Determining the Impact of Genotype × Environment on Oat Protein Isolate Composition Using HPLC and LC-MS Techniques.

The effect of genotype and environment on oat protein composition was analyzed through size exclusion-high-performance liquid chromatography (SE-HPLC) and liquid chromatography-mass spectrometry (LC-MS) to characterize oat protein isolate (OPI) extracted from three genotypes grown at three locations in the Canadian Prairies. SE-HPLC identified four fractions in OPI, including polymeric globulins, avenins, glutelins, and albumins, and smaller proteins. The protein composition was dependent on the environment, rather than the genotype. The proteins identified through LC-MS were grouped into eight categories, including globulins, prolamins/avenins, glutelins, enzymes/albumins, enzyme inhibitors, heat shock proteins, grain softness proteins, and allergenic proteins. Three main globulin protein types were also identified, including the P14812|SSG2-12S seed storage globulin, the Q6UJY8_TRITU-globulin, and the M7ZQM3_TRIUA-Globulin-1 S. Principal component analysis indicated that samples from Manitoba showed a positive association with the M7ZQM3_TRIUA-Globulin-1 S allele and Q6UJY8_TRITU-globulin, while samples from Alberta and Saskatchewan had a negative association with them. The results show that the influence of G × E on oat protein fractions and their relative composition is crucial to understanding genotypes' behavior in response to different environments.

Fate of veterinary antimicrobials in Canadian prairie soils - A critical review.

Veterinary antimicrobials (VAs) widely used in intensive livestock production are excreted in livestock manure. Manure is an essential component in agriculture for recycling critical nutrients and improving overall soil health. However, manure application on agricultural lands increases the risk of contaminating the ecosystem with antimicrobials. Antimicrobials in manure-amended soils can affect ecosystem functioning via their negative effect on biogeochemical cycles and increase human exposure. Also, the release of antimicrobials to the broader environment, including that arising because of offsite transport, is linked to the global increase in antibiotic resistance in bacteria. Antibiotic resistance is an emerging global threat to human health, particularly the pathogenic bacteria resistant to the main antimicrobial classes in use. Therefore, there is a need to review current literature to enhance our understanding of the fate of these contaminants across agricultural landscapes. This review focuses on (1) a detailed discussion of sorption mechanisms by exploring the structural attributes of antimicrobials, (2) specific sorption interactions with active adsorbent components in the soil as these comprehensive data are important to identify the sorption strengths of antimicrobials which control their fate in the ecosystem, and (3) the effects of on-farm management practices on VA transport and is focused on manure amendment and tillage practices. The key facts identified in this review are critical to identifying sustainable on-farm management practices to enhance the productivity of arable agricultural lands in Canada and across the globe while minimizing the risk of offsite transport of VAs. Further, the research gaps highlighted in the relevant sections are important to designing future research in Canada and globally under similar to variable land/farm management practices.

Critical review of phytoremediation for the removal of antibiotics and antibiotic resistance genes in wastewater.

Antibiotics in wastewater are a growing environmental concern. Increased prescription and consumption rates have resulted in higher antibiotic wastewater concentration. Conventional wastewater treatment methods are often ineffective at antibiotic removal. Given the environmental risk of antibiotics and associated antibiotic resistant genes (ARGs), finding methods of improving antibiotic removal from wastewater is of great importance. Phytoremediation of antibiotics in wastewater, facilitated through constructed wetlands, has been explored in a growing number of studies. To assess the removal efficiency and treatment mechanisms of plants and microorganisms within constructed wetlands for specific antibiotics of major antibiotic classes, the present review paper considered and evaluated data from the most recent published research on the topics of bench scale hydroponic, lab and pilot scale constructed wetland, and full scale constructed wetland antibiotic remediation. Additionally, microbial and enzymatic antibiotic degradation, antibiotic-ARG correlation, and plant effect on ARGs were considered. It is concluded from the present review that plants readily uptake sulfonamide, macrolide, tetracycline, and fluoroquinolone antibiotics and that constructed wetlands are an effective applied phytoremediation strategy for the removal of antibiotics from wastewater through the mechanisms of microbial biodegradation, root sorption, plant uptake, translocation, and metabolization. More research is needed to better understand the effect of plants on microbial community and ARGs. This paper serves as a synthesis of information that will help guide future research and applied use of constructed wetlands in the field antibiotic phytoremediation and wastewater treatment.

