Determination of the carbon budget of a pasture: effect of system boundaries  and flux uncertainties

Abstract. Carbon (C) sequestration in the soil is considered as a potential important mechanism to mitigate greenhouse gas (GHG) emissions of the agricultural sector. It can be quantified by the net ecosystem carbon budget (NECB) describing the change of soil C as the sum of all relevant import and export fluxes. NECB was investigated here in detail for an intensively grazed dairy pasture in Switzerland. Two budget approaches with different system boundaries were applied: NECBtot for system boundaries including the grazing cows and NECBpast for system boundaries excluding the cows. CO2 and CH4 exchange induced by soil/vegetation processes as well as direct emissions by the animals were derived from eddy covariance measurements. Other C fluxes were either measured (milk yield, concentrate feeding) or derived based on animal performance data (intake, excreta). For the investigated year, both approaches resulted in a small near-neutral C budget: NECBtot −27 ± 62 and NECBpast 23 ± 76 g C m−2 yr−1. The considerable uncertainties, depending on the approach, were mainly due to errors in the CO2 exchange or in the animal-related fluxes. The comparison of the NECB results with the annual exchange of other GHG revealed CH4 emissions from the cows to be the major contributor in terms of CO2 equivalents, but with much lower uncertainty compared to NECB. Although only 1 year of data limit the representativeness of the carbon budget results, they demonstrate the important contribution of the non-CO2 fluxes depending on the chosen system boundaries and the effect of their propagated uncertainty in an exemplary way. The simultaneous application and comparison of both NECB approaches provides a useful consistency check for the carbon budget determination and can help to identify and eliminate systematic errors.

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Determination of the carbon budget of a pasture: effect of system boundaries and flux uncertainties

Biogeosciences Discussions ◽

10.5194/bgd-12-20071-2015 ◽

2015 ◽

Vol 12 (23) ◽

pp. 20071-20100 ◽

Cited By ~ 1

Author(s):

R. Felber ◽

D. Bretscher ◽

A. Münger ◽

A. Neftel ◽

C. Ammann

Keyword(s):

Carbon Budget ◽

Agricultural Sector ◽

Ghg Emissions ◽

C Sequestration ◽

Co2 Exchange ◽

System Boundaries ◽

Simultaneous Application ◽

Soil C ◽

Ecosystem Carbon ◽

One Year

Abstract. Carbon (C) sequestration in the soil is considered as a potential important mechanism to mitigate greenhouse gas (GHG) emissions of the agricultural sector. It can be quantified by the net ecosystem carbon budget (NECB) describing the change of soil C as the sum of all relevant import and export fluxes. NECB was investigated here in detail for an intensively grazed dairy pasture in Switzerland. Two budget approaches with different system boundaries were applied: NECBtot for system boundaries including the grazing cows and NECBpast for system boundaries excluding the cows. CO2 and CH4 exchange induced by soil/vegetation processes as well as direct emissions by the animals were derived from eddy covariance measurements. Other C fluxes were either measured (milk yield, concentrate feeding) or derived based on animal performance data (intake, excreta). For the investigated year, both approaches resulted in a small non-significant C loss: NECBtot - 13 ± 61 g C m−2 yr−1 and NECBpast - 17 ± 81 g C m−2 yr−1. The considerable uncertainties, depending on the approach, were mainly due to errors in the CO2 exchange or in the animal related fluxes. The associated GHG budget revealed CH4 emissions from the cows to be the major contributor, but with much lower uncertainty compared to NECB. Although only one year of data limit the representativeness of the carbon budget results, they demonstrated the important contribution of the non-CO2 fluxes depending on the chosen system boundaries and the effect of their propagated uncertainty in an exemplary way. The simultaneous application and comparison of both NECB approaches provides a useful consistency check for the carbon budget determination and can help to identify and eliminate systematic errors.

