Methane Emission from Rice Fields:Necessity for Molecular Approach for Mitigation

Anthropogenic methane emissions are a leading cause of the increase in global averagetemperatures,often referred to as global warming.Flooded soils play a significant role in methaneproduction,where the anaerobic conditions promote the production of methane by methanogenicmicroorganisms.Rice fields contribute a considerable portion of agricultural methane emissions,as riceplants provide both factors that enhance and limit methane production.Rice plants harbor both methaneproducingand methane-oxidizing microorganisms.Exudates from rice roots provide source for methaneproduction,while oxygen delivered from the root aerenchyma enhances methane oxidation.Studies haveshown that the diversity of these microorganisms depends on rice cultivars with some genes characterizedas harboring specific groups of microorganisms related to methane emissions.However,there is still aneed for research to determine the balance between methane production and oxidation,as rice plantspossess the ability to regulate net methane production.Various agronomical practices,such as fertilizerand water management,have been employed to mitigate methane emissions.Nevertheless,studiescorrelating agronomic and chemical management of methane with productivity are limited.Moreover,evidences for breeding low-methane-emitting rice varieties are scattered largely due to the absence ofcoordinated breeding programs.Research has indicated that phenotypic characteristics,such as rootbiomass,shoot architecture,and aerenchyma,are highly correlated with methane emissions.This reviewdiscusses available studies that involve the correlation between plant characteristics and methaneemissions.It emphasizes the necessity and importance of breeding low-methane-emitting rice varieties inaddition to existing agronomic,biological,and chemical practices.The review also delves into the idealphenotypic and physiological characteristics of low-methane-emitting rice and potential breeding techniques,drawing from studies conducted with diverse varieties,mutants,and transgenic plants.

Dietary supplementation with xylooligosaccharides and exogenous enzyme improves milk production,energy utilization efficiency and reduces enteric methane emissions of Jersey cows

Background Sustainable strategies for enteric methane(CH_(4))mitigation of dairy cows have been extensively explored to improve production performance and alleviate environmental pressure.The present study aimed to investigate the effects of dietary xylooligosaccharides(XOS)and exogenous enzyme(EXE)supplementation on milk production,nutrient digestibility,enteric CH_(4) emissions,energy utilization efficiency of lactating Jersey dairy cows.Forty-eight lactating cows were randomly assigned to one of 4 treatments:(1)control diet(CON),(2)CON with 25 g/d XOS(XOS),(3)CON with 15 g/d EXE(EXE),and(4)CON with 25 g/d XOS and 15 g/d EXE(XOS+EXE).The 60-d experimental period consisted of a 14-d adaptation period and a 46-d sampling period.The enteric CO_(2)and CH_(4) emissions and O2 consumption were measured using two GreenFeed units,which were further used to determine the energy utilization efficiency of cows.Results Compared with CON,cows fed XOS,EXE or XOS+EXE significantly(P<0.05)increased milk yield,true protein and fat concentration,and energy-corrected milk yield(ECM)/DM intake,which could be reflected by the significant improvement(P<0.05)of dietary NDF and ADF digestibility.The results showed that dietary supplementation of XOS,EXE or XOS+EXE significantly(P<0.05)reduced CH_(4) emission,CH_(4)/milk yield,and CH_(4)/ECM.Furthermore,cows fed XOS demonstrated highest(P<0.05)metabolizable energy intake,milk energy output but lowest(P<0.05)of CH_(4) energy output and CH_(4) energy output as a proportion of gross energy intake compared with the remaining treatments.Conclusions Dietary supplementary of XOS,EXE or combination of XOS and EXE contributed to the improvement of lactation performance,nutrient digestibility,and energy utilization efficiency,as well as reduction of enteric CH_(4) emissions of lactating Jersey cows.This promising mitigation method may need further research to validate its long-term effect and mode of action for dairy cows.

