Study on Environmental and Economic Benefits of Rice and Wheat Rotation with Swine Manure-Straw Returning

[Objective] The aim was to investigate the application effect of swine manure-straw returning and to determine the best mode. [Method] A field experiment under rice and wheat rotation with different swine manure-straw treatments was con- ducted to study the growth characters and output of rice and wheat, calculate the economic benefit and carbon dioxide emission reduction, and analyze the best mode of swine manure applying-straw returning. [Result] The swine manure-straw returning was conducive to the growth of crop, the highest outputs of rice and wheat were on the treatment of ＂30% swine manure and 20% straw and 50% chemical fertiliz- er＂, they were 7 874.57 and 6 427.00 kg/hm^2, and saved cost about 5 146.35 Yuan/hm^2, increased input 5 312.56 and 3 931.93 Yuan/hm^2, the greenhouse gas e- mission reduction was 1.30 t/hm^2 （calculated according to carbon dioxide on a dry basis）. [Conclusion] The treatment of ＂30% swine manure and 20% straw and 50% chemical fertilizer＂ was the best mode of swine manure-straw returning.

Effects of different loading rates and types of biochar on passivations of Cu and Zn via swine manure composting

Pollution of arable land caused by heavy metals in livestock and poultry manure has become a potential threaten to human health in China.Safe disposal of the contained toxic pollution with animal manure by co-composting with biochar is one of the alternative methods.Biochars from different sources(wheat straw,peanut shells and rice husks)amended with different loading rates were investigated for passivations of copper and zinc(Cu and Zn)in swine manure composting.Results showed that the passivation effects of the three types of biochar on Cu and Zn were enhanced with increasing biochar dose.Contents of Cu and Zn measured by diethylenetriaminepentaacetic acid(DTPA)and Community Bureau of Reference(CBR)showed that wheat straw biochar with the loading rates of 10%–13%(w/w)was superior to the other two types of biochar in this study.Compared with the control,sample from wheat straw biochar was more favorable for the bacterial growth of Proteobacteria,Firmicutes and Actinobacteria.In addition,pot experiment showed that organic fertilizer amended with wheat straw biochar could significantly improve the growth of Chinese pakchoi and enzyme activities(superoxide dismutase,peroxidase,polyphenol oxidase and catalase)as compared with the control.Cu and Zn contents of Chinese pakchoi in the organic fertilizer group containing wheat straw biochar reduced by 73.2%and 45.2%,65.8%and 33.6%,respectively,compared with the group without loading biochar.There was no significant difference in the contents of vitamin C and reducing sugar between the groups of organic fertilizer amended with/without wheat straw biochar,however,there was significant difference compared with the heavy metal addition group.The application of organic fertilizer formed by adding biochar can effectively reduce the adverse effects of heavy metals on crops.

Effect of adding Lactobacillus plantarum and soluble carbohydrates to swine manure on odorous compounds, chemical composition and indigenous flora

Manure odor, which results in the increasing complaints and lawsuits, has increased the tension among swine producers and surrounding residents. The effects of Lactobacillus plantarum and different rates of soluble carbohydrates additions to swine manure on odorous compounds, chemical compounds and indigenous flora were evaluated. Additions were calculated on dried manure weight basis. Variables monitored included ammonia （NH3）, hydrogen sulfide （H2S）, odor offensiveness, pH, ammonium nitrogen（NH4^＋-N）, volatile fatty acids （VFAs）, urease and indigenous flora. The results indicated that the combination of L. plantarum and soluble carbohydrates dramatically reduced manure pH. Lower pH resulted in the reduction of NH3 volatilization （34.6%-92.4%, P〈0.01）, the increases of H2S （P〈 0.05） and NH4^＋-N （5.3%-17.5%, P〈0.05）. In addition, L. plantarum and soluble carbohydrates additions significantly reduced odor offensiveness, those VFAs related to malodor indicators（valeric acids, 12.3%-47.7%, P〈 0.05; iso-valeric, 3.5%-23.8%） and the main microorganisms responsible for odor production, with the number of Eubacteria in swine manure reducing by 4.9%, 11.6%, 17.4%, 34.1% and 32.2% respectively.

