Using Sterols to Detect Pig Slurry Contribution to Soil Organic Matter

Samples of pig slurry, as well as dairy and poultry manures collected in Brittany (western France) were analysed to test the ability of sterol profiles to provide a fingerprint of pig slurry contribution to soil organic matter. The data show that the 5β-stanol, known as coprostanol, is the most abundant sterol present in pig slurry, whereas this compound occurs only in minor amounts in both poultry and dairy manures. Moreover, systematic variations of (campesterol + sitosterol)/cholesterol (i.e., C₂₈₊₂₉/C₂₇) and (coprostanol + epi-coprostanol)/cholesterol (i.e., 5β/C₂₇) ratios allow to discriminate clearly pig slurry from poultry and dairy manures. The robustness of the pig slurry “sterol fingerprint” was tested by analysing the sterol profiles of soil samples from an experimental field that had received a massive pig slurry input between 10 to 14 years ago. The results indicate that the specific sterol profile of pig slurry is conservative once the slurry has been incorporated into the soil. In particular, the diagnostic 5β/C₂₇ ratio proves to be constant with time in soils having received pig slurry application, even 10 years after the end of the application. The “sterol fingerprint” of pig slurry is thus sufficiently distinctive from dairy and poultry manures, and also sufficiently time-resistant, to be of diagnostic value in determining whether a soil sample was once contaminated by pig slurry.     

Residue analysis of tetracyclines and their metabolites in eggs and in the environment by HPLC coupled with a microbiological assay and tandem mass spectrometry

Tetracyclines are widely used in farm animals. This can cause drug residues in products of animal origin and, after excretion of these substances, in animal slurry and in soil fertilized with that slurry. In this paper, we present a method based on a microbiological assay coupled with HPLC for the detection of oxytetracycline, tetracycline, and chlortetracycline in eggs. After a simple liquid extraction of the samples and HPLC separation, fractions were collected on microtiter plates, and the tetracyclines were analyzed using the Staphylococcus aureus assay. This method was able to identify residues of tetracyclines in eggs at a level set by regulatory agencies (i.e., 200 microg/kg). In addition, it was shown that the described microbiological method can be used as a screening assay for the detection of tetracyclines and possible biologically active metabolites in animal slurry and soil samples. Employing the same extraction procedure, it was demonstrated that LC-MS-MS allowed the quantification of 20-400 microg/kg in eggs with recoveries ranging from 71 to 109% and RSDs of 3-15%.     

不同有机物及其堆肥与化肥配施对小麦生长及氮素吸收的影响

采用15N示踪技术,选用水稻土和灰潮土在宜兴进行小麦盆栽试验,研究了稻草、猪粪及其堆肥与化肥配施对作物生长及氮素吸收的影响。结果表明,在水稻土和灰潮土上,不同有机物及其堆肥与化肥配施分别比单施化肥增产4.46%～24.82%和1.01%～20.53%,稻草堆肥和猪粪堆肥配施化肥处理籽粒产量分别高于稻草和猪粪直接与化肥配施处理。稻草和猪粪堆肥后更利于作物吸收氮素,增加植物体内15N累积。两种土壤上15N回收率表现为相同配比的堆肥处理未堆肥处理单施化肥处理。随着小麦生育期的推进,土壤微生物量氮和矿质态氮含量均呈下降趋势,稻草和猪粪处理的微生量氮含量始终高于稻草堆肥和猪粪堆肥处理。有机无机肥配施处理土壤矿质态氮在小麦生育前期低于单施化肥,成熟期则高于单施化肥。整个生育期中,稻草堆肥和猪粪堆肥处理土壤矿质态氮含量分别高于稻草和猪粪处理。因此,有机物堆肥后与化肥配施更有利于提高产量,促进作物对氮素的吸收利用。     

Bioaccumulation studies with <Emphasis Type="Italic">Eisenia fetida</Emphasis> using an established degradation test system

Background  

Earthworms are considered as an appropriate test system to assess the bioaccumulation potential of substances in the terrestrial environment. For regulatory purposes test methods were developed and incorporated in the validation process. A test design that is particularly suited for testing ¹⁴C-labelled substances will be described here. This design was adapted from an established degradation test system for bioaccumulation tests with earthworms in soil. The antibiotic sulfadiazine was used as test substance in this study. Due to the biological activity and the widespread entering into soil by manure application, veterinary medicines have become the target of ecotoxicological risk assessment. A German research group provided the soil samples mixed with liquid pig manure, which contained the ¹⁴C-labelled test substance after having passed through the gut of animals. This exposure pathway reflects the real environmental conditions. Therefore, sulfadiazine was tested even though a significant bioaccumulation potential was not expected to be detected owing to its chemical properties.     

