Decreased CH4 Emissions Research Articles

Mechanism of slag-based silicate fertilizer suppressing methane emissions from paddies

The addition of electron acceptors to boost soil microbes competitive to methanogens could minimize methane (CH4) emissions from paddy soils. To study the microbiological mechanisms underlying the suppression of CH4 emissions, silicate fertilizer made from blast furnace slag that contains electron acceptors, such as Fe, was applied to Japonica and Indica rice at a rate of 2 Mg ha−1. We found that silicate fertilization significantly reduced CH4 emissions from Japonica and Indica rice by 21.1% and 25.7%, respectively, and the decrease in CH4 emissions coincided with an increase in iron reduction in paddy soils. Silicate fertilization markedly suppressed several methanogens and abundance of genes involved in acetoclastic and hydrogenotrphic methanogenesis, albeit the suppression of acetoclastic gene abundance was larger. Conversely, it increased methanotrophs, their gene abundance, and CH4 oxidation potential of paddy soils, which could be explained by an increase in root oxidation potential. Iron-reducing and oxidizing microbes, and their gene abundance significantly increased by silicate fertilization. Structural equation modeling showed that the suppression of CH4 emissions was mainly due to the competitive inhibition of methanogens by iron-reducing bacteria and the proliferation of methonotrophs. These findings have implications for understanding the CH4 biogeochemistry under silicate fertilization, as it has the potential to mitigate CH4 emissions from paddies.

Assessing carbon greenhouse gas emissions from aquaculture in China based on aquaculture system types, species, environmental conditions and management practices

Aquaculture is one of the fastest growing food production sectors in the world, but many of the small-hold operations are poorly assessed for their climate impact. We analyzed the literature data on CO2 and CH4 fluxes from various aquaculture systems in China. The mean fluxes varied in the ranges of − 382.45–551.88 g CO2-C m−2 yr−1 and − 0.03–565.09 g CH4-C m−2 yr−1. Aquaculture system reclaimed from mudflat had the highest CH4 emission (54.92 ± 21.00 g C m−2 yr−1) but lowest CO2 emission. Shrimp aquaculture and semi-intensive farming tended to yield higher CH4 emission. Small and shallow systems had significantly higher CO2 and CH4 emissions, with chlorophyll a and dissolved oxygen concentrations as the main environmental drivers. Management practice such as drainage, exposure and desilting during the non-farming period significantly decreased CH4 emission. We estimated that aquaculture systems in China emitted 181.66 Tg CO2-eq yr−1, offsetting ~7% of the national terrestrial carbon sink, with most of the emission concentrated in coastal provinces and along the major rivers in the southeastern quadrant. This study highlights the importance of accounting for greenhouse gas emissions from aquaculture to improve the accuracy of the regional and national carbon budgets.

Phosphorus control and dredging decrease methane emissions from shallow lakes

Freshwater ecosystems are an important source of the greenhouse gas methane (CH4), and their emissions are expected to increase due to eutrophication. Two commonly applied management techniques to reduce eutrophication are the addition of phosphate-binding lanthanum modified bentonite (LMB, trademark Phoslock©) and dredging, but their effect on CH4 emissions is still poorly understood. Here, this study researched how LMB and dredging affected CH4 emissions using a full-factorial mesocosm design monitored for 18 months. The effect was tested by measuring diffusive and ebullitive CH4 fluxes, plant community composition, methanogen and methanotroph activity and community composition, and a range of physicochemical water and sediment variables. LMB addition decreased total CH4 emissions, while dredging showed a trend towards decreasing CH4 emissions. Total CH4 emissions in all mesocosms were much higher in the summer of the second year, likely because of higher algal decomposition and organic matter availability. First, LMB addition lowered CH4 emissions by decreasing P-availability, which reduced coverage of the floating fern Azolla filiculoides, and thereby prevented anoxia and decreased surface water NH4+ concentrations, lowering CH4 production rates. Second, dredging decreased CH4 emissions in the first summer, possibly it removed the methanogenic community, and in the second year by preventing autumn and winter die-off of the rooted macrophyte Potamogeton cripsus. Finally, methanogen community composition was related to surface water NH4+ and O2, and porewater total phosphorus, while methanotroph community composition was related to organic matter content. To conclude, LMB addition and dredging not only improve water quality, but also decrease CH4 emissions, mitigating climate change.

