The nitrogen transformation behavior based on the pyrolysis products of wheat straw

In order to provide basic design parameters for the industrial pyrolysis process,the transformation behavior of nitrogen was investigated using wheat straw as raw material.The distributions of nitrogen in pyrolysis char,oil,and gas were obtained and the nitrogenous components in the products were analyzed systematically by X-ray photoelectron spectroscopy(XPS),pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS)and thermogravimetric-Fourier transform infrared spectrometry(TG-FTIR).The nitrogen distribution ranges of the pyrolysis char,oil,and gas were 37.34%–54.82%,32.87%–40.94%and 10.20%–28.83%,respectively.More nitrogen was retained in char at lower pyrolysis temperature and the nitrogen distribution of oil was from rise to decline with increasing temperature.The most abundant N-containing compounds in three-phase products were pyrrole-N,amines,and HCN,respectively.In addition,the transformation mechanism of nitrogen from wheat straw to pyrolysis products was concluded.

Nitrogen transformation processes in soil along a High Arctic tundra transect

Soil nitrogen(N)transformation processes in the High Arctic tundra are poorly understood even though nitrogen is one of the main limiting nutrients.We analyzed soil samples collected along a High Arctic tundra transect to investigate spatial variability in key nitrogen transformation processes,functional gene abundances,ammonia-oxidizing archaea(AOA)community structures,and key nitrogen transformation regulators.The potential denitrification rates were higher than the nitrification rates in the soil samples,although nitrification may still regulate N2O emissions from tundra soil.The nutrient(total carbon,total organic carbon,total nitrogen,and NH_(4)^(+)-N)contents were important determinants of spatial variability in the potential denitrification rates of soil along the tundra transect.The total sulfurcontent was the main variable controlling potential nitrification processes,probably in association with sulfate-reducing bacteria.The nitrate content was the main variable affecting potential dissimilatory nitrate reduction to ammonium.AOA and ammonia-oxidizing bacteria amoA,nirS,and anammox 16S rRNA genes were found in all of the soil samples.AOA play more important roles than ammonia-oxidizing bacteria in soilnitrification.Anammox bacteria may utilize NO_(2)^(-)produced through nitrification.Phylogenetic analysis indicated that the AOA amoA sequences could be grouped into eight unique operational taxonomic units(OTUs)with a 97%sequence similarity and were affiliated with three group 1.1b Nitrososphaeraclusters.The results indicated that heterogeneous environmental factors(e.g.,the carbon and nitrogen contents of soil)along the High Arctic tundra transect strongly affected the nitrogen transformation rate and relevant functional gene abundances in soil.

Effects of muddy water irrigation with different sediment gradations on nitrogen transformation in agricultural soil of Yellow River Basin

Muddy water irrigation has been widely practiced in the Yellow River Basin for agricultural production and is an important method of economical and intensive utilization of water resources.In this study,the effects of sediment gradation,sand content,and soil moisture content on nitrogen(N)transformation were studied through a series of experimental tests.The results indicated that muddy water irrigation significantly affected agricultural soil physical and biological properties as well as N transformation.Soil bulk density,total porosity,pH,and microbial enzyme activities significantly correlated with N transformation as affected by the interaction between sediment and soil moisture.Sediment addition generally increased the soil bulk density and reduced the soil porosity and pH significantly,and the optimum moisture for promotion of the N transformation rate was 80%of the water-filled pore space.Therefore,muddy water irrigation has a potentially long-term influence on agricultural N cycles in semi-arid regions of northwestern China.This could provide a theoretical basis for scientific and rational use of muddy water for irrigation.

