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Beriot N, Zornoza R, Lwanga EH, Zomer P, van Schothorst B, Ozbolat O, Lloret E, Ortega R, Miralles I, Harkes P, van Steenbrugge J, Geissen V. Intensive vegetable production under plastic mulch: A field study on soil plastic and pesticide residues and their effects on the soil microbiome. Sci Total Environ 2023; 900:165179. [PMID: 37385505 DOI: 10.1016/j.scitotenv.2023.165179] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 06/25/2023] [Accepted: 06/26/2023] [Indexed: 07/01/2023]
Abstract
Intensive agriculture relies on external inputs to reach high productivity and profitability. Plastic mulch, mainly in the form of Low-Density Polyethylene (LDPE), is widely used in agriculture to decrease evaporation, increase soil temperature and prevent weeds. The incomplete removal of LDPE mulch after use causes plastic contamination in agricultural soils. In conventional agriculture, the use of pesticides also leaves residues accumulating in soils. Thus, the objective of this study was to measure plastic and pesticide residues in agricultural soils and their effects on the soil microbiome. For this, we sampled soil (0-10 cm and 10-30 cm) from 18 parcels from 6 vegetable farms in SE Spain. The farms were under either organic or conventional management, where plastic mulch had been used for >25 years. We measured the macro- and micro-light density plastic debris contents, the pesticide residue levels, and a range of physiochemical properties. We also carried out DNA sequencing on the soil fungal and bacterial communities. Plastic debris (>100 μm) was found in all samples with an average number of 2 × 103 particles kg-1 and area of 60 cm2 kg-1. We found 4-10 different pesticide residues in all conventional soils, for an average of 140 μg kg-1. Overall, pesticide content was ∼100 times lower in organic farms. The soil microbiomes were farm-specific and related to different soil physicochemical parameters and contaminants. Regarding contaminants, bacterial communities responded to the total pesticide residues, the fungicide Azoxystrobin and the insecticide Chlorantraniliprole as well as the plastic area. The fungicide Boscalid was the only contaminant to influence the fungal community. The wide spread of plastic and pesticide residues in agricultural soil and their effects on soil microbial communities may impact crop production and other environmental services. More studies are required to evaluate the total costs of intensive agriculture.
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Affiliation(s)
- Nicolas Beriot
- Soil Physics and Land Management Group, Wageningen University & Research, Droevendaalsesteeg 4, 6708 PB Wageningen, the Netherlands; Sustainable Use, Management and Reclamation of Soil and Water Research Group, Department of Agricultural Engineering, Universidad Politécnica de Cartagena, Paseo Alfonso XIII, 48, 30203 Cartagena, Spain
| | - Raúl Zornoza
- Sustainable Use, Management and Reclamation of Soil and Water Research Group, Department of Agricultural Engineering, Universidad Politécnica de Cartagena, Paseo Alfonso XIII, 48, 30203 Cartagena, Spain
| | - Esperanza Huerta Lwanga
- Soil Physics and Land Management Group, Wageningen University & Research, Droevendaalsesteeg 4, 6708 PB Wageningen, the Netherlands; Agroecologia, El Colegio de la Frontera Sur, Unidad Campeche, Mexico
| | - Paul Zomer
- Wageningen Food Safety Research, PO. Box 230, 6700 AE Wageningen, the Netherlands
| | - Benjamin van Schothorst
- Soil Physics and Land Management Group, Wageningen University & Research, Droevendaalsesteeg 4, 6708 PB Wageningen, the Netherlands
| | - Onurcan Ozbolat
- Sustainable Use, Management and Reclamation of Soil and Water Research Group, Department of Agricultural Engineering, Universidad Politécnica de Cartagena, Paseo Alfonso XIII, 48, 30203 Cartagena, Spain
| | - Eva Lloret
- Sustainable Use, Management and Reclamation of Soil and Water Research Group, Department of Agricultural Engineering, Universidad Politécnica de Cartagena, Paseo Alfonso XIII, 48, 30203 Cartagena, Spain
| | - Raúl Ortega
- Department of Agronomy & Center for Intensive Mediterranean Agrosystems and Agri-food Biotechnology (CIAIMBITAL), University of Almeria, E-04120 Almería, Spain
| | - Isabel Miralles
- Department of Agronomy & Center for Intensive Mediterranean Agrosystems and Agri-food Biotechnology (CIAIMBITAL), University of Almeria, E-04120 Almería, Spain
| | - Paula Harkes
- Soil Physics and Land Management Group, Wageningen University & Research, Droevendaalsesteeg 4, 6708 PB Wageningen, the Netherlands
| | - Joris van Steenbrugge
- Laboratory of Nematology, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB Wageningen, the Netherlands
| | - Violette Geissen
- Soil Physics and Land Management Group, Wageningen University & Research, Droevendaalsesteeg 4, 6708 PB Wageningen, the Netherlands
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Micallef SA, Callahan MT, McEgan R, Martinez L. Soil Microclimate and Persistence of Foodborne Pathogens Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella enterica Newport in Soil Affected by Mulch Type. J Food Prot 2023; 86:100159. [PMID: 37703940 DOI: 10.1016/j.jfp.2023.100159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 08/30/2023] [Accepted: 09/06/2023] [Indexed: 09/15/2023]
Abstract
Mulching is a common agricultural practice that benefits crop production through soil moisture retention, weed suppression, and soil temperature regulation. However, little is known about the effect of mulch on foodborne pathogens present in soil. In this study, the influence of polyethylene plastic, biodegradable corn-based plastic, paper, and straw mulches on Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella enterica Newport populations in soil was investigated. Silt loam soil in troughs was inoculated with a cocktail of the pathogens and covered with mulch or left bare, then incubated for 21 days, during which bacteria were enumerated and environmental parameters monitored. Bacterial counts declined in all treatments over time (p < 0.001) but persisted at 21 days at 0.8-0.95 log CFU/g. Pathogens also declined as a factor of mulch cover (p < 0.01). An exponential decay with asymptote model fit to the data revealed slower rates of decline in soil under mulches for all pathogens (p < 0.05) relative to bare soil. Compared to the average for all treatments, rates of decay in bare soil were 0.60 (p < 0.001), 0.45 (p < 0.05), and 0.63 (p < 0.001) log CFU/g/d for E. coli O157:H7, L. monocytogenes, and Salmonella, respectively. Linear multiple regression revealed that soil hydrological parameters were positively correlated (p < 0.05) with bacterial counts, while day soil temperatures were negatively correlated (p < 0.001), suggesting that higher day temperatures and lower moisture content of bare soil contributed to the faster decline of pathogens compared to mulched soil. A microcosm experiment using field soil from lettuce cultivation suggested no influence of prior mulch treatment on pathogens. In summary, pathogen decline in soil was modified by the soil microclimate created under mulch covers, but the effect appeared was restricted to the time of soil cover. Slower decline rates of pathogens in mulched soil may pose a risk for contamination of fresh market produce crops.
