Animal Waste Application Research Articles

Towards evaluating the conditional probability of waterborne microbial risks associated with critical rainfall events following land application of animal waste — A focus on Irish pastures

ABSTRACT Modelling surface runoff and infiltration in an agricultural watershed is essential for understanding the nutrient cycle and water quality management. This research evaluates the critical rainfall events causing maximum surface runoff and infiltration. Empirical models such as Soil Conservation Service (SCS) curve number and Explicit Green-Ampt (EGA) were analysed for different soil hydraulic conditions and storm events with specific return periods. The present study forecasted the maximum daily rainfall and intensity as 113.6 mm and 19.9 cm h–1, respectively, considering a 100-year return period storm. The deterministic part of the model calculates the daily maximum surface runoff as 5.51 cm (from the SCS model). The EGA model revealed that the rainfall intensity of 0.143, 0.163, 0.175, 0.179, 0.181, 0.182, and 0.182 cm h−1 (duration of 24 h) was found critical for 1, 2, 5, 10, 25, 50, 100 year return period of the storm, respectively in different soil texture classes (sand, loamy sand, sandy loam, loam, silt loam, sandy clay loam, clay loam, silty clay soils). Exceptions imply for three occasions where the intensity of 0.407 cm h−1 and duration of 18 h produced maximum infiltration for silty clay loam, and intensity of 0.352 and 0.354 cm h−1 with 9 h rainfall (each) produced maximum infiltration for clay. The probabilistic model revealed that a daily storm event probability of 2.74 × 10–5 is associated with a simulated mean runoff depth of 0.69 cm and infiltration of 20.7 cm. Critical rainfall probabilities calculated in this study can be multiplied with the overall microbial/pollutant human health risk assessment framework to calculate conditional probability and better estimate microbial risk through the drinking water pathway. This study is very relevant for the wet climatic condition of Ireland, where most land use is pastures.

Esterco bovino e substâncias húmicas estimulam a morfofisiologia e a nutrição em pimentão

ABSTRACT Species of the genus Capsicum, especially peppers, are economically important and widely consumed worldwide. The application of animal waste as organic fertilizer is a simple and cost-effective technique for applying nutrients to the soil. Combining cattle manure with humic substances can stimulate plant metabolism, resulting in increased nutrient absorption and assimilation. Therefore, the objective in this study was to evaluate doses of cattle manure combined with humic substances for stimulating plant metabolism and morphophysiological and nutritional processes in pepper plants. A randomized block design with four replicates was used, in a 4×3 factorial arrangement consisting of four cattle manure doses (8, 18, 28, and 38 Mg ha-1) and three humic substance doses (0, 8, and 12 kg ha-1). Humic substances (12 kg ha-1) enhanced gas exchange, increasing net photosynthesis (34.2%), stomatal conductance (12.7%), instantaneous water use efficiency (15.87%), instantaneous carboxylation efficiency (37.37%), and absorbed energy conversion efficiency (23.53%). Cattle manure adequately met the crop’s nutritional requirements, while humic substances increased the number and thickness of plant root hairs. The most effective combination to increase photosynthetic activity in pepper plants was 38 Mg ha-1 of cattle manure combined with 8 kg ha-1 of humic substances. Humic substances stimulated positive morphophysiological responses in organic pepper crops, which resulted in increased production.