Elevated atmospheric CO_(2) impact on carbon and nitrogen transformations and microbial community in replicated wetland

Background:Elevated atmospheric CO_(2) has direct and indirect influences on ecosystem processes.The impact of elevated atmospheric CO_(2) concentration on carbon and nitrogen transformations,together with the microbial community,was evaluated with water hyacinth(Eichhornia crassipes)in an open-top chamber replicated wetland.The responses of nitrogen and carbon pools in water and wetland soil,and microbial community abundance were studied under ambient CO_(2) and elevated CO_(2)(ambient+200μL L^(−1)).Results:Total biomass for the whole plant under elevated CO_(2) increased by an average of 8%(p=0.022).Wetlands,with water hyacinth,showed a significant increase in total carbon and total organic carbon in water by 7%(p=0.001)and 21%(p=0.001),respectively,under elevated CO_(2) compared to that of ambient CO_(2).Increase in dissolved carbon in water correlates with the presence of wetland plants since the water hyacinth can directly exchange CO_(2) from the atmosphere to water by the upper epidermis of leaves.Also,the enrichment CO_(2) showed an increase in total carbon and total organic carbon concentration in wetland soil by 3%(p=0.344)and 6%(p=0.008),respectively.The total nitrogen content in water increased by 26%(p=0.0001),while total nitrogen in wetland soil pool under CO_(2) enrichment decreased by 9%(p=0.011)due to increased soil microbial community abundance,extracted by phospholipid fatty acids,which was 25%larger in amount than that of the ambient treatment.Conclusion:The study revealed that the elevated CO_(2) would affect the carbon and nitrogen transformations in wetland plant,water,and soil pool and increase soil microbial community abundance.

Effect of orchard age on soil nitrogen transformation in subtropical China and implications

A better understanding of nitrogen transformation in soils could reveal the capacity for biological inorganic N supply and improve the efficiency of N fertilizers. In this study, a15 N tracing study was carried out to investigate the effects of converting woodland to orchard, and orchard age on the gross rates of N transformation occurring simultaneously in subtropical soils in Eastern China. The results showed that inorganic N supply rate was remained constant with soil organic C and N contents increased after converting woodland into citrus orchard and with increasing orchard age. This phenomenon was most probably due to the increase in the turnover time of recalcitrant organic-N, which increased with decreasing soil p H along with increasing orchard age significantly. The amo A gene copy numbers of both archaeal and bacterial were stimulated by orchard planting and increased with increasing orchard age. The nitrification capacity（defined as the ratio of gross rate of nitrification to total gross rate of mineralization） increased following the Michaelis–Menten equation, sharply in the first 10 years after woodland conversion to orchard, and increased continuously but much more slowly till 30 years. Due to the increase in nitrification capacity and unchanged NO3-consumption, the dominance of ammonium in inorganic N in woodland soil was shifted to nitrate dominance in orchard soils. These results indicated that the risk of NO3-loss was expected to increase and the amount of N needed from fertilizers for fruit growth did not change although soil organic N accumulated with orchard age.

Transformation of ammonium nitrogen and response characteristics of nitrifying functional genes in tannery sludge contaminated soil

High concentrations of ammonium nitrogen released from tannery sludge during storage in open air may cause nitrogen pollution to soil and groundwater.To study the transformation mechanism of NH_(4)^(+)-N by nitrifying functional bacteria in tannery sludge contaminated soils,a series of contaminated soil culture experiments were conducted in this study.The contents of ammonium nitrogen(as NH_(4)^(+)-N),nitrite nitrogen(as NO_(2)^(−)-N)and nitrate nitrogen(as NO_(3)^(−)-N)were analyzed during the culture period under different conditions of pollution load,soil particle and redox environment.Sigmodial equation was used to interpret the change of NO_(3)^(−)-N with time in contaminated soils.The abundance variations of nitrifying functional genes(amoA and nxrA)were also detected using the real-time quantitative fluorescence PCR method.The results show that the nitrification of NH_(4)^(+)-N was aggravated in the contaminated silt soil and fine sand under the condition of lower pollution load,finer particle size and more oxidizing environment.The sigmodial equation well fitted the dynamic accumulation curve of the NO_(3)^(−)-N content in the tannery sludge contaminated soils.The Cr(III)content increased with increasing pollution load,which inhibited the reproduction and activity of nitrifying bacteria in the soils,especially in coarse-grained soil.The accumulation of NO_(2)^(−)-N contents became more obvious with the increase of pollution load in the fine sand,and only 41.5%of the NH_(4)^(+)-N was transformed to NO_(3)^(−)-N.The redox environment was the main factor affecting nitrification process in the soil.Compared to the aerobic soil environment,the transformation of NH_(4)^(+)-N was significantly inhibited under anaerobic incubation condition,and the NO_(3)^(−)-N contents decreased by 37.2%,61.9%and 91.9%under low,medium and high pollution loads,respectively.Nitrification was stronger in the silt soil since its copy number of amoA and nxrA genes was two times larger than that of fine sand.Moreover,the copy numbers of amoA and nxrA genes in the silt soil under the aerobic environment were 2.7 times and 2.2 times larger than those in the anaerobic environment.The abundance changes of the amoA and nxrA functional genes have a positive correlation with the nitrification intensity in the tannery sludge-contaminated soil.