Selected parameters of soil health in Cumilla district at the Golden Jubilee of Bangladesh and strategies for their sustainable improvement towards rice production

Soil fertility and rice production were the most frequently mentioned issues identified not only in all the countries of Asia but also in the rest of the world. Hence, it is essential to pay attention for sustainable rice production, climate-smart agriculture and soil health. Accordingly, assessments of selected soil health indicators, such as, pH, organic matter and cation exchange capacity (CEC) in all 17 Upazilas of Cumilla district of Bangladesh were completed under the financial support of the Climate Change Trust Fund (CCTF). A few strategies were used for the improvement of soil health in response to smart rice production at the field site using locally available organic-fertilizers, viz. Vermicompost (V), Rice husk ash (RHA) and Burned poultry litters (BPL) at the rates of 0, 4 and 8 t ha-1 under the soil temperature elevation of 2 to 3°C (i.e. 25 to 28°C) and moisture levels of 60 and 90%. The above mentioned parameters of soil health at the Golden Jubilee of Bangladesh were found to be improved slightly compared to those of the 1970s and 2000s. These trends of improvement were found to be enhanced by the stated treatments. The yields of different rice varieties were increased from 4.4 - 5.5 to 8.4 – 9.1 t ha-1 by the treatments and the order of their effectiveness for grain yields and protein contents were V > BPL > RHA. Organic matter contents, pH and CEC of the studied soils were increased by these treatments and decreased CH4 emissions from the studied rice field. However, these approaches of sustainability cannot be provided by the poor farmers and therefore, the government should come forward to help these farmers in order to build a ‘Developed Bangladesh’ – the dream of Bangabandhu Sheikh Mujibur Rahman, the Father of the Nation and the Honorable Prime Minister Sheikh Hasina, the Mother of Humanity and the Champion of the Earth. Dhaka Univ. J. Biol. Sci. 30(3 CSI): 511-531, 2022 (June)

Changes in the Metagenome-Encoded CAZymes of the Rumen Microbiome Are Linked to Feed-Induced Reductions in Methane Emission From Holstein Cows.

Enteric methane (CH4) emission from cattle is strongly linked to the feeding regime and the rumen microbial community structure. Here, we report that feed-induced CH4-reducing effects correlate with specific alterations in the profile of the microbiome-encoded carbohydrate-active enzymes predicted from the rumen fluid metagenome. Rumen microbiome samples were obtained by mouth-tube sampling from 12 lactating Holstein cows after 3–4 weeks of feeding with three different concentrate-to-forage-ratio diets, i.e., standard, high, and extremely high levels of concentrate (4 cows per group; constant dry matter intake in the three groups). Increased inclusion of concentrate involved increased starch levels in the diet at the expense of fiber. The extreme diet resulted in 48% reduction of the CH4 emission per kg dry matter intake compared to the standard diet. From metagenome sequencing of the rumen fluid samples from each cow, 561 different microbial strains (bins) could be derived from analysis of 260 billion DNA base pairs. In the cows fed, the extreme diet, the relative abundance of the majority of the bins, was significantly altered compared to the other groups. Fibrobacterota and Verrucomicrobiota were less abundant in the Extreme group. Surprisingly, no significant abundance changes were observed among Archaea and Bacteroidota, although abundance changes of individual bins of these phyla were found. For each of the 561 bins, the functions of the metagenome-encoded carbohydrate-active enzymes were predicted by bioinformatics using conserved unique peptide pattern (CUPP) analysis. By linking each of the predicted molecular functions of the enzymes to their substrates, changes were found in the predicted abundance of the different enzyme types. Notably, the decreased CH4 emission of the extreme diet group was concurrent with a profound decrease in the xylan-active enzymes, targeting the xylan backbone β-1,4-linkages, acetyl-, feruloyl-, and methyl-glucuronoyl substitutions in xylan. This work provides a first enzyme-conversion-based characterization of how extreme feeding, i.e., lowered forage, can drive rumen microbiome changes that support decreased CH4 emission via a changed carbohydrate-active enzyme profile. The data, furthermore, provide a metagenome-wide catalog of enzymes, underpinning the microbial conversion of different feed fibers (the enzymes attacking specific carbohydrate linkages) in the rumen of Holstein cows.

