.54 cm
water ha-1 wk-1. The estimated annual usage of irrigation
electricity was 7452 kW yr-1. EPA (2014) emission factors
were used to determine emissions associated with elec-
tricity use.
Soil carbon sequestration
To account for soil C change in each system, we consid-
ered a C-response gradient ranging from -3 Mg C ha-1 yr-1
to 3 Mg C ha-1 yr-1. Grazing lands have the potential to act
as C sinks, but reported rates of SCS due to grazing sys-
tem management vary considerably based on climate,
biome, time of observation, and site-specific conditions.
A review of 81 ranch sites reported SCS rates ranging
from 0.11 to 3.04 Mg C ha-1 yr-1 (Conant, Paustian, & Elli-
ott, 2001). More recent attention to emerging intensive
rotational grazing practices has indicated even greater
potential SCS rates. Teague et al. (2011) reported annual
sequestration rates of 3 Mg C ha-1 yr-1 in a 10 year chron-
osequence study in Texas comparing stocking rate and
grazing management influence on beef production and
ecosystems services. Machmuller et al. (2015) observed
SCS of 8.0 Mg C ha-1 yr-1 in a 7 year chronosequence of
irrigated management-intensive grazing in the south-
eastern USA. Thus, the relatively wide range of SCS rates
used for this LCA provides an opportunity to incorporate
soil C dynamics and uncertainties.
Results and Discussion
LCA results of MOB and IRG systems on a kg CO2-eq ha-1
production cycle and animal basis derived from Eq.1 are
indicated in Figure 2. The MOB system had lower emis-
sions on a land basis when compared to the IRG system
(3.3 vs. 7.1 Mg CO-eq ha-1) due to lower stocking rates.
The IRG farm energy use was 1064 kg CO-eq ha-1 due to
the electricity used for irrigation, compared to no energy
use for the MOB system. For both systems, enteric CH
was the largest contributor to overall emissions, ranging
from 62 to 66% for the IRG and MOB systems, respective-
ly. This finding is lower than results found by Pelletier,
Pirog, & Rasmussen (2010), who estimated enteric CH
emissions to make up 79% of total GHG emissions from
a grass-finishing system.
Enteric emissions ranged from 142 to 268 g CH d-1 (Chi-
avegato et al., 2015a). These results are similar to those
reported by DeRamus, Clement, Giampola, and Dicki-
son (2003), who indicated yearling heifers, first calf heif-
ers and mature cows ranged from emitting 120 to 255
g CH d-1. Similarly, Pavao-Zuckerman, Waller, Ingle, and
Fribourg (1999) reported a range of 150 to 240 g CH d-1.
However, these data fall slightly lower than estimates by
McCaughey, Wittenberg, and Corrigan et al. (1999) and
Pinares-Patiño, Baumont, and Martin (2003), who found
ranges in emissions from 173 to 273 g CH d-1. The lower
stocking rate in MOB also resulted in lower enteric CH4
emissions compared to IRG (2165 vs. 4430 kg CO-eq ha-
1) on a land area basis. However, on a per steer basis, IRG
enteric emissions were 393 kg CO-eq steer-1 less than
MOB. The grazing effect on enteric CH emissions may
be explained by the observed increase in forage crude
protein and reduction in fiber content for IRG compared
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to MOB (Chiavetago et al., 2015a).
The beef production systems used to calculate this LCA
represent improved grazing management as compared
to continuous set stocking strategies, which have been
shown to reduce plant diversity and productivity due to
overgrazing of preferred plants and patches (Murphy,
1998; Gerrish, 2004; Teague, Provenza, Kreuter, Steffens,
& Barnes, 2013). The lower enteric CH emissions in the
observations reported here might be due to the relative-
ly high plant diversity we observed in the well-managed
systems. Both systems included multiple daily to weekly
moves to new pasture, allowing for greater forage resid-
ual biomass and longer recovery periods, feeding back
to the ecosystem by increasing the plant diversity and
forage quality (Chiavegato et al., 2015a). Conceptually,
this agrees with Bannink et al. (2010), who indicated that
forage quality is a primary driver in relative daily enteric
emissions.