Effects of Glucose Addition on N Transformations in Paddy Soils with a Gradient of Organic C Content in Subtropical China

To better understand the interaction of N transformation and exogenous C source and manage N fertilization, the effects of glucose addition on N transformation were determined in paddy soils with a gradient of soil organic C content. Changes in N mineralization, nitrification and denitrification, as well as their response to glucose addition were measured by incubation experiments in paddy soils derived from Quaternary red clay in subtropical China. Mineralization and denitrification were changed in order of increasing soil fertilities： high 〉 middle 〉 low. During the first week of incubation, net N mineralization and denitrification rates in paddy soil with high fertility were 1.9 and 1.1 times of those in soil with middle fertility and 5.3 and 2.9 times of those in soil with low fertility, respectively. Addition of glucose decreased net N mineralization by approximately 78.8, 109.2 and 177.4% in soils with high, middle and low fertility, respectively. However, denitrification rates in soils with middle and low fertility were increased by 14.4 and 166.2% respectively. The highest nitrate content among the paddy soils tested was 0.62 mg kg-1 and the highest nitrification ratio was 0.33%. Addition of glucose had no obvious effects on nitrate content and nitrification ratio. It was suggested that the intensity of mineralization and denitrification was quite different in soils with different fertility, and increased with increasing soil organic C content. Addition of glucose decreased mineralization, but increased denitrification, and the shifts were greater in soil with low than in soil with high organic C content. Neither addition of glucose nor inherent soil organic C had obvious effects on nitrification in paddy soils tested.

Determination of forest soil organic nitrogen determination using technique of X-ray absorption near-edge structure

The forest soil organic N was investigated using N K-edge X-ray absorption near-edge structure （XANES） to gain an insight into the relationship between N speciation and its transformation in quantity. Soil samples were collected from spruce, hemlock and pine forests in central Taiwan. Results showed that various organic N types could be revealed by XANES spectra. Amide and pyrrolic N are the major parts of the composition in the humic substance, soluble organic nitrogen and original soils. The relative distribution of N speciation differed in treatments and vegetations samples. The spruce had a significant difference from the hemlock in soluble organic nitrogen （SON） spectra at 402.3 eV energy peak. In the A-horizon soils, the relative amount of pyridinic N was much higher than that in the O-horizon soils, indicating N transformation in quantity in the mineral horizon was different from that in the organic horizon, which might play an important role in N cycling of forest ecosystems.