Responses of ecosystem respiration and methane fluxes to warming and nitrogen addition in a subtropical littoral wetland

Subtropical wetlands sequester vast carbon (C) and their C cycles are sensitive to global changes, such as climate warming and increased nitrogen (N) deposition. However, little is known about the effects of warming and increased N deposition on ecosystem respiration (Re) and methane (CH4) emission from subtropical wetland ecosystems. In this study, a manipulated warming and N addition experiment was conducted at a subtropical wetland in the littoral zone of Poyang Lake, China. Both Re and CH4 fluxes presented clear seasonal variations under all treatments. Warming significantly decreased Re by 20% compared with no warming and warming effect varied with growing season. Nevertheless, effects of N addition and the interaction of two treatments on Re were not detectable throughout the experimental period. Regardless of growing seasons, no treatments affected the temperature sensitivity of Re compared with the control. Contrary to the Re, CH4 flux was not affected by warming, but significantly affected by N addition and its interaction with warming in the whole and spring growing seasons. N addition decreased CH4 emission by 60% and 52% in the whole and spring growing seasons regardless of warming. Soil temperature was the primary driver for Re and explained about 60% of Re variation, while its explanation on CH4 flux was 13%. Soil moisture was not a limiting factor for Re and CH4 flux in this region. Our results imply that effects of warming and N addition on Re and CH4 flux varied with seasons, and these global changes tend to suppress carbon dioxide (CO2) and CH4 emission from this subtropical littoral wetland based on a short-term experiment. However, longer-term experiments are needed to see if this trend would persist and these effects should be included to project how the C sink function of subtropical littoral wetlands would respond to global changes.

Greenhouse Gas Mitigation Potential of Alternate Wetting and Drying for Rice Production at National Scale—A Modeling Case Study for the Philippines

AbstractWorldwide, rice production contributes about 10% of total greenhouse gas (GHG) emissions from the agricultural sector, mainly due to CH4 emissions from continuously flooded fields. Alternate Wetting and Drying (AWD) is a promising crop technology for mitigating CH4 emissions and reducing the irrigation water currently being applied in many of the world's top rice‐producing countries. However, decreased emissions of CH4 may be partially counterbalanced by increased N2O emissions. In this case study for the Philippines, the national mitigation potential of AWD is explored using the process‐based biogeochemical model LandscapeDNDC. Simulated mean annual CH4 emissions under conventional rice production for the time period 2000–2011 are estimated as 1,180 ± 163 Gg CH4 yr−1. During the cropping season, this is about +16% higher than a former estimate using emission factors. Scenario simulations of nationwide introduction of AWD in irrigated landscapes suggest a considerable decrease in CH4 emissions by −23%, while N2O emissions are only increased by +8%. Irrespective of field management, at national scale, the radiative forcing of irrigated rice production is always dominated by CH4 (>95%). The reduction potential of GHG emissions depends on, for example, number of crops per year, residue management, amount of applied irrigation water, and sand content. Seasonal weather conditions also play an important role since the mitigation potential of AWD is almost double as high in dry as compared to wet seasons. Furthermore, this study demonstrates the importance of temporal continuity, considering off‐season emissions and the long‐term development of GHG emissions across multiple years.

Reduced methane emissions in former permafrost soils driven by vegetation and microbial changes following drainage.

In Arctic regions, thawing permafrost soils are projected to release 50 to 250 Gt of carbon by 2100. This data is mostly derived from carbon‐rich wetlands, although 71% of this carbon pool is stored in faster‐thawing mineral soils, where ecosystems close to the outer boundaries of permafrost regions are especially vulnerable. Although extensive data exists from currently thawing sites and short‐term thawing experiments, investigations of the long‐term changes following final thaw and co‐occurring drainage are scarce. Here we show ecosystem changes at two comparable tussock tundra sites with distinct permafrost thaw histories, representing 15 and 25 years of natural drainage, that resulted in a 10‐fold decrease in CH4 emissions (3.2 ± 2.2 vs. 0.3 ± 0.4 mg C‐CH4 m−2 day−1), while CO2 emissions were comparable. These data extend the time perspective from earlier studies based on short‐term experimental drainage. The overall microbial community structures did not differ significantly between sites, although the drier top soils at the most advanced site led to a loss of methanogens and their syntrophic partners in surface layers while the abundance of methanotrophs remained unchanged. The resulting deeper aeration zones likely increased CH4 oxidation due to the longer residence time of CH4 in the oxidation zone, while the observed loss of aerenchyma plants reduced CH4 diffusion from deeper soil layers directly to the atmosphere. Our findings highlight the importance of including hydrological, vegetation and microbial specific responses when studying long‐term effects of climate change on CH4 emissions and underscores the need for data from different soil types and thaw histories.