Enteric CH emissions were also assessed using Tier 1
IPCC daily enteric emission predictive equations (Eq.1)
(IPCC, 2006), as it is a commonly used methodology
when site- or regionally-specific data are lacking. There
was very little difference between the MOB GHG foot-
print calculated using our field observations compared
to the IPCC approach (3.3 vs 3.5 Mg CO-eq yr-1, respec-
tively) (Figures 2 & 3). However, when evaluating the
IRG system, the IPCC approach generated a greater en-
teric CH4 value and concurrently a larger footprint on a
land and steer basis by 34%. In a review of measured and
simulated enteric emission rates, Stackhouse et al. (2012)
indicated the IPCC overestimated emissions by 16.4% on
average, with a differential range of -0.01 to 55%.
___________Net GHG (Mg C ha-1 yr-1)__________
On-farm IPCC
Soil C Emission MOB IRG MOB IRG
(Mg C ha-1 yr-1)
-3 -2.11 -1.07 -2.05 -0.45
0 0.89 1.93 0.95 2.55
3 3.89 4.93 3.95 5.55
Figure 2 : Life cycle assessment of on-farm data estimated with metabolic body weight
Table 1: Impact of soil C emission gradient on net GHG in two man-
agement systems
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Table 1 denotes overall C footprint balance (in CO2-eq)
based on a plausible gradient of soil C flux, representing
soil C loss or gain ranging from ±3 Mg C ha-1 yr-1. Assum-
ing a sequestration rate of 3 Mg C ha-1 yr-1, all systems
and methods indicate an overall GHG sink ranging from
2.11 to 1.07 (MOB) and 2.0 and 0.45 Mg C ha-1 yr-1 (IRG),
representing on-farm and IPCC calculations, respective-
ly. A soil C flux gradient allows for a greater understand-
ing of soil C influence on the overall environmental foot-
print. As Stackhouse et al. (2012) indicated, LCA’s often
consider soil C to be in dynamic equilibrium. However,
empirical data suggest otherwise (e.g. Machmuller et al.,
2015; Teague et al., 2011). Recent studies such as Ripple
et al. (2014) and Eshel et al. (2014) have reported the
emissions from ruminants in food production without
accounting for the beneficial ecosystem services that
well-managed grazing systems can provide. In our study,
we used 3 Mg C ha-1 yr-1 as a potential C sequestration
figure, which is relatively high (Conant et al., 2001) but
viable based on existing studies (Teague et al., 2011; Del-
gado et al., 2011; Machmuller et al., 2015; Teague et al.,
2016). Importantly, the results presented here suggest
that with appropriately managed grazing, a grass-fin-
ished beef model can not only contribute to food pro-
visioning but also be ecologically regenerative as well.
Conclusions
The recent call for improved management of grazing
systems as part of an international climate change miti-
gation strategy is critical, particularly in light of many ex-
isting beef LCAs that have concluded that beef cattle pro-
duced in grazing systems are a particularly large sources
of GHG emissions. To identify the best opportunities to
reduce GHG emissions from beef production, a systems
approach that considers the potential to increase soil C
and reduce ecosystem-level GHG emissions is essential.
Using a combination of on-farm collected data, litera-
ture values, and IPCC Tier 1 methodology, we generat-
ed an LCA that indicates highly-managed grass-finished
beef systems in the Upper Midwestern United States can
mitigate GHG emissions through SCS while contribut-
ing to food provisioning at stocking rates as high as 2.5
AU ha-1. From this data, we conclude that well-managed
grazing and grass-finishing systems in environmentally
appropriate settings can positively contribute to reduc-
ing the carbon footprint of beef cattle, while lowering
overall atmospheric CO concentrations.
Acknowledgements
The authors express their thanks to the Michigan Animal
Agriculture Alliance and Thornburg Foundation for par-
tial support of this project. Moreover, the authors would
like to thank the anonymous reviewers.
Conict of Interests
The authors hereby declare that there are no conflicts of
interest.
Figure 3 : Life cycle assessment of IPCC data to estimate enteric methane emissions
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Future of Food: Journal on Food, Agriculture
and Society, 4 (3)
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... One of the major concerns in grazingland ecosystems is the substantial amount of GHGs emitted by ruminant livestock (Capper, 2012;Capper and Bauman, 2013;Eshel et al., 2014;Ripple et al., 2014). Although many scientists have concluded that ruminant production systems are a particularly large source of GHG emissions, others have shown it is possible to convert many ruminant-based production chains into net C sinks by changing management (Wang et al., 2014Rowntree et al., 2016;Teague et al., 2016). Previous assessments of capacity for CH 4 uptake in grazed rangeland ecosystems have not considered improved livestock management practices and thus underestimated potential for CH 4 uptake. ...