Safeguarding ecosystems using innovative approaches to manage animal wastes

Animal wastes (AWs) are excreta or discarded materials associated with animal production industries. It could be in solid, liquid, or gaseous form, such as animal dung or droppings, discarded feed, feathers, fur, decayed bodies of dead animals, blood waste, effluent from animal farms, milk wastes, urine, and fart. Animal wastes are generated in high quantity, even beyond the control of animal farmers, due to the increase in animal production globally. These wastes pollute the ecosystem. They release greenhouse gases (GHGs) such as methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) into the atmosphere through anaerobic fermentation which deplete ozone layer. Nitrogen and phosphorus constituents of Aws alter soil texture and pollute water bodies through run-off and direct disposal into water systems. The resultant effects of the pollution include climate change, degradation of soil and burning of crops, death of aquatic biota, release of offensive odour, especially ammonia (NH3) and hydrogen sulphide (H2S), and cause diseases of public health concern to human beings and animals. These consequences are due to the emission of harmful gases and compounds and the presence of pathogens in the waste. Animal wastes are potential sources of income and resources, and their environmental consequences could be reduced if farmers could use innovative approaches such as vermicomposting, production of biogas using wastes, membrane filtration, liquid – solid separation, thermal treatment and chemical treatment approaches to manage animal wastes. Government regulation and policies against indiscriminate disposal and application of animal wastes, coupled with the sensitization of people to the benefits and dangers associated with animal waste, could also prevent environmental challenges.

PSX-6 From Bright Leaf to Berkshires: an Alternative Swine Production Course and Outreach Program

Abstract The From Bright Leaf to Berkshires program is a two-year extension outreach initiative funded by the North Carolina Tobacco Trust Fund Commission and facilitated by North Carolina Agricultural and Technical (N.C. A&T) State University. The objective of the program is to train small, limited-resource farmers from across North Carolina in low-cost, alternative swine production systems, retaining ownership of their processed pork, adding value to their pork products, and the targeting of local niche markets. Small farmers in the region have been financially impacted by tobacco-related, healthcare, and social changes that have shifted both price and demand for North Carolina's top cash crop, tobacco. As opposed to tobacco, the demand for one of North Carolina's leading livestock commodities, pork, has remained strong. Therefore, training these farmers in low-cost swine production systems will allow them to diversify their operations, while producing high-end pork products that can be marketed at premium prices. Using the "farmer field school" extension approach, the training of the first cohort of participants took place between March and May of 2023 at the N.C. A&T Farm Pavilion and Swine Facility. The ages of the participants ranged from mid-twenties to mid-sixties. They were trained in employing both pasture-based and hoop structure swine production systems. The participants were also introduced to the digestive system, nutritional needs, reproductive and breeding systems, required disease surveillance, welfare considerations, and appropriate waste management of outdoor swine. The N.C. A&T Swine Specialist, Dr. Derrick J. Coble, served as the director of the program, providing the participants with some of the basic training in swine physiology and management systems. Additional experts were invited to train the cohort in other areas of swine and pork production. The North Carolina Pork Council Representative and former President of the National Pork Board, Jan Archer, facilitated a workshop in which the participants were trained in animal welfare and swine transport. The participants received Pork Quality Assurance and Transport Quality Assurance certifications from the National Pork Board for their participation in this workshop. The Technical Program Coordinator for N.C. Choices, Lee Menius, facilitated a workshop pertaining to the local food systems and niche markets for pasture-based pork in North Carolina. Dr. Stephanie Kulesza, a Nutrient Management and Animal Waste Specialist for the North Carolina Department of Agriculture and Consumer Services, facilitated a workshop in sustainability and the application of animal waste as fertilizer. The program concluded with small-scale, niche swine producers sharing their experiences in pork production. Upon graduation from the program, the participants receive their own hoop structure. Their swine operations will be monitored for three years to track their on-farm practices, participation in alternative swine production, and the economic impact of their operations to their communities.

Epilithic biofilms, POCIS, and water samples as complementary sources of information for a more comprehensive view of aquatic contamination by pesticides and pharmaceuticals in southern Brazil

Spatial-temporal monitoring of the presence of pesticides and pharmaceuticals in water requires rigor in the choice of matrix to be analyzed. The use of matrices, isolated or combined, may better represent the real state of contamination. In this sense, the present work contrasted the effectiveness of using epilithic biofilms with active water sampling and with a passive sampler—POCIS. A watershed representative of South American agriculture was monitored. Nine sites with different rural anthropic pressures (natural forest, intensive use of pesticides, and animal waste), and urban areas without sewage treatment, were monitored. Water and epilithic biofilms were collected during periods of intensive pesticide and animal waste application. After the harvest of the spring/summer crop, a period of low agrochemical input, the presence of pesticides and pharmaceuticals was monitored using the POCIS and epilithic biofilms. The spot water sampling leads to underestimation of the level of contamination of water resources as it does not allow discrimination of different anthropic pressures in rural areas. The use of endogenous epilithic biofilms as a matrix for the analysis of pesticides and pharmaceuticals is a viable and highly recommended alternative to diagnose the health of water sources, especially if associated with the use of POCIS.