N Transformation of Green Manure Incorporated Directly or Returned into Soil After Feeding Pig and Its Efficiency

?15)N-labelled green manure was used to feed pigs. Its nitrogen recovery by pig body, feces and urine was23.5%, 23.8% and 28.8% respectively, totalling 76. 1%. Feces and green manure coordinated respectively withequal amount of CO(NH_2)_2-N as well as urine alone were applied as basic fertilizer in microplot experiments.The ￣(15)N recovery from feces and urine was equivalent to 2.51% and 4.82% by rice grain, and 0.98% and1.94% by straw respectively, and soil residual ￣(15)N from them took 13.3% and 4.90% of the ￣(15)N in greenmanure. After feeding pigs with green manure and returning their feces and urine into soil, the ￣(15)N recoveryby pig body and rice grain was 30.8%, and that by pig body, and rice plant as well as soil residual took 52.7%of the ￣(15)N in feed. ￣(15)N loss was 23.9% in pig feeding and 23.4% in rice planting. When green manure wasincorporated directly into soil, its ￣(15)N recovery by grain was 26.65%, that by rice plant plus soil residual was65.2%, and the loss was 34.8%.

In-situ nitrogen fate in the vadose zone of different soil types and its implications for groundwater quality in the Huaihe River Basin,China

This paper focused on nitrate fate in the vadose zone(VZ)and its implications for groundwater vulnerability under different soil types in the agricultural area of Huaihe River Basin,China.Isotopic compositions of nitrate(δ15N andδ18O)along with NO3-and Cl-concentrations were determined in the VZ-shallow groundwater continuum beneath silty-loam and silty-clay-loam,which are distinctive in texture and organic carbon(OC).In the soil zone(<1 m in depth),measuredδ18O-NO3-suggested the ubiquitous of nitrification regardless of soil types.In the subsoil zone(>1 m in depth),however,the concurrent enrichment ofδ15N-NO3-andδ18O-NO3-indicated the occurrence of denitrification,which showed a dependence on subsoil properties.Specifically,during wheat and maize land uses,denitrification removed as much as 76%-88%of the total nitrate where the subsoil was dominated by stratified OC-rich silty-clay-loam.In contrast,only 0%-28%of the nitrate was degraded via denitrification where the subsoil was composed of uniform,OC-depleted silty-loam.Furthermore,inactive denitrification and higher permeability in the silty-loam VZ implied higher groundwater vulnerability.This observation was consistent with the fact that groundwater NO3--N concentration beneath silty-loam(11.24 mg L-1)was over two times higher than that of the silty-clay-loam(5.32 mg L-1),where stricter fertilization management and conservation strategies should be applied to protect groundwater quality.

Clear felling and burning effects on soil nitrogen transforming bacteria and actinomycetes population in Chittagong University campus, Bangladesh

The effect of forests clear felling and associated burning on the population of soil nitrogen transforming bacteria and actinomycetes are reported at three pair sites of Chittagong University campus, Bangla- desh in monsoon tropical climate. Clear felled area or burnt site and 15-21 year mixed plantation of native and exotic species, situated side by side on low hill having Typic Dystrochrepts soil was represented at each pair site. At all the three pair sites, clear felled area or burnt site showed very significantly （p~_0.001） lower population of actinomycetes, Rhizobium, Nitrosomonas, Nitrobacter and ammonifying as well as deni- trifying bacteria compared to their adjacent mixed plantation. From en- vironmental consideration, this finding has implication in managing natural ecosystem.

Responses of nitrogen cycling and related microorganisms to brackish wetlands formed by evapotranspiration

Elevated evapotranspiration due to warmer air temperature could raise salinity and nutrient levels of some inland wetlands, potentially impacting nitrogen cycling. To characterize the impact of high evapotranspiration on soil microbial nitrogen cycling in inland wetlands, we compared freshwater and brackish marsh(or non-marsh) wetlands in terms of sediment ammonia-oxidizing rate(AOR), denitrifying rate(DR), and related microbial communities in a typical inland basin, the Hulun Lake basin, in China. Results showed that marsh ecosystems(ME) exhibited 31% higher AOR and 65% higher DR than non-marsh ecosystems(NE). For NE, freshwater non-marsh wetland exhibited 12% higher AOR than brackish non-marsh wetland. This was probably due to the inhibitory effects of high NH_4~+ and salinity levels on ammonia-oxidizing archaea in brackish non-marsh wetland. Conversely, DR in brackish non-marsh wetland was 23% higher than that in freshwater non-marsh wetland, with total organic carbon(TOC) significantly influencing this difference,suggesting that the higher DR in brackish non-marsh wetland was mainly due to its higher TOC level. For ME, due to the direct and indirect interference of salinity, brackish marsh wetland displayed 26% lower AOR and 19% lower DR than freshwater marsh wetland. Besides, brackish wetlands harbored distinct ammonia-oxidizing and denitrifying microbial communities compared to freshwater wetlands. The assembly of these communities was dominated by stochastic processes, while brackish wetlands exhibited more prominent deterministic processes than freshwater wetlands. Overall, high evapotranspiration altered activities and community characteristics of ammonia oxidizers and denitrifiers in inland brackish wetlands by enhancing salinity and nutrient levels,while emergent plants occurring in ME could mitigate the adverse effects of salt stress of inland brackish wetlands on nitrogen cycling.