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Potential soil carbon sequestration of agricultural land around the world

10.5194/egusphere-egu21-3083 ◽

2021 ◽

Author(s):

Sylvia Vetter ◽

Michael Martin ◽

Pete Smith

Keyword(s):

Organic Carbon ◽

Management Practices ◽

Agricultural Land ◽

Ghg Emissions ◽

C Sequestration ◽

Organic Soils ◽

Soil C ◽

Sequestration Potential ◽

The World ◽

Soil C Sequestration

Reducing greenhouse gas (GHG) emissions in to the atmosphere to limit global warming is the big challenge of the coming decades. The focus lies on negative emission technologies to remove GHGs from the atmosphere from different sectors. Agriculture produces around a quarter of all the anthropogenic GHGs globally (including land use change and afforestation). Reducing these net emissions can be achieved through techniques that increase the soil organic carbon (SOC) stocks. These techniques include improved management practices in agriculture and grassland systems, which increase the organic carbon (C) input or reduce soil disturbances. The C sequestration potential differs among soils depending on climate, soil properties and management, with the highest potential for poor soils (SOC stock farthest from saturation).Modelling can be used to estimate the technical potential to sequester C of agricultural land under different mitigation practices for the next decades under different climate scenarios. The ECOSSE model was developed to simulate soil C dynamics and GHG emissions in mineral and organic soils. A spatial version of the model (GlobalECOSSE) was adapted to simulate agricultural soils around the world to calculate the SOC change under changing management and climate.Practices like different tillage management, crop rotations and residue incorporation showed regional differences and the importance of adapting mitigation practices under an increased changing climate. A fast adoption of practices that increase SOC has its own challenges, as the potential to sequester C is high until the soil reached a new C equilibrium. Therefore, the potential to use soil C sequestration to reduce overall GHG emissions is limited. The results showed a high potential to sequester C until 2050 but much lower rates in the second half of the century, highlighting the importance of using soil C sequestration in the coming decades to reach net zero by 2050.

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A comparison between vegetable intercropping systems and monocultures in greenhouse gas emissions under organic management

10.5194/egusphere-egu2020-13415 ◽

2020 ◽

Author(s):

Virginia Sánchez-Navarro ◽

Mariano Marcos-Pérez ◽

Raúl Zornoza

Keyword(s):

Climate Change ◽

Greenhouse Gas ◽

Cropping Systems ◽

Ghg Emissions ◽

Experimental Period ◽

C Sequestration ◽

Organic Management ◽

Soil C ◽

Dynamic Chamber ◽

Cucumis Melo L

Legume crops have been proposed as a way of reducing greenhouse gas (GHG) emissions because both, their rhizosphere behaviour and their ability to fix atmospheric N reducing the need of external N fertilizer. Moreover, the establishment of organic agriculture has been proposed as a sustainable strategy to enhance the delivery of ecosystem services, including mitigation of climate change by decreases in GHG emissions and increases in soil C sequestration. The aim of this study was to assess the effect of the association between cowpea (Vigna unguiculata L.) and melon (Cucumis melo L.) growing in different intercropping patterns on soil CO2 and N2O emissions compared to cowpea and melon monocultures under organic management as a possible strategy for climate change mitigation. Soil CO2 and N2O emissions were weekly measured in melon and cowpea rows using the dynamic chamber method during one cropping cycle in 2019. Results indicated that melon growing as monoculture was related to increases in O cumulative emissions (0.431 g m-2) compared to the average of the rest of treatments (0.036 g m-2). Cowpea growing as monoculture was related to decreases in CO2 cumulative emissions (390 g m-2) compared with the other treatments (512 g m-2 average). However, N2O and CO2 emission patterns did not directly follow soil moisture patterns in the experimental period, with no significant correlations. Finally there were no significant differences among intercropping treatments with regard to NO2 and CO2 emissions. Further measurements are needed to monitor the evolution of GHG emissions under these cropping systems and confirm the trend observed.

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Humus, nitrogen and energy balances, and greenhouse gas emissions in a long-term field experiment with compost compared with mineral fertilisation

Soil Research ◽

10.1071/sr15127 ◽

2016 ◽

Vol 54 (2) ◽

pp. 254 ◽

Cited By ~ 3

Author(s):

Eva Erhart ◽

Harald Schmid ◽

Wilfried Hartl ◽

Kurt-Jürgen Hülsbergen

Keyword(s):