... Previous assessments of capacity for CH 4 uptake in grazed rangeland ecosystems have not considered improved livestock management practices and thus underestimated potential for CH 4 uptake. Optimal fertilization, appropriate adaptive stocking, moderate grazing with adequate recovery, and intensification of livestock grazing management significantly contribute to mitigation potential (Delgado et al., 2011;Wang et al., 2014;Rowntree et al., 2016). ...
... As soils can be a significant sink of carbon depending on management practices (Conant et al., 2001;Liebig et al., 2010;Teague et al., 2011;Machmuller et al., 2015), soil carbon (C) dynamics are an important component of calculating accurate beef life-cycle assessments (LCA; Wang et al., 2015;Teague et al., 2016;Rowntree et al., 2016). However, changes in C have usually been unaccounted for in LCAs (Stackhouse-Lawson et al., 2012;Capper and Bauman, 2013;Eshel et al., 2014;Ripple et al., 2014), even though it has been shown to have a large impact on net GHG footprints when explicitly included in calculations of net carbon footprints of alternate combinations of agricultural management options (Liebig et al., 2010;Pelletier et al., 2010;Lupo et al., 2013;Wang et al., 2015;Rowntree et al., 2016). ...
Article
I explore the hypothesis that managing grazing using regenerative grazing principles to improve soil health is a sustainable base to improve net farm profits. Carbon-rich soil is healthy soil and beneficial for the entire ecosystem. Changing current unsustainable high-input agricultural practices to low-input practices that regenerate ecosystem function will be necessary for sustainable, resilient agro-ecosystems. Current reductionist, small-scale, short-term research managed without goals to find what management framework will deliver positive outcomes for ranchers has produced very erroneous conclusions. Healthy ecosystems function by increasing soil carbon to improve water infiltration and retention; soil nutrient access and retention; and the diversity of fungi, microbes, plants, insects, and wildlife that contribute to both improved livestock nutrition and human nutrition. I will give an overview of our research endeavors using a systems-science, multi-discipline framework to find the best grazing management for regenerating: soil health and function; delivery of ecosystem goods and services; and farmer livelihoods and social resilience. To accomplish this, we partner with farmers who have improved the environment and excel financially to convert experimental results into sound environmental, social, and economic benefits regionally and globally.
... Differentially lagged grazing effects on such variables necessitates consistent application of grazing management treatments for 5 years, 10-15 years or decades in humid, mesic and dry environments, respectively, to capture diverse environmental changes at the landscape level (Franzluebbers and Stuedemann, 2010). The relatively few studies that have incorporated realistic contexts of scale and complexity, coupled with a well-planned adaptive application of treatment, have shown numerous benefits of AMP grazing over continuous grazing, even where the latter is practiced at low stocking rates (Earl and Jones, 1996;Murphy, 1998;Gerrish, 2004;Jacobo et al., 2006;Provenza, 2008;Ferguson et al., 2013;Teague et al., 2013;Flack, 2016;Rowntree et al., 2016;Wang et al., 2016;Dowhower et al., 2019). ...
... Paleo records provide evidence that management of grassland agroecosystems can create a large C sink (Retallack, 2013). Equally, changing management approaches in ruminant-based production chains can improve soil health and thereby create net C sinks Rowntree et al., 2016;Stanley et al., 2018). Given that most agricultural producers have not used conservation practices outlined by Delgado et al. (2011), applying such practices more broadly could lead to substantial soil health improvements and, therefore, a significant increase in C sink (Conant and Elliott, 2001;Liebig et al., 2010;Teague et al., 2011;Machmuller et al., 2015;Dowhower et al., 2019;Hillenbrand et al., 2019). ...
... Life cycle analyses that include all GHG emissions associated with the production of grain-based feeds, including the production and application of inorganic fertilizers and irrigation water to produce grain, show that the C footprint as well as soil erosion associated with grain-finished beef substantially exceeds the C footprint of grass-finished beef Stanley et al., 2018). Additionally, C sequestered by plants grazed by cattle exceeds the enteric emissions of the grazing animals Rowntree et al., 2016). The C footprint of the beef production chain can be substantially reduced when ruminants are finished on forages and grains produced using regenerative cropping practices that have a negative C footprint (Gattinger et al., 2012;Aguilera et al., 2013). ...
