145 research outputs found
What is needed for reducing the greenhouse gas footprint?
Livestock production is responsible for a large amount of greenhouse gas (GHG) emissions. However, numerous approaches have been developed to reduce these emissions and thus lower environmental pollution caused by livestock husbandry. This article shows where interventions are possible and which hurdles have to be cleared in implementing the various measures needed
Development of key components of a nitrogen budget for a forested watershed on the Canadian boreal plain
This investigation, which took place as part of the Forest Watershed and Riparian Disturbance (FORWARD) study in west-central Alberta on the Boreal Plain, measured key components of a nitrogen (N) budget in a relatively undisturbed, forested watershed. The first component examined was N inputs from bulk deposition and the effect of different forest soil/canopy types (upland deciduous, upland conifer and wetland conifer stands) on N flux from the bulk deposition to the forest floor
Estimating global terrestrial denitrification from measured NO:(NO + N) product ratios
The use of nitrogen (N) fertilizers and cultivation of N-fixing crops has grown exponentially over the last century, with severe environmental consequences. Most of the anthropogenic reactive nitrogen will ultimately be returned by denitrification to the atmosphere as inert N, but the magnitude of denitrification and the ratio of NO to (NO + N) emitted (R) is unknown for the vast majority of terrestrial ecosystems. This paper provides estimates of terrestrial denitrification and R by reviewing existing literature and compiling a N budget for the global land surface. We estimate that terrestrial denitrification has doubled from 80 Tg-N year in pre-industrial times to 160 Tg-N year in 2005 with a mean R of approximately 0.08. We conclude that upscaling of R can provide spatial estimates of terrestrial denitrification when data from acetylene inhibition methods are excluded. Recent advances in methodologies to measure N emissions and R under field conditions could open the way for more effective management of terrestrial N flows
Soil N intensity as a measure to estimate annual NO and NO fluxes from natural and managed ecosystems
As natural and managed terrestrial ecosystems are major sources of the potent greenhouse gas nitrous oxide (NO) and of the atmospheric pollutant nitric oxide (NO), predicting the source strengths of these ecosystems is central to understanding and sustainably managing the N-oxides fluxes. Here we reviewed 82 high temporal resolution datasets on NO and 57 on NO fluxes collected from multi-site and multi-year field measurements, including grasslands, forests, and agricultural crops, to assess whether soil N intensity, that is, the time-weighted sum of soil NH and/or NO concentrations, can be used to estimate annual N-oxides emissions. We show that soil N intensity alone can accurately predict annual NO and NO emissions, and that the NO emission strength is exponentially related to the soil inorganic N load. Thus, measuring soil inorganic N loads should improve current estimates of N-oxide emissions from global terrestrial ecosystems, and open possibilities for monitoring NO mitigation efforts
Nitrous oxide emission factors for cattle dung and urine deposited onto tropical pastures: A review of field-based studies
Livestock excreta on pastures is an important source of nitrous oxide (N2O) emissions, however studies measuring these emissions in tropical regions, particularly Africa, remain limited. Therefore we measured N2O emissions from different quantities of dung patches during three observation periods (dry, wet and transition from dry to wet season) and different volumes of urine patches during wet and dry seasons. Dung patches did not stimulate soil N2O emissions in any of the three observation periods, while urine application stimulated soil N2O emissions during both seasons, with higher emissions observed during the wet season. The dung EFs (0.00–0.03%) and the urine EFs (0.04–0.40%) showed no detectable effects of dung quantity or urine volume. We further synthesized observations from other studies in wet and dry tropical regions, which indicated that the excreta N2O EFs were similar to the default values provided in the IPCC 2019 refinement (0.11% vs 0.07% for dung and 0.41% vs 0.32% for urine in dry climates, and 0.13% vs 0.13% for dung and 0.65% vs 0.77% for urine in wet climates). However, sub-Saharan African (SSA) studies had consistently lower EFs, possibly due to the lower urine-N: dung-N ratio in SSA compared with the other tropical regions, suggesting that the refinement may still overestimate excreta emissions in SSA. Moreover, considering the large variations in the summarized tropical excreta N2O EFs, from -0.01 to 1.77% for dung and 0.00 to 4.90% for urine, more studies under diverse conditions across tropical regions are recommended
Greenhouse gas emissions from natural ecosystems and agricultural lands in sub-Saharan Agrica:synthesis of available data and suggestions for further research
This paper summarizes currently available data on greenhouse gas (GHG)
emissions from African natural ecosystems and agricultural lands. The
available data are used to synthesize current understanding of the drivers
of change in GHG emissions, outline the knowledge gaps, and suggest future
directions and strategies for GHG emission research. GHG emission data were
collected from 75 studies conducted in 22 countries (n =  244) in sub-Saharan