Quantification and prediction of enteric methane emissions from Chinese lactating Holstein dairy cows fed diets with different dietary neutral detergent fiber/non-fibrous carbohydrate(NDF/NFC)ratios

Methane(CH_(4))emissions from ruminant production are a significant source of anthropogenic greenhouse gas production,but few studies have examined the enteric CH_(4)emissions of lactating dairy cows under different feeding regimes in China.This study aimed to investigate the influence of different dietary neutral detergent fiber/non-fibrous carbohydrate(NDF/NFC)ratios on production performance,nutrient digestibility,and CH_(4)emissions for Holstein dairy cows at various stages of lactation.It evaluated the performance of CH_(4)prediction equations developed using local dietary and milk production variables compared to previously published prediction equations developed in other production regimes.For this purpose,36 lactating cows were assigned to one of three treatments with differing dietary NDF/NFC ratios:low(NDF/NFC=1.19),medium(NDF/NFC=1.54),and high(NDF/NFC=1.68).A modified acid-insoluble ash method was used to determine nutrient digestibility,while the sulfur hexafluoride technique was used to measure enteric CH4 emissions.The results showed that the dry matter(DM)intake of cows at the early,middle,and late stages of lactation decreased significantly(P<0.01)from 20.9 to 15.4 kg d^(–1),15.3 to 11.6 kg d^(–1),and 16.4 to 15.0 kg d^(–1),respectively,as dietary NDF/NFC ratios increased.Across all three treatments,DM and gross energy(GE)digestibility values were the highest(P<0.05)for cows at the middle and late lactation stages.Daily CH_(4)emissions increased linearly(P<0.05),from 325.2 to 391.9 kg d^(–1),261.0 to 399.8 kg d^(–1),and 241.8 to 390.6 kg d^(–1),respectively,as dietary NDF/NFC ratios increased during the early,middle,and late stages of lactation.CH_(4)emissions expressed per unit of metabolic body weight,DM intake,NDF intake,or fat-corrected milk yield increased with increasing dietary NDF/NFC ratios.In addition,CH_(4)emissions expressed per unit of GE intake increased significantly(P<0.05),from 4.87 to 8.12%,5.16 to 9.25%,and 5.06 to 8.17%respectively,as dietary NDF/NFC ratios increased during the early,middle,and late lactation stages.The modelling results showed that the equation using DM intake as the single variable yielded a greater R^(2)than equations using other dietary or milk production variables.When data obtained from each lactation stage were combined,DM intake remained a better predictor of CH_(4)emissions(R^(2)=0.786,P=0.026)than any other variables tested.Compared to the prediction equations developed herein,previously published equations had a greater root mean square prediction error,reflecting their inability to predict CH_(4)emissions for Chinese Holstein dairy cows accurately.The quantification of CH_(4)production by lactating dairy cows under Chinese production systems and the development of associated prediction equations will help establish regional or national CH_(4)inventories and improve mitigation approaches to dairy production.

Decadal Methane Emission Trend Inferred from Proxy GOSAT XCH4 Retrievals:Impacts of Transport Model Spatial Resolution

In recent studies,proxy XCH_(4)retrievals from the Japanese Greenhouse gases Observing SATellite(GOSAT)have been used to constrain top-down estimation of CH_(4)emissions.Still,the resulting interannual variations often show significant discrepancies over some of the most important CH_(4)source regions,such as China and Tropical South America,by causes yet to be determined.This study compares monthly CH_(4)flux estimates from two parallel assimilations of GOSAT XCH_(4)retrievals from 2010 to 2019 based on the same Ensemble Kalman Filter(EnKF)framework but with the global chemistry transport model(GEOS-Chem v12.5)being run at two different spatial resolutions of 4°×5°(R4,lon×lat)and 2°×2.5°(R2,lon×lat)to investigate the effects of resolution-related model errors on the derived long-term global and regional CH_(4)emission trends.We found that the mean annual global methane emission for the 2010s is 573.04 Tg yr^(-1)for the inversion using the R4 model,which becomes about 4.4 Tg yr^(-1)less(568.63 Tg yr^(-1))when a finer R2 model is used,though both are well within the ensemble range of the 22 top-down results(2008-17)included in the current Global Carbon Project(from 550 Tg yr^(-1)to 594 Tg yr^(-1)).Compared to the R2 model,the inversion based on the R4 tends to overestimate tropical emissions(by 13.3 Tg yr^(-1)),which is accompanied by a general underestimation(by 8.9 Tg yr^(-1))in the extratropics.Such a dipole reflects differences in tropical-mid-latitude air exchange in relation to the model’s convective and advective schemes at different resolutions.The two inversions show a rather consistent long-term CH_(4)emission trend at the global scale and over most of the continents,suggesting that the observed rapid increase in atmospheric methane can largely be attributed to the emission growth from North Africa(1.79 Tg yr^(-2)for R4 and 1.29 Tg yr^(-2)for R2)and South America Temperate(1.08 Tg yr^(-2)for R4 and 1.21 Tg yr^(-2)for R2)during the first half of the 2010s,and from Eurasia Boreal(1.46 Tg yr^(-2)for R4 and 1.63 Tg yr^(-2)for R2)and Tropical South America(1.72 Tg yr-2 for R4 and 1.43 Tg yr^(-2)for R2)over 2015-19.In the meantime,emissions in Europe have shown a consistent decrease over the past decade.However,the growth rates by the two parallel inversions show significant discrepancies over Eurasia Temperate,South America Temperate,and South Africa,which are also the places where recent GOSAT inversions usually disagree with one other.