Methane mitigation potential of 3-nitrooxypropanol in lactating cows is influenced by basal diet composition

The objective of this study was to investigate whether the CH4 mitigation potential of 3-nitrooxypropanol (3-NOP) in dairy cattle was affected by basal diet (BD) composition. The experiment involved 64 Holstein-Friesian dairy cows (146 ± 45 d in milk at the start of trial; mean ± SD) in 2 overlapping crossover trials, each consisting of 2 measurement periods. Cows were blocked according to parity, d in milk, and milk yield, and randomly allocated to 1 of 3 diets: a grass silage-based diet (GS) consisting of 30% concentrates and 70% grass silage (DM basis), a grass silage- and corn silage-mixed diet (GSCS) consisting of 30% concentrates, 42% grass silage, and 28% corn silage (DM basis), or a corn silage-based diet (CS) consisting of 30% concentrates, 14% grass silage, and 56% corn silage (DM basis). Two types of concentrates were formulated, viz. a concentrate for the GS diet and a concentrate for the CS diet, to meet the energy and protein requirements for maintenance and milk production. The concentrate for the GSCS diet consisted of a 50:50 mixture of both concentrates. Subsequently, the cows within each type of BD received 2 treatments in a crossover design: either 60 mg of 3-NOP/kg of DM (NOP60) and a placebo with 0 mg of 3-NOP/kg of DM (NOP0) in one crossover or 80 mg of 3-NOP/kg of DM (NOP80) and NOP0 in the other crossover. Diets were provided as total mixed ration in feed bins, which automatically recorded feed intake. Additional concentrate was fed in the GreenFeed system that was used to measure emissions of CH4 and H2. The CS diets resulted in a reduced CH4 yield (g/kg DMI) and CH4 intensity (g/kg milk). Feeding 3-NOP resulted in a decreased DMI. Milk production and composition did not differ between NOP60 and NOP0, whereas milk yield and the yield of major components decreased for NOP80 compared with NOP0. Feed efficiency was not affected by feeding 3-NOP. Interactions between BD and supplementation of 3-NOP were observed for the production (g/d) and yield (g/kg DMI) of both CH4 and H2, indicating that the mitigating effect of 3-NOP depended on the composition of the BD. Emissions of CH4 decreased upon 3-NOP supplementation for all BD, but the decrease in CH4 emissions was smaller for GS (-26.2% for NOP60 and -28.4% for NOP80 in CH4 yield) compared with both GSCS (-35.1% for NOP60 and -37.9% for NOP80 for CH4 yield) and CS (-34.8% for NOP60 and -41.6% for NOP80 for CH4 yield), with no difference between the latter 2 BD. Emissions of H2 increased upon 3-NOP supplementation for all BD, but the H2 yield (g/kg DMI) increased 3.16 and 3.30-fold, respectively, when NOP60 and NOP80 were supplemented to GS, and 4.70 and 4.96 fold, respectively, when NOP60 and NOP80 were supplemented to CS. In conclusion, 3-NOP can effectively decrease CH4 emissions in dairy cows across diets, but the level of CH4 mitigation is greater when supplemented in a corn silage-based diet compared with a grass silage-based diet.

Single midseason drainage events decrease global warming potential without sacrificing grain yield in flooded rice systems

Rice (Oryza sativa L.) cultivation is an important part of global food security, yet it is also responsible for a significant portion of agricultural greenhouse gas (GHG) emissions, particularly methane (CH4). Midseason drainage of flooded rice fields can decrease CH4 emissions, but the magnitude of CH4 reduction and its effect on grain yield are variable due to variation in the timing and soil-drying severity of drainage across studies. Therefore, in this two-year study, we aimed to quantify the effect of timing and severity of a single midseason drainage event on seasonal GHG emissions and grain yields, compared to a continuously flooded (CF) control. Treatments varied in terms of soil-drying severity (low, medium, and high, corresponding to approximately 5, 8, and 12 days of drying, respectively) and the timing of when drainage events occurred (between 34–49 and 45–59 days after seeding, or roughly between tillering and panicle initiation). Soil moisture parameters (perched water table, volumetric water content, gravimetric water content (GWC), and soil water potential), soil mineral nitrogen, CH4 and nitrous oxide (N2O) emissions, grain yield, and yield components were all quantified. Midseason drainage reduced seasonal CH4 emissions by 38–66%, compared to the CF control. Seasonal CH4 emissions decreased with increasing drain severity, and for every 1% reduction in soil GWC during the drainage period, seasonal CH4 emissions were reduced by 2.5%. The timing of drainage had no significant impact on CH4 emissions. Emissions of N2O were low (average = 0.035 kg N2O-N ha−1) and accounted for only 0.5% of the seasonal global warming potential (GWP) across all drainage treatments. Within each year, drainage did not significantly affect grain yield compared to the CF control. Additionally, midseason drainage reduced both GWP and yield-scaled GWP by approximately the same amount as seasonal CH4 emissions, as N2O emissions were minimal and yields were similar across treatments. These results indicate that midseason drainage may be a viable GHG mitigation practice in flooded rice systems with limited risk for yield reduction, however, this practice should also be further tested under a broad range of soil types and different environments to determine its widespread adoptability.

