Swine Manure Application Research Articles

Animal manures application increases the abundances of antibiotic resistance genes in soil-lettuce system associated with shared bacterial distributions

An increasing amount of animal manures is being used in agriculture, and the effect of animal manures application on the abundance of antibiotics resistance genes (ARGs) in soil-plant system has attracted widespread attention. However, the impacts of animal manures application on the various types of bacterial distribution that occur in soil-lettuce system are unclear. To address this topic, the effects of poultry manure, swine manure or chemical fertilizer application on ARG abundance and the distribution of shared bacteria were investigated in this study. In a lettuce pot experiment, 13 ARGs and 2 MGEs were quantified by qPCR, and bacterial communities in the soil, lettuce endosphere and lettuce phyllosphere were analysed by 16S rRNA sequence analysis. The results showed that the application of poultry or swine manure significantly increased ARG abundance in the soil, a result attributed mainly to increases in the abundances of tetG and tetC. The application of poultry manure, swine manure and chemical fertilizer significantly increased ARG abundance in the lettuce endosphere, and tetG abundance was significantly increased in the poultry and swine manure groups. However, animal manures application did not significantly increase ARG abundance in the lettuce phyllosphere. Flavobacteriaceae, Sphingomonadaceae and 11 other bacterial families were the shared bacteria in the soil, lettuce endosphere, and phyllosphere. The Streptomycetaceae and Methylobacteriaceae were significantly positively correlated with intI1 in both the soil and endosphere. Chemical fertilizer application increased both the proportions of Sphingomonadaceae and tetX abundance, which were positively correlated in the endosphere. Comamonadaceae and Flavobacteriaceae were not detected in the lettuce endosphere under swine manure application. Cu was related to Flavobacteriaceae in the lettuce endosphere. Overall, poultry and swine manure application significantly increased ARG abundance in the soil-lettuce system, which might be due to the shared bacterial distribution.

Occurrence of microplastic in livestock and poultry manure in South China.

Microplastic (MP) contamination in soil has attracted much attention, and increasing evidence suggests that MPs can accumulate in agricultural soils through fertilization by compost. In addition, the most common raw materials for composting are livestock and poultry manure wastes. Because the presence of MPs may threaten the safe utilization of fertilizers composted by livestock and poultry wastes during crop planting, it is necessary to understand the contamination risk of MPs present in livestock and poultry manure. In this study, the distribution of MPs in 19 livestock and poultry farms with 3 different species was investigated by using FTIR microscopy. A total of 115 items manure MPs and 18 items feed MPs were identified as PP and PE types dominated by colorful fragments and fibers. Furthermore, after comparing the compositions of plastic products used in the feeding process, we proposed two transport pathways for MP pollution in manure and one potential transport pathway in feeds. Our result proved that the application of swine and poultry manure directly could be a new route of MPs in agricultural soil, furthermore, the presence of MPs could threaten the safety of resource utilization in agricultural soil by using swine and poultry manure for manure potentially. Not, only that, our study also provided a reference for the remediation of MP-contaminated soil.

Thermal stability of soil organic carbon after long-term manure application across land uses and tillage systems in an oxisol

The pool of carbon (C) present in soil systems is larger than the amount of organic C stored in living biomass and the atmosphere. Soil degradation has increased soil C emissions at the expense of C accumulation. Climate-smart management practices may be adapted to increase C sequestration as soil organic carbon (SOC). To avoid the SOC loss, different strategies have been applied, including no-tillage and organic fertilizer. Here, we investigated thermal stability of SOC after long-term manure application across land uses and tillage systems in weathered soils of Brazil. We chose five commercial areas with different land uses: pasture with swine manure (SM) application (PA + SM), conventional tillage (CT) with SM application (CT + SM), natural vegetation (NV), no-tillage with SM application (NT + SM), and no-tillage (NT). Thermal analysis revealed that SOC oxidation and CO2 emission started around 240 °C, close to gibbsite and goethite structural collapse, suggesting preferential adsorption of SOC onto these minerals. Approximately 50% of SOC for all sites was oxidizable at lower temperature (~315 °C) which suggests the prevalence of polysaccharides, decarboxylation of acidic groups and dehydration of hydroxylate aliphatic structures, regardless of land-use. The energy content of SOC for NV (6.5) and PA + SM (10.6) were in average, 46% lower than other treatments which suggest a higher necromass contribution to SOC in these systems. However, the higher energy content in CT + SM (14.9), NT + SM (16.5), and NT (15.8), suggests a higher contribution of plant-derived compounds in SOC. Our results showed that SM application on pastureland reached similar SOC accumulation to NV and increment of ~33% when applied to no-till system. We conclude that SM could a drive higher C accumulation and stabilization if preferentially associated to soil conservative system.