Effects of anaerobic composting on tetracycline degradation in swine manure

Oxytetracycline(OTC) and tetracycline(TC) are the most common TC antibiotics used in human and veterinary medicine.Residual amounts of these antibiotics in manure pose a potential threat to public and ecological health as a result of the potential for them to be released to the environment following land application of manure from animals treated with antibiotics.We investigated the degradation of OTC and TC during anaerobic composting.We tested the effects of temperature and antibiotic concentration on degradation rates in a control and in manure spiked with TCs.We examined changes in p H,biological degradation material(BDM),and moisture corresponding with antibiotic degradation of TCs in the swine manure.Results showed that the OTC and TC concentrations decreased by between 68.54% and 95.50% in all nine treatments following 14 days of anaerobic composting,and the highest removal ef ficiencies were observed at an incubation temperature of 55°C and initial concentrations of 10.36 μg·g^(-1),and 5.96 μg·g^(-1) of OTC and TC,respectively,which were degraded by 95.50%,and 90.06%.During composting at 55 °C and at added concentrations of 5 μg·g^(-1),OTC decreased rapidly,and the time required for50% and 90% degradation was 4.1 and 9.8 days,respectively;for TC,these values were 4.4 and 14.0 days,respectively.Removal ef ficiencies for all TCs correlated well with moisture content of the manure.These results show that composting may be a practical and useful means to reduce concentrations of OTC and TC in swine manure prior to its land application.

In-depth observations of fermentative hydrogen production from liquid swine manure using an anaerobic sequencing batch reactor

In this study,experiments were designed to reveal in-depth information of the effect of pH and hydraulic retention time（HRT）on biohydrogen fermentation from liquid swine manure supplemented with glucose using an Anaerobic Sequencing Batch Reactor（ASBR）System.Five values of HRT（8,12,16,20,and 24 h）were first tested and the best HRT determined was further studied at five p H levels（4.4,4.7,5.0,5.3,and 5.6）.The results showed that for HRT 24 h,there was a dividing H2 content（around 37%）related to the total biogas production rate for the ASBR System running at p H 5.0.When the H2 content went beyond 37%,an appreciable decline in biogas production rate was observed,implying that there might exist an H2 content limit in the biogas.For other HRTs（8 through 20 h）,an average H2 content of 42%could be achieved.In the second experiment（HRT 12 h）,the highest H2 content（35%）in the biogas was found to be associated with p H 5.0.The upswing of p H from 5.0 to 5.6 had a significantly more impact on biogas H2 content than the downswing of p H from5.0 to 4.3.The results also indicated good linear relationships of biogas and H2 production rates with HRT（r=0.9971 and0.9967,respectively）.Since the optimal ASBR operating conditions were different for the biogas/H2 production rates and the H2 yield,a compromised combination of the running parameters was determined to be HRT 12 h and pH 5.0 in order to achieve good biogas/H2 productions.

Fate of tetracyclines in swine manure of three selected swine farms in China

Veterinary antibiotics can enter the environment due to the common practice of land application of manure from treated animals.The environmental fate of tetracyclines in swine manure after composting and field application remains largely unknown.This study analyzed the concentrations of tetracyclines in manure,manure-based compost and compost amended soil in selected swine farms from Beijing,Jiaxing and Putian,China to determine the dilution effects of antibiotics when released into the soil environment.The results demonstrate that residues of antibiotics were detected in all samples and chlortetracycline as well as its degradation products should be regarded critically concerning their potential ecotoxicity.Application of manure-based compost to soil could reduce the possible risk posed by antibiotic contamination,but the trigger value of 100 μg/kg was still exceeded in soil samples （776.1 μg/kg dw） from Putian City after application of compost.Field studies such as the present one can help to improve the routine administration of antibiotic-containing composted manure.

Effects of chlortetracycline,Cu and their combination on the performance and microbial community dynamics in swine manure anaerobic digestion

Swine manure was typical for the combined pollution of heavy metals and antibiotics. The effects of widely used veterinary antibiotic chlortetracycline（CTC）, Cu and their combination on swine manure anaerobic digestion performance and microbial community have never been investigated. Thus, four 2 L anaerobic digestion reactors were established including reactor A（control）, B（CTC spiked by 0.5 g/kg dry weight, dw）, C（Cu spiked by 5 g/kg dw） and D（combination of CTC, 0.5 g/kg dw, and Cu, 5 g/kg dw）, and dynamics of bacterial and archaeal community structure was investigated using high throughput sequencing method. Results showed that addition of CTC and Cu separately could increase the total biogas production by21.6% and 15.8%, respectively, while combination of CTC and Cu severely inhibited anaerobic digestion（by 30.3%）. Furthermore, corresponding to different stages and reactors, four kinds of microbes including bacteria and archaea were described in detail, and the effects of CTC, Cu and their combination mainly occurred at hydrolysis and acidification phases. The addition of Cu alone changed the dynamics of archaeal community significantly. It was genus Methanomassiliicoccus that dominated at the active methane production for A, B and D, while it was genus Methanobrevibacter and Methanoculleus for C.

