Research & reports

Pay Drechsel, Andrew Adam‐Bradford, Liqa Raschid-Sally, Drechsel, Pay, Adam-Bradford, A., Raschid-Sally, Liqa · AgEcon Search (University of Minnesota, USA) · Ghana

This chapter introduces urbanization in West Africa, particularly Ghana, the general role of urban agriculture, and the common use of polluted irrigation water. It focuses on irrigated smallholder vegetable production, reflecting on the key challenges, dynamics, and resilience of this farming system.

Jin‐Won Kim, In‐Wook Choi, Won-Seok Na, Enkhjargar Baljii, Yong-Man Yu, Young Nam Youn, Young‐Ha Lee · Journal of Food Hygiene and Safety · South Korea (Seoul)

From September to October 2012, 530 samples of nine vegetable types were collected from 11 urban community gardens in Seoul to assess their microbiological quality. Mean total aerobic bacteria and coliforms were detected at 6.3 log CFU/g and 4.3 log CFU/g, respectively, with coliforms found in 67% of samples and E. coli in 2.3%. While foodborne pathogens were not detected, the presence of coliforms and E. coli indicates room for improvement in microbiological safety.

Ashley S. Harms, DeAnn Presley, Ganga M. Hettiarachchi, Chammi P. Attanayake, Sabine Martin, Steven J. Thien · Natural sciences education · United States (Kansas City)

This case study examines the decision faced by Mr. John Holloway in Harmony Park, Kansas City, MO, regarding establishing a community garden on a vacant brownfield site in 2009. Concerns arose about soil contaminants on the site, leading to a dilemma about the potential harm versus benefits of gardening in a food desert. The case requires students to evaluate environmental, agronomic, human health, social, and economic issues related to urban soil contamination.

Ande O.T, Adetunji A. M, Akinpelu M. E, Senjobi B.A · Journals & Books Hosting (International Knowledge Sharing Platform) · Nigeria

Ibadan metropolis, Nigeria, home to about 6 million people, has raised growing concern over lowland soils in its periurban area, where much of the industrial waste transported by the River Ona is deposited; these soils are used for dry-season farming and contribute to food security. This study aimed to characterize periurban lowland soils around Ibadan and determine their vulnerability to industrial pollution, using a 50m x 50m grid with surface samples taken at 50m intervals, plus representative profile pits described using the USDA method, and particle-size and chemical analyses (phosphorus, nitrogen, exchangeable cations Ca/Mg/Na/K, manganese, and heavy metals including lead, copper, zinc, chromium, iron, and cadmium). Results showed the floodplain's surface soil was fertile, with high nitrogen (0.35 cmol/kg), phosphorus (51.25 cmol/kg), and potassium (0.61 cmol/kg), and phosphorus levels ranging from very high to toxic, between 28.99 and 87.70 ppm. Average heavy metal concentrations were lead 34.30 mg/kg, zinc 171.20 mg/kg, iron 83.97 mg/kg, copper 19.11 mg/kg, manganese 31.10 mg/kg, chromium 0.69 mg/kg, and cadmium 0.3 mg/kg. Predicted soil-to-plant heavy metal transfer coefficients (Pb 35-343; Cr 0.46-4.6; Zn 171-1712; Cu 19-191; Fe 83-840; Mn 31-281; Cd 0.1-10) indicated crops grown in the area could contain toxic levels of these metals; however, high yields and healthy plant condition observed in the field, together with farmer interviews, suggested that the high phosphorus level (28.99-87 ppm) may have inhibited uptake of some metals such as lead, zinc, and copper.

Sam E. Wortman, Sarah Taylor Lovell · Journal of Environmental Quality · United States

This review paper characterized the limited state of scientific knowledge regarding abiotic environmental factors threatening the growth of urban agriculture in the United States. It identified challenges influencing urban cropping systems, including soil contamination and remediation, atmospheric pollutants and altered climatic conditions, and water management, sources, and safety. The development of a science-based approach in these areas is noted as essential for the economic and environmental sustainability of urban agriculture.