Intensified river salinization alters nitrogen-cycling microbial communities in arid and semi-arid regions of China

Freshwater salinization is receiving increasing global attention due to its profound influence on nitrogen cycling in aquatic ecosystems and the accessibility of water resources.However,a comprehensive understanding of the changes in river salinization and the impacts of salinity on nitrogen cycling in arid and semi-arid regions of China is currently lacking.A meta-analysis was first conducted based on previous investigations and found an intensification in river salinization that altered hydrochemical characteristics.To further analyze the impact of salinity on nitrogen metabolism processes,we evaluated rivers with long-term salinity gradients based on in situ observations.The genes and enzymes that were inhibited generally by salinity,especially those involved in nitrogen fixation and nitrification,showed low abundances in three salinity levels.The abundance of genes and enzymes with denitrification and dissimilatory nitrate reduction to ammonium functions still maintained a high proportion,especially for denitrification genes/enzymes that were enriched under medium salinity.Denitrifying bacteria exhibited various relationships with salinity,while dissimilatory nitrate reduction to ammonium bacterium(such as Hydrogenophaga and Curvibacter carrying nirB)were more inhibited by salinity,indicating that diverse denitrifying bacteria could be used to regulate nitrogen concentration.Most genera exhibited symbiotic and mutual relationships,and the highest proportion of significant positive correlations of abundant genera was found under medium salinity.This study emphasizes the role of river salinity on environment characteristics and nitrogen transformation rules,and our results are useful for improving the availability of river water resources in arid and semi-arid regions.

Driving mechanisms of nitrogen transport and transformation in lacustrine wetlands

As an essential component of proteins and genetic material for all organisms, nitrogen(N) is one of the major limiting factors that control the dynamics, biodiversity and functioning of lacustrine wetlands, in which intensified N biogeochemical activities take place. Reactive N loaded into wetland ecosystems has been doubled due to various human activities, including industrial, agricultural activities and urbanization. The main driving mechanisms of N transport and transformation in lacustrine wetlands are categorized to pushing forces and pulling forces in this study. Geomorphology, wetland age, N concentrations, and temperature are the main pushing forces(passive forces); whereas water table variation, oxygen concentration, other elements availability, oxidation-reduction potential(Eh) and p H, and microorganisms are the predominant pulling forces(active forces). The direction and kinetic energy of reactions are determined by pulling forces and then are stimulated by pushing forces. These two types of forces are analyzed and discussed separately. Based on the analysis of driving mechanisms, possible solutions to wetland N pollutions are proposed at individual, regional and global scales, respectively. Additional research needs are addressed to obtain a thorough understanding of N transport and transformations in wetlands and to reduce detrimental impacts of excessive N on such fragile ecosystems.