Estimation of the amount of nutrients in livestock manure

(Jpn. J. Soil Sci.Plant Nutr., 77, 283–291, 2006)

Nutrient amounts in livestock manure management, including manure treatment and use, were estimated using published statistical data and other information. The eight categories for manure treatment were defined in this study as composting at facility, composting at stockyard, raw feces, dried feces, urine, slurry, purification and other. The three categories for use of manure were defined as application to farmland, sale and exchange and other.

The regional daily excretion units per head of dairy and beef cattle, including the amount of excreta, nitrogen (N), phosphorus (P) and potassium (K), were calculated based on the quantities and qualities of feed in each region. There was found to be a difference in the values for Hokkaido and other regions.

Concerning manure treatment methods in the dairy sector, the sum of the proportion of raw feces and compost at stockyard was high in Hokkaido. On the other hand, the sum of the proportion of composting at facility and dried feces was high in Hokuriku, Tokai, Kinki and Shikoku. In Kyushu, the proportion of slurry production was higher than in any other region.

The amounts of N, P, and K in compost estimated in this study were compared with those calculated from published statistics. The results were as follows. The amounts of N, P, and K in dairy cattle compost, N and K in beef cattle compost, and N in poultry compost in this study were similar to the amounts cited in reported statistics. The amounts of P in beef cattle, swine, and poultry compost in this study were lower than those cited in reported statistics.

As for the use of manure, application to farmland is the most common use of manure in the dairy and beef cattle sector. The proportions of purification, and sale and exchange were high for the swine and poultry sectors, respectively.

Large amounts of liquid manure, such as urine and slurry, are applied to farmland. To clarify the nutrient load resulting from liquid manure, the usable amount of dairy slurry was calculated based on both the standard application rate of fertilizer and the area of grassland and forage crops. As a result, the amount of usable N was lower than the amount of liquid manure N in the Kanto-Tosan, Tokai and Kinki regions.     

Effect of different pig feeding strategies on the nitrogen fertilizing value of slurry for Lolium multiflorum

The objective of this study was to evaluate the extent to which altering pig nutrition for environmental reasons could affect the N fertilizing value of slurry. This was assessed by studying the nitrification of NH₄-N and the N use efficiency of slurries obtained from growing pigs offered feeds either with commonly applied contents of crude protein (CP) and bacterially fermentable substrates (BFS) or reduced CP levels and/or elevated BFS levels. Soil/slurry mixtures were incubated for 16 weeks at 20°C using 0.2 g total slurry N addition per kg soil. In a 15 weeks lasting pot experiment with Lolium multiflorum, N derived from the same slurries was applied at two N doses with overall either 0.4 or 0.8 g total slurry N/kg soil. In the pot experiment the effect of slurry on plant growth and N uptake was compared with a mineral N fertilizer (NH₄NO₃) treatment and a non-fertilized control. Slurries obtained from pigs fed at reduced CP content had lower pH, total N content and proportion of NH₄-N than slurries obtained from pigs fed at higher CP. Accordingly incubation of soil/slurry mixtures using slurries obtained from low CP feeds resulted in lower NO₃-N concentration in the soil. Furthermore, a lower proportion of the added NH₄-N was nitrified in treatments involving slurries derived from low CP feeds. Modifying the BFS content in feeds had minor effects both on slurry characteristics and on slurry NH₄-N nitrification in soil. Although reduced CP and, to a lesser extent, elevated BFS altered the N release pattern to plants, slurry N use efficiency during the four cuts following the first fertilization ranged at a similar level of 32 to 33% for all types of slurry. This apparent use was significantly lower than that of the mineral N fertilizer which amounted to 72 to 75% of the added N. Nitrogen balance showed that less than 22% of the added mineral N fertilizer was lost from the soil/plant systems while from 32 to 47% of the N added with the slurries was lost independently of the type of slurry. So overall N utilization by crop and rate of slurry N recovery did not significantly differ which indicates that the investigated modifications of pig feeding appear to have no short term negative effect on the N fertilizing value of slurries.     