Effect of soil mulching on agricultural greenhouse gas emissions in China: A meta-analysis.

Human demand for food has been increasing as population grows around the world. Meanwhile, global temperature has been rising with the increase of greenhouse gas (GHG) emissions. Although soil mulching (SM) is an effective method to increase crop yield because it could conserve soil moisture and temperature, it is also an important factor affecting GHG productions and emissions. At present, research results in terms of the impact of SM on agricultural GHG emissions are still inconsistent. Therefore, a meta-analysis was used to quantitatively analyze the impact of SM on crop yield and GHG emissions in China. Overall, SM significantly enhanced not only crop yield, but also GHG emissions. Compared with no soil mulching (NSM), SM improved crop yield by 21.84%, while increased global warming potential (GWP) by 11.38%. To minimize the negative impact of SM on GHG, for maize and wheat in arid, semi-arid and semi-humid zones, it is recommended to use flat full mulching with grave or straw plus drip irrigation under neutral or weakly alkaline soil with bulk density <1.3g cm-3. For rice in humid regions, it is advisable to apply SM to minimize GHG emissions by significantly decreasing CH4 emissions.

Effect of timing of paddock allocation in tropical grass on performance, nitrogen excretion, and enteric methane emissions from dairy cows.

The objective of this study was to investigate the influence of timing of paddock allocation (AM or PM) in tropical grass on nutritive value of the herbage, dry matter intake (DMI), milk yield and composition, ruminal fermentation, nitrogen excretion, and enteric CH4 emissions of dairy cows. Twenty cows were grouped in pairs and randomly distributed within pair to one of two treatments. PM herbage had greater contents of dry matter (DM), soluble carbohydrates, starch, and nonfibrous carbohydrate to protein ratio and lower contents of neutral detergent fiber and acid detergent fiber. There was no treatment effect on DMI, N excretion, milk yield, and CH4 emissions. However, milk protein and casein yields tended to be greater for PM than AM, while milk urea nitrogen concentration was lower for PM than AM. The increase in nutritive value of the afternoon relative to the morning herbage within the framework of this study was not large enough to increase DMI and milk yield or to decrease CH4 emission intensity by the dairy cows as hypothesized. The findings indicate that PM treatment can be a simple and useful grazing strategy that results in an herbage harvest with greater nutritional value and in lower excretion of urea N into milk.

Evaluating the effects of high-oil rapeseed cake or natural additives on methane emissions and performance of dairy cows

We evaluated the potential of feeding high-oil rapeseed cake or natural additives as rumen modifiers on enteric methane (CH4) emissions, nutrient utilization, performance, and milk fatty acid (FA) profile of dairy cows. Eight Nordic Red dairy cows averaging (mean ± SD) 81 ± 21 d in milk and 41.0 ± 1.9 kg of milk yield at the beginning of the study were randomly assigned to a replicated 4 × 4 Latin square design with 21-d periods. Treatments comprised grass silage-based diets (45:55 forage to concentrate ratio on dry matter basis) including (1) control containing 19.3% rapeseed meal (CON), (2) CON with full replacement of rapeseed meal with rapeseed cake (RSC), (3) supplementation of CON with 50 g/d of yeast hydrolysate product plus coniferous resin acid-based compound (YHR), and (4) supplementation of CON with 20 g/d of combination of garlic-citrus extract and essential oils in a pellet (GCE). Apparent total-tract digestibility was measured using total collection of feces, and CH4 emissions were measured in respiratory chambers on 4 consecutive days. Data collected during d 17 and 21 in each period were used for ANOVA analysis using a mixed model. Treatments did not affect dry matter intake (DMI), whereas feeding RSC increased crude protein and ether extract digestibility compared with the other diets. Emissions of CH4 per day, per kilogram of DMI, and per kilogram of energy-corrected milk, and gross energy intake were lower for RSC compared with other diets. We found no effect of YHR on daily CH4 emissions, whereas CH4 yield (g of CH4/kg of DMI or as percentage of gross energy intake) decreased with GCE compared with CON. Treatments did not influence energy balance. Further, RSC reduced the proportion of N intake excreted in feces, and YHR improved N balance compared with CON diet. Feeding RSC resulted in greatest yields of milk and energy-corrected milk, and feed efficiency. Relative to the CON diet, RSC decreased saturated FA by 10% in milk fat by increasing cis-monounsaturated FA but also increased the proportion of trans FA. Proportion of odd- and branched-chain FA increased with GCE and YHR compared with CON. We conclude that replacing rapeseed meal by rapeseed cake decreased CH4 emissions, whereas YHR or GCE had no effect on CH4 emissions in this study.