Soil nutrient distribution on cattle farms in three physiographic regions of North Carolina

AbstractBeef cattle production systems are sometimes considered a source of nutrient enrichment due to alteration of botanical composition and excretion of nutrients in isolated zones of pastures. However, research on environmental effects from livestock grazing in the eastern United States has been scant. We conducted an intensive soil sampling campaign on six private farms in three physiographic regions of North Carolina to determine the impacts of landscape features, pasture management, and animal behavior on a suite of soil nutrients. Total and particulate organic C and soil‐test biological activity (STBA) increased with increasing elevation due to edaphic and climate factors. Within farms, fields with different management illustrated that: (a) swine and poultry manure application can favorably enrich soil with infrequent application, but lead to excessive soil‐test P and K with repeated application; (b) positive impacts on total and particulate organic C and STBA occur with grazed perennial forages compared with annual forages and previous cropping; and (c) enrichment of total and particulate organic C and STBA occurs with winter hay feeding, but excessive nutrient accumulation can occur if fed in the same location repeatedly. Aggregated enrichment of soil organic C, STBA, and soil‐test P and K occurred on 30% of fields near drinking water tanks, shade sources, gates, and hay feeding stations. Improved grazing management with rotational stocking and more year‐round grazing helped to minimize occurrence and magnitude of nutrient enrichment zones. We conclude that improved grazing management systems can have positive impacts on the environment, and likely on farm livelihoods.

Growth components and chemical composition of some improved dual-purpose cowpea (Vigna unguiculata L. Walp) varieties as influenced by manure application

Field experiment was conducted to determine the effect of swine manure application on the growth components and chemical composition of nine varieties of improved dual-purpose cowpea (Vigna unguiculata L. Walp). The experiment was laid out as a 2 x 9 factorial design with two levels of manure application (0kg ha-1 and 5kg ha-1) and nine varieties of improved dual-purpose cowpea at three replicates. Agronomy parameters and dry matter yield of the cowpea were determined six weeks after sowing. Results showed that unfertilized variety IT- 332 recorded highest leaf proportion (57.27) above others. Varieties IT-193 with manure (80.00 cm) and IT-297 without manure (30) recorded significantly higher (P<0.05) values for plant height and leaf number respectively. Dry matter yield of cowpea ranged significantly higher (P<0.05) from 7.20 t ha-1 in variety IT-817 without manure to 14.85 t ha-1 in variety IT-321 with manure. The average crude protein content of improved cowpea varieties ranged significantly (P < 0.05) from 97.69 g kg-1 dry matter in unfertilized IT-817 and IT-834 to 141.17 g kg-1 dry matter in fertilized IT-819. The study showed that application of swine manure into cowpea increased the dry matter yield and chemical composition which is necessary to provide sufficient feed for ruminants that can be used as a supplement during the dry season.