Comparison of Chemical Methods of Assessing Potentially Available Organic Nitrogen from Organic Residues Applied to a Sandy Soil

Abstract

More than 90% of the nitrogen (N) in soils is bond as organic N compounds. The available N can be estimated on the mineral N released during time‐consuming incubations of soil. Several chemical methods have been developed as substitutes for incubations. On the other hand, there has been an increase in waste production. Residues could potentially offset the need for mineral fertilizers, being both an economic and environmental benefit. Thus, the development of a routine method for prediction of N supply both from soil organic matter (SOM) and the application of organic residues is of great interest. An incubation experiment was performed in a Cambic Arenosol to evaluate different chemical methods. Air‐dried soil was mixed with increasing amounts of composted solid municipal waste, secondary pulp‐mill sludge, hornmeal, poultry manure, the solid phase from pig slurry, and composted pig manure. Samples were incubated for 244 days under a controlled environment. Among the chemical extractants studied, hot 2 M potassium chloride (KCl) and hot 0.01 M calcium chloride (CaCl₂) showed promise in indicating values of N₀ (potentially available nitrogen), and these simple methods are suitable for use in routine laboratory conditions.     

典型粪污处理模式下规模养猪场农牧结合规模配置研究Ⅰ.固液分离 液体厌氧发酵模式

不同粪污处理模式下畜禽粪便的养分损失存在较大差异,从而影响其后续地农田利用。固液分离-液体厌氧发酵模式是当前我国畜禽粪污处理的主要模式之一。研究粪污固液分离-液体厌氧发酵处理模式下规模养猪场农牧结合适宜规模配置对于减少畜禽粪便污染、促进畜牧业可持续发展具有重要意义。本研究根据猪群体结构比例、废弃物产生量及氮磷含量、废弃物处理利用过程中养分损失率以及作物氮磷钾需求量等资料,以存栏万头猪场为例,采用分步逐级计算的方法估算了典型粪便处理模式——固液分离-液体厌氧发酵下,规模养猪场废弃物完全消纳的不同种植模式农田匹配面积,并研究了基于作物养分需求的不同种植模式农田畜禽粪便承载量。结果表明:固液分离-液体厌氧发酵粪便处理模式,以沼液安全消纳为目标,万头猪场需要配置的最少农田面积分别为粮油作物地12.4~13.7 hm2,或茄果类蔬菜地14.2~17.9 hm2,或果树苗木地16.4~51.3 hm2。以有机肥和沼液全部在农田安全消纳为目标,万头猪场需要配置的最少农田面积分别为粮油作物地299.3~312.9 hm2,或茄果类蔬菜地145.1~179.0 hm2,或果树苗木地553.1~1 343.8 hm2。因此,规模养猪场应根据猪养殖数量及其周边农田面积,选择适宜的有机肥利用方式及种植作物类型,因地制宜,合理调控。     

Impact on C and N dynamics of simultaneous application of pig slurry and wheat straw, as affected by their initial locations in soil

The joint management of animal manures and plant biomass as straw on agricultural soils may be a viable option for reducing the environmental impacts associated with livestock production and recycling nutrients efficiently. To investigate this option, an incubation in controlled conditions examined how the simultaneous addition of ¹⁵N-labeled pig slurry and ¹³C-labeled wheat straw, either on the soil surface or incorporated into the soil, affected the mineralization of C from the organic materials and the soil N dynamics. Samples from a typic hapludalf were incubated for 95 days at 25°C with eight treatments: unamended soil (S), wheat straw left on the soil surface (Ws), wheat straw incorporated in the soil (Wi), pig slurry on the soil surface (Ps), pig slurry incorporated in the soil (Pi) and three combinations of the two amendments: Pi?+?Ws, Pi?+?Wi, and Ws?+?Ps. Carbon dioxide and ¹³CO₂ emissions and soil N content were measured throughout the incubation. Pig slurry stimulated the decomposition of straw C only when wheat straw and pig slurry were left together on the soil surface. Incorporation of both wheat straw and pig slurry did not modify straw C mineralization when compared to straw incorporation alone but this promoted a higher rate of N immobilization. The results suggest that when pig slurry is used in field under no-till conditions, the best strategy to preserve environmental quality with regard to CO₂ emissions would be to apply pig slurry underneath the crop residues.     