Methane emissions from shale gas production sites in southern Sichuan,China:A field trial of methods

Shale gas is an important alternative natural gas source that can meet China's growing energy demand.However,methane emissions during shale gas production could largely determine whether it could be considered as a bridging clean energy source.In this study,we performed methane emission measurements using three methods(on-site optical gas imaging,on-site methane patrolling,and downwind measurement)at shale gas production sites in Sichuan province,China,covering 18 well sites with 81 wells.The results showed that flowback water tanks were the major methane sources,with valves,separators,chemical injection pumps,and pneumatic controllers as other sources.The methane concentrations inside the 18 sites ranged from 1.42 to 459μmol mol−1,with over 59%of the sites having the highest concentration less than 50μmol mol−1.The optical gas imaging method,with its low detection limit over 5000μmol mol−1,could not capture the emission effectively.The three successful downwind measurements resulted in site level emission rates between 0.02 and 0.17 kg h−1.When divided by the number of wells at each site,the emission intensity was 4%–28%of the wellhead emission factor for natural gas production in China.More measurements are required to better quantify methane emissions from shale gas sites in China.For sites in mountainous regions or long-term low-wind regions,detection methods other than downwind measurements should be suitable for quantifying site-level emissions.

Geological emission of methane from the Yakela condensed oil/gas field in Talimu Basin, Xinjiang, China

A static flux chamber method was applied to study natural emissions of methane into the atmosphere in the Yakela condensed oil/gas field in Talimu Basin, Xinjiang, China. Using an online method, which couples a gas chromatography/high-temperature conversion/isotope ratio mass spectrometry (GC/C/MS) together, the 13C/12C ratios of methane in the flux chambers were measured. The results demonstrated that methane gases were liable to migrate from deep oil/gas reservoir to the surface through microseepage and pervasion, and that a part of the migrated methane that remained unoxidized could emit into the atmosphere. Methane emission rates varied less in the oil/gas field because the whole region was homogeneous in geology and geography, with a standard deviation of less than 0.02 mg/(m2·h). These were the differences in methane emission flux in the day and at night in the oil/gas field. The maximum methane emission flux reached 0.15 mg/(m2·h) at 5:00-6:00 early in the morning, and then decreased gradually. The minimum was shown 0.10 mg/(m2·h) at 17:00-18:00 in the afternoon, and then increased gradually. The daily methane released flux of the study area was 2.89 mg/(m2·d), with a standard deviation of 0.43 mg/(m2·d), using the average methane flux of every hour in a day for all chambers. δ13C of methane increased with the increase of methane concentration in the flux chambers, further indicating that the pyrogenetic origin of methane was come from deep oil/gas reservoirs.

The effect of ensiled paulownia leaves in a high-forage diet on ruminal fermentation,methane production,fatty acid composition,and milk production performance of dairy cows

Background:The use of industrial by-products rich in bioactive compounds as animal feeds can reduce greenhouse gas production.Paulownia leaves silage(PLS)was supplemented to dairy cows'diet and evaluated in vitro(Exp.1;Rusitec)and in vivo(Exp.2,cannulated lactating dairy cows and Exp.3,non-cannulated lactating dairy cows).The study investigated the PLS effect on ruminal fermentation,microbial populations,methane production and concentration,dry matter intake(DMI),and fatty acid(FA)proportions in ruminal fluid and milk.Results:Several variables of the ruminal fluid were changed in response to the inclusion of PLS.In Exp.1,the p H increased linearly and quadratically,whereas ammonia and total volatile fatty acid(VFA)concentrations increased linearly and cubically.A linear,quadratic,and cubical decrease in methane concentration was observed with increasing dose of the PLS.Exp.2 revealed an increase in ruminal p H and ammonia concentrations,but no changes in total VFA concentration.Inclusion of PLS increased ruminal propionate(at 3 h and 6 h after feeding),isovalerate,and valerate concentrations.Addition of PLS also affected several populations of the analyzed microorganisms.The abundances of protozoa and bacteria were increased,whereas the abundance of archaea were decreased by PLS.Methane production decreased by 11%and 14%in PLS-fed cows compared to the control in Exp.2 and 3,respectively.Exp.3 revealed a reduction in the milk protein and lactose yield in the PLS-fed cows,but no effect on DMI and energy corrected milk yield.Also,the PLS diet affected the ruminal biohydrogenation process with an increased proportions of C18:3 cis-9 cis-12 cis-15,conjugated linoleic acid,C18:1 trans-11 FA,polyunsaturated fatty acids(PUFA),and reduced n6/n3 ratio and saturated fatty acids(SFA)proportion in milk.The relative transcript abundances of the 5 of 6 analyzed genes regulating FA metabolism increased.Conclusions:The dietary PLS replacing the alfalfa silage at 60 g/kg diet can reduce the methane emission and improve milk quality with greater proportions of PUFA,including conjugated linoleic acid,and C18:1 trans-11 along with reduction of SFA.