Trihalomethanes in drinking water from three First Nation reserves in Manitoba, Canada.

Previous research indicates that the water distribution system used has a significant impact on the microbial quality of tap water sampled in First Nations reserves in Canada. This study tested tap water from homes in three First Nations reserves to compare the concentrations of four trihalomethanes and related water quality parameters between homes receiving piped water from a water treatment plant (WTP) versus homes equipped with cisterns that are filled by a water truck. Of all the samples collected across time from household taps, 75% of piped samples and 70% of cistern samples had TTHM concentrations exceeding Health Canada's maximum acceptable concentration (MAC) of 100 µg L-1 total trihalomethanes (TTHMs) in treated water. In all communities and across sampling times, trichloromethane (CHCl3) was the dominant trihalomethane (42-96%) followed by bromodichloromethane (CHBrCl2) (3-37%) and dibromochloromethane (CHClBr2) (1-18%). Tribromomethane (CHBr3) always accounted for < 5% of TTHMs. Within each of the three First Nations reserves, the water distribution system had no significant effect on TTHM concentration at the household level. Sampling month had a significant effect on TTHM concentration due to temporal changes in dissolved organic carbon of the source water. Results suggest that families in the studied First Nations reserves receive drinking water with high TTHM concentrations and that improvements to the water treatment plant might be the most effective way to minimize trihalomethane formation.

Aluminum phosphate sludge as a phosphorus source for maize production under low soil phosphorus availability.

Background: With increasing food demand as a consequence of the growing world population, there is a corresponding demand for additional sources of phosphorus (P). Alum-phosphate (Al-P) sludge is a by-product of wastewater treatment and can be a good source of P. In this study, the response of maize (Zea mays L.) to Al-P sludge was tested. Maize was chosen as the test crop due to its prevalent use as human and animal food and as a source of biofuel. The objective of the study was to investigate Al-P sludge as a source of P compared to a commercial fertilizer (monoammonium phosphate, MAP). Methods: A growth chamber assay was conducted over four cropping cycles (45 d each). The application rate was 9.7, 19.4, 29.1 and 38.8 mg P kg-1 dry soil. Amendments were applied once at the start of the first cropping cycle. Plants were harvested after each cycle and pots were re-seeded. Dry matter yield (DMY), total P uptake, Al-P uptake, soil total P and Olsen-P concentrations, pH, and EC were measured. Results: DMY was significantly greater in pots amended with Al-P sludge than in pots treated with MAP. There was a significant rate × cropping cycle interaction effect on DMY with the differences among rates in cycle 1 different from those in cycle 4. Phosphorus uptake depended on cropping cycle, P source and P application rate. With sludge uptake higher than MAP in all cycles, the highest P uptake was observed at the highest application rate except for cycle 2 where this was observed at the rate of 29.1 mg kg-1. For MAP, phosphorus recovery efficiency (PRE) at the highest rate was significantly greater than that at the lowest rate whereas PRE in cycle 1 was significantly higher than that in cycle 4. In the first two cycles, aluminum uptake was negligible in both MAP and Al-P sludge treatments; however, in cycles 3 and 4, there was significantly more Al in maize from sludge amended pots. Our results show that Al-P sludge was as effective as MAP in supplying enough P for biomass yield. We, therefore, conclude that Al-P sludge could be an alternative source of P, especially for growing maize as feedstock for bioenergy.

Degradation of antimicrobial resistance genes within stockpiled beef cattle feedlot manure.