Marcelo Ortega Romero, Juan Mingot Marcilla, María Jesús García Martínez, Eduardo de Miguel, Miguel Izquierdo‐Díaz, Amaya Gómez · · Spain (Madrid)

This study evaluated the potential health risk from trace elements in urban garden soils in Madrid, Spain. Thirty-six composite soil samples were collected from the top 20 cm of six urban gardens, and concentrations of cobalt, chromium, copper, nickel, lead, and zinc were determined. The findings indicated that urban soils are significantly enriched in trace elements relative to background levels, suggesting a potential health risk.

Mucig Charlotte · · France

A survey on rainwater harvesting in community gardens in France indicates that while this practice has been ongoing for years, it is poorly documented and faces challenges in adapting to new French regulations. The findings highlight public health issues for both garden users and consumers of fruits and vegetables, as well as environmental and operational concerns.

Prem José Vazhacharickal, Martina Předotová, D. Chandrasekharam, Sharit K. Bhowmik, Buerkert, Andreas · Journal of Agriculture and Rural Development in the Tropics and Subtropics (University of Kassel) · India (Mumbai)

A study surveyed 38 railway gardeners to characterize urban and peri-urban agricultural production along railway tracks in the Mumbai Metropolitan Region. Irrigation water contained nutrients but also heavy metals such as lead, cadmium, and mercury, and pathogens like Escherichia coli. Heavy metal levels exceeded critical thresholds in surface soils for chromium, nickel, and strontium, and in produce for lead, cadmium, and strontium.

Laura Knapp, Jodi L. Sangster, Shannon L. Bartelt‐Hunt · International Journal for Service Learning in Engineering Humanitarian Engineering and Social Entrepreneurship · United States (Omaha NE)

This study investigated the influence of lead hyperaccumulating plants on lead uptake by vegetables in an urban community garden in Omaha, NE, a region with significant lead contamination. Tomatoes, carrots, and amaranth were grown alongside sunflowers and mustard greens (hyperaccumulators) in lead-contaminated soil. Data showed higher lead concentrations in the hyperaccumulators and suggested that their presence might have impacted the amount of lead available to surrounding vegetation. Previous work at the garden detected lead in produce, indicating a potential exposure pathway for humans.

Kyle Kessler, Seth Umbenhauer, Alison R. Noble · Journal of the Pennsylvania Academy of Science · United States (Harrisburg)

Eight soil samples were collected from an urban land plot in Harrisburg, PA, to determine concentrations of copper, nickel, zinc, and lead and assess suitability for an urban garden. While copper, nickel, and zinc concentrations were below EPA recommended limits, lead concentrations ranged from 26 ± 1 mg/kg to 402+ mg/kg, with some samples exceeding EPA standards for heavy metals in home and vegetable gardens. This indicates potential lead contamination in the soil.

Chris Zimmerman · Soil Horizons · United States

A narrative article profiling the work of soil scientist Samantha Langley-Turnbaugh of the University of Southern Maine, investigating lead contamination in urban soils in Portland, Maine. It traces the concern to the Great Fire of 1866, whose lead paint ash was spread across the city and used as landfill to extend the Portland peninsula, compounded by the city's historical ties to lead-producing industries. The article states that, across US cities generally, lead paint and leaded gasoline are the primary sources of soil lead contamination, and that this contamination is becoming a concern as urban gardening expands.

Nahed N. Mahrous · The Journal of Pediatrics · Canada (Hamilton)

This project investigated metal, bacteria, and corn root interactions in metal-contaminated soils from Blackfrairs Community Garden and a Hamilton home. It found that bacterial numbers were lower than in uncontaminated soils, and bioavailable metal concentrations increased over time. High concentrations of metals were detected in grains, with copper, iron, and manganese accumulating in rhizospheres, and zinc distributed throughout root tissue in Blackfrairs plants.

Lori Leonard, W. J. S. Mwegoha, Charles Kihampa · International Journal of Plant Animal and Environmental Sciences · Tanzania (Dar es Salaam)

This study investigated public awareness and health risks from heavy metal pollution in vegetables irrigated with Msimbazi River water in Dar es Salaam, Tanzania. Over 71% of 35 respondents used the river for irrigation, and high levels of chromium, lead, and copper were detected in popular vegetables. 69% of respondents were unaware of industrial pollution, and 63% were unaware of potential health effects. The study found that 95.6% of adults, 30.7% of children aged 6-12, and 12.5% of children aged 2-6 were at risk of lead carcinogenic effects, while 5% of children aged 2-6, 2.8% of children aged 6-12, and 1.2% of adults were at risk from carcinogenic cadmium effects.