Africa (SSA). Carbon dioxide (CO2) emissions were by far the largest
contributor to GHG emissions and global warming potential (GWP) in SSA
natural terrestrial systems. CO2 emissions ranged from 3.3 to 57.0 Mg CO2 ha−1 yr−1, methane (CH4) emissions ranged from −4.8
to 3.5 kg ha−1 yr−1 (−0.16 to 0.12 Mg CO2 equivalent (eq.) ha−1 yr−1), and nitrous oxide (N2O) emissions ranged from
−0.1 to 13.7 kg ha−1 yr−1 (−0.03 to 4.1 Mg CO2 eq. ha−1 yr−1). Soil physical and chemical properties, rewetting,
vegetation type, forest management, and land-use changes were all found to
be important factors affecting soil GHG emissions from natural terrestrial
systems. In aquatic systems, CO2 was the largest contributor to total
GHG emissions, ranging from 5.7 to 232.0 Mg CO2 ha−1 yr−1,
followed by −26.3 to 2741.9 kg CH4 ha−1 yr−1 (−0.89 to 93.2 Mg CO2 eq. ha−1 yr−1) and
0.2 to 3.5 kg N2O ha−1 yr−1 (0.06 to 1.0 Mg CO2 eq. ha−1 yr−1). Rates of all
GHG emissions from aquatic systems were affected by type, location,
hydrological characteristics, and water quality. In croplands, soil GHG
emissions were also dominated by CO2, ranging from 1.7 to 141.2 Mg CO2 ha−1 yr−1,
with −1.3 to 66.7 kg CH4 ha−1 yr−1 (−0.04 to 2.3 Mg CO2 eq. ha−1 yr−1) and
0.05 to 112.0 kg N2O ha−1 yr−1 (0.015 to 33.4 Mg CO2 eq. ha−1 yr−1). N2O emission factors (EFs) ranged from 0.01
to 4.1 %. Incorporation of crop residues or manure with inorganic
fertilizers invariably resulted in significant changes in GHG emissions, but
results were inconsistent as the magnitude and direction of changes were
differed by gas. Soil GHG emissions from vegetable gardens ranged from 73.3
to 132.0 Mg CO2 ha−1 yr−1 and 53.4 to 177.6 kg N2O ha−1 yr−1 (15.9 to 52.9 Mg CO2 eq. ha−1 yr−1)
and N2O EFs ranged from 3 to 4 %. Soil CO2 and
N2O emissions from agroforestry were 38.6 Mg CO2 ha−1 yr−1 and 0.2 to 26.7 kg N2O ha−1 yr−1
(0.06 to 8.0 Mg CO2 eq. ha−1 yr−1), respectively. Improving fallow with
nitrogen (N)-fixing trees led to increased CO2 and N2O emissions
compared to conventional croplands. The type and quality of plant residue in
the fallow is an important control on how CO2 and N2O emissions
are affected. Throughout agricultural lands, N2O emissions slowly
increased with N inputs below 150 kg N ha−1 yr−1 and increased
exponentially with N application rates up to 300 kg N ha−1 yr−1.
The lowest yield-scaled N2O emissions were reported with N application
rates ranging between 100 and 150 kg N ha−1. Overall, total CO2 eq. emissions from SSA natural ecosystems and agricultural lands were
56.9 ± 12.7  ×  109 Mg CO2 eq. yr−1 with natural ecosystems
and agricultural lands contributing 76.3 and 23.7 %, respectively.
Additional GHG emission measurements are urgently required to reduce
uncertainty on annual GHG emissions from the different land uses and
identify major control factors and mitigation options for low-emission
development. A common strategy for addressing this data gap may include
identifying priorities for data acquisition, utilizing appropriate
technologies, and involving international networks and collaboration
Global assessment of manure management policies and practices
In 2014 an assessment of livestock manure policies was performed in 34 countries in Asia, Africa and
Latin America, followed by an in-depth assessment of manure management practices in Bangladesh, Viet Nam, Ethiopia, Malawi, Argentina and Costa Rica. The assessments revealed the key barriers for improving integrated manure management and identified six opportunities for actual practice changes to improve manure related policies as well as farm practices with the overall objective of improving food security while mitigating methane emissions at the same tim
Effect of feeding practices and manure quality on CH and NO emissions from uncovered cattle manure heaps in Kenya
Countries in sub-Saharan Africa (SSA) rely on IPCC emission factors (EF) for GHG emission reporting. However, these were derived for industrialized livestock farms and do not represent conditions of smallholder farms (small, low-producing livestock breeds, poor feed quality, feed scarcity). Here, we present the first measurements of CH and NO emissions from cattle-manure heaps representing feeding practices typical for smallholder farms in the highlands of East Africa: 1) cattle fed below maintenance energy requirements to represent feed scarcity, and 2) cattle fed tropical forage grasses (Napier, Rhodes, Brachiaria). Sub-maintenance feeding reduced cumulative manure NO emissions compared to cattle receiving sufficient feed but did not change EF. Sub-maintenance feeding did not affect cumulative manure CH emissions or EF. When cattle were fed tropical forage grasses, cumulative manure NO emissions did not differ between diets, but manure EF from Brachiaria and Rhodes diets were lower than the IPCC EF for solid storage (1%, 2019 Refinement of IPCC Guidelines). Manure CH emissions were lower in the Rhodes grass diet than when feeding Napier or Brachiaria, and manure EF from all three grasses were lower than the IPCC default (4.4 g CH kg VS, 2019 Refinement of IPCC Guidelines). Regression analysis revealed that manure N concentration and C:N were important drivers of NO emissions, with low N concentrations and high C:N reducing NO emissions. Our results show that IPCC EFs overestimate excreta GHG emissions, which calls for additional measurements to develop localized EFs for smallholder livestock systems in SSA
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