Dynamics and Model Fitting of Nitrogen Transformations in Pig Slurry Amended Soils

Abstract

To optimize the efficient use of nutrients in pig slurry by crops and to reduce the pollution risks to surface and groundwater, a full knowledge of the fate of nitrogen (N) in amended soils is needed. A 120 day laboratory incubation experiment was conducted to study the effects of pig slurry application on soil N transformations. Pig slurry was added at the rates of 50 and 100 g kg^?1. A nonamended soil was used as a control treatment. Soil samples were taken after 0, 7, 14, 30, 45, 60, and 120 days of incubation and analyzed for NH₄ ⁺‐N and NO₃ ^?‐N. Initially, the application of pig slurry produced significant increases in NH₄ ⁺‐N, especially at the highest application rate, whereas NO₃ ^?‐N content was not affected. Nitrification processes were active during the entire incubation time in the three treatments. In the control soil, the net N mineralization rate was highest during the 1st week (5.7 mg kg^?1 d^?1), followed by a low‐steady phase. Initially, net N mineralization rate was slower in soil with the lowest slurry rate (2.7 mg kg^?1 d^?1), whereas in the treatment with the highest slurry rate, a net N immobilization was observed during the 1st week (4.8 mg kg^?1 d^?1). Mineral‐N concentrations after 120 days were 180, 310, and 475 mg kg^?1 in soils amended with 0, 50, and 100 g kg^?1 of pig slurry, respectively. However, when results were expressed as net mineralized N, the opposite trend was observed: 74, 65, and 44 mg kg^?1. Of the six kinetic models tested to describe the mineralization process, a two‐component, first exponential model (double model) offered the best results for all treatments.     

Relationship between N immobilization and volatile fatty acids in soil after application of pig and cattle slurry

Summary A laboratory study was performed to determine decomposition of fatty acids and mineralization of C and N from slurries in soil. Fatty acids present in slurries decomposed within 1–2 days at 25°C in soil. Parallel to the fatty acid decomposition, immobilization of N was measured in soil. The correlation between the initial fatty acid concentrations in the slurries and the amounts of N immobilized were found to be highly significant (R ²=0.97). It was concluded that fatty acids act as an easily decomposable C source for microorganisms and cause immobilization of N. Immobilization of N was followed by a curvilinear mineralization of N in all slurrytreated soils. Despite mineralization, only fresh pig slurry and anaerobically digested pig slurry showed a net release of N over 70 days whereas cattle slurry and anaerobically fermented pig slurry did not. The percentage of slurry C evolved during 70 days was fresh pig slurry, 65%; anaerobically fermented pig slurry, 48%; anaerobically digested pig slurry, 45%; and anaerobically fermented cattle slurry, 42%.     

Differences in the chemical composition of dissolved organic matter from waste material of different sources

The chemical composition of waste-material-derived dissolved organic matter (DOM) was characterized by chemolytic analyses and ¹H, ¹³C and ³¹P nuclear magnetic resonance (NMR) spectroscopy. Dissolved organic matter was extracted by water from an aerobic fermented urban waste compost, a sewage sludge and a pig slurry and then fractionated using the XAD-8 method. The amount of water-extractable dissolved organic carbon (DOC) ranged from 3% in the sewage sludge to 22% in the pig slurry. Dissolved organic matter isolated from pig slurry was equally distributed between hydrophilic and hydrophobic DOC, whereas in the sewage-sludge-derived material the hydrophobic fraction was predominant. Dissolved organic C from the urban waste compost was mainly within the hydrophilic fraction. Wet-chemical analysis and ¹H- and ¹³C-NMR spectra showed that both DOM fractions from the urban waste compost were low in neutral, acidic and amino sugars as well as in lignin-derived compounds. In turn, the materials were rich in low-molecular-weight aliphatic compounds. The chemical structure of both fractions is probably the result of the intensive transformation of urban waste compost during its fermentation. The hydrophilic fractions of DOM from sewage sludge and pig slurry contained considerable amounts of carbohydrates but were also rich in low-molecular-weight aliphatics. The respective hydrophobic fractions had the largest contents of CuO-extractable phenols which may in part derive from sources other than lignin. By contrast with the other materials, the hydrophobic fraction from the pig slurry seemed to contain polymeric rather than low-molecular-weight material. The ³¹P-NMR spectrum of the hydrophilic DOM fraction from urban waste compost did not show signals of inorganic or organic P compounds while the spectrum of the hydrophobic fraction revealed traces of monoester P, diester P, and orthophosphate. ³¹P-NMR spectroscopy suggested that both the hydrophobic and hydrophilic fractions from pig slurry did not contain organic P. The hydrophilic DOM fraction from sewage sludge contained orthophosphate, organic monoester P and a little pyrophosphate. The hydrophobic fraction contained mainly organic diester P and smaller amounts of teichoic acids and organic monoester P. Considering that water-soluble fractions of urban waste compost contained no easily plant-available P and a low content of labile organics, we conclude that this material contains less labile nutrients and is more refractory than the soluble constituents of pig slurry and sewage sludge.     