Response of two Brachiaria species to swine manure application rates: effect on biomass yield, nutritive quality and acceptability by WAD sheep

Rising inorganic fertilizer prices have led to return to the use of organic nutrient sources to reduce cost and improve pasture productivity. The present study determined the response of Brachiaria ruziziensis and Brachiaria mulato II to swine manure application rates: effect on biomass yield, nutritive quality and acceptability by WAD sheep. The experiment was a 3 × 2 factorial arrangement laid out as a split-plot design with three swine manure application -1rates (0, 5, 10 t ha ) as the main plot and two Brachiaria species (B. ruziziensis and B. mulato II) as the sub-plot replicated three times. Growth parameters were determined at 2, 4, 6 and 8 weeks after sowing, while dry matter yield was determined at 8 weeks after sowing. Chemical composition and in vitro gas production of the harvested grass samples were conducted and the acceptability of the forage material by WAD sheep was also determined. Results showed that B. ruziziensis was morphologically taller than B. mulato II at all weeks of growth. The heights of the plants significantly (P < 0.05) increased with increasing manure application rate at all weeks of growth. A significantly (P < 0.05) higher dry matter yield was recorded for -1B. ruziziensis than in B. mulato (6.24 vs. 4.16 t ha ). Dry matter yield of the plants increased as the rate of manure application increased. The crude protein content of both grasses increased significantly (P<0.05) as the level of manure inclusion increased. The highest significant (P<0.05) (14.00 ml/200mg DM) gas volume produced was recorded for B. -1ruziziensis fertilized with 10 t ha of manure while the least gas volume (7.50 ml/200mg DM) was recorded for B. mulato unfertilized at 24 hours of incubation. Brachiaria ruziziensis -1fertilized with 5 t ha of swine manure was most preferred by the sheep. In conclusion, herbage yield increased as the swine manure application rate increased, also chemical composition and acceptability by sheep was higher in B. ruzuziensis than with B. mulato II.

Sulfadiazine dissipation as a function of soil bacterial diversity.

Antibiotic residues in the environment are concerning since results in dispersion of resistance genes. Their degradation is often closely related to microbial metabolism. However, the impacts of soil bacterial community on sulfadiazine (SDZ) dissipation remains unclear, mainly in tropical soils. Our main goals were to evaluate effects of long-term swine manure application on soil bacterial structure as well as effects of soil microbial diversity depletion on SDZ dissipation, using "extinction dilution approach" and 14C-SDZ. Manure application affected several soil attributes, such as pH, organic carbon (OC), and macronutrient contents as well as bacterial community structure and diversity. Even minor bacterial diversity depletion impacted SDZ mineralization and non-extractible residue (NER) formation rates, but NER recovered along 42d likely due to soil diversity recovery. However, this period may be enough to spread resistance genes into the environment. Surprisingly, the non-manured natural soil (NS-S1) showed faster SDZ dissipation rate (DT90=2.0 versus 21d) and had a great number of bacterial families involved in major SDZ dissipation pathways (mineralization and mainly NER), such as Isosphaeraceae, Ktedonobacteraceae, Acidobacteriaceae_(Subgroup_1), Micromonosporaceae, and Sphingobacteriaceae. This result is unique and contrasts our hypothesis that long-term manured soils would present adaptive advantages and, consequently, have higher SDZ dissipation rates. The literature suggests instantaneous chemical degradation of SDZ in acidic soils responsible to the fast formation of NER. Our results show that if chemical degradation happens, it is soon followed by microbial metabolism (biodegradation) performed by a pool of bacteria and the newly formed metabolites should favors NER formation since SDZ presented low sorption. It also showed that SDZ mineralization is a low redundancy function.

Simulated Winter Incubation of Soil With Swine Manure Differentially Affects Multiple Antimicrobial Resistance Elements.