Effects of different biochars on antibiotic resistance genes during swine manure thermophilic composting

Elimination of antibiotic resistance genes(ARGs)in animal manure from concentrated animal feeding operations by thermophilic composting has drawn increasing attention.This study investigated the effects of sawdust biochar,corn stover biochar and peanut hull biochar with three spiked levels on ARGs in swine manure during thermophilic composting.Thirteen ARGs corresponding to four classes of antibiotics(tetracyclines,sulfonamides,macrolides and quinolones)were determined in the composting piles.Results indicated that the ten tested composting groups became fully mature after 30-day thermophilic composting process.tetM,tetO and ermB were reduced in all tested groups;tetC and tetG,tetX,sul1,sul2,ermF,qnrD and aac(6’)-Ib were mostly reduced under low level biochar addition but increased under higher level biochar addition;gyrA increased under medium biochar addition and reduced in other groups;oqxB remained comparatively stable throughout the composting process.The addition levels of spiked biochar are more important than types of spiked biochar on the removal of ARGs in the composting pile.The average removal rates of ARGs in the control group,low,medium and high level biochar addition groups were 0.24 logs,0.52-0.72 logs,-0.52-0.18 logs and-0.19-0.21 logs,respectively.In summary,low level biochar addition could enhance the elimination of studied ARGs in swine manure during the composting process,while medium level biochar addition to the composting piles would increase the risk of ARGs’propagation.

Anaerobic co-digestion of rice straw and digested swine manure with different total solid concentration for methane production

This study aimed to investigate potential methane production through anaerobic co-digestion of rice straw and digested swine manure with different total solids.The research was carried out in bench scale with utilizing batch system.To evaluate the stability of anaerobic co-digestion process,the experiment was run in triplicate.The anaerobic co-digestion process was operated in 500 mL batch digesters under constant agitation speed and temperature.The agitation speed was maintained at 270 r/min.Temperature of the batch system was set and maintained at 35℃.Digested swine manure utilized in this experiment was obtained from semi-continuous digesters run at steady state condition,with 25 days of hydraulic retention time under mesophilic condition.Rice straw(RS)generated the highest methane production at 3% total solids(TS)which was around(1814±47.43)mL,where in this concentration,it had C:N ratio at 10.6:1.Rice straw obtained the highest methane yield at 3% TS,which was around(141.4±3.70)mL CH_(4)/g volatile solids(VS)added.Rice straw also had the highest chemical oxygen demand(COD)removal and VS reduction at 3% TS which were around(52.97%±1.46%)and(61.81%±1.04%),respectively.

Two-phase anaerobic co-digestion of dairy manure with swine manure

In order to solve the problems associated with high fiber content,and the ensuing lower biogas volume yield in anaerobic digestion of dairy manure,a study of the co-digestion of separated liquids from dairy manure combined with swine manure using a two-phase anaerobic digestion process was conducted.The influence of level of total solids(TS)and hydraulic retention time(HRT)of the mixed liquor on the specific methane production were studied.Three TS levels 8%,10%and 12%were investigated.Analysis of the results show that a maximum specific methane yield of 132.99 L/kg volatile solids(VS),can be obtained with a TS of 9%,an inoculation rate of 30%,the duration of hydrolytic acidification phase of 5 d,and an HRT of the methanogenic phase of 10 d.These findings could provide directions for improving the biogas production by performing the co-digestion of dairy manure with swine manure.

Field scale measurement of greenhouse gas emissions from land applied swine manure

Greenhouse gas emissions （GHGs） from swine production systems are relatively well researched with the exception of emissions from land application of manure. GttGs inventories are needed for process- based modeling and science-based regulations. Thus, the objective of this observational study was to measure GHG fluxes from land application of swine manure on a typical corn field. Assessment of GHG emissions from deep injected land-applied swine manure, Phil and reapplication in the spring, on a typical US Midwestern corn-on-corn farm was completed. Static chambers were used Ibr flux measurement along with gas analysis on a GC-FID-ECD＋ Measured gas concentrations were used to estimate GHGs flux using four different models： linear regression, nonlinear regression, first order linear regression and the revised Hutchinson and Mosier （HMR） model, respectively for comparisons.Cumulative flux esmnates after manure apphcatmn of 5.85×10 g·ha^-1（1 ha = 0.01 km） of CO2 6.60×10^1g·ha^-1 of CH4 and3.48 ×10^3g·ha^-1 N2O for the fall trial and 3.11×10^6g·ha^-1 of CO2,2.95×10^3g·ha^-1 of OH4, and 1.47×10^4g·ha^-1 N2O after the spnng reapphcation trial were observed. The N2O net cumulative flux represents 0.595% of nitrogen applied in swine manure for the fall trial.