Organic Matter ◽

Field Experiment ◽

Greenhouse Gas ◽

Ghg Emissions ◽

Organic Matter Content ◽

C Sequestration ◽

Organic C ◽

Soil C ◽

Positive Balance ◽

Energy Balances

Compost fertilisation is one way to close material cycles for organic matter and plant nutrients and to increase soil organic matter content. In this study, humus, nitrogen (N) and energy balances, and greenhouse gas (GHG) emissions were calculated for a 14-year field experiment using the model software REPRO. Humus balances showed that compost fertilisation at a rate of 8 t/ha.year resulted in a positive balance of 115 kg carbon (C)/ha.year. With 14 and 20 t/ha.year of compost, respectively, humus accumulated at rates of 558 and 1021 kg C/ha.year. With mineral fertilisation at rates of 29–62 kg N/ha.year, balances were moderately negative (–169 to –227 kg C/ha.year), and a clear humus deficit of –457 kg C/ha.year showed in the unfertilised control. Compared with measured soil organic C (SOC) data, REPRO predicted SOC contents fairly well with the exception of the treatments with high compost rates, where SOC contents were overestimated by REPRO. GHG balances calculated with soil C sequestration on the basis of humus balances, and on the basis of soil analyses, indicated negative GHG emissions with medium and high compost rates. Mineral fertilisation yielded net GHG emissions of ~2000 kg CO2-eq/ha.year. The findings underline that compost fertilisation holds potential for C sequestration and for the reduction of GHG emissions, even though this potential is bound to level off with increasing soil C saturation.

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Managing pasture for animals and soil carbon

Proceedings of the New Zealand Grassland Association ◽

10.33584/jnzg.2009.71.2775 ◽

2009 ◽

pp. 77-84 ◽

Cited By ~ 1

Author(s):

A.J. Parsons ◽

J.S. Rowarth ◽

P.C.D. Newton

Keyword(s):

Soil Carbon ◽

Greenhouse Gas ◽

Kyoto Protocol ◽

Ghg Emissions ◽

C Sequestration ◽

Grazing Management ◽

Soil C ◽

National Trends

There has been growing interest in including soil carbon (C) sequestration, as an offset to greenhouse gas (GHG) emissions, within New Zealand's commitment to the Kyoto Protocol, even though national trends report soil C concentrations in many areas is declining. There are different schools of thought as to what drives changes in soil C (e.g. grazing management, fertiliser inputs, species) and so in our capacity to increase the rate of sequestration of C since 1990 to gain C credits.

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143 Impacts of soil carbon sequestration on life cycle greenhouse gas emissions in midwestern USA beef finishing systems

Journal of Animal Science ◽

10.1093/jas/skz258.302 ◽

2019 ◽

Vol 97 (Supplement_3) ◽

pp. 147-148

Author(s):

Jason Rowntree ◽

Paige Stanley ◽

David Beede ◽

Marcia DeLonge ◽

Michael Hamm

Keyword(s):

Life Cycle ◽

Soil Carbon ◽

Energy Use ◽

Ghg Emissions ◽

C Sequestration ◽

Grazing Impact ◽

Mineral Supplement ◽

Soil C ◽

Continuous Grazing ◽

On Farm

Abstract Using life cycle analysis (LCA), several studies have concluded that grass-finished beef systems have greater GHG intensities than feedlot-finished (FL) beef systems. These studies evaluated only one grazing management system– continuous grazing – and assumed steady-state soil carbon (C), to model the grass-finishing environmental impact. However, by managing for more optimal forage growth and recovery, adaptive multi-paddock (AMP) grazing can improve animal and forage productivity, potentially sequestering more soil organic carbon (SOC) than continuous grazing. To examine impacts of AMP grazing and related SOC sequestration on net GHG emissions, a comparative LCA was performed of two different beef finishing systems in the Upper Midwest, USA: AMP grazing and FL. We used on-farm data collected from the Michigan State University Lake City AgBioResearch Center for AMP grazing. Impact scope included GHG emissions from enteric methane, feed production and mineral supplement manufacture, manure, and on-farm energy use and transportation, as well as the potential C sink arising from SOC sequestration. Across-farm SOC data showed a 4-year C sequestration rate of 3.59 Mg C ha−1 yr−1 in AMP grazed pastures. After including SOC in the GHG footprint estimates, finishing emissions from the AMP system were reduced from 9.62 to −6.65 kg CO2-e kg carcass weight (CW)−1, whereas FL emissions increased slightly from 6.09 to 6.12 kg CO2-e kg CW−1 due to soil erosion. This indicates that AMP grazing has the potential to offset GHG emissions through soil C sequestration, and therefore the finishing phase could be a net C sink. However, FL production required only half as much land as AMP grazing. This research suggests that AMP grazing can contribute to climate change mitigation through SOC sequestration and challenges existing conclusions that only feedlot-intensification reduces the overall beef GHG footprint through greater productivity.