Effects of tetracycline on the soil microflora: function,diversity, resistance

Background  Tetracycline is a widely used antibiotic in animal production. Significant amounts of the substance reach the soil via feces, urine and manure application. As tetracycline is a persistent compound with antibacterial activity, its presence in soil may have undesired direct and indirect effects. These have been investigated so far focusing on effects on selected microbial functions. Objectives  The aim of the present study was to obtain comprehensive information on potential effects of tetracycline on the soil microflora under environmentally relevant conditions. The investigations included function and structure of the microbial biocoenosis and the distribution of resistance genes. Methods  Pig manure rich in tetracycline resistance genes was applied to a sandy soil. This soil as well as an unamended soil were additionally treated with several concentrations of tetracycline. The spiked soils were incubated in outdoor lysimeters for several months. Substrate induced respiration, PLFAs, ten selected resistance genes, and the concentrations of tetracycline were determined. Results  The test concentrations, though far exceeding environmental relevance, caused only small effects. An establishment of resistance could not be detected. Applied resistance genes were not detectable at the end of the study even in the presence of added tetracycline. Conclusion  Due to the high sorption capacity of the antibiotic, environmentally relevant concentrations of tetracycline do not seem to cause undesired effects on the soil microflora.     

光催化降解沼液中四环素类抗生素效果及反应动力学研究

该文采用光催化降解途径探究沼液中四环素类抗生素降解的最佳光源、pH值以及光催化对不同初始质量浓度抗生素的降解效果,同时进行不同初始浓度、pH值条件下抗生素光催化降解动力学研究。结果表明:不同光源对四环素类抗生素的降解效果为:高压汞灯紫外消毒灯长弧氙灯无光。高压汞灯催化2 h后,四环素、土霉素、金霉素的降解率分别达到91.68%、85.58%、81.18%。四环素类抗生素的初始质量浓度越低,光催化效果越好。四环素、土霉素、金霉素初始质量浓度为5 mg/L时,其降解率最高可达94.80%、88.35%和95.39%,沼液初始pH值对四环素、金霉素的降解率影响存在显著性差异(P0.05)。当pH值为6时,四环素的降解率最大为96.16%,反应速率常数为1.5971h-1,半衰期为0.355 3 h;当pH值为10时,金霉素的降解率最大为90.47%,反应速率常数为1.084 4 h-1,半衰期为0.338 3 h。沼液初始pH值对土霉素的降解率影响无显著差异(P0.05)。当pH值为10时,3种抗生素的平均降解率最大为89.88%。采用高压汞灯在沼液初始pH值为10时,催化降解5 mg/L四环素类抗生素效果最佳。     