Exploring the abundance and influencing factors of antimicrobial resistance genes in manure plasmidome from swine farms

Plasmids play a critical role in the dissemination of antimicrobial resistance genes(ARGs),however,a systematical understanding of ARGs originated from plasmids in swine production is currently lacking.Herein,quantitative polymerase chain reaction was applied to determine the prevalence of ten ARGs and the class1 integron gene intI1 of plasmid source in swinemanure from 44 farms in Sichuan,Hubei and Hebei provinces,China.All assayed ARGs were observed in plasmid DNA samples,and the average absolute abundance of aac(6’)-Ib-cr,blaNDM,blaCTX-M,optrA,ermB,floR,mcr-1,qnrS,tetM,sul1 and intI1 were 7.09,2.90,4.67,6.62,7.55,7.14,4.08,4.85,7.16,7.11 and 8.07 of 10 log copies/gram,respectively.IntI1 showed a high correlation(r>0.8,P<0.01)with the abundance of aac(6’)-Ib-cr and sul1 in swine manure.Moreover,the farm scale(i.e.,herd population)and geographical location were not found to be critical factors influencing the absolute abundance of ARGs of plasmid DNA in swine farms.However,the concentrations of florfenicol,Cu,Zn,Fe,total phosphorus(TP)and total potassium(TK)demonstrated a significant correlation with the abundance of several ARGs.Particularly,Cu and Zn had high correlations with optrA and blaCTX-M,respectively.Our results demonstrated that antibiotics,heavy metals and environmental nutrients are likely jointly contributing to the long-term persistence of ARGs in swine production.This study provides insights into the abundance and influencing factors of ARGs from swine manure,which is of significance for assessing and reducing the public health risks in livestock production.

INTEGRATED CROP-LIVESTOCK SYSTEMS:LESSONS FROM NEW YORK,BRITISH COLUMBIA,AND THE SOUTH-EASTERN UNITED STATES

Livestock production in the United States(US)and Canada is diverse,but shows a common trend in most livestock sectors toward fewer farms producing the majority of animal products despite a large number of farms still small in production scale.The migration to larger and more concentrated animal feeding operations in beef finishing and poultry,swine,and dairy production allows processors to streamline supplies to meet market demand for abundant,low-cost livestock products,whether that be for packaged meat,dairy products,or eggs.With concentration of livestock operations comes the challenge of managing manures.When sufficient land is available and nutrients are needed,livestock manure is an excellent nutrient source and land application is the preferred method of recycling this resource.However,when livestock production is constrained in a geographical area and animal densities are high,manure may become an environmental liability with potentially greater risk for runoff and leaching of nutrients,emission of odors,ammonia,and greenhouse gases,and release to the environment of pathogens and chemicals of emerging concern.Addressing these challenges now and into the future requires learning from mistakes and adopting successful approaches.We describe different levels of integration between livestock and crop producers in New York,British Columbia,and the south-eastern US as learning opportunities to improve economic and environmental sustainability.Examples show that effective solutions should recognize(1)manure has value and is not just a cost,(2)farmers,farm advisors,extension educators,nutrient management planners,crop advisors,nutritionists,state agency personnel,regulators,and university researchers need to be active participants in development of solutions,and(3)change to a sustainable future requires a combination of government regulation and outcome-based incentives.

Selected dark sides of biomass-derived biochars as environmental amendments

With the rapid increase in the application of biochars as amendments, studies are needed to clarify the possible environmental risks derived from biochars to use safely the biomass resources. This work reported selected dark sides of maize straw-and swine manurederived biochars pyrolyzed at 300 and 500°C. During the pyrolysis processes, total heavy metals in the biochars were enriched greatly accompanying with considerable emission of the heavy metals into atmosphere and the trends became increasingly obvious with pyrolysis temperature. Meanwhile, the biochars showed distinctly decreased available heavy metals compared with raw feedstocks, which could be mainly attributed to the sorption by the inorganics in the biochars. The water-and acid-washing treatments significantly increased the releasing risks of heavy metals from biochars into the environments. Electron paramagnetic resonance analysis indicated that persistent free radicals, emerged strongly in the biochars as a function of the aromatization of biomass feedstocks, were free from the influence of water-, acid-, or organic-washing of the biochars and could remain stable even after aged in soils for 30 days. Dissolved biochars, highly produced during pyrolysis processes, showed distinct properties including lower molecular weight distribution while higher aromaticity compared with soil dissolved organic carbon.The results of this study provide important perspectives on the safe usage of biochars as agricultural/environmental amendments.