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Affiliation(s)
- Shirley A Micallef
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD, USA; Center for Produce Safety and Security Systems, University of Maryland, College Park, MD, USA.
| | - Mary Theresa Callahan
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD, USA
| | - Rachel McEgan
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD, USA
| | - Louisa Martinez
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD, USA
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Qiang L, Hu H, Li G, Xu J, Cheng J, Wang J, Zhang R. Plastic mulching, and occurrence, incorporation, degradation, and impacts of polyethylene microplastics in agroecosystems. Ecotoxicol Environ Saf 2023; 263:115274. [PMID: 37499389 DOI: 10.1016/j.ecoenv.2023.115274] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 07/14/2023] [Accepted: 07/17/2023] [Indexed: 07/29/2023]
Abstract
Polyethylene microplastics have been detected in farmland soil, irrigation water, and soil organisms in agroecosystems, while plastic mulching is suggested as a crucial source of microplastic pollution in the agroecosystem. Plastic mulch can be broken down from plastic mulch debris to microplastics through environmental aging and degradation process in farmlands, and the colonization of polyethylene-degrading microorganisms on polyethylene microplastics can eventually enzymatically depolymerize the polyethylene molecular chains with CO2 release through the tricarboxylic acid cycle. The selective colonization of microplastics by soil microorganisms can cause changes in soil microbial community composition, and it can consequently elicit changes in enzyme activities and nutrient element content in the soil. The biological uptake of polyethylene microplastics and the associated disturbance of energy investment are the main mechanisms impacting soil-dwelling animal development and behavior. As polyethylene microplastics are highly hydrophobic, their presence among soil particles can contribute to soil water repellency and influence soil water availability. Polyethylene microplastics have been shown to cause impacts on crop plant growth, as manifested by the effects of polyethylene microplastics on soil properties and soil biota in the agroecosystems. This review reveals the degradation process, biological impacts, and associated mechanisms of polyethylene microplastics in agroecosystems and could be a critical reference for their risk assessment and management.
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Affiliation(s)
- Liyuan Qiang
- College of Mechanical and Electrical Engineering, Shihezi University, Shihezi, Xinjiang 832003, China; Key Laboratory of Northwest Agricultural Equipment, Ministry of Agriculture and Rural Affairs, Xinjiang 832003, China
| | - Huibing Hu
- College of Mechanical and Electrical Engineering, Shihezi University, Shihezi, Xinjiang 832003, China; Key Laboratory of Northwest Agricultural Equipment, Ministry of Agriculture and Rural Affairs, Xinjiang 832003, China
| | - Guoqiang Li
- College of Mechanical and Electrical Engineering, Shihezi University, Shihezi, Xinjiang 832003, China; Key Laboratory of Northwest Agricultural Equipment, Ministry of Agriculture and Rural Affairs, Xinjiang 832003, China
| | - Jianlong Xu
- College of Mechanical and Electrical Engineering, Shihezi University, Shihezi, Xinjiang 832003, China; Key Laboratory of Northwest Agricultural Equipment, Ministry of Agriculture and Rural Affairs, Xinjiang 832003, China
| | - Jinping Cheng
- Department of Science and Environmental Studies, The Education University of Hong Kong, New Territories, Hong Kong SAR, China; The Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China.
| | - Jiaping Wang
- Agricultural College, Shihezi University, Shihezi, Xinjiang 832003, China
| | - Ruoyu Zhang
- College of Mechanical and Electrical Engineering, Shihezi University, Shihezi, Xinjiang 832003, China; Key Laboratory of Northwest Agricultural Equipment, Ministry of Agriculture and Rural Affairs, Xinjiang 832003, China.
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Tang KHD. Microplastics in agricultural soils in China: Sources, impacts and solutions. Environ Pollut 2023; 322:121235. [PMID: 36754198 DOI: 10.1016/j.envpol.2023.121235] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 02/03/2023] [Accepted: 02/06/2023] [Indexed: 06/18/2023]
Abstract
The detection of microplastics (MPs) in agricultural soils has raised alarms on their potential impacts on agricultural production, particularly in China where agriculture has great importance for domestic consumption and export. This review aims to present the abundance, sources and impacts of MPs in the agricultural soils of China. It has the novelty of synthesizing sustainable agronomic practices to reduce MPs pollution of agricultural soils based on the sources identified. According to the extant study, the abundance of MPs in the agricultural soils in China ranged from 4.94 items/kg in the lower reaches of Yangtze River to 40,800 items/kg in Yunnan Province. The MPs were predominantly ≤1 mm and were mainly composed of fragments, films and fibers. Polyethylene and polypropylene MPs were most reported. Plastic mulching films were the most significant source of MPs in agricultural soils, followed by abandoned greenhouses and the use of organic fertilizers containing fugitive MPs or whose sources were often MPs-polluted. MPs were found to alter soil physicochemical properties for instance, water flow, water-stable aggregates, soil aggregation, soil pH, bulk density and nutrient contents. MPs also affect soil biota through changing the richness and diversity of soil microbial community while retarding growth and disrupting physiological functions of soil macrofauna. The effects of MPs on crops vary and range from alteration of biomass, metabolism and nutrient demands to impacted photosynthesis. Sustainable solutions include the use of grass clippings - straw mix as organic mulches, the use of compost as soil amendment in conjunction with grass-straw mix and incorporation of weed-suppressing biomass into compost, the use of jute and biodegradable plastics for greenhouses, proper decommissioning of abandoned greenhouses as well as setting standards for allowable MPs contents in organic fertilizers and irrigation water.