Characterization and mitigation option of greenhouse gas emissions from lactating Holstein dairy cows in East China

Background:This study investigated greenhouse gas(GHG)emission characteristics of lactating Holstein dairy cows in East China and provided a basis for formulating GHG emission reduction measures.GreenFeed system was used to measure the amount of methane(CH_(4))and carbon dioxide(CO_(2))emitted by the cows through respiration.Data from a commercial cow farm were used to observe the effects of parity,body weight,milk yield,and milk component yield on CH_(4) and CO_(2) emissions.Results:Mean herd responses throughout the study were as follows:111 cows completed all experimental processes,while 42 cows were rejected because they were sick or had not visited the GreenFeed system 20 times.On average,lactating days of cows was 138±19.04 d,metabolic weight was 136.5±9.5 kg,parity was 2.8±1.0,dry matter intake(DMI)was 23.1±2.6 kg/d,and milk yield was 38.1±6.9 kg/d.The GreenFeed system revealed that CH_(4) production(expressed in CO_(2) equivalent,CO_(2)-eq)was found to be 8304 g/d,CH_(4)_(CO_(2)−eq)/DMI was 359 g/kg,CH_(4)_(CO_(2)−eq)/energy-corrected milk(ECM)was 229.5 g/kg,total CO_(2) production(CH_(4) production plus CO_(2) production)was 19,201 g/d,total CO_(2)/DMI was 831 g/kg,and total CO_(2)/ECM was 531 g/kg.The parity and metabolic weight of cows had no significant effect on total CO_(2) emissions(P>0.05).Cows with high milk yield,milk fat yield,milk protein yield,and total milk solids yield produced more total CO_(2)(P<0.05),but their total CO_(2) production per kg of ECM was low(P<0.05).The total CO_(2)/ECM of the medium and high milk yield groups was 17%and 27%lower than that of the low milk yield group,respectively.Conclusions:The parity and body condition had no effect on total CO_(2) emissions,while the total CO_(2)/ECM was negatively correlated with milk yield,milk fat yield,milk protein yield,and total milk solids yield in lactating Holstein dairy cows.Measurement of total CO_(2) emissions of dairy cows in the Chinese production system will help establish regional or national GHG inventories and develop mitigation approaches to dairy production regimes.

Methane Generation and Capture of U.S.Landfills

Analysis of the U.S.EPA(Environmental Protection Agency)database of 2,549 MSW(Municipal Solid Waste)landfills showed that there were 1,164 operating landfills in which 348 million short tons(316 million metric tons)of waste were landfilled in 2017.In total,these landfills occupy about 370 million square meters of land so it is not possible to monitor the generation of LFG(Landfill Gas)generation accurately,or collect most of the LFG generated.This study was based on the hypothesis that,on the average,methane generation is proportional to the tonnage of wastes landfilled annually.The Landfill Methane Outreach Program of the EPA(EPA-LMOP)compiles annual operating data of all methane-capturing landfills.Our analysis of the 2018 data for 396 LMOP operating landfills showed that 210 million short tons of wastes were deposited and 5.06 million short tons of methane were captured,i.e.,an average capture of 0.024-ton CH4/ton waste.On the basis of the anaerobic reaction of the DOC(Degradable Organic Carbon)in landfilled wastes,the average rate of methane generation from all operating U.S.landfills was estimated to be 0.05 ton of CH4 per ton of annual capacity;this number corresponds to bioreaction of about one half of the total organic carbon in MSW.On this basis,the average rate of CH4 emission from the 396 LMOP landfills was estimated to be 0.026-ton CH4 per annual ton of deposition and the average efficiency of LFG capture,48%.Adding up all 1,164 operating landfills,their total emission of methane was estimated at 11.9 million metric tons of CH4.At CH4/CO2 equivalence of 25,this number corresponds to CO2-eq emissions of 270 million metric tons,i.e.,5.1%of the U.S.energy related carbon dioxide emissions.