Gastrointestinal bacteria that harbor antibiotic resistance genes (ARG) become enriched with antibiotic use. Livestock manure application to cropland for soil fertility presents a concern that ARG and bacteria may proliferate and be transported in the environment. In the United States, manure applications typically occur during autumn with slow mineralization until spring planting season. A laboratory soil incubation study was conducted mimicking autumn swine manure application to soils with concentrations of selected ARG monitored during simulated 120-day winter incubation with multiple freeze-thaw events. Additionally, the effects of two soil moistures [10 and 30% water holding capacity (WHC)] and two manure treatments [raw versus hydrated lime alkaline stabilization (HLAS)] were assessed. Fourteen tetracycline resistance genes were evaluated; tet(D), tet(G), and tet(L) were detected in background soil while swine manure contained tet(A), tet(B), tet(C), tet(G), tet(M), tet(O), tet(Q), and tet(X). By day 120, the manure-borne tet(M) and tet(O) were still detected while tet(C), tet(D), tet(L), and tet(X) genes were detected less frequently. Other tet resistance genes were detected rarely, if at all. The sum of unique tet resistance genes among all treatments decreased during the incubation from an average of 8.9 to 3.8 unique tet resistance genes. Four resistance elements, intI1, blactx–m–32, sul(I), erm(B), and 16s rRNA genes were measured using quantitative PCR. ARG abundances relative to 16S abundance were initially greater in the raw manure compared to background soil (−1.53 to −3.92 log abundance in manure; −4.02 to <−6.7 log abundance in soil). In the mixed manure/soil, relative abundance of the four resistance elements decreased (0.87 to 1.94 log abundance) during the incubation largely because 16S rRNA genes increased by 1.21 log abundance. Throughout the incubation, the abundance of intI1, blactx–m–32, sul(I), and erm(B) per gram in soil amended with HLAS-treated manure was lower than in soil amended with raw manure. Under low initial soil moisture conditions, HLAS treatment reduced the abundance of intI1 and resulted in loss of blactx–m–32, sul(I), and erm(B)] compared to other treatment-moisture combinations. Although one might expect antibiotic resistance to be relatively unchanged after simulated winter manure application to soil, a variety of changes in diversity and relative abundance can be expected.

Agronomic and productivity efficiency of two animal manure sources on intercropped maize-groundnut in the derived savannah

Abstract Two animal manure sources (swine and sheep / goat manures) each at 5 Mt·ha−1, were applied in mono- and intercropped maize (Zea mays L.) and groundnut (Arachis hypogea L.). A general control (no manure treatment of the component crops was established) for productivity assessment. The trial, conducted at the Federal College of Agriculture, Ishiagu (04º 30′ N, 06º 45′ E, 150 m above sea level), in the derived savannah plains, Ishiagu, Nigeria in 2012 and 2013 mid-cropping seasons used a randomised complete block design with three replications. It assessed the agronomic performance, cropping system (CS) and plant nutrient (PN) productivity of maize-groundnut in mono-and intercrop as influenced by two animal manure sources. The two-year combined analysis indicated that animal manure sources significantly (P &lt; 0.05) increased growth and yield components of the crop species in the systems. Swine manure application gave the significantly (P &lt; 0.05) highest maize grain yield in both mono- and intercropped strategies in contrast to sheep / goat manure that had the highest grain yield in both cropping strategies in groundnut. The biological and economic productivity indices of the cropping system (CS) and plant nutrient (PN) indicated that the application of sheep / goat manure in the maize / groundnut mixture exhibited greater intercrop advantage whose total CS and PN land equivalent ratios (LERs) were higher by 4.79% and 13.57%, respectively, relative to swine manure application. Therefore, the application of animal manure demands encouragement in maize-groundnut intercrop, especially sheep / goat manure as it enhances crop yield, food security and protein intake of people living in Sub-Saharan Africa practicing different strokes of farming system technology. The results of this study showed that intercropping system exhibited positive growth, yield, biological and economic advantages over monocropping of the component species. The study further indicated that intercropped maize / groundnut that received sheep / goat manure exhibited the highest cropping system and plant nutrient yield advantage and agronomic efficiency compared to swine manure alone under the same environment.

Microbial community composition and antimicrobial resistance in agricultural soils fertilized with livestock manure from conventional farming in Northern Italy