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Affiliation(s)
- Kuok Ho Daniel Tang
- Department of Environmental Science, The University of Arizona, Tucson, AZ, 85721, USA.
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Khalid N, Aqeel M, Noman A, Fatima Rizvi Z. Impact of plastic mulching as a major source of microplastics in agroecosystems. J Hazard Mater 2023; 445:130455. [PMID: 36463747 DOI: 10.1016/j.jhazmat.2022.130455] [Citation(s) in RCA: 25] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 11/18/2022] [Accepted: 11/20/2022] [Indexed: 06/17/2023]
Abstract
The contamination of agroecosystems by microplastics (MPs) has raised great concerns recently. Plastic mulching has contributed a lot in the building of MP pollution in farmlands. This technique has been in use for decades worldwide because of its immense advantages, preferably in drier and colder regions. The physical extraction of plastic mulches at the end of the growing season is very laborious and ineffective, and thus small pieces of mulches are left in the field which later convert into MP particles after aging, weathering, or on exposure to solar radiation. MPs not only influence physical, chemical, or biological properties of soils but also reduce crop productivity which could be a threat to our food security. They also interact with and accumulate other environmental contaminants such as microbial pathogens, heavy metals, and persistent organic pollutants on their surfaces which increase their risk of toxicity in the environment. MPs also transfer from one trophic level to the other in the food chain and ultimately may impact human health. Because of the ineffectiveness of the recovery of plastic film fragments from fields, researchers are now mainly focusing on alternative solutions to conventional plastic mulch films such as the use of biodegradable mulches. In this review, we have discussed the issue of plastic mulch films in agroecosystems and tried to link already existing knowledge to the current limitations in research on this topic from cropland soils and future prospects have been identified and proposed.
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Affiliation(s)
- Noreen Khalid
- Department of Botany, Government College Women University, Sialkot, Pakistan.
| | - Muhammad Aqeel
- State Key Laboratory of Grassland Agroecosystems, College of Ecology, Lanzhou University, Lanzhou 730000, Gansu, PR China
| | - Ali Noman
- Department of Botany, Government College University, Faisalabad, Pakistan
| | - Zarrin Fatima Rizvi
- Department of Botany, Government College Women University, Sialkot, Pakistan
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Palansooriya KN, Sang MK, Igalavithana AD, Zhang M, Hou D, Oleszczuk P, Sung J, Ok YS. Biochar alters chemical and microbial properties of microplastic-contaminated soil. Environ Res 2022; 209:112807. [PMID: 35093312 DOI: 10.1016/j.envres.2022.112807] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 01/11/2022] [Accepted: 01/21/2022] [Indexed: 05/06/2023]
Abstract
The occurrence of microplastics (MPs) in soils can negatively affect soil biodiversity and function. Soil amendments applied to MP-contaminated soil can alter the overall soil properties and enhance its functions and processes. However, little is known about how soil amendments improve the quality of MP-contaminated soils. Thus, the present study used a microcosm experiment to explore the potential effects of four types of biochar on the chemical and microbial properties of low-density polyethylene (LDPE) MP-contaminated soil under both drought and well-watered conditions. The results show that the biochars altered soil pH, electrical conductivity (EC), available phosphorous, and total exchangeable cations (TEC) with some variability depending on the biochar type. Oilseed rape straw (OSR)-derived biochars increased soil pH, EC, and TEC under both water conditions with the highest values of 7.94, 0.54 dS m-1 and 22.0 cmol(+) kg-1, respectively. Soil enzyme activities varied under all treatments; in particular, under drought conditions, the fluorescein diacetate activity increased in soils with high temperature (700 °C) biochar. The application of soft wood pellet biochar (700 °C) to MP-contaminated soil increased urease activity by 146% under well-watered conditions. OSR-derived biochars significantly reduced soil acid phosphatase activity under both water conditions. With biochar supplementation, the diversity indices of the bacterial community increased in well-watered soil but not in soil under drought conditions. The abundance of bacterial phyla, such as Firmicutes, Proteobacteria, Actinobacteria, Dictyoglomi, and Gemmatimonadetes, was relatively high in all treatments. Biochar application resulted in negligible variations in bacterial communities under drought conditions but significant variations under well-watered conditions. The findings of this study imply that biochar can be used as a soil amendment to improve the overall soil quality of MP-contaminated soil, but its impact varies depending on the pyrolysis feedstock and temperature. Thus, selecting a suitable biochar is important for improving the soil quality in MP-contaminated soils.