Acclimation of CH_(4)emissions from paddy soil to atmospheric CO_(2)enrichment in a growth chamber experiment

Elevated levels of atmospheric CO_(2)(eCO_(2))promote rice growth and increase methane(CH_(4))emissions from rice paddies,because increased input of plant photosynthate to soil stimulates methanogenic archae.However,temporal trends in the effects of eCO_(2)on rice growth and CH_(4)emissions are still unclear.To investigate changes in the effects of eCO_(2)over time,we conducted a two-season pot experiment in a walk-in growth chamber.Positive effects of eCO_(2)on rice leaf photosynthetic rate,biomass,and grain yield were similar between growing seasons.However,the effects of eCO_(2)on CH_(4) emissions decreased over time.Elevated CO_(2)increased CH_(4)emissions by 48%-101%in the first growing season,but only by 28%-30%in the second growing season.We also identified the microbial process underlying the acclimation of CH4 emissions to atmospheric CO_(2)enrichment:eCO_(2)stimulated the abundance of methanotrophs more strongly in soils that had been previously exposed to eCO_(2)than in soils that had not been.These results emphasize the need for long-term eCO_(2)experiments for accurate predictions of terrestrial feedbacks.

Long-term and combined effects of N-[2-(nitrooxy)ethyl]-3-pyridinecarboxamide and fumaric acid on methane production,rumen fermentation, and lactation performance in dairy goats

Background:In recent years,nitrooxy compounds have been identified as promising inhibitors of methanogenesis in ruminants.However,when animals receive a nitrooxy compound,a high portion of the spared hydrogen is eructated as gas,which partly offsets the energy savings of CH4mitigation.The objective of the present study was to evaluate the long-term and combined effects of supplementation with N-[2-(nitrooxy)ethyl]-3-pyridinecarboxamide(NPD),a methanogenesis inhibitor,and fumaric acid(FUM),a hydrogen sink,on enteric CH4production,rumen fermentation,bacterial populations,apparent nutrient digestibility,and lactation performance of dairy goats.Results:Twenty-four primiparous dairy goats were used in a randomized complete block design with a 2×2factorial arrangement of treatments:supplementation without or with FUM(32 g/d)or NPD(0.5 g/d).All samples were collected every 3 weeks during a 12-week feeding experiment.Both FUM and NPD supplementation persistently inhibited CH4yield(L/kg DMI,by 18.8%and 18.1%,respectively)without negative influence on DMI or apparent nutrient digestibility.When supplemented in combination,no additive CH4suppression was observed.FUM showed greater responses in increasing the molar proportion of propionate when supplemented with NPD than supplemented alone(by 10.2%vs.4.4%).The rumen microbiota structure in the animals receiving FUM was different from that of the other animals,particularly changed the structure of phylum Firmicutes.Daily milk production and serum total antioxidant capacity were improved by NPD,but the contents of milk fat and protein were decreased,probably due to the bioactivity of absorbed NPD on body metabolism.Conclusions:Supplementing NPD and FUM in combination is a promising way to persistently inhibit CH4emissions with a higher rumen propionate proportion.However,the side effects of this nitrooxy compound on animals and its residues in animal products need further evaluation before it can be used as an animal feed additive.

Advances in methane emissions from agricultural sources:Part I.Accounting and mitigation

Methane is one of the major greenhouse gases(GHGs)and agriculture is recognized as its primary emitter.Methane accounting is a prerequisite for developing effective agriculture mitigation strategies.In this review,methane accounting methods and research status for various agricultural emission source including rice fields,animal enteric fermentation and livestock and poultry manure management were overview,and the influencing factors of each emission source were analyzed and discussed.At the same time,it analyzes the different research efforts involving agricultural methane accounting and makes recommendations based on the actual situation.Finally,mitigation strategies based on accounting results and actual situation are proposed.This review aims to provide basic data and reference for agriculture-oriented countries and regions to actively participate in climate action and carry out effective methane emission mitigation.