Presence of pharmaceuticals and bacterial resistance genes in river epilithic biofilms exposed to intense agricultural and urban pressure

The continuous discharge of pharmaceutical compounds into the aquatic environment has raised concerns over the contamination of water resources. Urban activities and intensive animal breeding are important sources of contamination. The accumulation of antibiotics may lead to the transfer or alternatively maintain the presence of resistance genes in natural microbial communities existing in epilithic biofilms. The objective of this study was to evaluate the pharmaceutical contamination levels and the presence of resistance genes in biofilms from a South Brazilian watershed. The Guaporé watershed exhibits a high diversity of land use, including agricultural and urban areas with differing levels of anthropogenic pressure. Seventeen sites along the Guaporé watershed were monitored. Biofilm samples were collected in two seasons (winter and summer), and the pharmaceutical concentration and quantity of resistance genes were analyzed. All monitored sites were contaminated with pharmaceuticals. Agricultural activities contribute through transferring pharmaceuticals derived from the application of animal waste to agricultural fields. The most contaminated site (pharmaceuticals and bacterial resistance genes) was located in an urban area exposed to high pressure. Decreases in the contamination of biofilms were also observed, exemplifying processes of natural attenuation in the watershed. The quality of the biofilms sampled throughout the watershed served as a useful tool to understand and monitor environmental pollution.

Factors associated with mortality in patients with tetanus in Cameroon.

Tetanus constitutes a significant cause of death in sub-Saharan Africa, with case fatality rates as high as 64%, 47%, and 43.1% reported in Nigeria, Uganda, and Tanzania, respectively. However, the knowledge gap on factors that influence tetanus mortality still exists in Cameroon. To identify the factors that influence the mortality of tetanus patients in three regional hospitals in the North West and South West Regions of Cameroon. This was a 7-year retrospective case-series study. Socio-demographic and clinical data of tetanus cases admitted in Bamenda, Buea, and Limbe Regional Hospitals from January 2010 to March 2017 were collected and analysed. This study recorded 38 cases, but excluded five due to missing inpatient files. Of the 33 cases considered in this study, 27 (81.8%) were males. The mean age of the patients was 32 years. A tetanus mortality rate of 48.5% was recorded - thus, 16 tetanus-related deaths. Mortality was higher amongst patients with incubation periods less than 7 days; the onset of trismus and generalized spasms less than 8 days after exposure; the presence of autonomic dysfunction; the presence of respiratory dysfunction; application or introduction of local regimens, soil or animal waste at the portal of entry; delayed debridement greater than 2 days after onset of tetanus; and a severe clinical disease state. This study, therefore, highlights the need to ensure universal vaccination coverage for high-risk populations; males, active population (20-40 years), and farmers. More still, this study emphasizes the need to improve access and utilisation of mechanical ventilation in severe tetanus cases.