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Ruminants including domestic livestock, have been accused of causing damaging impacts on the global environment and human well-being. However, with appropriate management, ruminant livestock can play a significant role in efforts to reverse environmental damages caused by human mismanagement and neglect. Worldwide, at least one billion people living in grazing ecosystems depend on them for their livelihoods, usually through livestock production, and for other ecosystem services that affect human well-being. For long-term rangeland sustainability and ecological resilience, agricultural production policies are urgently needed globally to transform current damaging industrial inorganic input agricultural practices to resource conservation practices that enhance ecosystem function. This is supported by evidence that farmers and ranchers who apply regenerative management practices to restore ecosystem functionality create sustainable, resilient agroecosystems cost-effectively. With enhanced management of grazing resources, domesticated ruminants can be used to produce higher permanent soil cover of litter and plants, which are effective in reducing soil erosion and increasing net biophysical carbon accumulation. Incorporating forages and ruminants into regeneratively managed cropping systems can also elevate soil organic carbon and improve soil ecological function and reduce production costs by eliminating the use of annual tillage, inorganic fertilizers and biocides. Ecosystem services that are enhanced using regenerative land management include soil stabilization and formation, water infiltration, carbon sequestration, nutrient cycling and availability, biodiversity, and wildlife habitat, which cumulatively result in increased ecosystem and economic stability and resilience. Scientists partnering with farmers and ranchers around the world who have improved their land resource base and excel financially have documented how such land managers produce sound environmental, social, and economic outcomes. Many of these producers have used Adaptive Multi-Paddock (AMP) grazing management as a highly effective approach for managing their grazing lands sustainably. This approach uses short-duration grazing periods, long adaptively varied post-grazing plant recovery periods requiring multiple paddocks per herd to ensure adequate residual biomass, and adjustment of animal numbers as environmental and economic conditions change. Using this approach, farmers and ranchers have achieved superior ecosystem and profitability outcomes. This manuscript summarizes the use of AMP grazing as regenerative tool for grazed and rotationally cropped lands.
... Several workers have described these methods in detail, using such terms as holistic planned grazing, managementintensive grazing and intensive rotational grazing (Savory, 1983;Butterworth, 1999, 2016;Gerrish, 2004;Flack, 2016;Salatin, 2019). Collectively, they are referred to as multi-paddock (MP), or adaptive multi-paddock (AMP) livestock management (Teague et al., 2011;Rowntree et al., 2019). Multi-paddock management attempts to mimic the evolved herding behaviors of wild, ungulates (Voisin, 1959;Acocks, 1966a,b). ...
... LCA studies by Pelletier et al. (2010) and Lupo et al. (2013) support these observations, suggesting a 24-30% reduction in net GHG production as a function of sequestration from grass-fed beef production. These observations are consistent with an LCA analysis by Wang et al. (2015) for beef production in Texas, and they track well with empirical observations (Teague et al., 2011;Dowhower et al., 2019;Rowntree et al., 2019). The importance of C-sequestration by grasslands is clearly critical to the efficacy of agriculture as a vehicle for GHG removal. ...
Article
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Herbivore-carnivore interactions are fundamental to grassland ecosystem functionality and to the human cultures that have long depended on these ecosystems for their nutrition. However, a large literature has developed during the past century indicating that animal agriculture is responsible for numerous negative environmental impacts. In this paper, I review literature on some of the environmental impacts of two different livestock management approaches, industrial-conventional (IC) management and regenerative-multi-paddock (RM) management. I consider the null hypothesis that the environmental impacts of ruminant livestock production are independent of the approach used to manage animals and grazing lands. It evident in the literature that managed grazing ecosystems are complex, and for certain system attributes, such as forage quality and plant community structure, the better management system is difficult to discern. In other areas definitive differences in impacts appear clearly management dependent. For instance, the soils of RM grasslands exhibit higher microbial biomass and diversity, and higher fungal: bacterial ratios than IC soils. Several impacts associated with livestock production appear to have less to do with grazing, per se, and more to do with support factors, such as feed production and manure management. The compilation of data from numerous sources suggests that RM management may reduce blue withdrawals and GHG emissions by >50%, relative to IC management. Accumulating data also suggest that a significant portion of anthropogenic CO2-eq emissions can be removed from the atmosphere and stored in the soil by applying RM management practices. Finally, it is suggested that while research design may affect the outcomes of some studies, the quality and quantity of the science may not resolve many discrepancies in the data. It is suggested that the viability and sustainability of animal agriculture may depend upon broadening the goals of practitioners to include both food production and the restoration and protection of agricultural ecosystem services.