Degradation of antimicrobial resistance genes (ARG) in manure from beef cattle administered (kg-1 feed) 44 mg of chlortetracycline (CTC), 44 mg of chlortetracycline plus sulfamethazine (CTCSMZ), 11 mg of tylosin (TYL), or no antimicrobials (Control) was examined. Manure was stockpiled and quantitative PCR (qPCR) was used to assess tetracycline [tet(C), (L), (M), (W)], erythromycin [erm(A), (B), (F), (X)], and sulfamethazine [sul(1), (2)] ARG and 16S rDNA. After 102 d, copies of all ARG decreased by 0.3 to 1.5 log10 copies (g dry matter)-1. Temperature in the interior of piles averaged ≥ 55 °C for 10 d, except for CTCSMZ, but did not reach 55 °C at pile exteriors. Compared to Control, CTCSMZ increased (P < 0.05) tet(C), tet(M), tet(W), sul(1), and sul(2) in stockpiled manure. Copies of 16S rDNA remained higher (P < 0.05) in CTCSMZ than Control for the first 26 d. Levels of most ARG did not differ between the interior and exterior of stockpiles. Our results suggest that stockpiled manure would still introduce ARG to land upon manure application, but at levels lower than if manure was applied fresh.

Water delivery system effects on coliform bacteria in tap water in First Nations reserves in Manitoba, Canada.

About one-half of the homes on First Nations (FN) reserves in Manitoba, Canada, receive piped water from a water treatment plant (WTP). Many other homes (31%) are equipped with cisterns that are filled by a water truck, and our objective was to determine how the use of cisterns affects drinking water safety relative to drinking water piped directly to homes from the WTP. The study included belowground concrete cisterns, belowground fiberglass cisterns, and aboveground polyethylene cisterns stored in insulated shelters, and all the data collection methods showed that the tap water in homes with cisterns were relatively more contaminated with coliform bacteria than the tap water in piped homes. The frequency and severity of Escherichia coli and total coliform contamination were numerically greater in drinking water samples from belowground concrete and fiberglass cisterns than in piped water samples in each community, and the contamination of belowground cisterns by coliform bacteria was greatest in late spring. As well, data obtained under the Access to Information Act showed no statistical differences in the percent of satisfactory samples (no detects) between 2014 and 2018, suggesting no clear indication of improved water quality in any of the Tribal Councils in which these three and other communities are a member off. Our results point to the need for additional treatment of drinking water in homes supplied by belowground concrete or fiberglass cisterns and replacement of belowground cisterns with aboveground cisterns or piped water to reduce the risk of water-borne illnesses.

Phytoextraction of ciprofloxacin and sulfamethoxaxole by cattail and switchgrass.

Cattail (Typha latifolia L.) and switchgrass (Panicum virgatum L.) can effectively remove inorganic contaminants from soils and biosolids, but their role in the attenuation of organic contaminants, such as antimicrobials, is currently poorly understood. Uptake by plants is one of several mechanisms by which plant-assisted attenuation of antimicrobials can be achieved. The objectives of this growth room study were to evaluate the plant uptake of ciprofloxacin (CIP) and sulfamethoxazole (SMX) and examine their partitioning between plant roots and aboveground biomass (AGB). Plant uptake of the two 14C labeled antimicrobials was studied at two environmentally relevant concentrations (5 and 10 µg L-1). Plants were destructively sampled every 3-4 d during the 21-d growth period. Accumulation of CIP and SMX in both plant species was greater in the roots than in the AGB. The percentage uptake values of the two antimicrobials were significantly greater for cattail (34% for CIP, 20% for SMX) than for switchgrass (10% for both CIP and SMX). Translocation factors of the two antimicrobials were <1 for both plants, indicating slow movement of the antimicrobials from the roots to the shoots. For cattail roots, the BCF for CIP (1.58 L g-1) was significantly greater than that for SMX (0.8 L g-1). By comparison, BCFs for switchgrass roots did not differ significantly between CIP (0.88 L g-1) and SMX (1.13 L g-1). These results indicate greater potential for cattail to phytoextract CIP and SMX and significantly contribute to the attenuation of these antimicrobials in systems designed for the phytoremediation of contaminated wastewater.

Bioavailability study of phosphorus in alum-phosphorus sludge using switchgrass.