Transcriptomic profiling reveals the molecular responses of Rhodococcus aetherivorans DMU1 to skatole stress

Skatole is a typical malodor compound in animal wastes. Several skatole-degrading bacterial strains have been obtained, whereas the molecular response of strains to skatole stress has not been well elucidated. Herein, the skatole degradation by a Gram-positive strain Rhodococcus aetherivorans DMU1 was investigated. Strain DMU1 showed high efficiency in skatole degradation under the conditions of 25–40 °C and pH 7.0–10.0. It could utilize various aromatics, including cresols, phenol, and methylindoles, as the sole carbon source for growth, implying its potential in the bioremediation application of animal wastes. Transcriptomic sequencing revealed that 328 genes were up-regulated and 640 genes were down-regulated in strain DMU1 when grown in the skatole-containing medium. Skatole increased the gene expression levels of antioxidant defense systems and heat shock proteins. The expression of ribosome-related genes was significantly inhibited which implied the growth inhibition of skatole. A rich set of oxidoreductases were changed, and a novel gene cluster containing the flavoprotein monooxygenase and ring-hydroxylating oxygenase genes was highly up-regulated, which was probably involved in skatole upstream degradation. The upregulation pattern of this gene cluster was further verified by qRT-PCR assay. Furthermore, skatole should be mainly degraded via the catechol ortho-cleavage pathway with cat25170 as the functional gene. The gene cat25170 was cloned and expressed in E. coli BL21(DE3). Pure enzyme assays showed that Cat25170 could catalyze catechol with Km 9.96 μmol/L and kcat 12.36 s−1.

Long-term application of animal and forest waste on a vineyard and its effect on yield and soil health

Long-term application of animal and forest waste on a vineyard and its effect on yield and soil health

A Meta-Analysis to Estimate Prevalence of Resistance to Tetracyclines and Third Generation Cephalosporins in Enterobacteriaceae Isolated from Food Crops.

Application of human and animal waste to fields and water sources and on-farm antimicrobial usage are documented contributors to the occurrence of antimicrobial resistance (AMR) in agricultural domains. This meta-analysis aimed to determine the prevalence of resistance to tetracycline (TET) and third generation cephalosporins (3GC) in Enterobacteriaceae isolated from food crops. TET was selected in view of its wide use in agriculture, whereas 3GC were selected because of the public health concerns of reported resistance to these critically important antibiotics in the environment. Forty-two studies from all six world regions published between 2010 and 2022 met the eligibility criteria. A random effects model estimated that 4.63% (95% CI: 2.57%, 7.18%; p-value: <0.0001) and 3.75% (95%CI: 2.13%, 5.74%; p-value: <0.0001) of surveyed food crops harboured Enterobacteriaceae resistant to TET and 3GC, respectively. No significant differences were observed between pre- and post-harvest stages of the value chain. 3GC resistance prevalence estimates in food crops were highest for the African region (6.59%; 95% CI: 2.41%, 12.40%; p-value: <0.0001) and lowest for Europe (1.84%; 95% CI: 0.00%, 6.02%; p-value: <0.0001). Considering the rare use of 3GC in agriculture, these results support its inclusion for AMR surveillance in food crops. Integrating food crops into One Health AMR surveillance using harmonized sampling methods could confirm trends highlighted here.

Using Near-Infrared Spectroscopy and Stacked Regression for the Simultaneous Determination of Fresh Cattle and Poultry Manure Chemical Properties

Excessive use of animal manure as fertilizers can lead to pollution through the introduction of nitrogen, phosphorus, and other mineral compounds to the environment. Wet chemical analytical methods are traditionally used to determine the precise chemical composition of manure to manage the application of animal waste to the soil. However, such methods require significant resources to carry out the processes. Affordable, rapid, and accurate methods of analyses of various chemical components present in animal manure, therefore, are valuable in managing soil and mitigating water pollution. In this study, a stacked regression ensemble approach using near-infrared spectroscopy was developed to simultaneously determine the amount of dry matter, total ammonium nitrogen, total nitrogen, phosphorus pentoxide, calcium oxide, magnesium oxide, and potassium oxide contents in both cattle and poultry manure collected from livestock production areas in France and Reunion Island. The performance of the stacked regression, an ensemble learning algorithm that is formed by collating the well-performing models for prediction was then compared with that of various other machine learning techniques, including support vector regression (linear, polynomial, and radial), least absolute shrinkage and selection operator, ridge regression, elastic net, partial least squares, random forests, recursive partitioning and regression trees, and boosted trees. Results show that stack regression performed optimally well in predicting the seven abovementioned chemical constituents in the testing set and may provide an alternative to the traditional partial least squares method for a more accurate and simultaneous method in determining the chemical properties of animal manure.