... Los impactos de las emisiones de GEI resultantes de la producción de carne y que por ende afectan a la tierra como un todo, son altamente dependientes del tipo de sistema de gestión de pastoreo utilizado (Brilli et al., 2017;Rowntree et al., 2016). Por lo tanto, sería útil explorar los impactos ambientales de sistemas alternativos de cría, recría y terminación teniendo como base de alimentación los pastizales antes de iniciar un proceso de intensificación, que en la mayoría de los casos implica una aceleración de los procesos productivos y el uso, en mayor o menor grado, de sistemas de confinamiento (FeedLotengorde a corral). ...
... Por lo tanto, sería útil explorar los impactos ambientales de sistemas alternativos de cría, recría y terminación teniendo como base de alimentación los pastizales antes de iniciar un proceso de intensificación, que en la mayoría de los casos implica una aceleración de los procesos productivos y el uso, en mayor o menor grado, de sistemas de confinamiento (FeedLotengorde a corral). Los posibles beneficios del pastoreo con carga animal ajustada incluyen un mejoramiento en la estructura del suelo y aumento de la actividad de los microorganismos que degradan la materia orgánica, una mayor capacidad de retención de agua y de nutrientes, reducción de la erosión del suelo, un aumento del secuestro de carbono del suelo (C), una reducción en las emisiones producto del pastoreo excesivo, propician además la mejor utilización del forraje y productividad animal, lo que podría reducir las emisiones netas de GEI (Teague et al., 2016). ...
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Resumen El presente trabajo fue realizado con el objetivo de evaluar el ciclo de carbono en ecosistemas de pastizal nativo en zona de pantanal paraguayo mediante la medición del crecimiento y la simulación de pastoreo animal. Para el efecto fueron realizados análisis de suelo, productividad anual y calidad forrajera en 4 sitios agroecológicos en una propiedad de 20.000 Has el Departamento de Alto Paraguayo (21º 1' 29,85" S y 58º 17' 38,55" O), desde el 21/12/19 al 12/02/2020. En cada sitio fue instalada una jaula de exclusión de 8*8 metros con los tratamientos (subparcelas de 4m 2) correspondientes a intervalos de corte (IC 35,IC 70 y IC 105 días). Se evaluaron la producción de materia seca por estación y tasa de crecimiento del pastizal, carga animal ajustada a tres niveles de producción (50%, 70% y 75% de tasa de marcación), carbono contenido en la biomasa aérea, radicular y el carbono almacenado en el suelo. Los datos fueron comparados mediante el Test de Tukey al 5% de probabilidad de error. Fue simulada la emisión de Gases de efecto invernadero por cabeza y por Ha, ajustada a una ganadería de cría sobre una superficie total de 6.600 has totales y 5.000 de pastizal. El IC 35 días presentó una productividad superior en 32% en relación al IC de 105 días al igual que la captación de carbono asociado. El mejor balance de captación/emisión por Ha se observa en el IC35 días con la tasa de marcación de 50% con 1.481 kg de CO2 e-Ha-1. Al intensificar y aumentar la tasa de marcación a 75 el balance disminuye a 1.294 kg de CO2-e ha-1. En todos los casos la Ganadería de pastizal ha presentado un balance positivo al contabilizar los GEI por unidad de superficie. Palabras clave: Manejo del pastoreo, pastoreo libre; alimentado con pasto; gases de invernadero; sistema de producción, emisión de gases. Abstract The present work was carried out with the objective of evaluating the carbon cycle in native grassland ecosystems in the Paraguayan pantanal area by measuring pasture growth and simulating animal grazing. For this purpose, analyzes of soil, annual productivity and forage quality were carried out in 4 agroecological sites on a property of 20,000 Has in the Department of Alto Paraguay (21º 1' 29.85"S and 58º 17' 38.55" W), from 12/21/19 to 02/12/2020. In each site, an 8 * 8 meter exclusion cage was installed with three treatments (4m 2 subplots) corresponding to cutting intervals (CI 35, CI 70 and CI 105 days). Dry matter production by season and pasture growth rate, adjusted stocking rate at three production levels (50%, 70% and 75% breeding rate), carbon contained in aboveground, root and aerial biomass were evaluated stored on the ground. The data were compared using the Tukey test with a 5% probability. The emission of greenhouse gases per head and per hectares was simulated, adjusted to a breeding livestock on a total area of 6,600 total hectares and 5,000 grassland hectares. The 35-day CI presented a 32% higher productivity in relation to the 105-day CI as well as the associated carbon sequestration. The best capture/emission balance per hectare is observed in the CI 35 days with the breeding rate of 50% with 1,481 kg of CO 2 e-Ha-1 but intensifying and increasing the breeding rate to 75,
... AMP grazing also involves adjusting animal numbers to match available forage, using short grazing periods of <1 to several days, retaining sufficient post-herbivory plant residue for regrowth, and providing long recovery periods to adaptively accommodate intra-and inter-seasonal variation in herbaceous plant growth. Incorporating multiple livestock species into enterprises gives multiple benefits and increases biodiversity, business benefits from multiple enterprises (animals and crops), and disease and parasite management control (Earl and Jones, 1996;Murphy, 1998;Jacobo et al., 2006;Provenza, 2008;Ferguson et al., 2013;Teague et al., 2013;Flack, 2016;Rowntree et al., 2016;Wang et al., 2016;Hillenbrand et al., 2019). ...