Long-Term and Carryover Effects of Supplementation with Whole Oilseeds on Methane Emission, Milk Production and Milk Fatty Acid Profile of Grazing Dairy Cows.

Simple SummaryDairy cow diets that include oils have shown potential to decrease methane emissions, which contribute to climate change. However, there is limited information on long-term interventions for animals in grazing systems. The aim of this study was to evaluate the effects of feeding oilseeds on the persistency of methane mitigation effects and milk production of dairy cows during a spring and summer grazing season. Carryover effects into autumn were studied. Eight weeks after beginning the feeding trial, cottonseed was more effective than linseed or rapeseed in decreasing methane per kilogram of ingested feed, but the mitigation effect did not persist when evaluated 11 weeks later. All oilseeds maintained milk production in spring, but in summer, milk yield was lower with cottonseed. There were no carryover effects of feeding oilseeds, once supplementation ended. Thus, adding oils to dairy cow diets through cottonseed supplementation had only a temporary effect on methane mitigation. This long-term study, conducted under grazing conditions, can help to assess how proposed interventions to mitigate methane can affect production and sustainability aspects of grazing dairy systems.Research is ongoing to find nutritional methane (CH4) mitigation strategies with persistent effects that can be applied to grazing ruminants. Lipid addition to dairy cow diets has shown potential as means to decrease CH4 emissions. This study evaluated the effects of oilseeds on CH4 emission and production performance of grazing lactating dairy cows. Sixty Holstein Friesian cows grazing pasture were randomly allocated to 1 of 4 treatments (n = 15): supplemented with concentrate without oilseeds (CON), with whole cottonseed (CTS), rapeseed (RPS) or linseed (LNS). Oilseeds were supplemented during weeks 1–16 (spring period) and 17–22 (summer period), and the autumn period (wk 23–27) was used to evaluate treatment carryover effects. Cows fed CTS decreased CH4 yield by 14% compared to CON in spring, but these effects did not persist after 19 weeks of supplementation (summer). Compared to CON, RPS decreased milk yield and CTS increased milk fat concentration in both spring and summer. In summer, CTS also increased milk protein concentration but decreased milk yield, compared to CON. In spring, compared to CON, CTS decreased most milk medium-chain fatty acids (FA; 8:0, 12:0, 14:0 and 15:0) and increased stearic, linoleic and rumenic FA, and LNS increased CLA FA. There were no carry-over effects into the autumn period. In conclusion, supplementation of grazing dairy cows with whole oilseeds resulted in mild effects on methane emissions and animal performance. In particular, supplementing with CTS can decrease CH4 yield without affecting milk production, albeit with a mild and transient CH4 decrease effect. Long term studies conducted under grazing conditions are important to provide a comprehensive overview of how proposed nutritional CH4 mitigation strategies affect productivity, sustainability and consumer health aspects.

Divergent responses of wetland methane emissions to elevated atmospheric CO2 dependent on water table

Elevated atmospheric CO2 may have consequences for methane (CH4) emissions from wetlands, yet the magnitude and direction remain unpredictable, because the associated mechanisms have not been fully investigated. Here, we established an in situ macrocosm experiment to compare the effects of elevated CO2 (700 ppm) on the CH4 emissions from two wetlands: an intermittently inundated Calamagrostis angustifolia marsh and a permanently inundated Carex lasiocarpa marsh. The elevated CO2 increased CH4 emissions by 27.6–57.6% in the C. angustifolia marsh, compared to a reduction of 18.7–23.5% in the C. lasiocarpa marsh. The CO2-induced increase in CH4 emissions from the C. angustifolia marsh was paralleled with (1) increased dissolved organic carbon (DOC) released from plant photosynthesis and (2) reduced (rate of) CH4 oxidation due to a putative shift in methanotrophic community composition. In contrast, the CO2-induced decrease in CH4 emissions from the C. lasiocarpa marsh was associated with the increases in soil redox potential and pmoA gene abundance. We synthesized data from worldwide wetland ecosystems, and found that the responses of CH4 emissions to elevated CO2 was determined by the wetland water table levels and associated plant oxygen secretion capacity. In conditions with elevated CO2, plants with a high oxygen secretion capacity suppress CH4 emissions while plants with low oxygen secretion capacity stimulate CH4 emissions; both effects are mediated via a feedback loop involving shifts in activities of methanogens and methanotrophs.