Optimization of C/N ratio preparation of protein-rich and multi-enzymes feed thallus through synergic fermentation of mixed distillers'grains

A new procedure of determining optimal C/N (the rate of carbon source to nitrogen source) of mixed distillers' grains for combined bacteria synergic fermentation is established. At the same time an improved method evaluating bacteria growth, called method of dry cell weighing by filtering is developed. For each combination of C and N, their initial and residual contents before and after fermentation respectively are determined. Then followed the calculation of utilization of C and N sources by the compound bacteria. The optimal C/N is finally located from among the utilization of C and N of several combinations and the weight of produced mass of oven dried thallus. The conditions of fermentation are: inoculum size 10%, temperature 30 0℃, rotational speed 170 r/min, shake culture time 48h. The best results obtained from orthogonal experiments are: maximum mass of oven dried thallus is 14 693g in a liter liquid medium, maximum utilization rate of carbon source is 98 13% and maximum utilization rate of nitrogen is 78 14%. Optimal C/N is 5 1.

Turnover and loss of nitrogenous compounds during composting of food wastes

Few people have so far explored into the research of the dynamics of various nitrogenous compounds(including water-soluble nitrogen)in composting of food wastes.This study aimed to investigate the solid-phase nitrogen,water-soluble nitrogen,nitrogen loss together with ammonia volatilization in the process of food wastes composting.A laboratory scale static aerobic reactor in the experiment was employed in the composting process of a synthetic food waste,in which sawdust was used as the litter amendment.In the experiment,oxygen was supplied by continuous forced ventilation for 15 days.The results have shown that the concentrations of total nitrogen and organic nitrogen decrease significantly in the composting process,whereasNH_(4)^(+)-N concentration increases together with little fluctuation in NO_(3)^(-)-N.After composting,the total content of the water-soluble nitrogen compounds in the compost greatly increased,the total nitrogen loss amounted to 50% of the initial nitrogen,mainly attributed to ammonia volatilization.56.7% of the total ammonia volatilization occurred in the middle and late composting of the thermophilic stage.This suggested that the control at the middle and late composting of thermophilic stage is the key to nitrogen loss in the food waste compost.

Response of aerobic sludge to AHL-mediated QS:Granulation,simultaneous nitrogen and phosphorus removal performance

The effects of different species and concentrations’signal molecules on aerobic activated sludge system were investigated through batch experiments.Results showed that the fastest NH^(+)_(4)-N oxidization rate and the most extracellular polymeric substances(EPS)secretion were obtained by adding 5 nmol/L N-hexanoyl-l-homoserine lactone(C_(6)-HSL)into the aerobic activated sludge.Further study investigated the correlation among N-acyl-homoserine lactones-mediated quorum sensing(AHLs-mediated QS),nutrient removal performances and microbial communities with the long-term addition of 5 nmol/L C_(6)-HSL.It was found that C_(6)-HSL-manipulation could enhance the stability and optimize the decontamination performance of aerobic granular sludge(AGS)system.Microbial compositions considerably shifted with long-term C_(6)-HSL-manipulation.Exogenous C_(6)-HSL-manipulation inhibited quorum quenching-related(QQ-related)activities and enhanced QS-related activities during the stable period.The proposed C_(6)-HSL-manipulation might be a potential technology to inhibit the growth of harmful bacteria in AGS,which could provide a theoretical foundation for the realization of more stable biological wastewater treatments.

Enrichment of bacteria involved in the nitrogen cycle and plant growth promotion in soil by sclerotia of rice sheath blight fungus

Rice sheath blight pathogen,Rhizoctonia solani,produces numerous sclerotia to overwinter.As a rich source of nutrients in the soil,sclerotia may lead to the change of soil microbiota.For this purpose,we amended the sclerotia of R.solani in soil and analyzed the changes in bacterial microbiota within the soil at different time points.At the phyla level,Proteobacteria,Acidobacteria,Bacteroidetes,Actinobacteria,Chloroflexi and Firmicutes showed varied abundance in the amended soil samples compared to those in the control.An increased abundance of ammonia-oxidizing bacterium(AOB)Nitrosospira and Nitrite oxidizing bacteria(NOB)i.e.,Nitrospira was observed,where the latter is reportedly involved in the nitrifier denitrification.Moreover,Thiobacillus,Gemmatimonas,Anaeromyxobacter and Geobacter,the vital players in denitrification,N2O reduction and reductive nitrogen transformation,respectively,depicted enhanced abundance in R.solani sclerotia-amended samples.Furthermore,asymbiotic nitrogen-fixing bacteria,notably,Azotobacter as well as Microvirga and Phenylobacterium with nitrogen-fixing potential also enriched in the amended samples compared to the control.Plant growth promoting bacteria,such as Kribbella,Chitinophaga and Flavisolibacter also enriched in the sclerotia-amended soil.As per our knowledge,this study is of its kind where pathogenic fungal sclerotia activated microbes with a potential role in N transformation and provided clues about the ecological functions of R.solani sclerotia on the stimulation of bacterial genera involved in different processes of N-cycle within the soil in the absence of host plants.