Article
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We examine Adaptive Multi-Paddock (AMP) grazed with short grazing events and planned recovery periods and paired ranches using Conventional Continuous Grazing (CG) at low stock density on vegetation, water infiltration, and soil carbon across SE USA. Increased vegetation standing biomass and plant species dominance-diversity were measured in AMP grazed ranches. Invasive perennial plant species richness and abundance increased with AMP grazing in the south, while in the north they increased on CG grazed ranches. Percent bare ground was significantly greater in CG at the Alabama and Mississippi sites, no different at the Kentucky and mid-Alabama sites, and greater on AMP at the Tennessee pair. On average, surface water infiltration was higher on AMP than paired CG ranches. Averaged over all locations, soil organic carbon stocks to a depth of 1 m were over 13% greater on AMP than CG ranches, and standing crop biomass was >300% higher on AMP ranches. AMP grazing supported substantially higher livestock stocking levels while providing significant improvements in vegetation, soil carbon, and water infiltration functions. AMP grazing also significantly increased available forage nutrition for key constituents, and increased soil carbon to provide significant resource and economic benefits for improving ecological health, resilience, and durability of the family ranch.
... Nevertheless, ruminants can be part of the solution, when they are analyzed as part of a complex ecosystem and not only as emitter units. In this context, a moderate intensification of grazing management contributes to neutralizing livestock emissions, even it may be negative because grazing, besides animal trampling-induced pressures, alters numerous fundamental landscape dynamics and ecological relationships that regulate soil organic carbon sink, such as its edaphic and chemical properties [89][90][91][92][93]. Also, this can occur through methanotrophic bacteria that consume methane and that are found in larger amounts in grasslands than in croplands. ...
Article
The livestock sector faces an important challenge in the medium and long term since it must satisfy an increasing demand for animal products as a result of the increase in population and the world economy but safeguarding natural resources and at the same time minimizing the environmental contamination, especially the greenhouse gas (GHG) emissions attributed to livestock husbandry. For Latin America and the Caribbean (LAC), this becomes more relevant given the importance of the sector for the food security of rural communities, particularly for small-scale producers. In this manuscript, we address the main challenges of LAC in this context, from a global perspective that includes the demographic, economic, cultural, and environmental effects. The biggest global challenge for the LAC livestock sector for the coming decades is how to satisfy the growing human demand for animal protein in a sustainable way maintaining the food security of their communities. The efforts to achieve these goals require focusing on improving the efficiency of both animal husbandry and production systems. Therefore, it is necessary to implement technologies of sustainable intensification and it is urgent that those who make political decisions become aware of these issues.
... According to Agyemang (2003), livestock integrated land uses refer to the utilizing the natural resources of soil and water to support plant growth, which is linked with incorporation of livestock grazing on the land (Agyemang, 2003). The potential of grazing to enhance SOC stocks in the soil, delivering a net reduction in greenhouse gas emissions has been studied globally (Conant et al., 2017;Rowntree et al., 2016). However, there is limited evidence in the literature on the effect of livestock integration on SOC storage in arid and semiarid regions of Africa. ...