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Affiliation(s)
- Kumuduni Niroshika Palansooriya
- Korea Biochar Research Center, APRU Sustainable Waste Management & Division of Environmental Science and Ecological Engineering, Korea University, Seoul, 02841, South Korea
| | - Mee Kyung Sang
- Division of Agricultural Microbiology, National Institute of Agricultural Science, Rural Development Administration, Wanju, 55365, South Korea
| | | | - Ming Zhang
- Department of Environmental Engineering, China Jiliang University, Hangzhou, 310028, China
| | - Deyi Hou
- School of Environment, Tsinghua University, Beijing, 100084, China
| | - Patryk Oleszczuk
- Department of Radiochemistry and Environmental Chemistry, Maria Curie-Sklodowska University, Lublin, 20-031, Poland
| | - Jwakyung Sung
- Department of Crop Science, College of Agriculture, Life Science and Environmental Chemistry, Chungbuk National University, Cheongju, Chungcheongbuk-do, 28644, South Korea.
| | - Yong Sik Ok
- Korea Biochar Research Center, APRU Sustainable Waste Management & Division of Environmental Science and Ecological Engineering, Korea University, Seoul, 02841, South Korea.
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Li S, Ding F, Flury M, Wang Z, Xu L, Li S, Jones DL, Wang J. Macro- and microplastic accumulation in soil after 32 years of plastic film mulching. Environ Pollut 2022; 300:118945. [PMID: 35122919 DOI: 10.1016/j.envpol.2022.118945] [Citation(s) in RCA: 82] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 01/29/2022] [Accepted: 01/31/2022] [Indexed: 06/14/2023]
Abstract
Plastic film mulch (PFM) is a double-edged-sword agricultural technology, which greatly improves global agricultural production but can also cause severe plastic pollution of the environment. Here, we characterized and quantified the amount of macro- and micro-plastics accumulated after 32 years of continuous plastic mulch film use in an agricultural field. An interactive field trial was established in 1987, where the effect of plastic mulching and N fertilization on maize yield was investigated. We assessed the abundance and type of macroplastics (>5 mm) at 0-20 cm soil depth and microplastic (<5 mm) at 0-100 cm depth. In the PFM plot, we found about 10 times more macroplastic particles in the fertilized plots than in the non-fertilized plots (6796 vs 653 pieces/m2), and the amount of film microplastics was about twice as abundant in the fertilized plots than in the non-fertilized plots (3.7 × 106 vs 2.2 × 106 particles/kg soil). These differences can be explained by entanglement of plastics with plant roots and stems, which made it more difficult to remove plastic film after harvest. Macroplastics consisted mainly of films, while microplastics consisted of films, fibers, and granules, with the films being identified as polyethylene originating from the plastic mulch films. Plastic mulch films contributed 33%-56% to the total microplastics in 0-100 cm depth. The total number of microplastics in the topsoil (0-10 cm) ranged as 7183-10,586 particles/kg, with an average of 8885 particles/kg. In the deep subsoil (80-100 cm) the plastic concentration ranged as 2268-3529 particles/kg, with an average of 2899 particles/kg. Long-term use of plastic mulch films caused considerable pollution of not only surface, but also subsurface soil. Migration of plastic to deeper soil layers makes removal and remediation more difficult, implying that the plastic pollution legacy will remain in soil for centuries.
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Affiliation(s)
- Shitong Li
- College of Land and Environment, Shenyang Agricultural University, Shenyang, 110866, China
| | - Fan Ding
- College of Land and Environment, Shenyang Agricultural University, Shenyang, 110866, China.
| | - Markus Flury
- Department of Crop and Soil Sciences, Washington State University, Pullman 99164 And, Puyallup, WA, 98371, USA
| | - Zhan Wang
- College of Land and Environment, Shenyang Agricultural University, Shenyang, 110866, China
| | - Li Xu
- Beijing Research Center for Agricultural Standards and Testing, Beijing Academy of Agriculture & Forestry Sciences, Beijing, 100095, China
| | - Shuangyi Li
- College of Land and Environment, Shenyang Agricultural University, Shenyang, 110866, China
| | - Davey L Jones
- Environment Centre Wales, Bangor University, Bangor, LL57 2UW, UK; Soils West, Centre for Sustainable Farming Systems, Food Futures Institute, Murdoch University, Murdoch, WA, 6105, Australia
| | - Jingkuan Wang
- College of Land and Environment, Shenyang Agricultural University, Shenyang, 110866, China
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Seyoum MM, Obayomi O, Bernstein N, Williams CF, Gillor O. The dissemination of antibiotics and their corresponding resistance genes in treated effluent-soil-crops continuum, and the effect of barriers. Sci Total Environ 2022; 807:151525. [PMID: 34748848 DOI: 10.1016/j.scitotenv.2021.151525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 10/16/2021] [Accepted: 11/04/2021] [Indexed: 06/13/2023]
Abstract
Irrigation with treated effluent is expanding as freshwater sources diminish, but hampered by growing concerns of pharmaceuticals contamination, specifically antibiotics and resistance determinants. To evaluate this concern, freshwater and effluent were applied to an open field that was treated with soil barriers including plastic mulch together with surface and subsurface drip irrigation, cultivating freshly eaten crops (cucumbers or melons) for two consecutive growing seasons. We hypothesized that the effluent carries antibiotics and resistance determinants to the drip-irrigated soil and crops regardless of the treatment. To test our hypothesis, we monitored for antibiotics abundance (erythromycin, sulfamethoxazole, tetracycline, chlortetracycline, oxytetracycline, amoxicillin, and ofloxacin) and their corresponding resistance genes (ermB, ermF, sul1, tetW, tetO, blaTEM and qnrB), together with class 1 integron (intl1), and bacterial 16S rRNA, in water, soil, and crop samples taken over two years of cultivation. The results showed that an array of antibiotics and their corresponding resistance genes were detected in the effluent but not the freshwater. Yet, there were no significant differences in the distribution or abundance of antibiotics and resistance genes, regardless of the irrigation water quality, or crop type (p > 0.05), but plastic-covered soil irrigated with effluent retained the antibiotics oxytetracycline and ofloxacin (p < 0.05). However, we could not detect significant correlations between the detected antibiotics and the corresponding resistance genes. Overall, our findings disproved our hypothesis suggesting that treated effluent may not carry antibiotics resistance genes to the irrigated soil and crops yet, plastic mulch covered soil retain some antibiotics that may inflict long term contamination.