Antimicrobials are commonly used in conventional livestock production and manure is widely applied to agricultural lands as fertilizer. This practice raises questions regarding the effects of fertilization on (i) soil microbiota composition and (ii) spread of antimicrobials and antimicrobial resistance (AMR) in the environment. This study was conducted in a high-density farming area of Northern Italy and aimed at assessing the impact of (dairy cattle, chickens and swine) manure application on soil microbiome, antimicrobial concentrations and antimicrobial resistance gene (ARG) abundance. We found the microbial community composition in manure to be different and less diverse than in soil, with manure application altering only marginally the soil microbiome. Exceptions were the phyla Firmicutes, Tenericutes and Cloacimonetes, which significantly enriched in fertilized soil. Of the antimicrobials investigated, only flumequine concentrations increased after manure application, albeit non-significantly. ARGs were more abundant in manure, with ermA, ermB, blaOXA-1 and oqxA being significantly enriched in fertilized soil. Positive correlations between oqxA and qnrS abundances and flumequine concentrations were observed, together with the co-occurrence of some ARGs and microbial taxa (e.g. oqxA correlated with Acidobacteria and Gemmatimonadetes). This study showed that manure application has little effect on soil microbiome but may contribute to the dissemination of specific ARGs into the environment. Moreover, flumequine residues seem to enhance the emergence of oqxA and qnrS in soil.

Effects of wastewater treatment and manure application on the dissemination of antimicrobial resistance around swine feedlots

China is the world’s largest swine producer and consumer of pork. The large amount of veterinary antibiotics used in swine production poses a significant environmental risk, and many wastewater treatment and manure application measures are taken to control the spread of antibiotic pollution from swine feedlots. However, the effectiveness of these measures in antibiotic and antibiotic resistance genes removal remains unclear. This study evaluated the fate of antibiotics and related resistance genes around 10 swine farms throughout China. A conventional wastewater treatment facility had limited ability to remove antibiotics and related resistance genes in effluent. Manure application increased the antibiotic concentration and related resistance genes abundance in agricultural soil, and simultaneously enhanced the correlation between class I integron and antibiotic resistance genes. Furthermore, the results revealed some factors such as heavy metals, dissolved oxygen and nutrients might play important roles in aggravating the antimicrobial resistance. The relevance network revealed that copper and zinc were significantly correlated with antibiotic resistance genes and class I/II integrons in manured soil and effluents from an anaerobic digester and membrane bioreactor, suggesting that excessive heavy metals could trigger co-selection and transfer of antibiotic resistance genes. Overall, the study revealed the risk of antibiotic residual and resistance gene pollution in swine wastewater treatment and manure application, highlighting the importance in the source control of antibiotic and heavy metal uses as well as the necessity to optimize wastewater treatment technology for resistance removal.

Responses of Soil Microbial Activity to Swine Manure Applications

The allocation of the large amount of swine waste from farms is an international concern. An efficient way of managing such waste is its use in farming. It is already known that the incorporation of organic waste into the soil significantly increases the microbial population. Therefore, the objective was to evaluate the impact of the use of swine manure on the soil microbiota in a Eutrophic Oxisol. The experiment was set up in a completely randomized design in a 6 &amp;times; 4 factorial scheme (sixconcentrations of swine manure and four evaluation periods) with four replications. We evaluate the following characteristics: microbial respiration (C-CO2), microbial biomass (&amp;micro;C g-1 soil) and pH.: microbial respiration (C-CO2), microbial biomass (&amp;micro;C g-1 soil) and pH. A significant effect was found in the interaction between concentrations and time of incubation (p &amp;lt; 0.05) of swine manure on microbial activity in the soil. The amount of microbial carbon increased as a function of increased levels of liquid swine manure. No interaction was observed between concentrations and time of incubation for the pH. The evaluation of the isolated factors allowed to observe that the pH decreased as the doses of manure were incremented. Higher and lower pH values were found after 5 and 30 days of incubation. The application of liquid swine manure up to 6000 L ha-1 increases the release of CO2 and carbon in the microbial biomass. The applications of liquid swine manure cause a gradual reduction in soil pH.