Coupling effects of water and nitrogen on photosynthetic characteristics,nitrogen uptake,and yield of sunflower under drip irrigation in an oasis

An experiment was conducted in an oasis area in northwest China to assess the coupling effects of water and nitrogen supply through drip irrigation on photosynthetic characteristics,nitrogen uptake,and yield of sunflower(Helianthus annuus L.),as well as the nitrate distribution in the root-zone soil.The experiment included three irrigation levels(210[W1],300[W2],and 390[W3]mm),three nitrogen levels(162[N1],232[N2],and 302[N3]kg/hm^(2)),and control treatment(no fertilization during whole growth period and only irrigated at the budding stage).A nitrogen content over-accumulation in the soil was observed under the low irrigation amount with high fertilizer supply,which cannot enhance the sunflowers’absorption of nitrogen.Excessive irrigation caused leach of the soil nitrogen,reduced nitrogen content in the root-zone soil(0-40 cm)and limited nitrogen uptake by the crop.Although low irrigation amount with high fertilizer supply can increase the nitrogen content in the soil,it cannot enhance the sunflowers’absorption of nitrogen.At the vegetative stage of sunflower growth,the accumulation of nitrogen in the organs was mainly concentrated in the leaves,while it was transferred to the flower disk at the reproductive growth stage.Reasonable coupling of water and nitrogen improved the transport of nitrogen from leaves and stems to the flower disk and promoted the formation of yield components.Six regression equations were established with irrigation and fertilization amount as independent variables,and seed rate,seed weight per flowerdisk,1000 grain weight,yield,water use efficiency and nitrogen partial factor productivity as dependent variables,respectively.Multiple regression and spatial analysis suggested that the irrigation amount of 241.62-253.35 mm and the fertilization application of 202.02-209.40 N kg/hm^(2)was a good irrigation strategy,under which all six factors exceed 75%of their maxima,and the yield of sunflower reached 3229.3 kg/hm^(2).

Effects of biochar carried microbial agent on compost quality,greenhouse gas emission and bacterial community during sheep manure composting

Although composting is a very effective way to dispose agricultural wastes,its development is greatly limited by the low compost quality and greenhouse gas emissions.At present,there is a lack of effective means to solve these two problems simultaneously.Here,the effects of three additives of compound microbial agent,biochar and biochar carried microbial agent on the composting performance,nitrogen transformation,greenhouse gas and ammonia emissions,and bacterial communities were investigated in sheep manure composting during 28 days.Results showed that biochar carried microbial agent prolonged the thermophilic stage and promoted compost maturity.At the same time,it was confirmed by the increase of the decomposition of organic nitrogen and the transformation of NH_(4)^(+)-N to NO_(3)^(−)-N.Besides,adding biochar carried microbial agent decreased CH_(4),NH_(3) and N_(2)O emissions by 65.23%,42.05%and 68.64%,respectively.The gas emissions were mainly correlated to Chloroflexi,Myxococcota,Acidobacteriota,Firmicutes,and Gemmatimonadota.Redundancy analysis showed that EC and TKN were closely related to bacterial community.Therefore,biochar carried microbial agent is recommended as an effective additive to enhance compost quality and reduce gas emissions during sheep manure composting.