Article
Livestock integrated land use systems are considered as viable options for enhancing soil organic carbon (SOC) sequestration in a changing climate. This study assessed the influence of water deficit and livestock stocking density on soil carbon stocks. A total of 101 matching data were extracted from map layers of water deficit and livestock stocking density for C storage in Arenosols of Omusati and Otjozondjupa regions of Namibia. Maps for water deficit and livestock stocking density were obtained from national databases. The SOC data were arranged into four treatment combinations represented by two levels of water deficit and two levels of livestock stocking density. Linear mixed models (LMM) were then used to evaluate differences in SOC stocks in response to livestock stocking density and water deficit. Results showed that there was a significant interaction (p = 0.013) between the effects of livestock stocking density and water deficit on C-stocks. In conditions where the water deficit was small, the SOC stock was larger under more intensive grazing. Whilst in conditions where water deficit was large, the SOC stock was larger under less intensive grazing. Furthermore, the difference between SOC stock at large and small water deficits was larger under more intensive grazing. This shows that the impacts of a changing climate, and changes in the intensity of grazing must be considered together to predict effects on the SOC stock.
... In particular, comparative LCAs that assess improved versus conventional beef management in nearby systems are useful for determining how much a given management shift might reduce GHG emissions in a given region. Some recent studies have found that beef GHG emissions can be reduced to net-zero or even negative emissions (i.e., net C sequestration) with improved management in temperate ecosystem grazed lands (Herrero et al., 2016;Paustian et al., 2016;Rowntree et al., 2016;Stanley et al., 2018;Teague et al., 2016), although management-related soil C sequestration rates may diminish over time, with added soil C storage potentially reversible under subsequent disturbances and/or climate change (Godde et al., 2020). Meanwhile, ongoing enteric methane emissions from cattle are unavoidable, and are likely to increase with increased beef production. ...
Article
Full-text available
The global demand for beef is rapidly increasing (FAO, 2019), raising concern about climate change impacts (Clark et al., 2020; Leip et al., 2015; Springmann et al., 2018). Beef and dairy contribute over 70% of livestock greenhouse gas emissions (GHG), which collectively contribute ~6.3 Gt CO2‐eq/year (Gerber et al., 2013; Herrero et al., 2016) and account for 14%–18% of human GHG emissions (Friedlingstein et al., 2019; Gerber et al., 2013). The utility of beef GHG mitigation strategies, such as land‐based carbon (C) sequestration and increased production efficiency, are actively debated (Garnett et al., 2017). We compiled 292 local comparisons of “improved” versus “conventional” beef production systems across global regions, assessing net GHG emission data from Life Cycle Assessment (LCA) studies. Our results indicate that net beef GHG emissions could be reduced substantially via changes in management. Overall, a 46 % reduction in net GHG emissions per unit of beef was achieved at sites using carbon (C) sequestration management strategies on grazed lands, and an 8% reduction in net GHGs was achieved at sites using growth efficiency strategies. However, net‐zero emissions were only achieved in 2% of studies. Among regions, studies from Brazil had the greatest improvement, with management strategies for C sequestration and efficiency reducing beef GHG emissions by 57%. In the United States, C sequestration strategies reduced beef GHG emissions by over 100% (net‐zero emissions) in a few grazing systems, whereas efficiency strategies were not successful at reducing GHGs, possibly because of high baseline efficiency in the region. This meta‐analysis offers insight into pathways to substantially reduce beef production's global GHG emissions. Nonetheless, even if these improved land‐based and efficiency management strategies could be fully applied globally, the trajectory of growth in beef demand will likely more than offset GHG emissions reductions and lead to further warming unless there is also reduced beef consumption. Global demand for beef is rapidly increasing, raising concern about climate change impacts. We compiled 292 local comparisons of “improved” versus “conventional” beef production systems across global regions, assessing net greenhouse gas (GHG) emission data from Life Cycle Assessments (LCA). Overall, strategies for carbon (C) sequestration on grazed lands reduced net beef GHG emissions by 62%, and growth efficiency strategies reduced net GHG emissions by 30%. Despite these improvements, net‐zero emissions were achieved only in 2% of studies. Brazilian studies had the greatest reductions in beef GHG emissions. This meta‐analysis offers insight into management strategies to reduce beef GHG emissions across global regions.
... Grazing activities can promote SOC accumulation via increased plant biomass input from stimulated compensatory photosynthesis after defoliation (Doescher et al., 1997;Sollenberger et al., 2019), and litter fragmentation and mixing in soils through animal trampling (Naeth et al., 1991). Overgrazing, however, can be detrimental to SOC accumulation (Ma et al., 2016), mainly because of reduced C inputs due to animal consumption (Bagchi et al., 2017), increased soil degradation through trampling (Villamil et al., 2001), and increased enteric methane emission via animal respiration (Rowntree et al., 2016). ...