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The role of temperate treed swamps as a carbon sink in southwestern Nova Scotia

Canadian Journal of Forest Research ◽

10.1139/cjfr-2019-0311 ◽

2021 ◽

Vol 51 (1) ◽

pp. 78-88

Author(s):

Rachel A. Kendall ◽

Karen A. Harper ◽

David Burton ◽

Kevin Hamdan

Keyword(s):

Climate Change ◽

Nova Scotia ◽

Carbon Sink ◽

Ghg Emissions ◽

Forested Wetlands ◽

C Sequestration ◽

Soil C ◽

C Storage ◽

C Cycle

Forested wetlands may represent important ecosystems for mitigating climate change effects through carbon (C) sequestration because of their slow decomposition and C storage by trees. Despite this potential importance, few studies have acknowledged the role of temperate treed swamps in the C cycle. In southwestern Nova Scotia, Canada, we examined the role of treed swamps in the soil C cycle by determining C inputs through litterfall, assessing decomposition rates and soil C pools, and quantifying C outputs through soil greenhouse gas (GHG) emissions. The treed swamps were found to represent large supplies of C inputs through litterfall to the forest floor. The swamp soils had substantially greater C stores than the swamp–upland edge or upland soils. We found growing season C inputs via litterfall to exceed C outputs via GHG emissions in the swamps by a factor of about 2.5. Our findings indicate that temperate treed swamps can remain a C sink even if soil GHG emissions were to double, supporting conservation efforts to preserve temperate treed swamps as a measure to mitigate climate change.

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How does soil carbon sequestration affect greenhouse gas emissions from a sheep farming system? Results of an life cycle assessment case study

Italian Journal of Agronomy ◽

10.4081/ija.2021.1789 ◽

2021 ◽

Author(s):

Pasquale Arca ◽

Enrico Vagnoni ◽

Pierpaolo Duce ◽

Antonello Franca

Keyword(s):

Life Cycle ◽

Production System ◽

Emission Intensity ◽

Ghg Emissions ◽

C Sequestration ◽

Dairy Sheep ◽

Soil C ◽

Sheep Farm ◽

Enteric Methane ◽

Soil C Sequestration

Highlights Extensification of dairy sheep systems provides an environmental benefit when soil C sequestration is considered. Extensification of dairy sheep systems determines lower environmental impact per hectare of utilized agricultural area. Enteric methane emissions are the main source of GHG emissions of the sheep milk life cycle. Carbon sequestration in permanent grasslands can considerably contribute to climate change mitigation. Abstract A life cycle assessment (LCA) study of a transition from semi-intensive to semi-extensive Mediterranean dairy sheep farm suggests that the latter has a strong potential for offsetting greenhouse gas (GHG) emissions through the soil C sequestration (Cseq) in permanent grasslands. The extensification process shows clear environmental advantage when emission intensity is referred to the area-based functional unit (FU). Several LCA studies reported that extensive livestock systems have greater GHG emissions per mass of product than intensive one, due to their lower productivity. However, these studies did not account for soil Cseq of temporary and permanent grasslands, that have a strong potential to partly mitigate the GHG balance of ruminant production systems. Our LCA study was carried out considering the transition from a semi-intensive (SI) towards a semi-extensive (SE) production system, adopted in a dairy sheep farm located in North-Western Sardinia (Italy). Impact scope included enteric methane emissions, feed production, on-farm energy use and transportation, infrastructures as well as the potential C sink arising from soil Cseqwith respect to the emission intensity. In order to provide a more comprehensive analysis, we used the following FUs: 1 kg of fat and protein corrected milk (FPCM) and 1 ha of utilised agricultural area (UAA). We observed that the extensification of production system determined contrasting environmental effects when using different FUs accounting for soil Cseq. When soil Cseq in emission intensity estimate was included, we observed slightly lower values of GHG emissions per kg of FPCM in the SI production system (from 3.37 to 3.12 kg CO2 equivalents – CO2-eq), whereas a greater variation we observed in the SE one (from 3.54 to 2.90 kg CO2-eq). Considering 1 ha of UAA as FU and including the soil Cseq, the emission intensity in SI moved from 6,257 to 5,793 kg CO2-eq, whereas values varied from 4,020 to 3,299 kg CO2-eq in SE. These results indicated that the emission intensity from semi-extensive Mediterranean dairy sheep farms can be considerably reduced through the soil Cseq, although its measurement is influenced by the models used in the estimation.