Metabolic Benefit of Bulls Being Fed Moringa Leaves Twigs and Branches as a Major Concentrate Ingredient

The study was conducted to investigate nutrient metabolism and semen quality of bulls fed with moringa (Moringa oleifera) leaves, twigs, and branches as a major concentrate ingredient. Twenty-one Red Chittagong bulls of about 204 (±50) kg initial live weight (LW) were randomly divided into three equal LW groups. They were fed maize silage as a basal feedstuff for 65 days with the supplementation of concentrate mixtures at 1% of LW, consisting of either 0, 25, or 50% moringa mash on a fresh basis. Moringa mash was a sun-dried ground preparation of leaves, twigs, and branches of moringa. The results indicated that different levels of moringa in concentrate mixtures (0, 25, and 50%) did not change daily DM intake, digestibility, and LW gain of bulls (p &amp;gt; 0.05). However, increasing dietary moringa (up to 203 g/kg DM) significantly decreased production cost of methane (CH4) (methane emission [kg/kg gain] = 1.6422—[0.0059 × moringa intake, g/kg DM], n = 12, R2 = 0.384, P = 0.032) in a similar metabolizable energy intake level (0.21 ± 0.01 MJ/kg LW). Also, higher dietary moringa significantly reduced urinary nitrogen loss (urinary nitrogen [% digested nitrogen] = 43.0 – 0.069 × moringa intake [g/kg DM]; R2 = 0.3712, P = 0.034). Thus, increasing moringa by 1 g/kg DM decreased CH4 emission by 6 g/kg gain and absorbed nitrogen loss by 0.069 %. Also, progressive motility of sperm increased significantly (33.0, 51.0, and 60.1%, respectively; p = 0.03) in bulls fed with concentrate mixtures containing moringa at 0, 25, or 50%. It may be concluded that feeding moringa mash at 203 g/kg DM may decrease energy loss as methane and urinary nitrogen loss without impacting the production of beef cattle. Feeding moringa mash to beef cattle may abate dietary energy and nitrogen loss and consequently decrease the environmental pollution.

Variations and Drivers of Methane Fluxes from Double-Cropping Paddy Fields in Southern China at Diurnal, Seasonal and Inter-Seasonal Timescales

Methane (CH4) is the second most important anthropogenic greenhouse gas (GHG) after carbon dioxide (CO2), and paddy fields are among the largest sources of CH4 emissions. Owing to the scarcity of observational data, the characteristics and influencing factors of CH4 fluxes in paddy fields at different timescales need to be further investigated. Observations of CH4 fluxes via eddy covariance (EC) data were performed over four seasons in two paddy fields in Nanchang, Jiangxi Province, China. The pattern, magnitude and biophysical controls of CH4 emissions were explored by wavelet analysis and stepwise multiplicative modelling. The results revealed a distinct, single-peak diurnal pattern in CH4 fluxes during the vegetative stage in all four rice growing seasons and the reproductive stage of early rice. Large seasonal variations in daily CH4 emissions were observed in the two double-cropping paddy fields, and the soil temperature at a depth of 5 cm (Ts5) explained most of the seasonality of the CH4 fluxes. At the inter-seasonal scale, under local farms’ traditional field management method, reducing the amount and frequency of irrigation during the vegetative stage could decrease CH4 emissions in southern China. This study improves the understanding of CH4 emissions and helps in developing GHG management strategies for paddy fields.

Inhibited Methanogenesis in the Rumen of Cattle: Microbial Metabolism in Response to Supplemental 3-Nitrooxypropanol and Nitrate.