The study investigated biomass yield and the uptake of P and aluminum by switchgrass grown in a low-P soil amended with alum-P sludge and a conventional fertilizer, monoammonium phosphate (MAP), at rates of 9.7, 19.4, 29.1 and 38.8 mg P kg-1 dry soil. Potted soil (amended and control) units were seeded with pre-germinated switchgrass and harvested three times at 50-day intervals. Over the three growth cycles, P from alum-P sludge gradually became available. Amendment rate showed no significant effect on switchgrass biomass yield. P availability was greater for alum-P sludge than MAP and this may have been enhanced by the properties and activities of the plant root system. Aluminum (Al) uptake by switchgrass increased with the number of cycles, but did not differ significantly among treatments. Cumulative Al uptake over the 3 cycles was greater for below-ground biomass than for above-ground biomass. Maximum P recovery efficiency of 28% was achieved at the 9.7 mg P kg soil-1 rate. These results demonstrate that alum-P sludge is an effective source of available P for cropping switchgrass in a high pH and low Olsen-P soil.

Dissipation of sulfamethoxazole and trimethoprim during temporary storage of biosolids: A microcosm study.

Little is known about the dissipation rate of microcontaminants in biosolids during storage and stabilization in stockpiles (unsaturated) or storage lagoons/tanks (saturated). The objective of this study was to characterize the dissipation in biosolids of two antibiotics, sulfamethoxazole (SMX) and trimethoprim (TMP), in microcosms under saturated and unsaturated conditions that simulate biosolids that are stockpiled on land or deposited in lagoons/tanks, respectively. The laboratory experiment was conducted at 22 °C using biosolids spiked at an initial nominal concentration of 10 mg kg-1 for both antibiotics. Biosolids were sampled in triplicate at seven sampling times over a 42-d period. Concentrations of SMX and TMP in extracts prepared from biosolids were quantified using liquid chromatography with tandem mass spectrometry. Dissipation data fitted to a first-order kinetic model indicated that the time to 50% dissipation (DT50) for SMX was significantly shorter in the unsaturated microcosms (2.8 d) than the saturated microcosms (4.4 d), while the DT50 for TMP was significantly shorter in microcosms under saturated conditions (10 d) relative to unsaturated conditions (116 d). These results indicate that the reducing conditions that develop in biosolids deposited in lagoons or placed in storage tanks might be effective for enhancing the microbial degradation of antibiotics that are otherwise persistent under aerobic conditions (i.e., TMP), while also being effective for removing other antibiotics including those that dissipate relatively readily under aerobic conditions (i.e., SMX).

Sulfamethoxazole sorption by cattail and switchgrass roots.

Sorption to roots is one of several mechanisms by which plant-assisted attenuation of antibiotics can be achieved. The objectives of this study were to (1) evaluate the sorption of sulfamethoxazole (SMX) by cattail and switchgrass roots, (2) determine the kinetics of SMX sorption by cattail and switchgrass roots, and (3) characterize the temperature-dependency of SMX sorption. A batch sorption experiment was conducted to measure SMX sorption by roots of the two plant species using five initial antibiotic concentrations (2.5, 5, 10, 15, and 20 µg L-1) and eight sampling times (0, 0.5, 1, 2, 4, 8, 12, and 24 h). Another batch experiment was conducted at three temperatures (5, 15, and 25 °C) to determine the effect of temperature on sorption kinetics. SMX sorption followed pseudo-second-order kinetics. The pseudo-second-order rate constant (k2) decreased with increasing temperature for both plant species. The rate constant followed the order: 5 °C = 15 °C > 25 °C for cattail and 5 °C > 15 °C = 25 °C for switchgrass. Results from this study show that switchgrass roots are more effective than cattail roots in the removal of SMX. Therefore, the use of switchgrass in systems designed for phytoremediation of contaminants might also provide an efficient removal of some antibiotics.

Options for Improved Phosphorus Cycling and Use in Agriculture at the Field and Regional Scales.