Probability of Health Risk, Bioaccumulation, and Geochemical Fractions of Toxic Elements in Soils and Vegetables Impacted by Manures in Nigeria

The intensive application of manures for the improvement of plant yield is a global practice by farmers notwithstanding the associated negative effects. The probability of health risk, bioaccumulation, and speciation of arsenic (As), cadmium (Cd), nickel (Ni), and lead (Pb) in soils and vegetables (Talinum triangulare and Telfairia occidentalis) impacted by untreated wastes from animal farms and inorganic fertilizers used as manures in the oil producing section of Nigeria were investigated. The total metal was determined using spectrophotometric methods while its geochemical fractions were identified following the modified Community Bureau of Reference (BCR) procedures of sequential extraction. The results obtained indicated the following mean concentrations (mg kg-1): 1.64 ± 0.70, 3.17 ± 1.47, 62.22 ± 8.83, and 187 ± 29.73 for As, Cd, Ni, and Pb, respectively. The results revealed that the mean concentrations of all the metals in the studied locations, except As, were above their recommended limits by the Food and Agricultural Organization/World Health Organization (FAO/WHO). The mean values of As and Pb in T. triangulareand T. occidentalis were also above the acceptable limits. Relatively higher levels of the metals were recorded at the studied locations as compared to the control site. The transfer factors of metals determined were generally lower than one; hence, the human exposure rate to these metals may not be high. The sequential extractions of metal indicated that As and Pb existed in the reducible fraction, Cd in the acid extractable fraction, and Ni in the residual fraction. The contamination factor of the metals revealed that As and Ni belong to the low contamination class, while Cd and Pb fall within the very high contamination category. The study showed that all the studied locations were heavily contaminated, with Uyo being the most polluted site. The principal component analysis identified anthropogenic factor as the main contributor to the presence of these metals in the investigated area. Daily intake rates for these metals via vegetable consumption by both the elderly and young populations were generally lower than their recommended oral reference doses. The non-carcinogenic risks obtained for both populations were less than one. However, the consumers of T. triangulare and T. occidentalis from the studied locations were exposed to Pb toxicity, with children being more vulnerable. This study has shown that the application of untreated animal wastes and inorganic fertilizers as manures has the potential to affect human health, bioavailability of metals, and the geochemical fractions of metals in soil over time.

(Invited) Electrified Resource Recovery Via Nutrient Reduction from Wastewater

Significant anthropogenic activity has been crucial in maintaining global population growth by fixing macronutrients required for crop growth into the soil. Two of these macronutrients – nitrogen (N) and phosphorus (P) – are also responsible for detrimental environmental impact via eutrophication. This eutrophication is driven by excess application of inorganic fertilizer products and organic animal waste from animal feeding operations; components that eventually end up in natural bodies of water due to erosion and leaching. Furthermore, in digester-equipped municipal wastewater treatment facilities, elevated N and P levels in the liquid stream recycled to the head of the facility drives increased resource consumption for nutrient reduction: chemicals for P management and energy for N management. Therefore, opportunities exist to simultaneously minimize environmental impact and energy consumption through improved nutrient management techniques, thus addressing issues at the Food-Energy-Water nexus.Various electrochemical techniques are in early-stage development for an electrified approach to recovering these nutrients and reducing their environmental impact including bio-electrochemical1, electro-deionization2 and electrocoagulation3 approaches. This talk will focus on the indirect electrochemical approach: oxygen/water reduction to promote favorable pH conditions at the electrode surface for nutrient precipitation. Preliminary work4,5 has shown the viability and utility of this approach for nitrogen and phosphorus reduction in synthetic wastewater simulating animal waste. Additional findings describing the impact of competing ions, mass transport and electrolyte thermodynamics on nutrient reduction and recovery will be presented at the conference. An outlook on how this approach impacts energy consumption within the context of decarbonization of the manufacturing sector will also be discussed.References Y. Lei et al., ACS Sustain. Chem. Eng., 7, 8860–8867 (2019).Y. Bian, X. Chen, L. Lu, P. Liang, and Z. J. Ren, ACS Sustain. Chem. Eng., 7, 7844–7850 (2019).L. Kékedy-Nagy et al., J. Am. Chem. Soc., 142, 18844–18858 (2020).Z. Belarbi and J. P. Trembly, J. Electrochem. Soc., 165, E685–E693 (2018).Z. Belarbi, D. A. Daramola, and J. P. Trembly, J. Electrochem. Soc., 167, 155524 (2020).