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Affiliation(s)
- Mitiku Mihiret Seyoum
- Zuckerberg Institute for Water Research, Blaustein Institutes for Desert Research, Ben Gurion University, Midreshet Ben Gurion, Israel
| | - Olabiyi Obayomi
- Zuckerberg Institute for Water Research, Blaustein Institutes for Desert Research, Ben Gurion University, Midreshet Ben Gurion, Israel
| | - Nirit Bernstein
- Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, Volcani Center, Israel
| | - Clinton F Williams
- USDA-ARS, Arid Land Agricultural Research Center, 21881 N. Cardon Ln, Maricopa, AZ 85138, USA
| | - Osnat Gillor
- Zuckerberg Institute for Water Research, Blaustein Institutes for Desert Research, Ben Gurion University, Midreshet Ben Gurion, Israel.
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Beriot N, Zomer P, Zornoza R, Geissen V. A laboratory comparison of the interactions between three plastic mulch types and 38 active substances found in pesticides. PeerJ 2020; 8:e9876. [PMID: 33005488 PMCID: PMC7513747 DOI: 10.7717/peerj.9876] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 08/14/2020] [Indexed: 01/19/2023] Open
Abstract
Background In semi-arid regions, the use of plastic mulch and pesticides in conventional agriculture is nearly ubiquitous. Although the sorption of pesticides on Low Density Polyethylene (LDPE) has been previously studied, no data are available for other plastics such as Pro-oxidant Additive Containing (PAC) plastics or "biodegradable" (Bio) plastics. The aim of this research was to measure the sorption pattern of active substances from pesticides on LDPE, PAC and Bio plastic mulches and to compare the decay of the active substances in the presence and absence of plastic debris. Methods For this purpose, 38 active substances from 17 insecticides, 15 fungicides and six herbicides commonly applied with plastic mulching in South-east Spain were incubated with a 3 × 3 cm2 piece of plastic mulch (LDPE, PAC and Bio). The incubation was done in a solution of 10% acetonitrile and 90% distilled water at 35 °C for 15 days in the dark. The Quick Easy Cheap Effective Rugged Safe approach was adapted to extract the pesticides. Results The sorption behavior depended on both the pesticide and the plastic mulch type. On average, the sorption percentage was ~23% on LDPE and PAC and ~50% on Bio. The decay of active substances in the presence of plastic was ~30% lesser than the decay of active substances in solution alone. This study is the first attempt at assessing the behavior of a diversity of plastic mulches and pesticides to further define research needs.
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Affiliation(s)
- Nicolas Beriot
- Soil Physics and Land Management Group, Wageningen University and Research, Wageningen, Netherlands.,Sustainable Use, Management and Reclamation of Soil and Water Research Group, Universidad Politécnica de Cartagena, Cartagena, Murcia, Spain
| | - Paul Zomer
- Wageningen Food Safety Research, Wageningen University and Research, Wageningen, Netherlands
| | - Raul Zornoza
- Sustainable Use, Management and Reclamation of Soil and Water Research Group, Universidad Politécnica de Cartagena, Cartagena, Murcia, Spain
| | - Violette Geissen
- Soil Physics and Land Management Group, Wageningen University and Research, Wageningen, Netherlands
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Todd-Searle J, Friedrich LM, Oni RA, Shenge K, LeJeune JT, Micallef SA, Danyluk MD, Schaffner DW. Quantification of Salmonella enterica transfer between tomatoes, soil, and plastic mulch. Int J Food Microbiol 2020; 316:108480. [PMID: 31862511 DOI: 10.1016/j.ijfoodmicro.2019.108480] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Revised: 11/15/2019] [Accepted: 12/11/2019] [Indexed: 11/25/2022]
Abstract
Tomatoes have been linked to Salmonella outbreaks in the United States (US). Plasticulture systems, that combine raised beds, plastic mulch, drip irrigation and fumigation, are common in commercial staked fresh tomato production in the US. The US FDA Produce Safety Rule prohibits the distribution of any produce covered by the rule (including fresh market tomatoes) that drops to the ground before harvest. This research was undertaken to better characterize the risks posed by tomatoes that touch plastic mulch or soil immediately before or during harvest. Research was conducted in three states (Florida, Maryland, and Ohio). Each state utilized tomatoes from their state at the point of harvest maturity most common in that state. Each state used indigenous soil and plastic mulch for transfer scenarios. New plastic mulch obtained directly from the application roll and used plastic mulch that had been present on beds for a growing season were evaluated. A five-strain cocktail of Salmonella enterica isolates obtained from tomato outbreaks was used. Mulch (new or used), soil, or tomatoes were spot inoculated with 100 μl of inoculum to obtain a final population of ~6 log CFU/surface. Items were either touched to each other immediately (1-2 s) after inoculation (wet contact) or allowed to dry at ambient temperature for 1 h or 24 h (dry contact). All surfaces remained in brief (1-5 s) or extended (24 h) contact at ambient temperature. Transfer of Salmonella between a tomato and plastic mulch or soil is dependent on contact time, dryness of the inoculum, type of soil, and contact surface. Transfer of Salmonella to and from the mulch and tomatoes for wet and 1 h dry inocula were similar with mean log % transfers varying from 0.7 ± 0.2 to 1.9 ± 0.1. The transfer of Salmonella between soil or plastic mulch to and from tomatoes was dependent on moisture with wet and 1 h dry inocula generally yielding significantly (p < 0.05) higher transfer than the 24 h dry inoculum. Results indicate that harvesting dry tomatoes significantly (p < 0.05) reduces the risk of contamination from soil or mulch contact. Transfer to tomatoes was generally significantly greater (p < 0.05) from new and used plastic mulch than from soil. If contamination and moisture levels are equivalent and contact times are equal to or <24 h before harvest, significantly (p < 0.05) more Salmonella transfers to tomatoes from mulch than from soil. Our findings support that harvesting tomatoes from soil has similar or lower risk than harvesting from plastic mulch.