Aubin Ondo, Pascale Prudent, C. Massiani, Menye Biyogo, Mariane Domeizel, Jacques Rabier, François Eba · Journal of the Serbian Chemical Society · Gabon (Libreville)

An assessment of urban agriculture's impact on soil properties and metal uptake by leafy vegetables in Libreville, Gabon, found strong soil acidification and decreased nutrient/metal concentrations due to agricultural practices. Metal transfer to plants was significant, with amaranth accumulating more metals than other vegetables, though cadmium and lead were not detectable in plant tissues. Amaranth and roselle preferentially concentrated metals in their leaves.

Zbigniew Ziembik, Agnieszka Dołhańczuk-Śródka, Grzegorz Kusza · Proceedings of ECOpole · Poland

Soil samples were collected from the former "Piast" cement plant within Opole city borders, Poland, and nearby allotment gardens to study radioisotope activity concentrations. Naturally occurring radioisotopes and artificial Cs were found, with K and Cs showing the biggest radioactivity concentration. No significant differences in radionuclide activities were found between soil samples from the former industrial estate and the allotment gardens.

Jodi L. Sangster, Andrew Nelson, Shannon L. Bartelt‐Hunt · International Journal for Service Learning in Engineering Humanitarian Engineering and Social Entrepreneurship · United States (Omaha)

Soil and vegetable samples were collected from a community garden in Omaha, Nebraska, which had known soil lead contamination. Total lead content was evaluated using atomic absorption spectroscopy, revealing lead concentrations in soil ranging from 4 to 574 ppm, with an average of 128.4 ppm in growing beds and 31.5 ppm in OmaGro compost. Lead was also present in vegetable samples at or below 16.25 ppm.

Adam J Long · Scholarship @ Claremont (The Claremont Colleges) · United States (Washington, DC)

This study investigated heavy metal soil contaminants in 13 urban community gardens in Washington, DC, analyzing 45 soil samples using X-ray fluorescence (XRF). While most samples fell below US EPA action levels for common contaminants, high concentrations of lead (above the US EPA action level of 400 ppm) were found in the native soil of three garden sites, meriting concern due to potential health problems in children.

Iwona Makuch · Soil Science Annual · Global

This study investigated the influence of intensive horticulture on lead content and its fractions in soil profiles from house gardens, allotment gardens, and arable fields. It was not determined that the manner of usage had any influence on total lead content or its distribution in soil profiles. However, the usage manner did influence the content and distribution of lead fraction III, which is connected with organic matter, with humus horizons of garden soils showing the highest content.

Anna‐Katarina Schilling, Helmut Hotzel, Ulrich Methner, Lisa D. Sprague, Gernot Schmoock, Hosny El‐Adawy, Ralf Ehricht, Anna-Caroline Wöhr, Michael Erhard, Lutz Geue · Applied and Environmental Microbiology · Germany

This study investigated the presence of zoonotic agents in small ruminants kept on city farms in southern Germany, sampling feces and nasal liquid from 48 animals (28 goats, 20 sheep) across 7 city farms and one activity playground. Findings revealed that 100% of sampled sheep and 89.3% of goats carried Shiga toxin-producing Escherichia coli (STEC). Staphylococcus spp. were detected in 75% of both sheep and goats, and Campylobacter spp. in 25% of sheep and 14.3% of goats. Neither Salmonella spp. nor Coxiella burnetii was found.

John Jacob, Samuel E. Kakulu · American Journal of Chemistry · Nigeria

Soil and vegetable samples (spinach, jute mallow, and tomato) were collected from farms and gardens across 20 zones within Kaduna, Nigeria, plus two rural control villages about 30 km from the city, and analyzed for heavy metals by Flame Atomic Absorption Spectrophotometer. Pollution Load Index results showed soils in the city farms were moderately enriched with cadmium and chromium and strongly enriched with lead and nickel from anthropogenic sources. Mean soil concentrations of lead and cadmium exceeded WHO/FAO permissive limits for agricultural soil (nickel and chromium did not), while vegetable metal concentrations exceeded the permissive limits for every metal except nickel — a finding flagged as concerning given the toxicity of lead and cadmium in particular, which have no known biological use.