Impacts of different sources of animal manures on dissemination of human pathogenic bacteria in agricultural soils

The human pathogenic bacteria (HPB) in animal feces may disseminate to agricultural soils with their land application as organic fertilizer. However, the knowledge about the impacts of different sources and rates of animal manures on the temporal changes of soil HPB remains limited, which hamper our ability to estimate the potential risks of their land application. Here, we constructed an HPB database including 565 bacterial strains. By blasting the 16 S rRNA gene sequences against the database we explored the occurrence and fate of HPB in soil microcosms treated with two rates of swine, poultry or cattle manures. A total of 30 HPB were detected in all of manure and soil samples. Poultry manure at the high level obviously improved the abundance of soil HPB. The application of swine manure could introduce concomitant HPB into the soils. Of which, Pseudomonas syringae pv. syringae B728a and Escherichia coli APEC O78 may deserve more attention because of their survival for a few days in manured soils and being possible hosts of diverse antibiotic resistance genes (ARGs) as revealed by co-occurrence pattern. Bayesian source tracking analysis showed that the HPB derived from swine manure had a higher contribution to soil pathogenic communities than those from poultry or cattle manures in early days of incubation. Mantel test together with variation partitioning analysis suggested that bacterial community and soil physicochemical properties were the dominant factors determining the profile of HPB and contributed 64.7% of the total variations. Overall, our results provided experimental evidence that application of animal manures could facilitate the potential dissemination of HPB in soil environment, which should arouse sufficient attention in agriculture practice and management to avoid the threat to human health.

Effects of swine manure application and row spacing on growth of pearl millet (&lt;i&gt;Cenchrus americanus&lt;/i&gt;) during the establishment period and quality of silage produced in Southwest Nigeria

The effects of swine manure application and row spacing on dry matter yields of Cenchrus americanus (pearl millet) at 6 weeks after sowing and chemical composition, fermentative characteristics and in vitro gas production of silage produced from the forage were studied. The design was a 2 × 2 factorial with 2 row spacings (0.5 and1.0 m) and 2 levels of manure application [no manure (Control) and swine manure at 5 t/ha (22% DM; 0.34% N on DM basis)] replicated 3 times. Swine manure application had no effect (P&gt;0.05) on dry matter yield but a row spacing of0.5 m produced higher (P&lt;0.05) dry matter yields than 1.0 m spacing (mean 7.05 vs. 5.57 t DM/ha). Fresh forage from manured treatments had significantly higher crude protein concentration (114.9–124.2 g/kg DM) than from unfertilized plots (86.2–95.1 g/kg DM). After being ensiled for 42 days, CP% in the forage had declined by 16–18% but relative differences remained. Quality measurements indicated that silages from the various treatments were all of acceptable standard although CP% of silage from Control plots was barely high enough to provide a maintenance diet. This study suggests that, under the experimental conditions, planting of pearl millet at a spacing of0.5 m rather than 1.0 m would increase DM yields obtained in the first 6 weeks of growth, while application of swine manure would not affect yields but would increase CP% of forage produced. The laboratory study indicates that the forage produced could be ensiled successfully although there was significant loss of crude protein during the process. Since there were no significant increases in DM yields of forage, other benefits, e.g. increase in N concentration, improved soil organic matter, etc., would need to be considered in justifying the additional cost of drying and applying the manure.

Copper and Zn distribution in humic substances of soil after 10 years of pig manure application in south of Santa Catarina, Brazil.

This study aims to evaluate available Cu and Zn levels in soil and related in soil organic matter (SOM) fractions (fulvic acids-FA, humic acids-HA, and humins-HU) after 10years of application of pig slurry (PS) and pig deep litter (PL). Soil samples were collected from an experiment with black oat/corn succession under no-tillage in southern Brazil. The treatments consisted of fertilization of 90 and 180kgNha-1 applied as PS and PL from 2002 to 2012 and a control treatment without any fertilization. SOM chemical fractionation was performed in air-dried samples. Copper and Zn concentrations were analyzed in soil (total, EDTA- and CaCl2-extracted) and in SOM fractions. The amount of Cu and Zn (in mol) related to each fraction of SOM (Cu/C and Zn/C molar ratios) was established. The applications of PS and PL promoted the accumulation of total and available Cu and Zn, especially in the PL180 treatment. The highest amount of Zn was found with HU, while for Cu both HA and HU were important retention compartments. The highest Cu/CFA, Cu/CHA and Cu/CHU ratios were found with the addition of PL. Increases in Zn/C ratio were found mainly in FA fraction. The high levels of Cu and Zn obtained in the HCl-extracted SOM fraction suggest that a considerable part is bound to SOM and clay minerals with low energy. However, the SOM is an important source of metal adsorption in soils with swine manure application.