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Affiliation(s)
- Jennifer Todd-Searle
- Department of Food Science, Rutgers, the State University of New Jersey, 65 Dudley Road, New Brunswick, NJ 08901, United States of America
| | - Loretta M Friedrich
- Citrus Research and Education Center, University of Florida, IFAS, 700 Experiment Station Rd, Lake Alfred, FL 33850, United States of America
| | - Ruth A Oni
- Department of Nutrition and Food Science, University of Maryland, Marie Mount Hall, 7814 Regents Dr, College Park, MD 20740, United States of America
| | - Kenneth Shenge
- National Biosafety and Biocontainment Training Program, National Institutes of Health, Bldg. 13, Room 3K04, Bethesda, MD 20892, United States of America
| | | | - Shirley A Micallef
- Department of Plant Science and Landscape Architecture, University of Maryland, 4291 Fieldhouse Drive, College Park, MD 20742, United States of America; Centre for Food Safety and Security Systems, University of Maryland, Plant Sciences Building, College Park, MD 20742, United States of America
| | - Michelle D Danyluk
- Citrus Research and Education Center, University of Florida, IFAS, 700 Experiment Station Rd, Lake Alfred, FL 33850, United States of America
| | - Donald W Schaffner
- Department of Food Science, Rutgers, the State University of New Jersey, 65 Dudley Road, New Brunswick, NJ 08901, United States of America.
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11
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Al-Shammary AAG, Kouzani A, Gyasi-Agyei Y, Rodrigo-Comino J. A comparison of different solarisation systems and their impacts on soil thermal characteristics-an application in cultivated soils close to Baghdad, a highly populated city in Iraq. Environ Monit Assess 2019; 192:13. [PMID: 31811402 DOI: 10.1007/s10661-019-7985-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 11/22/2019] [Indexed: 06/10/2023]
Abstract
Solarisation application by mulching the soil with a polyethene plastic film has a significant influence on soil thermal characteristics (TCs), which, in turn, show a strong impact on soil energy balance and agricultural productivity. In countries like Iraq with highly populated cities, such as Baghdad, that need large quantities of agriproducts, this kind of clean energy should play a key role in sustainable agricultural production. However, little is known about the effects of different soil solarisation systems in specific cultivated fields for this country characterised by an arid climate and silty clay soils. Therefore, an experimental study was conducted to investigate changes in soil TCs under different soil solarisation systems (black and clear plastics) at three different soil depths in a two-factor factorial design. Also, both the black and clear plastic plots were compared with a control (without mulch) plot treatment. Three different soil TCs were assessed, namely soil thermal flux (qℎ), soil thermal conductivity (k), and soil volumetric heat capacity (Cv). The results of this study indicated that the soil solarisation application had a significant influence on soil TCs. Soil qℎ decreased with increasing soil depth, while k and Cv exhibited an opposite trend. The black plastic mulch treatment produced higher soil qℎ, k, and Cv values than both the clear plastic and the control treatments. Moreover, high diurnal variability of the TCs was also registered, and the clear plastic conserved a higher temperature than the black one during the night hours. During daylight, the black mulch reached a maximum temperature of 70 °C. It is recommended that more research should be conducted to get new insights on the interplay of the different seasons, and different crops and soil types.
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Affiliation(s)
- Ahmed Abed Gatea Al-Shammary
- School of Engineering, Deakin University, Geelong, VIC, 3216, Australia.
- Soil Science and Water Resources Departments, College of Agriculture, University of Wasit, Kut, Iraq.
| | - Abbas Kouzani
- School of Engineering, Deakin University, Geelong, VIC, 3216, Australia
| | - Yeboah Gyasi-Agyei
- School of Engineering and Technology, Central Queensland University, Rockhampton, QLD, 4702, Australia
| | - Jesús Rodrigo-Comino
- Department of Physical Geography, University of Trier, 54296, Trier, Germany
- Soil Erosion and Degradation Research Group, Department of Geography, University of Valencia, Avda. Blasco Ibáñez, 28, 46010, Valencia, Spain
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12
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Chen G, Kolb L, Cavigelli MA, Weil RR, Hooks CRR. Can conservation tillage reduce N 2O emissions on cropland transitioning to organic vegetable production? Sci Total Environ 2018; 618:927-940. [PMID: 29111244 DOI: 10.1016/j.scitotenv.2017.08.296] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2017] [Revised: 08/28/2017] [Accepted: 08/29/2017] [Indexed: 06/07/2023]
Abstract
Nitrous oxide (N2O) is an important greenhouse gas and a catalyst of stratospheric ozone decay. Agricultural soils are the source of 75% of anthropogenic N2O emissions globally. Recently, significant attention has been directed at examining effects of conservation tillage on carbon sequestration in agricultural systems. However, limited knowledge is available regarding how these practices impact N2O emissions, especially for organic vegetable production systems. In this context, a three-year study was conducted in a well-drained sandy loam field transitioning to organic vegetable production in the Mid-Atlantic coastal plain of USA to investigate impacts of conservation tillage [strip till (ST) and no-till (NT)] and conventional tillage (CT) [with black plastic mulch (CT-BP) and bare-ground (CT-BG)] on N2O emissions. Each year, a winter cover crop mixture (forage radish: Raphanus sativus var. longipinnatus, crimson clover: Trifolium incarnatum L., and rye: Secale cereale L.) was grown and flail-mowed in the spring. Nearly 80% of annual N2O-nitrogen (N) emissions occurred during the vegetable growing season for all treatments. Annual N2O-N emissions were greater in CT-BP than in ST and NT, and greater in CT-BG than in NT, but not different between CT-BG and CT-BP, ST and NT, or CT-BG and ST. Conventional tillage promoted N mineralization and plastic mulch increased soil temperature, which contributed to greater N2O-N fluxes. Though water filled porosity in NT was higher and correlated well with N2O-N fluxes, annual N2O-N emissions were lowest in NT suggesting a lack of substrates for nitrification and denitrification processes. Crop yield was lowest in NT in Year 1 and CT-BP in Year 3 but yield-scaled N2O-N emissions were consistently greatest in CT-BP and lowest in NT each year. Our results suggest that for coarse-textured soils in the coastal plain with winter cover crops, conservation tillage practices may reduce N2O emissions in organic vegetable production systems.
