Research & reports

Moisés Savian, Mari Inês Caríssimi Boff, Pedro Boff · Cadernos de Agroecologia · Brazil

This study evaluated Brazilian scientific production from 2009 to 2018 on urban agriculture's contribution to food and nutritional security, analyzing 34 selected articles out of 612. It found that while agrobiodiversity is present in urban agriculture areas, pesticide use is a reality in some crop plots. The research suggests urban agriculture must be based on agroecology to avoid environmental contamination and produce healthy food.

Baptiste Grard, Nastaran Manouchehri, Christine Aubry, Nathalie Frascaria‐Lacoste, Claire Chenu · International Journal of Environmental Research and Public Health · Global

A five-year experimental trial quantified the food production potential, soil fertility, and potential contamination of Technosols created from urban wastes for rooftop edible production. The cropping system showed promising results for food production and maintained high fertility. However, a concern was identified regarding the trace metal content of certain edible crops, specifically zinc (Zn) and copper (Cu), although most trace metal levels were below existing norms.

Hillary A. Craddock, Elisabeth Fost Maring, Stephanie Grutzmacher · African Journal of Food Agriculture Nutrition and Development · Ethiopia

A mixed-methods pilot survey of 21 teachers and parents in Debre Berhan, Ethiopia, investigated household agricultural practices to understand foodborne illness risks. The study found that half of respondents using manure applied uncomposted manure as fertilizer, and many kept multiple animal species. This suggests a high risk of pathogen exposure for children and adults through contact with uncomposted manure and animals.

Joycelyn K. Quansah, Cesar L. Escalante, Angela Parry‐Hanson Kunadu, Firibu Kwesi Saalia, Jinru Chen · Agriculture · Ghana (Accra)

A survey was conducted among 102 urban leafy green vegetable farmers from 12 farming areas in Accra, Ghana, to determine agricultural practices and their association with microbial safety of vegetables produced. It was observed that 70% of farmers used water from waste drains for irrigation, 99% used incompletely composted manure, 96% harvested with bare hands, and over 60% disagreed that polluted irrigation water can contaminate vegetables or make consumers sick. Vegetables cultivated by farmers with no formal education, less food safety knowledge, and those who disagreed about contaminated water causing illness were associated with higher fecal coliform and Enterococcus sp. counts.

Jennifer Engels, Sheree J. Watson, Henrietta Dulai, Kimberly Burnett, Christopher A. Wada, ‘Ano‘ilani Aga, Nathan DeMaagd, J. J. McHugh, Barbara Sumida, Leah L. Bremer · PLoS ONE · United States (O‘ahu)

A researcher-farmer collaboration on O‘ahu's Sumida watercress farm conducted a 25-year trend analysis and a year of intensive spring water sampling. Negative correlations were found between historical crop yields and increases in the Oceanic Niño Index, temperature thresholds, and pest outbreaks. Despite urbanization, on-farm water quality was very high, and microbial analyses suggested the farm provides nutrient retention services to downstream systems. The study demonstrates that challenges facing urban agricultural systems shift over time.

F. Waswa, M. Mwamburi, I. I. C. Wakindiki, Roseline Chemutai · Journal of applied science and environmental management · Kenya

This study focused on soil physicochemical properties and fertility management in Ruiru Sub County, a peri-urban area in Kiambu County, Kenya. Soil samples from ten small contact farms (~0.1 ha) were analyzed, revealing that most farmers were tenants growing leafy vegetables, maintaining soil fertility with organic manures, and performing tillage by hand. These practices signal limitations imposed by small farm size and lack of land ownership, with soil fertility primarily limited by the interaction of soil pH, K, and Ca.

Silke Cram, Pilar Fernández, Horacio Carranza, M.C. Gómez Hernández, Claudia Ponce de León, Ana M. Noguez Gálvez · Open Journal of Soil Science · Global

This study evaluated metal inputs, transfer, and translocation in lettuce (Lactuca sativa L.) grown in an urban plot during dry and rainy seasons in 2013, using treated wastewater and rainwater respectively. While soil characteristics and metal transfer/translocation factors varied temporally, leading to different metal concentrations in lettuce tissues, the results indicated that the metal concentration in lettuce tissues posed no harm to human health. However, site-specific studies are necessary for urban agriculture management.