R. Plant, Jeremy Walker, Scott Rayburg, J Gothe, Teresa Leung · Australian Geographer · Australia

A study of the Hawkesbury-Nepean River in Sydney, Australia, examines the effects of pesticide use by the small-scale horticulturalists supplying the city's fresh vegetable markets on aquatic biodiversity. Through interviews with actors across the institutions responsible for agriculture, water quality, and environmental protection, it assesses the effectiveness of pesticide governance in the Greater Sydney Basin. It finds that pesticide pollution is rarely measured or monitored and is not a priority for any particular agency, meaning the pollution remains effectively uncontrolled. The study concludes that although public health, the long-term viability of local farming, and the ecological health of the river are compatible goals, they currently exist under a system of "organised irresponsibility."

Laura Whitzling, Michelle M. Wander, Ellen Phillips · Journal of Agriculture Food Systems and Community Development · United States (Chicago)

This study profiled soil quality, including lead levels, in 10 Chicago community gardens, comparing raised beds to non-raised beds and adjacent bare soil. The overall mean soil lead level was 135 ppm (n=86) by EPA method, with a range of 10-889 ppm. While most gardens' lead levels were not a concern, higher lead in adjacent bare soil suggested contamination risk. Use of raised beds reduced lead levels, but further study is needed.

Mamadou Ndiaye, S. Niang, H.‐R. Pfeifer, Raffaele Peduzzi, Mauro Tonolla, Y Dieng · Irrigation and Drainage · Senegal

Lettuces grown at two urban agricultural sites (Pikine and Patte d'Oie) near Dakar, Senegal, and sold in local markets were tested for microbial contamination linked to irrigation water. Salmonella spp. positivity was 6% at Pikine and 7% at Patte d'Oie farm sites, with lettuces irrigated by shallow 'Ceanes' groundwater most contaminated at both sites (8%), compared to wastewater irrigation (4% at Pikine) and well water (5% at Patte d'Oie); at market, Salmonella was isolated at every marketplace surveyed, with higher rates around Patte d'Oie (9% at Grand Yoff, 11% at Dalifort) than around Pikine (4% at Zinc, 2% at Sham) or the control site Rufisque (2%), and lettuces washed with Ceanes water before sale were more contaminated than those rinsed with tap water. Reusing wastewater for irrigation is presented as an alternative to animal manure, with the microbial contamination risk significantly reducible by washing vegetables with tap water before sale.

G. M. Hettiarachchi, Sabine Martin, A. David Rae, Phillip P. Defoe, Dennis Presely, G. M. Pierzysnki · · United States

Using a newly established urban community garden in Kansas City as a case example, this study examines the challenges of converting brownfield sites — abandoned or underutilized properties where environmental concerns impede redevelopment — into community gardens. Soil at the site was found to contain mildly elevated levels of lead (Pb) and detectable levels of DDT/DDE (an organochlorine pesticide). Based on an evaluation of soil properties, safety and corrective measures were proposed and implemented to reduce both direct (soil-to-human) and indirect (soil-to-plant-to-human) exposure for gardeners and their children, and field test plots with three crop types showing different contaminant-uptake patterns were established to evaluate site-specific soil amendments for reducing lead bioavailability.

O. Muñiz, M. Ternero, Álvarez Montero, F. Martínez, T. Limeres, O. Jouber, M. Orphee, Julia Vidan Estevez, B. Calero, F. A. de Alcantara, Adriana María de Aguiar Accioly · Portuguese National Funding Agency for Science, Research and Technology (RCAAP Project by FCT) · Global

This paper situates its topic within the urban agriculture movement, which it describes as having successfully enabled low-input food production in cities, noting that organoponicos — plots focused on producing leafy vegetables and condiment crops in organic substrates — have driven up demand for organic material sources. The title indicates the study addresses the effect of using heavy-metal-contaminated compost on vegetable production, but the available abstract provides only this background context, with no results on contamination or crop impact stated.