Effect of Natural Feed Supplement on Methane Mitigation Potential and Performance in Holstein Bull Calves

Introduction of solid feeds in the ration of calves has been shown to increase rumen size and stimulate rumen fermentation. With the initiation of bacterial fermentation in the rumen, the intermediary metabolism moves from a glucose-based to a volatile fatty acid-based metabolism, which releases methane. MootralTM has been identified as a promising plant-derived feed supplement to reduce methane emission in dairy and beef cattle. Therefore, the present study aimed at quantifying and mitigating the methane emissions in calves until the slaughtering age of 28 weeks. The study consisted of 20 Holstein bull calves at a commercial farm, assigned randomly into 2 groups (control n = 10;treatment n = 10), for 2 weeks of adaptation and 8 weeks of sample collection. The calves were fed an increasing amount of milk replacer and ad libitum wheat straw. Mootral was fed once a day to the treatment calves. Methane was measured using GreenFeed units where concentrate feed was offered as bait. The calves were weighed at the start and every four weeks during the experiment. The calves in the treatment group had lower methane emissions (54 g/d) compared to the control group (70 g/d), a reduction of 22.8%. In contrast, carbon dioxide emission and dry matter intake did not differ significantly between the study groups. Moreover, no negative impact on the average daily weight gain and carcass weight was observed in Mootral fed calves. Although the methane emission (g/kg body weight) was lower in treatment than in the control group, the absolute difference between the groups narrowed with increasing age of the calves. The results suggest a need to increase the dose in line with the increased body weight and intake of the calves. In conclusion, Mootral effectively reduced methane in calves. Further trials to determine the optimal dose for calves are warranted, and as well studies to investigate if interventions (such as Mootral) applied at an earlier life cycle stage would have an impact on methane emissions at later stages of cattle’s life, would be of scientific interest.

Energy and protein requirements for maintenance of Hu sheep during pregnancy

This study aimed to determine the effect of stage and level of feed intake on energy metabolism,carbon-nitrogen(C-N)balance,and methane emission to determine energy and protein requirements for maintenance of maternal body including pregnancy tissues during pregnancy using the method of C-N balance.Twenty-one ewes carrying twin fetuses were randomly divided into three groups of seven ewes each in the digestion and respirometry trial at d 40,100,and 130 of gestation,respectively.Three groups were fed a mixed diet either for ad libitum intake,70 or 50%of the ad libitum intake during pregnancy.The results showed that the apparent digestibility of C and N were increased as feeding levels decreased at each stage of gestation.The daily net energy requirements for maintenance(NE_m)were 295.80,310.09,and 323.59 k J kg^(–1)BW^(0.75)(metabolic body weight)with a partial efficiency of metabolisable energy utilization for maintenance of 0.664,0.644,and 0.620 at d 40,100,and 130 of gestation,respectively.The daily net protein requirements for maintenance were 1.99,2.35,and 2.99 g kg^(–1 )BW^(0.75) at d 40,100,and 130 of gestation,respectively.These results for the nutritional requirements of the net energy and protein may help to formulate more balanced diets for Hu sheep during pregnancy.

Nexus of Climate Change and USA Mid-South Rice (<i>Oryza sativa</i>L.) Production

Climate change is manifesting across the USA Mid-South and is impacting agricultural productivity, including the production of rice. This manuscript is a review of pertinent global literature concerning the effect of increasing temperature and carbon dioxide concentrations involving: 1) rice growth and development with an emphasis on spikelet sterility, 2) water availability for irrigation with the specter of aquifer overdraft and emerging water management technologies intended to improve water use efficiency, 3) the soil-plant continuum related to greenhouse gas emission and research avenues supporting agronomic practices that limit these emissions, and 4) region wide assessment of the economic and agronomic indicators to infer changes in the agricultural infrastructure and markets. Based on the global literature review and specific circumstances for USA Mid-South rice production, explicit proposals to mitigate and alleviate climate change are proposed. Key climate change mitigation proposals include: 1) support irrigation technologies that limit water usage and reduce methane emissions, 2) support soil carbon enhancement and newly emerging soil health agronomic practices, 3) achieve a greater usage of remote sensing activities to detect, in real time, field stresses, 4) support rice breeding activities that benefit furrow irrigation and provide heat tolerance, and 5) coordinate a rice region wide consensus to achieve farm gate activities that address climate change.