3-Nitrooxypropanol (3-NOP) supplementation to cattle diets mitigates enteric CH4 emissions and may also be economically beneficial at farm level. However, the wider rumen metabolic response to methanogenic inhibition by 3-NOP and the intermediary metabolite requires further exploration. Furthermore, supplementation potently decreases CH4 emissions from cattle. The reduction of utilizes H2 and yields , the latter of which may also inhibit rumen methanogens, although a different mode of action than for 3-NOP and its derivative was hypothesized. Our objective was to explore potential responses of the fermentative and methanogenic metabolism in the rumen to 3-NOP, and their metabolic derivatives using a dynamic mechanistic modeling approach. An extant mechanistic rumen fermentation model with state variables for carbohydrate substrates, bacteria and protozoa, gaseous and dissolved fermentation end products and methanogens was extended with a state variable of either 3-NOP or . Both new models were further extended with a state variable, with exerting methanogenic inhibition, although the modes of action of 3-NOP-derived and -derived are different. Feed composition and intake rate (twice daily feeding regime), and supplement inclusion were used as model inputs. Model parameters were estimated to experimental data collected from the literature. The extended 3-NOP and models both predicted a marked peak in H2 emission shortly after feeding, the magnitude of which increased with higher doses of supplement inclusion. The H2 emission rate appeared positively related to decreased acetate proportions and increased propionate and butyrate proportions. A decreased CH4 emission rate was associated with 3-NOP and supplementation. Omission of the state variable from the 3-NOP model did not change the overall dynamics of H2 and CH4 emission and other metabolites. However, omitting the state variable from the model did substantially change the dynamics of H2 and CH4 emissions indicated by a decrease in both H2 and CH4 emission after feeding. Simulations do not point to a strong relationship between methanogenic inhibition and the rate of and formation upon 3-NOP supplementation, whereas the metabolic response to supplementation may largely depend on methanogenic inhibition by .

Plummeting global warming potential by chemicals interventions in irrigated rice: A lab to field assessment

Methane (CH4) emissions are responsible for the higher global warming potential of rice cultivation. There are scattered reports on the use of chemical interventions for reducing CH4 emissions from rice. A laboratory study was carried out to estimate the CH4 mitigation potential of oxygen releasing chemicals such as magnesium peroxide (MgO2) and calcium peroxide (CaCO2), chelating agent ethylene diamine tetra acetic acid (EDTA), nitrification inhibitors thiourea and neem oil, limus (urease inhibitors), phosphogypsum (PG) a byproduct of phosphate fertilizer industry and ammonium sulfate (AS). The cumulative CH4 emission from soil reduced by 2.0–32.3% under the different treatments during the 45 days’ incubation study. Subsequently, four chemicals having the highest CH4 reduction potential i.e. PG, EDTA, AS, and MgO2 were further evaluated for the mitigation of CH4 and their concurrent impact on nitrous oxide (N2O) emission in a two-year experiment growing rice. PG, EDTA, AS, and MgO2 significantly (p = 0.0025) decreased CH4 emissions by 9.3−27.5% as compared to the control. The cumulative N2O emission were significantly lower by 13.9% under PG as compared to control. The global warming potential decreased by 6.8% with MgO2 to 23.6% with PG. The grain yield increased by 3.1–11.2% under the different treatments. The greenhouse gas intensity (GHGI) was the highest in control (0.309 kg CO2 eq. kg-1 grain yield) and lowest in PG (0.212 kg CO2 eq. kg-1 grain yield). The findings suggest that PG, EDTA, AS, and MgO2 can be used to plummet the global warming potential of irrigated rice soils without any yield penalty. More research is required to be undertaken to evaluate the impact of these chemicals from the perspective of food security in the farmers’ fields.

Environmental sustainability assessment of rice management practices using decision support tools

Rice has a large water demand and its cultivation is responsible for 8% of global anthropogenic methane (CH4) emissions. In this context, on-farm practices to increase water use efficiency and decrease greenhouse gas (GHG) emissions are increasingly being considered by rice producers. In this study, four water saving practices implemented in ten Arkansas rice farms during two consecutive years were evaluated: Multiple-Inlet Rice Irrigation (MIRI), zero grade (land leveling), Furrow-Irrigated Rice (FIR), and Alternate Wetting and Drying (AWD). The sustainability of these practices at the field level was evaluated with two decision support tools, Fieldprint Platform (FPP) and Cool Farm Tool (CFT). From a GHG perspective, both tools agreed that FIR and AWD were the best practices to decrease CH4 emissions. A sensitivity analysis with FPP was performed to detect which variables and management practices most affect metric scores. FIR was the best practice regarding GHG emissions due to the decrease in CH4 emissions; however, when considering energy use, FIR and zero grade increased energy use due to greater chemical applications. Initiatives such as AWD irrigation, burning the straw or other straw removal practices when practicing a rice-rice rotation, or making decisions about crop planting based on differences in soil type inside the farm should be encouraged to decrease CH4 emissions. The energy cost of agrochemical production had a large impact whereby even 10–20% reductions in application rates can significantly reduce the energy use. These decision support tools offer farmers an opportunity to evaluate their practices and increase farm sustainability; however, policy makers need to incentivize conservation practices and encourage creation of farmer networks to support adoption of sustainability practices.