Phosphorus Contents in the Profile of an Oxisol With Continuous Application of Liquid Swine Manure

This study aimed to evaluate the dynamics of phosphorus in the soil by the determination of phosphorus contents in an Oxisol cultivated with soybean during the 2016/2017 crop season, after 17 years of successive applications of liquid swine manure (LSM). The experiment was conducted in the experimental area of the University of Rio Verde. The treatments were: T1-control; T2-25 m3 ha-1 of LSM; T3-50 m3 ha-1 of LSM; T4-75 m3 ha-1 of LSM; T5-100 m3 ha-1 of LSM and T6-fertilization with mineral fertilizer. The subplots refer to soil depths: 0-10; 10-20 and 20-40 cm. The LSM was applied to the soil surface by spraying, before soybean sowing and the mineral fertilizer was applied to the furrow at the time of planting. After soybean harvesting, soil samples were collected at the studied depths for the determination of the contents of P in the soil. The contents of P in percolated water are within the concentration range considered adequate for human consumption. As for the contents of P in the soil, LSM applications on the soil surface increased the available soil P up to the depth of 20 cm. The highest dose of LSM applied to the soil promoted an increment of P contents that are within the safety range of the critical environmental limit of phosphorus (LCA-P), corresponding to 37% of this limit.

Antibiotic resistance gene profile changes in cropland soil after manure application and rainfall.

Land application of manure introduces gastrointestinal microbes into the environment, including bacteria carrying antibiotic resistance genes (ARGs). Measuring soil ARGs is important for active stewardship efforts to minimize gene flow from agricultural production systems; however, the variety of sampling protocols and target genes makes it difficult to compare ARG results between studies. We used polymerase chain reaction (PCR) methods to characterize and/or quantify 27 ARG targets in soils from 20 replicate, long-term no-till plots, before and after swine manure application and simulated rainfall and runoff. All samples were negative for the 10 b-lactamase genes assayed. For tetracycline resistance, only source manure and post-application soil samples were positive. The mean number of macrolide, sulfonamide, and integrase genes increased in post-application soils when compared with source manure, but at plot level only, 1/20, 5/20, and 11/20 plots post-application showed an increase in erm(B), sulI, and intI1, respectively. Results confirmed the potential for temporary blooms of ARGs after manure application, likely linked to soil moisture levels. Results highlight uneven distribution of ARG targets, even within the same soil type and at the farm plot level. This heterogeneity presents a challenge for separating effects of manure application from background ARG noise under field conditions and needs to be considered when designing studies to evaluate the impact of best management practices to reduce ARG or for surveillance. We propose expressing normalized quantitative PCR (qPCR) ARG values as the number of ARG targets per 100,000 16S ribosomal RNA genes for ease of interpretation and to align with incidence rate data.

Soil nutrients and heavy metal availability under long-term combined application of swine manure and synthetic fertilizers in acidic paddy soil