Oso Adeola Abiola · Zenodo (CERN European Organization for Nuclear Research) · South Africa

This review discusses vegetable production in South Africa, focusing on the impacts of root-knot nematodes (Meloidogyne species) on small-scale farming communities. The review highlights that these nematodes are a primary pest, causing delayed crop maturity, reduced yields, poor quality produce, and escalating production costs. This leads to substantial income losses for farmers and the abandonment of community gardens, intensifying challenges for vegetable production and food security.

Remigio Paradelo, Antía Villada, María Teresa Barral · International Journal of Environmental Research and Public Health · Global

A two-month pot experiment studied heavy metal transference from five metal-rich urban waste composts and a manure vermicompost to lettuce and Italian ryegrass under controlled conditions. Plant concentrations of Zn, Cu, and Cd increased with their concentrations in compost, while no such relation was observed for Pb. The study found that the ratio of element concentration in plant to compost was much higher for Zn, Cd, and Cu than for Pb, indicating lower bioavailability of Pb.

Ada Górna, Krzysztof Górny · Miscellanea Geographica · Cuba

An exploratory, classification-based study combining fieldwork with satellite and aerial imagery analysis characterized urban agriculture across the built-up areas of Havana, Cuba. It found urban gardens distributed unevenly across the city, concentrated in lower-density districts where land was intentionally left between buildings by modernist planners, with organopónico (organoponics) as the most common production technique — but found that the material commonly used to build the bordering walls of these plots is asbestos, posing a significant health threat to both producers and consumers.

Delphine Manka’abusi, Désiré Jean‐Pascal Lompo, Christoph Steiner, Mariko Ingold, Edmund Kyei Akoto-Danso, Steffen Werner, Volker Häring, George Nyarko, Bernd Marschner, Andreas Buerkert · Journal of Plant Nutrition and Soil Science · Sub-Saharan Africa

To quantify carbon and nitrogen losses in urban and peri-urban agriculture soils in West Africa, this study measured CO2-C, N2O-N, and NH3-N fluxes from irrigated fields in Ouagadougou, Burkina Faso, and Tamale, Ghana, under different fertilization and (waste)water regimes. Compared with unamended controls, fertilizer application increased average cumulative CO2-C emissions by 103% over eight cropping cycles in Ouagadougou and by 42% over seven cropping cycles in Tamale. Total emissions across all cropping cycles reached 14 t C/ha in Ouagadougou — 73% of the carbon applied as organic fertilizer over two years at that site — and 9 t C/ha in Tamale. Fertilizer application increased N2O-N emissions in Ouagadougou by 37-360% across cropping cycles and NH3-N losses by an average of 670%, but had no significant effect on N2O-N losses in Tamale. Wastewater irrigation did not significantly raise CO2-C emissions in Ouagadougou, but in Tamale CO2-C emissions were 71% higher on wastewater plots (1.6 t C/ha) than on controls (0.9 t C/ha); wastewater had no significant effect on N2O-N or NH3-N emissions at either site. Biochar did not affect N2O-N or NH3-N losses but could help reduce CO2-C emissions from urban garden soils.

Cosmos C. Alamanjo, Abimbola O. Adepoju, H. Martin, R.N. Baines · Zenodo (CERN European Organization for Nuclear Research) · Nigeria (Jos)

This mixed-methods study investigated farmers' perceptions, willingness, and capacity to use household sewage sludge as organic resources for peri-urban agriculture around Jos, Nigeria. Farmers were found to use a complex mix of fertilizers and were keen to utilize household sewage sludge for soil fertility, though constrained by accessibility. A critical finding was that household sewage sludge observed in the field is heterogeneous due to its proximity to urban refuse disposal, raising concerns for possible cross-contamination of pollutants and indicating a lack of extension guidance.