Article
Full-text available
Soil organic carbon (SOC) plays a key role in sustaining pasture agroecosystem function and its rate of accumulation can be influenced by management practices including manure deposition and grazing intensity. This study was conducted to determine the impacts of 13-years of different pasture management practices on SOC content and aggregation. The field experiment was conducted in a watershed consisted of five pasture management practices: (i) hayed (H), (ii) continuously grazed (CG), (iii) rotationally grazed (R), (iv) rotationally grazed with a grass buffer strip (RB), and (v) rotationally grazed with a fenced riparian buffer (RBR). Since 2004, all treatments received 5.6 Mg ha −1 of poultry litter annually except the buffer area located at the base of RB and RBR. Starting from the top of hillslope, each plot was divided into three landscape positions (A, B, and C). In addition, the ungrazed, unfertilized riparian buffer strip (RBS) in RBR was also studied. In general, upper landscape positions showed greater SOC than lower positions for most of the treatments, and in particular, soils in the landscape position A had greater SOC than RBS. However, permanganate oxidizable C (POXC) was higher in all poultry litter amended pasture systems compared to the RBS. Rotational grazing practice promoted the formation of large macroaggregates compared to other pasture management practices and RBS. All five pasture management treatments improved large macroaggregate-associated SOC content as compared to RBS, and it was higher in grazed plots than the hayed plots. Overall, this study showed that organic manure addition improved total SOC, POXC and SOC associated with large macroaggregates, while differences in SOC among different pasture management strategies were subtle even after 13 years of continuous management.
Article
Microbial communities in pasture and hayfield soils in upstate New York were studied to ascertain how land and livestock management practices influence microbial community structure. Three management approaches were compared: conventional pasture management (CM; low livestock density, low rotation frequency), multi-paddock management (MP; high livestock density, high rotation frequency) and mowing for hay (no livestock). Microbial functional groups were quantified by PLFA analysis. Soil attributes were measured, and management details were obtained by interviewing landowners. Microbial biomass in MP soils was higher, more diverse and contained proportionately more fungal (F) than bacterial (B) biomass than did CM and hayfield soils. Microbial biomass, diversity and F:B ratios in CM and hayfield soils were not different. Multivariate analyses suggest that different variables control microbial community structure in MP and CM soils.
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There is a lack of information regarding carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2 O) emissions from pasture soils and the effects of grazing. The objective of this study was to quantify greenhouse gas (GHG) fluxes from pasture soils grazed with cow-calf pairs managed with different stocking rates and densities. The central hypothesis was that irrigated low-density stocking systems (SysB) would result in greater GHG emissions from pasture soils than nonirrigated high-density stocking systems (SysA) and grazingexclusion (GRE) pasture sites. The nonirrigated high-density stocking systems consisted of 120 cow-calf pairs rotating on a total of 120 ha (stocking rate 1 cow/ha, stocking density 112,000 kg BW/ha, rest period of 60 to 90 d). The irrigated low-density stocking systems consisted of 64 cow-calf pairs rotating on a total of 26 ha of pasture (stocking rate 2.5 cows/ha, stocking density 32,700 kg BW/ha, rest period of 18 to 30 d). Both systems consisted of mixed cool-season grass-legume pastures. Static chambers were randomly placed for collection of CO2, CH4, and N2 O samples. Soil temperature (ST), ambient temperature (temperature inside the chamber; AT), and soil water content (WC) were monitored and considered explanatory variables for GHG emissions. GHG fluxes were monitored for 3 yr (2011 to 2013) at the beginning (P1) and at the end (P2) of the grazing season, always postgrazing. Paddock was the experimental unit (3 pseudoreplicates per treatment), and chambers (30 chambers per paddock) were considered multiple measurements of each experimental unit. A completely randomized design considered the term year × period as a repeated measure and chamber nested within paddock and treatment as the random term. Generally, SysB had greater CO2 emissions than SysA and GRE pasture sites across years and periods (P < 0.01). Soil temperature, AT, and WC had effects on CO2 emissions. Methane and N2 O emissions were observed from pasture sites of the 3 systems, but the effect of grazing was not constantly significant for CH4 and N2 O emissions. In addition, ST, AT, and WC did not conclusively explain CH4 and N2 O emissions. No clear trade-offs between GHG were observed; generally, GHG emissions increased from 2011 to 2013, which was likely associated with weather conditions, such as higher daily temperature and precipitation events. The central hypothesis that SysB would result in greater GHG emissions from pasture soils than SysA and GRE was not confirmed. © 2015 American Society of Animal Science. All rights reserved.
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