Importance of periphytic biofilms for carbon cycling in paddy fields:A review

Paddy fields play an important role in global carbon(C) cycling and are an important source of methane(CH_(4)) emissions. Insights into the processes influencing the dynamics of soil organic C(SOC) in paddy fields are essential for maintaining global soil C stocks and mitigating climate change. Periphytic biofilms composed of microalgae, bacteria, and other microorganisms are ubiquitous in paddy fields, where they directly mediate the transfer of elements at the soil-water interface. However, their contributions to C turnover and exchange have been largely neglected. Periphytic biofilms affect and participate in soil C dynamics by altering both abiotic(e.g., pH and redox potential) and biotic conditions(e.g., microbial community composition and metabolism). This review summarizes the contributions of periphytic biofilms to soil C cycling processes, including carbon dioxide fixation, SOC mineralization, and CH_(4) emissions. Future research should be focused on: i) the mechanisms underlying periphytic biofilm-induced C fixation and turnover and ii) quantifying the contributions of periphytic biofilms to soil C uptake, stabilization, and sequestration in paddy fields.

Meta-analysis quantifying the potential of dietary additives and rumen modifiers for methane mitigation in ruminant production systems

Increasingly countries are seeking to reduce emission of greenhouse gases from the agricultural industries,and livestock production in particular,as part of their climate change management.While many reviews update progress in mitigation research,a quantitative assessment of the efficacy and performance-consequences of nutritional strategies to mitigate enteric methane(CH_(4))emissions from ruminants has been lacking.A meta-analysis was conducted based on 108 refereed papers from recent animal studies(2000-2020)to report effects on CH4 production,CH_(4) yield and CH_(4) emission intensity from 8 dietary interventions.The interventions(oils,microalgae,nitrate,ionophores,protozoal control,phytochemicals,essential oils and 3-nitrooxypropanol).Of these,macroalgae and 3-nitrooxypropanol showed greatest efficacy in reducing CH_(4) yield(g CH_(4)/kg of dry matter intake)at the doses trialled.The confidence intervals derived for the mitigation efficacies could be applied to estimate the potential to reduce national livestock emissions through the implementation of these dietary interventions.

Potential use of garlic products in ruminant feeding:A review

The addition of antibiotics as growth promoters to ruminant feed can result in bacterial resistance and antibiotic residues in ruminant products.Correspondingly,there is serious public concern regarding the presence of antibiotic residue in ruminant products and the consequent threat to human health.As a result,the addition of plants and their products to ruminant feeds,as an alternative to antibiotics,has received much attention recently.Garlic and its products are rich in organosulphur compounds,which have a variety of biological activities and have been widely used as natural additives in animal production.This review presents recent knowledge on the addition of garlic products(powder,skin,oil,leaf and extracts)to the diets of ruminants.In this paper,garlic products are evaluated with respect to their chemical composition,bioactive compounds,and their impacts on the rumen ecosystem,antioxidant status,immune response,parasitic infection,growth performance and product quality of ruminants.This review provides valuable guidance and a theoretical basis for the development of garlic products as green,highly efficient and safe additives,with the aims of promoting ruminant growth and health,reducing methane emissions and improving ruminant product quality.Garlic extracts have the potential to control parasite infections by decreasing the faecal egg count.Garlic powder,oil and allicin are able to reduce the methane emissions of ruminants.Organosulphur compounds such as allicin,which is present in garlic products,have the potential to inhibit membrane lipid synthesis of the archaeal community,thus influencing the population of methanogenic archaea and resulting in a reduction in methane emissions.Some garlic products are also able to increase the average daily gain(garlic skin,water extract,and leaf)and the feed conversion ratio(garlic skin and leaf)of ruminants.Garlic stalk silage fed to sheep has the potential to improve the nutritional value of mutton by increasing the concentrations of linoleic and linolenic acids and essential amino acids.Sheep fed a diet containing garlic powder or oil are able to produce milk with higher concentrations of the conjugated linoleic acids and n-3 fatty acids,which has health benefits for consumers,due to the widely recognized positive impact of n-3 polyunsaturated fatty acids and conjugated linoleic acids on human heart health,improving platelet aggregation,vasodilation and thrombotic tendency.Overall,garlic products have the potential to enhance growth performance and product quality and reduce parasite infections,as well as methane emissions of ruminants.