Simon Tresch, David Frey, Renée‐Claire Le Bayon, Paul Mäder, Bernhard Stehle, Andreas Fließbach, Marco Moretti · Scientific Reports · Switzerland (Zurich)

A study in 85 urban gardens across Zurich, Switzerland, investigated the impact of gardening on five soil functions and the relationship between plant (600 spp.) and soil fauna (18 earthworm spp., 39 springtail spp.). High plant diversity positively affected soil fauna and multifunctionality, but intense garden management decreased plant diversity. This indicates a trade-off where intensive gardening, while potentially beneficial for some aspects, can negatively impact overall plant diversity.

Gaston E. Small, Sara Osborne, Paliza Shrestha, Adam D. Kay · International Journal of Environmental Research and Public Health ·

This study measured phosphorus (P) concentrations in native soil below four- and six-year-old urban garden plots, collecting soil cores from five plots of each age. It found that inorganic weakly exchangeable P was significantly elevated in native soil below garden plots (>35 cm deep) compared to reference profiles, indicating accumulation of excess P from compost. This suggests that while urban agriculture can recycle P, over-application of compost may contribute to soil and water pollution.

L.C. Obuseng · Botswana Journal of Agriculture and Applied Sciences · Botswana (Gaborone)

This review highlights the potential for heavy metal accumulation in soil and crops from urban and peri-urban agriculture (UPA) around Gaborone, Botswana, due to the intensive use of chemical fertilizers, pesticides, wastewater, sludges, and industrial effluents. A literature review showed that fertilizers contain heavy metals, and the use of treated or untreated sewage water by UPA farmers can lead to heavy metal accumulation in soil and crops, posing a danger to human health. Information on heavy metal accumulation in soils is limited in Botswana, despite high agrochemical use in UPA vegetable production.

Wendy Johanna Murcia Gulumá, Óscar Andrés Pérez Soler, Sindy Rodríguez Rodríguez · · Colombia (Bogotá)

This study provided advisory support to an urban garden in Bogotá, Colombia, named "Guerreros y Guerreras Unidos en Accion," which had been operating empirically since 2005 without formal legal status or strategic planning. The garden, primarily involving individuals over 50 without formal employment, sought to formalize its activities by establishing a foundation. The intervention aimed to guide the garden's members through the legal and administrative steps for formalization.

Gaston E. Small, Paliza Shrestha, Geneviève S. Metson, Katherine Polsky, Ivan Jimenez, Adam D. Kay · Environmental Research Communications · United States

Survey data from 142 gardeners and urban farmers in the Twin Cities Metropolitan Area, USA, characterized phosphorus (P) and nitrogen (N) inputs and harvest, and measured soil P concentrations at a subset of sites. Median application rates were 300 kg P/ha and 1400 kg N/ha, with low nutrient use efficiencies (2.5% for P, 5.0% for N). Garden soils had a median Bray P value of 80 ppm, far exceeding recommended levels, indicating a buildup and potential loss of P and N. Urban gardens, though only 0.1% of land area, constitute one of the largest inputs of P to the watershed.

Surendra K. Pradhan, Olufunke Cofie, Josiane Nikiema, Helvi Heinonen‐Tanski · Sustainability · Global

This research determined the fertilizer value of sawdust and fecal sludge (SDFS) pellets and compared their effect on lettuce cultivation with other fertilizers in a greenhouse and open field. SDFS pellets, with or without enrichments, resulted in higher saleable fresh weight lettuce yields than commercial compost, poultry manure, mineral fertilizer, or no fertilizer. Open field cultivation yielded more than greenhouse cultivation. While no helminth eggs were detected, some fecal coliforms were found in lettuces fertilized with almost all tested fertilizers, including NPK and the non-fertilized control.