RESPON PERTUMBUHAN DAN PRODUKSI TANAMAN JAGUNG (Zea mays L.) VARIETAS JANTAN F1 TERHADAP BERBAGAI DOSIS PUPUK KOTORAN HEWAN YANG BERBEDA PADA MEDIA TAILING

Post-tin mining areas dominated by sand tailings cause low nutrients and low water holding capacity. Application of animal waste on tailings medium will provide nutrients and help to increase water holding capacity. The purpose of this study was to determine the dose and type of animal waste that can improve the growth and yield of corn in tailings medium. This research was conducted from January to May 2021 at Experimental and Research Field (KP2), Faculty of Agriculture, Fisheries and Biology, University of Bangka Belitung. The study used a single factor randomized block design with five replicates. This study consisted of four levels of treatment there were sand tailings and cow waste 10 t ha-1 (MS1), tailings sand and cow waste 20 t ha-1 (MS2), tailings sand and chicken waste 10 t ha-1 (MA1), tailings sand and chicken waste 20 t ha-1 (MA2). Results showed that different doses and types significant affected the growth and yield of corn in tailings medium. A dose of 20 t chicken waste ha-1 showed the best growth and yield on F1 male cultivar of corn.

Characterization of the Soil Prokaryotic Community With Respect to Time and Fertilization With Animal Waste–Based Digestate in a Humid Continental Climate

There is a renewed global awareness to improve soil health through the intensification and management of organic inputs such as the application of animal waste–based digestate and other types of organic fertilizers to the soil. The objective of this study was to evaluate the influence of different types of animal waste–based digestate application on soil prokaryotic diversity and composition in an agricultural cropping system over a period of 3 years, cultivated with three different annual cereal crops (spring wheat, triticale, and barley). Treatments were laid out in a randomized design with five conditions (three replicates per condition): fertilizer treatments included three different types of digestate (pig manure, chicken manure, and cow manure digestates), synthetic mineral nitrogen, and unfertilized control. Prokaryotic soil communities were characterized by Illumina MiSeq sequencing. The three most abundant phyla identified were Actinobacteria, Acidobacteria, and Proteobacteria, which accounted for over 55% of the total prokaryotic community. Other phylogenetic groups such as Verrucomicrobia and Bacteroidetes were also identified as part of the native soil microbiota. It was observed that the period of digestate application did not significantly influence the prokaryotic diversity in the soil. On the contrary, sampling time was a major factor in driving β-diversity. A correlation with soil pH was also observed for several taxonomic groups, indicating its importance in shaping prokaryotic community composition. Our study showed that the richness and diversity of the soil prokaryotic community were not affected by digestate application, while other factors such as the yearly crop varieties and seasonal/climate changes were the major contributors to differentiating the prokaryotic community composition over time.