Soil phosphorus (P) cycling in agroecosystems is highly complex, with many chemical, physical, and biological processes affecting the availability of P to plants. Traditionally, P fertilizer recommendations have been made using an insurance-based approach, which has resulted in the accumulation of P in many intensively managed agricultural soils worldwide and contributed to the widespread water quality issue of eutrophication. To mitigate further environmental degradation and because future P fertilizer supplies are threatened due to finite phosphate rock resources and associated geopolitical and quality issues, there is an immediate need to increase P use efficiency (PUE) in agroecosystems. Through cultivar selection and improved cropping system design, contemporary research suggests that sufficient crop yields could be maintained at reduced soil test P (STP) concentrations. In addition, more efficient P cycling at the field scale can be achieved through agroecosystem management that increases soil organic matter and organic P mineralization and optimizes arbuscular mycorrhizal fungi (AMF) symbioses. This review paper provides a perspective on how agriculture has the potential to utilize plant and microbial traits to improve PUE at the field scale and accordingly, maintain crop yields at lower STP concentrations. It also links with the need to tighten the P cycle at the regional scale, including a discussion of P recovery and recycling technologies, with a particular focus on the use of struvite as a recycled P fertilizer. Guidance on directions for future research is provided.

Nitrogen and Phosphorus Phytoextraction by Cattail (Typha spp.) during Wetland-based Phytoremediation of an End-of-Life Municipal Lagoon.

Spreading biosolids on farmland can be an effective and beneficial option for managing end-of-life municipal lagoons. Where the spreading of biosolids on farmland is restricted or unavailable, in situ phytoremediation could be a sustainable alternative. This study examined nitrogen (N) and phosphorus (P) phytoextraction by cattail ( spp.) from biosolids in a wetland constructed within a lagoon cell previously used for primary treatment of municipal wastewater. The effect of harvesting season as well as harvest frequency on N and P removal were evaluated. Forty-eight 4-m plots within the constructed wetland were used to determine the effect of cattail harvest frequency on plant N and P phytoextraction. Harvesting twice per season resulted in a 50 to 60% decrease in phytoextraction of N and P relative to a single harvest per season, which produced biomass yields of 0.58 to 0.6 kg m per year and accumulated 36.7 g N m and 5.6 g P m over the 4-yr period. Compared with August, harvesting cattails in November or April reduced N and P phytoextraction by 63 to 85%. These results demonstrate that phytoextraction of nutrients is more effective with a single harvest compared with two harvests per season. Additionally, we found that while harvesting in November and April is appealing logistically (since the wetland is frozen and provides easier access to harvest equipment), nutrient removal rates are significantly reduced.

A Field Bioassay of Nitrogen and Phosphorus Phytoextraction from Biosolids in a Seasonally Frozen End-of-Life Municipal Lagoon Vegetated with Cattail.

Managing biosolids from end-of-life municipal lagoons is a major challenge for many small communities where landfilling or spreading of biosolids on farmland is restricted. Contaminant removal via phytoextraction may be a viable remediation option for end-of-life lagoons in such communities. This study examined the effect of harvest frequency (once or twice per season) on cattail ( L.) biomass yield and N and P removal under a terrestrial phytoremediation system designed to treat the dewatered secondary cell of a municipal lagoon in Manitoba, Canada. Cattail was harvested once or twice per season from eight vegetation transects, each divided into two plots (2.5 × 2.5 m) to accommodate the two harvest frequencies. Biomass yields were greater for the single harvest (5.7 t ha yr) than for two harvests per season (4.8 t ha yr). This was mirrored by N phytoextraction, which was also greater for the single harvest (71 kg ha yr) than the two-harvest frequency (58 kg ha yr). Phosphorus phytoextraction varied with year of harvest and ranged from 8 to 14 kg ha yr. Cumulative N and P phytoextraction amounts during the 5 yr were 330 kg N ha and 57 kg P ha. A greater fraction of N (51-91 kg ha yr) and P (23-40 kg ha yr) was sequestered in the belowground biomass (11-17 t ha yr) and therefore was not removed by harvesting. These results show that phytoremediation using cattail is a viable option for managing N and P in end-life lagoons.

Dissipation of antimicrobial resistance genes in compost originating from cattle manure after direct oral administration or post-excretion fortification of antimicrobials.