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Modelling the influence of soil carbon on net greenhouse gas emissions from grazed pastures

Animal Production Science ◽

10.1071/an15508 ◽

2016 ◽

Vol 56 (3) ◽

pp. 585 ◽

Cited By ~ 6

Author(s):

Rachelle Meyer ◽

Brendan R. Cullen ◽

Richard J. Eckard

Keyword(s):

Organic Matter ◽

Soil Organic Matter ◽

Annual Variation ◽

Ghg Emissions ◽

C Sequestration ◽

N2o Emissions ◽

Soil C ◽

High Rainfall ◽

Sequestration Potential ◽

Ch4 And N2o

Sequestering carbon (C) in soil organic matter in grassland systems is often cited as a major opportunity to offset greenhouse gas (GHG) emissions. However, these systems are typically grazed by ruminants, leading to uncertainties in the net GHG balance that may be achieved. We used a pasture model to investigate the net balance between methane (CH4), nitrous oxide (N2O) and soil C in sheep-grazed pasture systems with two starting amounts of soil C. The net emissions were calculated for four soil types in two rainfall zones over three periods of 19 years. Because of greater pasture productivity, and consequent higher sheep stocking rates, high-rainfall sites were associated with greater GHG emissions that could not be offset by C sequestration. On these high-rainfall sites, the higher rate of soil organic carbon (SOC) increase on low-SOC soils offset an average of 45% of the livestock GHG emissions on the modelled chromosol and 32% on the modelled vertosol. The slow rate of SOC increase on the high-SOC soils only offset 2–4% of CH4 and N2O emissions on these high-rainfall sites. On low-rainfall sites, C sequestration in low-SOC soils more than offset livestock GHG emissions, whereas the modelled high-C soils offset 75–86% of CH4 and N2O emissions. Greater net emissions on high-C soils were due primarily to reduced sequestration potential and greater N2O emissions from nitrogen mineralisation and livestock urine. Annual variation in CH4 and N2O emissions was low, whereas annual SOC change showed high annual variation, which was more strongly correlated with weather variables on the low-rainfall sites compared with the high-rainfall sites. At low-soil C concentrations, with high sequestration potential, there is an initial mitigation benefit that can in some instances offset enteric CH4 and direct and indirect N2O emissions. However, as soil organic matter increases there is a trade-off between diminishing GHG offsets and increasing ecosystem services, including mineralisation and productivity benefits.

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Greenhouse gas balance related to conventional and sustainable fruit production systems in the Highlands region of Pasto, Colombia

Agronomía Colombiana ◽

10.15446/agron.colomb.v34n2.55417 ◽

2016 ◽

Vol 34 (2) ◽

pp. 277-284

Author(s):

Hernando Criollo E. ◽

Amanda Silva P. ◽

Hernando Delgado H.

Keyword(s):

Greenhouse Gas ◽

Production Systems ◽

Ghg Emissions ◽

C Sequestration ◽

Fruit Production ◽

Production Cycle ◽

Greenhouse Gas Balance ◽

Soil C ◽

Sequestration Potential ◽

Gas Balance

This research focused on the greenhouse gas (GHG) emissions and potential sinks associated with conventional and sustainable fruit production systems in the Highlands region of Pasto, Nariño, Colombia. Based on the IPCC (2006) methodologies, the annual emission balance for a 6-year production cycle included agricultural sources and gasoline consumption related to the main agricultural activities and the potential for soil C accumulation and biomass C fixation in all of the studied systems. The multivariate analysis showed that positive GHG balance emissions would be achieved in all sustainable fruit production systems, as compared to conventional fruit production systems with greater impact on (SS1): Rubusglaucus Benth. associated with Acacia decurrens trees and live coverage of kikuyu Pen-nisetum clandestinum grass. According to the results of this study, (SS1) showed the beneficial total GHG balance emission accounting for -21,079 kg of atmospheric CO2eq ha-1 yr-1 divided into -4,587 kg CO2eq ha-1 yr-1 and -17,102 kg CO2eq ha-1 yr-1 due an annual soil and biomass C sequestration potential that could help offset its emissions (610 kg CO2eq ha-1 yr-1).

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