Feeding of processed vegetable wastes to bulls and its potential environmental benefit

The study was conducted with the objectives to quantify year round availability of different vegetables waste(VW) in a wholesale market and to determine the inclusion level of a processed VW(VWP) in the diets of bulls. The daily VW biomass availability at Kawran bazaar, Dhaka, Bangladesh was quantified by weighing the vegetable supply and their wastes by visiting 2 days in a week. Concurrently, VW of cucumber, bitter gourd, spotted gourd, brinjal, pumpkin, potato, tomato, ladies finger, and snake gourd representing 0.21, 0.18, 0.17, 0.16, 0.09, 0.07, 0.06, 0.03, and 0.02 as fresh fractions, respectively were blended, dried and stored while adding rice polish and common salt at 200 and 20 g/kg DM, respectively;it was tested in bulls as an ingredient of concentrate mixture. Four dietary groups, each of 6 bulls, with initial average live weight(LW) of 85.47 ± 17 kg, were fed fresh German grass(Echinochloa polystachya)ad libitum supplemented with 4 different concentrates containing 0, 10%, 20% and 30% VWP at the rate of1% of LW for 89 days. The availability of VW biomass of the market was 42.51 t/d and recycling of them as feed, instead of using landfills, might reduce annual methane emission by 0.43 Gg. The inclusion of VWP in the diet up to 9.7% of DM, or 0.30% of LW of bulls showed no significant effect on the DM intake,digestibility, growth performance and health status of bulls. The dietary DM intake represented 3.10%,3.09%, 3.20% and 3.14% of LW resulting in daily gain of 302, 300, 312 and 344 g, respectively. The digestibility of DM of diets was 56.9%, 62.8%, 62.8% and 63.4%, respectively. It was concluded that VWP may be included at a level of 9.7% of the diet(DM basis) or 0.30% of LW of bulls.

Lateral detrital C transfer across a Spartina alternifora invaded estuarine wetland

Background:The lateral movements of mass and energy across the terrestrial-aquatic interface are being increasingly recognized for their importance in the carbon(C)balance of coastal/estuarine wetlands.We quantifed the lateral fux of detrital C in the Yangtze estuary where invasive Spartina alternifora has substantially and extensively altered the ecosystem structure and functions.Our overall objective was to close the C budget of estuarine wetlands through feld sampling,tower-based measurements,and modeling.Methods:A lateral detrital C exchange evaluation platform was established in a case study of the Yangtze River Estuary to investigate the efect of ecosystem structural changes on lateral detrital C transfer processes.This study estimated the lateral detrital C exchange based on the gross primary production(GPP)by performing coupled modeling and feld sampling.Tower-based measurements and MODIS time series and CH4 outgassing and biomass simultaneously measured the lateral detrital C fux to characterize the relative contributions of lateral(i.e.,detritus)C fuxes to the annual marsh C budget.Results:The C pools in the plants and soil of Spartina marshes were signifcantly higher than those of the native community dominated by Phragmites australis.The GPP based on MODIS(GPPMODIS)was 472.6 g C m^(−2) year^(−1) and accounted for 73.0%of the GPP estimated from eddy covariance towers(GPPEC)(646.9±70.7 g C m^(−2) year^(−1)).We also detected a higher GPPMODIS during the pre-growing season,which exhibited a similar lateral detrital C fux magnitude.On average,25.8%of the net primary production(NPP),which ranged from 0.21 to 0.30 kg C m^(−2) year^(−1),was exported during lateral exchange.The annual C loss as CH4 was estimated to be 17.9±3.7 g C m^(−2) year^(−1),accounting for 2.8%of the GPPEC.The net positive detrital C fux(i.e.,more detritus leaving the wetlands),which could exceed 0.16 kg C m^(−2) day^(-1),was related to daily tides.However,the observed lateral detrital C fux based on monthly sampling was 73.5%higher than that based on daily sampling(i.e.,the sum of daily sampling),particularly in March and October.In addition,spatiotemporal granularities were responsible for most of the uncertainty in the lateral detrital C exchange.Conclusion:This research demonstrated that an integrated framework incorporating modeling and feld sampling can quantitatively assess lateral detrital C transport processes across the terrestrial-aquatic interface in estuarine wetlands.However,we note some limitations in the application of the light-use efciency model to tidal wetlands.Spartina invasion can turn the lateral C balance from a C source(209.0 g C m^(−2) year^(−1))of Phragmites-dominated marshes into a small C sink(-31.0 g C m^(−2) year^(−1)).Sampling over a more extended period and continuous measurements are essential for determining the contribution of diferent lateral detrital C fux processes to closing the ecosystem C budgets.The sampling spatiotemporal granularities can be key to assessing lateral detrital C transfer.