Nicolette Tamara Jonkman, Esmee D. Kooijman, Karsten Kalbitz, Nicky Pouw, Boris Jansen · SOIL · Kenya (Kisumu)

This study in Nyalenda urban gardens, Kisumu, Kenya, investigated how female farmers' knowledge and practices influence soil nutrient status. Soil analysis revealed that intercropped fields had significantly lower total soil nutrients than fields with only manure, despite cowpeas theoretically increasing soil N. Female farmers' knowledge was limited to practical and sensory aspects, and intercropping did not increase soil nutrient content due to socioeconomic factors like poverty.

Odiney Alvarez‐Campos, Gregory K. Evanylo · Journal of Environmental Quality · Global

The impacts of exceptional quality (EQ) biosolids and inorganic fertilizer applied for rehabilitating anthropogenic soils on potential nitrogen (N) and phosphorus (P) water quality impairment risk were compared. After two years, reclamation rates of biosolids resulted in soil P saturation ratios greater than the recommended 30% but lower than the 65% limit. While nitrate N (NO3–N) posed the greatest nutrient leaching risk, lysimeter-collected mass loading of NO3–N from reclamation rates was not greater than for the inorganic fertilizer.

Delphine Bernadette Ouédraogo, Delwendé Innocent Kiba, Zacharia Gnankambary, Sheick K. Sangaré, Diakouba Sirima, Hassan Bismarck Nacro, Michel Papaoba Sédogo · Journal of Agricultural Science · Burkina Faso (Ouagadougou)

This study investigated cropping practices and their drivers in 133 peri-urban farms near Ouagadougou, Burkina Faso. Soil sample analysis revealed that monoculture led to low soil organic carbon, while polyculture led to low soil available potassium. The socio-economic conditions of the farms explained up to 60% of the variability in cropping practices.

Obinna Elijah Nworie, Junhao Qin, Chuxia Lin · Toxics · Global

This study investigated trace element uptake by wild herbaceous plants at a multiple trace element-contaminated site. It found significant variability in bioaccumulation and translocation factors among plant species, identifying some as hyperaccumulators for specific elements. The marked accumulation of trace elements in plant tissues suggests that the site may not be suitable for urban agricultural production.

A. Hegazy · Scientific Journal of Flowers and Ornamental Plants /Scientific Journal of Flowers and Ornamental Plants · Egypt

This landscaping study, conducted from 2017-2018, investigated eight school gardens in Mansoura City and Talkha District, Dakahlia Governorate, Egypt. The study revealed that most school gardens contained toxic plants like weeds and cacti, and that utilized areas were not correctly used with poor maintenance. Roof gardens and improved irrigation systems were suggested.

Timo Falkenberg, Deepak Saxena · Indian Journal of Community Medicine · India (Ahmedabad)

A 12-month case-cohort study of 187 households in four communities of Ahmedabad, India, purposively selected by irrigation water type (groundwater, surface water, wastewater), with bimonthly self-reported health diaries and most-probable-number measurement of Escherichia coli in water. Mean E. coli concentrations per 100 mL were 3.04×10^4 (groundwater), 9.28×10^5 (surface water) and 4.02×10^9 (wastewater) — all exceeding international irrigation water standards. Diarrhoea incidence was 7.92 episodes per 1000 person-weeks in the groundwater area versus 13.1 (wastewater) and 13.4 (surface water), with a positive correlation between irrigation water quality and diarrhoea. Wastewater reuse is often promoted as a water-scarcity fix for urban agriculture; this study shows it carries a health cost borne by the farming households themselves.

Robert McDougall, Paul Kristiansen, Romina Rader · Proceedings of the National Academy of Sciences · Australia

This study evaluated small-scale urban agriculture systems in Australia using economic and emergy (embodied energy) analyses. While these systems used land efficiently, they were relatively inefficient in their use of material and labor resources. Benefit-to-cost ratios demonstrated that, on average, the gardens ran at a financial loss, and emergy transformity was one to three orders of magnitude greater than many conventional rural farms. Only 14.66% of all inputs were considered "renewable," resulting in a moderate mean environmental loading ratio (ELR) of 5.82.