The challenges and perspectives for anaerobic digestion of animal waste and fertilizer application of the digestate

The increase in livestock production creates a serious problem of managing animal waste and by-products. Among the wide range of waste valorization methods available, anaerobic digestion is very promising. It is a form of material recycling that also produces renewable energy in the form of biogas, which is reminiscent of energy recycling. The effluent and digestate from the anaerobic digestion process need to be processed further. These materials are widely used in agriculture due to their composition. Both the liquid and solid fractions of digestate are high in nitrogen, making them a valuable source for plants. Before soil or foliar application, conditioning (e.g., with inorganic acids) and neutralization (e.g., with potassium hydroxide) is required to eliminate odorous compounds and microorganisms. Various methods of conducting the process by anaerobic digestion (use of additives increasing activity of microorganisms, co-digestion, multiple techniques of substrate preparation) and the possibility of controlling process parameters such as optimal C/N ratio (15–30), optimal temperature (psychrophilic (<20 °C), mesophilic (35–37 °C) and thermophilic (55 °C) for microorganism activity ensure high efficiency of the process. Literature data describing tests of various digestates on different plants prove high efficiency, determined by yield increase (even by 28%), nitrogen uptake (by 20%) or phosphorus recovery rate (by 43%) or increase of biometric parameters (e.g., leaf area).

A Review on the Current State of Knowledge of Growing Conditions, Agronomic Soil Health Practices and Utilities of Hemp in the United States

Hemp (Cannabis sativa L.) is an emerging high-value specialty crop that can be cultivated for either fiber, seed, or cannabidiol (CBD). The demand for hemp and its products has been consistently on the rise in the 21st century. The United States of America (USA) has reintroduced hemp and legalized its production as an agricultural commodity through the 2018 Federal Farm Bill. Although there is a renewed interest in the adoption of hemp due to the emerging market, its production in the United States (US) remains limited partly because of unclear agronomic guidance and fertilization recommendations. This review article provides information on the current agronomic management practices that are available in the literature and identifies the future research needs for cultivating this multipurpose crop to address the growing market demands. Hemp production could be beneficial if managed properly. Hemp fertilizer requirements vary in accordance with the type of hemp grown (seed, fiber, or CBD), soil, environmental conditions and requires a wide range of macro- and micronutrients. Integrating management practices in hemp cultivation intended to build soil health is promising since the hemp cropping system is suitable for crop rotation, cover cropping, and livestock integration through animal waste applications. Hemp also has significant environmental benefits since it has the potential to remediate contaminated soils through phytoremediation, convert high amounts of atmospheric CO2 to biomass through bio-sequestration, and hemp biomass for bioenergy production. This review identifies that most of the agronomic research in the past has been limited to hemp fiber and, to some extent, hemp seed but not CBD hemp. With the increase in the global markets for hemp products, more research needs to be conducted to provide agronomic guidelines for sustainable hemp production.

Impacts of multi-year field exposure of agricultural soil to macrolide antibiotics on the abundance of antibiotic resistance genes and selected mobile genetic elements

Exposure of environmental bacteria to antibiotics may be increasing the global resistome. Antibiotic residues are entrained into agricultural soil through the application of animal and human wastes, and irrigation with reclaimed water. The impact of a mixture of three macrolide antibiotics on the abundance of selected genes associated with antibiotic resistance and genetic mobility were determined in a long-term field experiment undertaken in London, Canada. Replicated plots received annual applications of a mixture of erythromycin, clarithromycin and azithromycin every spring since 2010. Each antibiotic was added directly to the soil at a concentration of either 0.1 or 10 mg kg soil−1 and all plots were cropped to soybeans. By means of qPCR, no gene targets were enriched in soil exposed to the 0.1 mg kg soil−1 dose compared to untreated control. In contrast, the relative abundance of several gene targets including int1, sul2 and mphE increased significantly with the annual exposure to the 10 mg kg soil−1 dose. By means of high-throughput qPCR, numerous gene targets associated with resistance to aminoglycosides, sulfonamides, trimethoprim, streptomycin, quaternary ammonium chemicals as well as mobile genetic elements (tnpA, IS26 and IS6100) were detected in soil exposed to 10 mg kg soil−1, but not the lower dose. Overall, exposure of soil to macrolide antibiotics increased the relative abundance of numerous gene targets associated with resistance to macrolides and other antibiotics, and mobile genetic elements. This occurred at an exposure dose that is unrealistically high, but did not occur at the lower more realistic exposure dose.