Fertilization is a vital approach to increase the crop yield by enhancing soil fertility, but some of the fertilizer sources such as pig manure contain non-essential toxic heavy metals, which can produce the environmental and public health risk. Therefore, the purpose of this study was to investigate the soil fertility and heavy metal pollution risk under long-term fertilization in acidic paddy soil. Fertilizer treatments that were arranged in randomized complete block design (RCBD) included CK (no fertilization), NK (inorganic nitrogen and potassium fertilization), NPK (inorganic NK and phosphorus fertilization), NPKM1 (70% of NPK and 30% pig manure application), NPKM2 (50% of NPK and 50% of pig manure application), and NPKM3 (30% of NPK and 70% of pig manure application). The rice grain yield and soil nutrient contents were highest under NPKM3 treatment. Long-term addition of manure significantly (P ≤ 0.05) increased soil pH and SOC content compared to the NPK fertilization. Soil available and total Cr, Cd, and Hg contents were highest under NPKM3 treatments, while soil total and available Pb content was significantly (P ≤ 0.05) higher under NPK treatment. Highest ecological risk (IR) was (1904) under NPK treatment and highest pollution load index (PLI) was 1.5 under NPKM3 treatment. Cd concentration in rice grain exceeded the maximum permissible limit of 0.1 mg kg−1 under combined application of manure and inorganic fertilization treatments. Grain Cr, Hg, and Pb contents were within safe limits of their concentration in all treatments. Moreover, biological accumulation coefficients of Cr, Cd, Hg, Pb, Zn, and Cu were highest under NPK treatment. Redundancy analysis (RDA) showed that soil pH and nutrient contents showed significant correlation with heavy metal concentrations in soil. Soil pH showed significant (P ≤ 0.05) positive effect on Cd accumulation in rice grain. Heavy metals in pig manure should be monitored before application to the field to reduce the risk of heavy metal pollution in soil and plant. Furthermore, combined application at the rate of 70% inorganic fertilization and 30% of manure could be better strategy to produce high crop yield with minimum risk of heavy metal contamination in soil and food crops.

Fate and transport of antibiotics and antibiotic resistance genes in runoff and soil as affected by the timing of swine manure slurry application

Land application of swine manure slurry is a common practice to supplement nutrients to soil for crop production. This practice can introduce antibiotic residues and antibiotic resistance genes (ARGs) into the environment. Field testing is critical in identifying manure management practices effective in minimizing the environmental impacts of manure-borne antibiotic and ARGs. The objective of this study was to determine how the timing of swine manure application relative to rainfall events impacts the fate and transport of antibiotics and ARGs in surface runoff and manure-amended soil. Swine manure slurry was either broadcast or injected on test plots in the field. A set of three 30-min simulated rainfall events, 24 h apart, were initiated on manured plots 1 day, 1 week, 2 weeks, or 3 weeks after the manure application. Results showed that an interval longer than 2 weeks between application and rainfall often significantly reduced the levels of antibiotics and ARGs tested in runoff with the exception of tet(X). For soil samples from broadcast plots, concentrations of two of the three antibiotics tested (lincomycin and tiamulin) decreased substantially in the first two weeks after manure application. In contrast, concentrations of most of the ARGs tested (tet(Q), tet(X), and erm(A)) in soil did not change significantly during the test period. Information obtained from the study can be beneficial in designing manure management practices and estimating the environmental loading of antibiotics and ARGs resulting from manure application.

Environmental Soil Phosphorus Threshold under No-Tillage and Swine Manure Application

Abstract Swine manure is applied in agricultural fields as a source of nutrients for plant growth, however, excessive application over the years can promote soil phosphorus (P) accumulation. The objective of this study was to establish the environmental soil P threshold based on the degree of P saturation (DPS), as well, to evaluate the soil P storage capacity. The experiment was carried out in an Oxisol (sandy clay loam texture), under no-tillage and crop rotation. Treatments consisted of four annual doses of liquid swine manure (0, 100, 200, and 300 m3 ha-1 year-1), and three doses of mineral fertilizer (0, 50, and 100% of the crop nutrients requirement), in a randomized block with split-plot design (four replications). Soil P content was analyzed by PMehlich-1, PCaCl2, water-soluble P (WSP) and total P. The application of swine manure and mineral fertilizer increased soil P contents mainly at 0-10 cm depth. The DPS corresponding to the change point was 14.9% at depth 0-10 and 8.6% at depth 0-20 cm with WSP and 18.7% at 0-10 cm and 8.9% at 0-20 cm depth with PCaCl2. The lowest change point value was DPS 8.6% which corresponds to 43 mg kg-1 of PMehlich-1, so, in practical terms, we suggest this value as the environmental soil P threshold. The soil P storage capacity indicated negative values with the higher doses of swine manure and mineral fertilizer which increases the vulnerability of P loss by surface and subsurface hydrological transfer pathway.