添加不同基质对含四环素土壤玉米幼苗生理特性的影响

为探究兽用四环素对玉米幼苗生理特性的影响,通过玉米盆栽试验,研究四环素外源污染胁迫下施用不同基质(单施蚯蚓粪、菌糠、菌剂、生物炭及其与菌剂配施)对玉米生长的影响。结果表明,四环素对玉米生物量有明显的抑制作用,其中对根长的抑制作用显著大于株高,而添加不同基质均能缓解四环素对玉米株高和根长的抑制作用,且JK和JJ处理效果最显著,升幅分别为17.29%和30.08%;四环素显著诱导玉米SOD活性上升,升幅为3.34%,抑制CAT和POD活性,降幅分别为10.98%和46.68%,添加不同基质处理中,QY处理对促进抗氧化酶系统平衡的效果最显著;四环素会增加玉米脯氨酸、丙二醛、可溶性糖、可溶性蛋白及总黄酮含量,添加不同基质处理中,对其减少效果最显著的依次为JK、JJ、QY、S和JK处理,降幅分别为29.09%,50.88%,42.01%,50.23%和35.79%;相关性分析表明,脯氨酸、丙二醛均与可溶性蛋白和总黄酮呈极显著正相关,POD活性与可溶性糖、丙二醛与总黄酮相关性最强。综上所述,添加不同基质可有效缓解四环素对玉米幼苗的毒害作用,总趋势为JK(菌糠)、JJ(菌糠+菌剂)和QY(蚯蚓粪)处理效果较好。通过此研究,可筛选有效减少四环素对植物生长影响的基质及其施用方式,可为四环素对植物生理毒性的研究提供参考,也可为抗生素对植物的风险评价提供科学依据。     

NH3 and N2O Emissions after Landspreading of Slurry as Influenced by Application Technique and Dry Matter-Reduction. I. NH3 Emissions

Ammonia volatilization from slurry is undesirable because of environmental N eutrophication and loss of fertilizer value. The dry matter content of slurry, the application technique and the weather conditions are the main factors influencing NH₃ losses from landspread slurry. In a field of winter wheat a two factor plot experiment was conducted to study single and combined effects of slurry separation and application techniques, including broadcast and banded application, as well as incorporation by injection and the flexible harrow. Ammonia volatilization from all treatments could be measured simultaneously, and at ambient climatic conditions by an indirect, open measurement technique. The experiment was repeated four times. Due to varying weather conditions and treatment effects, cumulative NH₃ volatilization from the slurry during the first 48 hours ranged from 4 to 90% of total ammoniacal nitrogen (TAN). Both separation and incorporation significantly decreased NH₃ losses, but only the combination of dry matter reduction and injection or harrowing reduced NH₃ volatilization to about 30% of TAN in all weather conditions. Banding alone did not efficiently conserve slurry N, but even enhanced NH₃ volatilization in wet conditions.     

Effects of yak excreta on soil organic carbon mineralization and microbial communities in alpine wetlands of southwest of China

Purpose

Improving knowledge of how soil organic carbon (SOC) mineralization responds to excreta application is essential to better understand whether wetland carbon (C) pools will react to grazing. We investigated microbial activity and community structure in the different treatments of excreta addition experiments to examine how soil C mineralization responds to the excreta input in terms of microbial activities and compositions in wetland soils.

Materials and methods

The microcosms of mineralization incubation of excreta addition were established. The structure of the microbial community was described by the fatty acid composition of the phospholipids (PLFA). The methylumbelliferyl-linked substrates (MUB) and l-dihydroxyphenylalanine (L-DOPA) substrates were used to investigate the activities of β-glucosidase (BG), N-acetyl-glucosaminidase (NAG), acid phosphatase (AP), cellobiohydrolase (CBH), and phenol oxidase (PO).

Results and discussion

Excreta addition altered the cumulative C mineralization in swamp meadow (SM) and peatland (PL) soils, but SM was lower than PL. Excreta addition increased the biomass of individual PLFA and the fungi/bacteria ratio, suggesting that microbes are stimulated by nutrients and that the soil microbial community composition is modified by excreta inputs. The hydrolytic enzyme activities were higher in the PL soils than in the SM soils, but the trend was opposite for PO activity. The changes in pH, fungi, actinomycetes (ACT), AP, and CBH after yak fecal input significantly influenced the soil CO₂ efflux. Our findings suggest that yak grazing could influence the rate of C cycling in wetland soils by influencing microbial communities, enzyme activities, and soil pH.

Conclusions

This study suggest that the yak excreta addition increased cumulative C mineralization in SM and PL soils, and the effect of dung addition was more significant than urine addition. The effect of yak excreta addition on SOC mineralization was related with the soil pH, microorganism structure, and enzyme activity which modified by the excreta addition. Soil pH, fungi, AP, and CBH were positively correlated with SOC mineralization, but ACT was negatively correlated with SOC mineralization. In addition, the changes in C and N sources with yak excreta addition play an important role in altering microbial enzyme activities. The input of yak feces into wetlands because of grazing could increase SOC mineralization and thereby promote C emission.