Dissipation of antimicrobial resistance genes (ARG) during composting of cattle manure generated through fortification versus administration of antimicrobials in feed was compared. Manure was collected from cattle fed diets containing (kg-1) dry matter (DM): (1) 44 mg chlortetracycline (CTC), (2) a mixture of 44 mg each of chlortetracycline and sulfamethazine (CTCSMZ), (3) 11 mg tylosin (TYL) or (4) Control, no antimicrobials. Manures were composted for 30 d with a single mixing after 16 d to generate the second heating cycle. Quantitative PCR (qPCR) was used to measure 16S rDNA and tetracycline (tet), erythromycin (erm) and sulfamethazine (sul) genes. Temperature peaks ranged from 48 to 68°C across treatments in the first composting cycle, but except for the control, did not exceed 55°C in the second cycle. Copy numbers of 16S rDNA decreased (P < 0.05) during composting, but were not altered by antimcrobials. Except tet(L), all ARG decreased by 0.1-1.6 log10 g DM-1 in the first cycle, but some genes (tet[B], tet[L], erm[F], erm[X]) increased (P < 0.05) by 1.0-3.1 log10 g DM-1 in the second. During composting, levels of tet(M) and tet(W) in CTC, erm(A), erm(B) and erm(X) in TYL, and sul(1) in CTCSMZ remained higher (P < 0.05) in fed than fortified treatments. The dissipation of ARG during composting of manure fortified with antimicrobials differs from manure generated by cattle that are administered antimicrobials in feed, and does not always align with the dissipation of antimicrobial residues.

Wetland-based phytoremediation of biosolids from an end-of-life municipal lagoon: A microcosm study.

This study examined the effectiveness of a wetland system for phytoremediation of biosolids from an end-of-life municipal lagoon. The microcosm experiment tested the effects of one vs. two harvests of cattail per growth cycle in biosolids without (PB) or with (PBS) the addition of soil on phytoremediation. Cattail (Typha latifolia) seedlings were transplanted into pots containing 4.5 kg (dry wt.) of biosolids, above which a 10-cm deep water column was maintained. Results showed that two harvests per growth cycle significantly increased N and P phytoextraction relative to a single harvest. Overall, the three cycles of cattail removed ∼3.7% of N which was originally present in the biosolids and ∼2% of the total P content. Phytoextraction rates are expected to be higher under field conditions where biomass yields are much higher than those obtained under growth room conditions in this study. These results indicate that wetland-based phytoremediation can effectively clean up nutrients from biosolids, and therefore presents a potential alternative to the spreading of biosolids on agricultural land, which may not be readily available in some communities. Phytoextraction rates of trace elements, however, were much lower (0.02-0.17%). Nonetheless, trace element concentrations were not high enough to be of significant concern.

Phytoextraction of nitrogen and phosphorus by crops grown in a heavily manured Dark Brown Chernozem under contrasting soil moisture conditions.

Phytoextraction of excess nutrients by crops in soils with a long history of manure application may be a viable option for reducing the nutrient levels. This greenhouse study examined the effectiveness of six growth cycles (40 d each) of barley, canola, corn, oat, pea, soybean, and triticale at extracting nitrogen (N) and phosphorus (P) from a Dark Brown Chernozem that had received 180 Mg ha-1 (wet wt.) of beef cattle feedlot manure annually for 38 years. Moisture content during the study was maintained at either 100% or 50% soil field capacity (SFC). Repeated cropping resulted in an overall decrease in dry matter yield (DMY). The decrease in N and P uptake relative to Cycle 1 was fastest for the cereal grains and less pronounced for the two legumes. However, cumulative N uptake values were significantly greater for corn than the other crops under both moisture regimes. The reduction in soil N was greater under the 100% than the 50% SFC. These results indicate that repeated cropping can be a useful management practice for reducing N and P levels in a heavily manured soil. The extent of reduction will be greater for crops with high biomass production under adequate moisture supply.

Phytoremediation of biosolids from an end-of-life municipal lagoon using cattail (Typha latifolia L.) and switchgrass (Panicum virgatum L.).