Processes and mechanisms controlling nitrate dynamics in an artificially drained field: Insights from high-frequency water quality measurements

Intensive agricultural activities, especially in artificially drained agricultural landscapes, generate a considerable amount of nutrient export, which has been identified as a primary cause of water quality impairment. Several management practices have been developed and installed in agricultural watersheds to reduce nutrient export, e.g. nitrate-nitrogen (NO3-N). Although published research reported considerable water quality benefits of these practices, there exist many unanswered questions regarding the inherent processes and mechanisms that control nitrate fate and transport from drained agricultural landscape. To advance our understanding of processes and mechanisms, we deployed two high-frequency sampling systems in a drained agricultural field to investigate the relationship between agricultural drainage and nitrate concentrations (C-Q relationship). Results indicated that the high-frequency measuring system was able to capture the rapidly changing C-Q relationships at the experimental site, e.g. hysteresis patterns. The 22 identified storm events exhibited anti-clockwise behavior with high variability of flushing/dilution effects. In addition, high drainage flows contributed far more nitrate loading compared with lower flows. For instance, the top 10 % of drainage flow exported more than 50 % of the nitrate lost via subsurface drainage during the monitoring period. Additionally, we observed that animal waste application was the most influential practice to change the C-Q relationship by increasing the size of soil nitrogen pools. The insights obtained from the high-frequency water quality measurements could help provide practical suggestions regarding the design and management of conservation practices, such as controlled drainage, bioreactors, and saturated buffers, to improve their nitrogen removal efficiencies. This subsequently leads to better nutrient management in drained agricultural lands.

A simple treatment method for phenylarsenic compounds: Oxidation by ferrate (VI) and simultaneous removal of the arsenate released with in situ formed Fe(III) oxide-hydroxide

p-Arsanilic acid (p-ASA) and roxarsone (ROX) are two major phenylarsenic feed additives that are still widely used in many countries, and the land application of animal waste containing these compounds could introduce large quantities of arsenic into the environment. In this study, we proposed a treatment scheme for animal waste that involves leaching of p-ASA/ROX out of the manure first by water, then oxidation by ferrate (Fe(VI)) and removal of the arsenate released by in situ formed Fe(III) oxide-hydroxide. The effects of solution pH, dosage of Fe(VI), solution ionic strength, and matrix species on the treatment performance were systematically evaluated. Initial solution pH values of 4.1 and 2.0 were chosen for the oxidation of p-ASA and ROX, respectively, while efficient arsenate removal could be achieved with relatively small adjustment of the final solution pH (to 4.0). The pH-dependent second-order rate constants for the reactions between ferrate and p-ASA and ROX over the pH range of 2.0–12.0 were estimated to be 7.13 × 105–2.01 × 10−1 and 8.91 × 103–1.65 × 10−1 M−1 s−1, respectively. The degradation pathways of p-ASA/ROX during ferrate oxidation were proposed based on the inorganic and organic intermediates identified. Depending on the levels of p-ASA/ROX, effective treatment could be achieved through flexible adjustment of the Fe(VI) dosage. p-ASA/ROX (10 mg-As/L) in swine manure leachate could be efficiently treated by ferrate oxidation within 5 min, with the overall arsenic removal efficiency higher than 99.2%. The treatment performance was barely affected by the presence of common ions (K+, Ca2+, Na+, Mg2+, SO42−, NO3−, and Cl−), while humic acid, Mn2+, Ni2+, Fe3+, and Co2+ inhibited p-ASA/ROX oxidation. The presence of PO43− and NH4+ could accelerate the oxidation of p-ASA/ROX, but PO43− and humic acid compromised sorptive removal of the released arsenate due to their competitive sorption on the Fe(III) oxide-hydroxide precipitate. Ferrate oxidation is green and fast, and the operation is simple, thus it could serve as a promising and environment-friendly option for mitigating the risk of phenylarsenic feed additives in animal waste.