     

Injection of pig slurry and its effects on dynamics of nitrogen and carbon in a loamy soil unter laboratory conditions

Dynamics of nitrogen (N) and carbon (C) were investigated in a loamy soil amended or injected with pig slurry. Treatments were with or without acetylene C₂H₂ (which is assumed to inhibit reduction of nitrous oxide (N₂O) to dinitrogen (N₂), and soil cores were conditioned for 15 days at 25°C while pH, production of CO₂ and N₂O, ammonia (NH₃) emission and (nitrate) (NO₃ ^–) and (ammonium) (NH₄ ⁺) concentrations were monitored. There was no significant difference in CO₂ production between the injected and surface applied pig slurry treatments, and within 15 days ca. 5% of the C applied had been mineralized, if no priming effect was assumed. Neither the production of N₂O nor the total gaseous production of the denitrification process (N₂O plus N₂) were affected by the way the pig slurry was added to the soil. NH₃ volatilization, however, decreased by 90% when pig slurry was injected. The addition of C₂H₂ significantly increased the CO₂ production and the concentration of NH₄ ⁺, but significantly decreased the concentration of NO₃ ^–. It was concluded that the injection of pig slurry to a dry soil was an acceptable alternative to its application to the soil surface, as not only was NH₃ volatilization reduced, but the production of N₂O and N₂ through denitrification was not stimulated. It is also suggested that the composition of the organic C fraction in the pig slurry, most likely the concentration of fatty acids, had an important effect on the dynamics of N and C in the soil. Received: 12 May 1997     

Effect of Manure Application Rate and Rainfall Timing on the Leaching of Antibiotic-Resistant Bacteria and Their Associated Genes

In this study, we investigate the effect of application rate and timing of liquid swine slurry on leaching of antibiotic-resistant bacteria (ARB) and their antibiotic resistance genes (ARGs) through soil columns. Swine slurry was added to laboratory soil columns at rates of 5000 or 30,000 gal ac^?1. For both application rates, rainfall was applied at either 1, 7, or 21 days after slurry application. Column effluent and the top centimeter of soil in the columns were sampled post-rainfall for cultivable bacteria and quantitative PCR was used to quantify tetracycline, methicillin, β-lactam, and erythromycin resistance genetic determinants. We also conducted similar experiments using swine lagoon slurry spiked with antibiotic-resistant E. coli and Salmonella. We found that the concentration of ARB and ARG recovered in the column effluent following application of the swine lagoon slurry generally decreased with increasing lag time between slurry application and simulated rainfall, though most of these decreases were not statistically significant. Moreover, no statistically significant differences in CFU or GU concentration in the column leachate were observed between the low and high slurry application rates. In the experiments using swine slurry spiked with E. coli and Salmonella, concentrations of both microorganisms eluted from fine sand columns were affected by both slurry application rate and lag time; recovery of ARGs, however, was mostly unaffected, but some differences were observed. In columns packed with loamy sand, no recovery was detected in the column effluent for either organism and recovery of ARG was unaffected by manure application rate or rainfall lag time.     

Changes in microbial biomass and microbial activity of pig slurry after the transit through the gut of the earthworm Eudrilus eugeniae (Kinberg, 1867)

Here we studied the effects of gut transit through the earthworm Eudrilus eugeniae, on the physicochemical, biochemical, and microbial characteristics of pig slurry, by analyzing fresh casts. The reduction in the dissolved organic C contents in casts we recorded suggests that during digestion, earthworms assimilated labile organic C preferentially, which is a limiting growth factor for them. Furthermore, both microbial biomass and activity in pig slurry were significantly decreased by earthworm gut transit. It appears that E. eugeniae is able to digest microorganisms, although the addition of glucose to the food increased respiration, indicating that growth of microorganisms in casts could be limited by depletion of labile C. Despite reduced microbial biomass and activity, the metabolic diversity of microbial communities was greater in casts than in original pig slurry. Community level physiological profiles obtained from Biolog Ecoplate data revealed that, after earthworm gut transit, the microbial communities in casts and pig slurry were clearly differentiated by their physiological profiles. The results indicate that first stage in vermicomposting of pig slurry by E. eugeniae, i.e., casting, produced changes that will influence the dynamics of the organic matter degradation by reducing forms of N and C available to microorganisms, hence restricting their growth and multiplication. Nevertheless, the reduced microflora of casts was characterized by an increased catabolic potential that might lead to thorough degradation of pig slurry.