Land spreading of biosolids as a disposal option is expensive and can disperse pathogens and contaminants in the environment. This growth room study examined phytoremediation using switchgrass (Panicum virgatum L.) and cattail (Typha latifolia L.) as an alternative to land spreading of biosolids. Seedlings were transplanted into pots containing 3.9 kg of biosolids (dry wt.). Aboveground biomass (AGB) was harvested either once or twice during each 90-day growth period. Switchgrass AGB yield was greater with two harvests than with one harvest during the first 90-day growth period, whereas cattail yield was not affected by harvest frequency. In the second growth period, harvesting frequency did not affect the yield of either plant species. However, repeated harvesting significantly improved nitrogen (N) and phosphorus (P) uptake by both plants in the first period. Phytoextraction of P was significantly greater for switchgrass (3.9% of initial biosolids P content) than for cattail (2.8%), while plant species did not have a significant effect on N phytoextraction. The trace element accumulation in the AGB of both plant species was negligible. Phytoextraction rates attained in this study suggest that phytoremediation can effectively remove P from biosolids and offers a potentially viable alternative to the disposal of biosolids on agricultural land.

Dissipation of Antimicrobials in a Seasonally Frozen Soil after Beef Cattle Manure Application.

Land application of manure containing antimicrobials results in the dispersion of the antimicrobials in agro-ecosystems. Dissipation of excreted antimicrobials in seasonally frozen agricultural soils has not been fully characterized under field conditions. This study investigated the field dissipation kinetics of chlortetracycline, sulfamethazine, and tylosin over a 10-mo period after fall application of manure from cattle () administered 44 mg chlortetracycline (chlortetracycline treatment [CTC]), 44 mg each of chlortetracycline and sulfamethazine (CTCSMZ), or 11 mg tylosin per kg feed daily. Antimicrobial concentrations in manured soil reflected the same relative concentrations in manure: chlortetracycline > sulfamethazine > tylosin. The first-order dissipation half-life (DT) for chlortetracycline from the CTCSMZ treatment was 77 d during the growing season and 648 d during the nongrowing season when the soil was frozen for an extended period. By comparison, dissipation of chlortetracycline added alone (treatment CTC) did not differ significantly between the two seasons (mean DT, 121 d). During the nongrowing season, chlortetracycline from CTC dissipated faster ( = 0.004) than that from the CTCSMZ treatment, indicating that the presence of sulfamethazine may have altered the dissipation of chlortetracycline. Dissipation kinetics for sulfamethazine and tylosin were not determined due to low detection in the manure-amended soil. Sulfamethazine was detected (up to 16 ± 10 µg kg) throughout the 10-mo monitoring period. Tylosin concentration was ≤11 ± 6.6 µg kg and gradually dissipated. Chlortetracycline was detectable 10 mo after application in the seasonally frozen soil, indicating a risk for residue build-up in the soil and subsequent offsite contamination.

Predicting Phosphorus Release from Anaerobic, Alkaline, Flooded Soils.

Anaerobic conditions induced by prolonged flooding often lead to an enhanced release of phosphorus (P) to floodwater; however, this effect is not consistent across soils. This study aimed to develop an index to predict P release potential from alkaline soils under simulated flooded conditions. Twelve unamended or manure-amended surface soils from Manitoba were analyzed for basic soil properties, Olsen P (Ols-P), Mehlich-3 extractable total P (M3P), Mehlich-3 extractable molybdate-reactive P (M3P), water extractable P (WEP), soil P fractions, single-point P sorption capacity (P), and Mehlich-3 extractable Ca (M3Ca), and Mg (M3Mg). Degree of P saturation (DPS) was calculated using Ols-P, M3P or M3P as the intensity factor, and an estimated adsorption maximum based on either P or M3Ca + M3Mg as the capacity factor. To develop the model, we used the previously reported floodwater dissolved reactive P (DRP) concentration changes during 8 wk of flooding for the same unamended and manured soils. Relative changes in floodwater DRP concentration (DRP), calculated as the ratio of maximum to initial DRP concentration, ranged from 2 to 15 across ten of the soils, but were ≤1.5 in the two soils with the greatest clay content. Partial least squares analysis indicated that DPS3 calculated using M3P as the intensity factor and (2 × P) + M3P as the capacity factor with clay percentage can effectively predict DRP ( = 0.74). Results suggest that P release from a soil to floodwater may be predicted using simple and easily measurable soil properties measured before flooding, but validation with more soils is needed.