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Affiliation(s)
- Guihua Chen
- University of Maryland, Department of Entomology, College Park, MD, USA.
| | - Lauren Kolb
- The City of Boulder's Open Space and Mountain Parks, Boulder, CO, USA
| | - Michel A Cavigelli
- United States Department of Agriculture, Agricultural Research Service, Beltsville Agriculture Research Center, Beltsville, MD, USA
| | - Ray R Weil
- University of Maryland, Department of Environmental Science and Technology, College Park, MD, USA
| | - Cerruti R R Hooks
- University of Maryland, Department of Entomology, College Park, MD, USA
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13
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Yun Z, Ning-Bo H, Xi-Guang F, Xue-Wen S, Xiong-Bin L, Wei-Dong Y, Gui-Lin M, Meng-Tao X, Ming-Shou W, Jing S, Jia-Yu S, Chun-Qiong C. [Short - term effects of two kinds of plastic mulch on Oncomelania hupensis snail control in irrigation and drainage ditches in Yunnan Province]. Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi 2016; 29:342-345. [PMID: 29469528 DOI: 10.16250/j.32.1374.2016152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
OBJECTIVE To evaluate and compare the short-term effects of two kinds of plastic mulch on Oncomelania hupensis snail control in irrigation and drainage ditches with snails in Yunnan Province. METHODS The irrigation and drainage ditches with high density of Oncomelania hupensis snails were chosen as the investigation sites, and then 4 groups were set, namely a colorless plastic mulch group, black plastic mulch group, colorless plastic mulch with molluscicide group and black plastic mulch with molluscicide group. The snail situation of the 4 groups was surveyed before the experiment and 7, 14, 21, 30 days after covering plastic mulch, and the snail death rates were compared among the 4 groups. Meanwhile, the hourly temperatures of soil surface, soil surface under plastic mulch and soil layer 5, 15 cm under the surface as well as the weather situation during the study period were measured and recorded. RESULTS The average snail mortality rate of the colorless plastic mulch group was only 15.29% that was higher than that of the black plastic mulch group (6.56%) (P < 0.01). The average snail mortality rates of the colorless and black plastic mulch with molluscicide groups were 40.80% and 50.15%, respectively, and there was no statistic difference between them (P > 0.05). Both kinds of plastic mulches could raise the temperature of the soil surface under plastic mulch and the soil layer below it, and the temperature of soil under the mulches increased over the cover time, and the average temperature of the soil surface under the black mulch in 30 days was higher than that under the colorless mulch. CONCLUSIONS It is not suitable to use plastic mulch only in irrigation and drainage ditches with snails widely in Yunnan Province because of its low effect, and if necessary, the molluscicide should be added.
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Affiliation(s)
- Zhang Yun
- Yunnan Institute of Endemic Diseases Control and Prevention, Dali 671000, China
| | - Huang Ning-Bo
- Yunnan Institute of Endemic Diseases Control and Prevention, Dali 671000, China
| | - Feng Xi-Guang
- Yunnan Institute of Endemic Diseases Control and Prevention, Dali 671000, China
| | - Shi Xue-Wen
- Eryuan Station of Schistosomiasis Control, Yunnan Province, China
| | - Li Xiong-Bin
- Eryuan Station of Schistosomiasis Control, Yunnan Province, China
| | - Yang Wei-Dong
- Eryuan Station of Schistosomiasis Control, Yunnan Province, China
| | - Mao Gui-Lin
- Eryuan Station of Schistosomiasis Control, Yunnan Province, China
| | - Xiong Meng-Tao
- Yunnan Institute of Endemic Diseases Control and Prevention, Dali 671000, China
| | - Wu Ming-Shou
- Yunnan Institute of Endemic Diseases Control and Prevention, Dali 671000, China
| | - Song Jing
- Yunnan Institute of Endemic Diseases Control and Prevention, Dali 671000, China
| | - Sun Jia-Yu
- Yunnan Institute of Endemic Diseases Control and Prevention, Dali 671000, China
| | - Chen Chun-Qiong
- Yunnan Institute of Endemic Diseases Control and Prevention, Dali 671000, China
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14
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Yin W, Feng F, Zhao C, Yu A, Hu F, Chai Q, Gan Y, Guo Y. Integrated double mulching practices optimizes soil temperature and improves soil water utilization in arid environments. Int J Biometeorol 2016; 60:1423-1437. [PMID: 26813883 DOI: 10.1007/s00484-016-1134-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Revised: 12/13/2015] [Accepted: 01/08/2016] [Indexed: 06/05/2023]
Abstract
Water shortage threatens agricultural sustainability in many arid and semiarid areas of the world. It is unknown whether improved water conservation practices can be developed to alleviate this issue while increasing crop productivity. In this study, we developed a "double mulching" system, i.e., plastic film coupled with straw mulch, integrated together with intensified strip intercropping. We determined (i) the responses of soil evaporation and moisture conservation to the integrated double mulching system and (ii) the change of soil temperature during key plant growth stages under the integrated systems. Experiments were carried out in northwest China in 2009 to 2011. Results show that wheat-maize strip intercropping in combination with plastic film and straw covering on the soil surface increased soil moisture (mm) by an average of 3.8 % before sowing, 5.3 % during the wheat and maize co-growth period, 4.4 % after wheat harvest, and 4.9 % after maize harvest, compared to conventional practice (control). The double mulching decreased total evapotranspiration of the two intercrops by an average of 4.6 % (P < 0.05), compared to control. An added feature was that the double mulching system decreased soil temperature in the top 10-cm depth by 1.26 to 1.31 °C in the strips of the cool-season wheat, and by 1.31 to 1.51 °C in the strips of the warm-season maize through the 2 years. Soil temperature of maize strips higher as 1.25 to 1.94 °C than that of wheat strips in the top 10-cm soil depth under intercropping with the double mulching system; especially higher as 1.58 to 2.11 °C under intercropping with the conventional tillage; this allows the two intercrops to grow in a well "collaborative" status under the double mulching system during their co-growth period. The improvement of soil moisture and the optimization of soil temperature for the two intercrops allow us to conclude that wheat-maize intensification with the double mulching system can be used as an effective farming model in alleviating water shortage issues experiencing in water shortage areas.
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Affiliation(s)
- Wen Yin
- Gansu Provincial Key Laboratory of Aridland Crop Science, Lanzhou, 730070, China
- College of Agronomy, Gansu Agricultural University, Lanzhou, 730070, China
| | - Fuxue Feng
- Gansu Provincial Key Laboratory of Aridland Crop Science, Lanzhou, 730070, China
| | - Cai Zhao
- Gansu Provincial Key Laboratory of Aridland Crop Science, Lanzhou, 730070, China
- College of Agronomy, Gansu Agricultural University, Lanzhou, 730070, China
| | - Aizhong Yu
- Gansu Provincial Key Laboratory of Aridland Crop Science, Lanzhou, 730070, China
- College of Agronomy, Gansu Agricultural University, Lanzhou, 730070, China
| | - Falong Hu
- Gansu Provincial Key Laboratory of Aridland Crop Science, Lanzhou, 730070, China
- College of Agronomy, Gansu Agricultural University, Lanzhou, 730070, China
| | - Qiang Chai
- Gansu Provincial Key Laboratory of Aridland Crop Science, Lanzhou, 730070, China.
- College of Agronomy, Gansu Agricultural University, Lanzhou, 730070, China.
| | - Yantai Gan
- Gansu Provincial Key Laboratory of Aridland Crop Science, Lanzhou, 730070, China.
- Agriculture and Agri-Food Canada, Semiarid Prairie Agricultural Research Centre, Swift Current, SK, S9H 3X2, Canada.
| | - Yao Guo
- Gansu Provincial Key Laboratory of Aridland Crop Science, Lanzhou, 730070, China
- College of Agronomy, Gansu Agricultural University, Lanzhou, 730070, China
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15
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Xu A, Buchanan RL, Micallef SA. Impact of mulches and growing season on indicator bacteria survival during lettuce cultivation. Int J Food Microbiol 2016; 224:28-39. [PMID: 26938806 DOI: 10.1016/j.ijfoodmicro.2016.02.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Revised: 11/11/2015] [Accepted: 02/19/2016] [Indexed: 11/22/2022]
Abstract
In fresh produce production, the use of mulches as ground cover to retain moisture and control weeds is a common agricultural practice, but the influence that various mulches have on enteric pathogen survival and dispersal is unknown. The goal of this study was to assess the impact of different mulching methods on the survival of soil and epiphytic fecal indicator bacteria on organically grown lettuce during different growing seasons. Organically managed lettuce, cultivated with various ground covers--polyethylene plastic, corn-based biodegradable plastic, paper and straw mulch--and bare ground as a no-mulch control, was overhead inoculated with manure-contaminated water containing known levels of generic Escherichia coli and Enterococcus spp. Leaves and soil samples were collected at intervals over a two week period on days 0, 1, 3, 5, 7, 10 and 14, and quantitatively assessed for E. coli, fecal coliforms and Enterococcus spp. Data were analyzed using mixed models with repeated measures and an exponential decline with asymptote survival model. Indicator bacterial concentrations in the lettuce phyllosphere decreased over time under all treatments, with more rapid E. coli declines in the fall than in the spring (p<0.01). Persistence of E. coli in spring was correlated with higher maximum and minimum temperatures in this season, and more regular rainfall. The survival model gave very good fits for the progression of E. coli concentrations in the phyllosphere over time (R(2)=0.88 ± 0.12). In the spring season, decline rates of E. coli counts were faster (2013 p=0.18; 2014 p<0.005) for the bare ground-cultivated lettuce compared to mulches. In fall 2014, the E. coli decline rate on paper mulch-grown lettuce was higher (p<0.005). Bacteria fluctuated more, and persisted longer, in soil compared to lettuce phyllosphere, and mulch type was a factor for fecal coliform levels (p<0.05), with higher counts retrieved under plastic mulches in all trials, and higher enterococci levels under straw in fall 2014 (p<0.05). This study demonstrates that mulches used in lettuce production may impact the fate of enteric bacteria in soil or on lettuce, most likely in relation to soil moisture retention, and other weather-related factors, such as temperature and rainfall. The data suggest that the time between exposure to a source of enteric bacteria and harvesting of the crop is season dependent, which has implications for determining best harvest times.
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Affiliation(s)
- Aixia Xu
- Department of Nutrition and Food Science, University of Maryland, College Park, MD 20742, USA
| | - Robert L Buchanan
- Department of Nutrition and Food Science, University of Maryland, College Park, MD 20742, USA; Center for Food Safety and Security Systems, University of Maryland, College Park, MD 20742, USA
| | - Shirley A Micallef
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD 20742, USA; Center for Food Safety and Security Systems, University of Maryland, College Park, MD 20742, USA.
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