Research & reports

Suarau Odutola Oshunsanya, Tolafe Olayinka Adeniran · Agricultura tropica et subtropica · Nigeria (Ibadan)

A field experiment in Ibadan investigated the quality of irrigation water used for dry season vegetable cultivation along Ona-stream. Water samples from five isolated ponds and one locally dug well were analyzed for heavy metal status. Results showed high concentrations of Pb, Cr, and Co in soil from five farms (A-E) near the stream, and isolated pond water also contained Cr, Co, and Pb exceeding safe consumption thresholds. All vegetables irrigated with untreated isolated ponds contained Cd, Pb, and Ni concentrations above maximum permissible standards, posing potential risks to human health.

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.

Shazia Iram, Ayesha Zaman, Zaiba Iqbal, Rabia Shabbir · Polish Journal of Environmental Studies · Global

This study screened soil samples from peri-urban agricultural areas to investigate heavy metal contamination and identify heavy metal-tolerant fungi. Results showed that the majority of isolated fungi were resistant to lead (Pb) and chromium (Cr). Among the strains, Aspergillus niger was the most tolerant to Pb with an MIC of 600 mg/l, and Aspergillus flavus was the most tolerant to Cr with an MIC of 400 mg/l.

K.G. Rosin, Ravinder Kaur, Sushma Singh, Prabhat Kumar Singh, Digvijay Dubey · Procedia Environmental Sciences · India

A study was conducted in peri-urban agricultural sites around Faridabad, Haryana, India, to assess groundwater contamination and the contribution of salt/trace metal-laden irrigation waters. Mean EC, Cl, and F concentrations in root zone leachates were found to be far beyond permissible limits, and some trace metals posed a threat to deep percolating waters. However, due to existing cropping patterns and deeper water table depths, the groundwaters were not yet vulnerable to these salts/trace metals, and the presence of salts in the groundwaters was primarily geogenic.

Evaristo Mwaba Kapungwe · Open Journal of Metal · Africa

Water, soil, and crop samples were analyzed by atomic absorption spectrometry for lead, copper, cobalt, nickel, and chromium at two peri-urban wastewater-irrigation farming sites in Zambia: New Farm Extension in Mufulira Town, Copperbelt Province, and Chilumba Gardens in Kafue Town, Lusaka Province. Heavy metal levels in wastewater, soil, and food crops exceeded acceptable limits at both sites, confirming contamination and a potential human health risk from consuming the crops grown there.

G. N. Egwu, John O. Agbenin · Archives of Agronomy and Soil Science · Nigeria

A study in northern Nigeria assessed cadmium, lead, and zinc contamination in soils and leaf vegetables (amaranthus, lettuce) irrigated with untreated wastewater. Total cadmium and zinc concentrations in soils exceeded safe limits, and lead and cadmium in edible portions of amaranthus and lettuce exceeded safe limits for human consumption by 7–17 times. The permissible limit for lead established for agricultural lands may not be suitable to ensure produce safety in urban and peri-urban agriculture in Kano.

Evaristo Mwaba Kapungwe · Indonesian Journal of Biotechnology (Universitas Gadjah Mada) · Zambia

This study investigated farming practices related to heavy metal contaminated wastewater irrigated farming in two peri-urban areas of Zambia: New Farm in Mufulira and Chilumba Gardens in Kafue. Data was collected by observing crop cultivation activities at field plots along transects in stratified land zones. The results revealed that farming practices were characterized by traditional land management and multiple cropping systems, influenced by agro-ecological factors and the availability of heavy metal contaminated wastewater, which has the potential to contaminate soils and crops.

Nancy Karanja, Mary Njenga, G.K. Mutua, Carl Johan Lagerkvist, E. Kutto, JJ Okello · Journal of Agriculture Food Systems and Community Development · Kenya (Nairobi)

A study in three peri-urban sites in Nairobi, Kenya, assessed heavy metal, nitrate, and pesticide residue levels in wastewater-irrigated kale. Elevated levels of boron, cobalt, chromium, copper, lead, zinc, and nickel were found in vegetables at two sites, with high soil loadings of nickel, arsenic, lead, chromium, copper, and zinc attributed to chicken manure. Pesticide residues of diazinon, cypermethrin, biternol, and profenofos exceeded permissible limits in kale at one site, suggesting consumers may ingest significant amounts of contaminants.

Catherine Rwamba Githuku · Abstracts of postgraduate thesis · Kenya (Nairobi)

This study investigated soil and crop pollution levels resulting from untreated wastewater reuse for irrigation in Kibera and Mailisaba wastewater irrigation farms in Nairobi, Kenya. Analysis of irrigation water, soil, and crop samples (maize, kales, black nightshade, arrowroots) revealed that the Electrical Conductivity (EC) of irrigation water at Mailisaba exceeded recommended levels. Farmers reported adverse effects on crops due to wastewater quality, and despite awareness of health risks, many farmers confessed to not using protective clothing.

Haruna Haruna · · Africa

A study of soils irrigated with sewage water on Fadama floodplain land in northern Nigeria used sequential extraction to determine the mobility and availability of cadmium, copper, nickel, lead and zinc. The residual fraction held the largest pool of all five metals, but 2.7-70.2% was present in the potentially available, non-residual fraction. Contamination by cadmium and nickel was less severe than by lead, copper and zinc, and mobility/bioavailability ranked Pb > Zn > Cu > Ni > Cd.

Kohei Makita, Eric M. Fèvre, Charles Waiswa, Mark Bronsvoort, Mark C. Eisler, Susan C. Welburn · Land Use Policy · Uganda

This paper describes a spatial representation of the peri-urban interface (PUI) of Kampala, Uganda, and identifies socio-economic factors related to peri-urbanicity using rapid rural mapping. It notes that urban and peri-urban agriculture (UPA) in rapidly expanding cities carries public health risks, such as zoonotic disease transmission. The study provides a methodology for describing the PUI in developing countries.

Rodrigue V.C. Diogo, Andreas Buerkert, Eva Schlecht · Nutrient Cycling in Agroecosystems · Niger (Niamey)

This 24-month study investigated nutrient efficiency and food safety in urban and peri-urban agriculture in Niamey, Niger. Nutrient inputs and offtakes were quantified for 10 vegetable gardens and 9 millet fields, and contamination of irrigation water and selected vegetables with fecal pathogens and heavy metals was determined. Above-threshold levels of Salmonella spp. and Escherichia coli were detected in lettuce irrigated with river water and fertilized with animal manure, and in lettuce irrigated with wastewater, indicating food safety concerns.

Shahzad Kouser, Mr. Abedullah, Abdus Samie · The Pakistan Development Review · Pakistan (Faisalabad)

This study, conducted in 2006 with 200 farmers in two peri-urban villages of Faisalabad, Pakistan, estimated the economic values of negative health externalities from wastewater use in cauliflower production. While wastewater use appeared profitable without considering externalities, factoring in health costs strongly discouraged its use. The health externalities for a three-month cauliflower crop on 741 acres amounted to Rs 3.2 million, and for 5,283 acres of vegetables cultivated with wastewater in Faisalabad, the annual total was Rs 90.7 million. The findings indicate a significant economic loss due to wastewater use, suggesting that installing a water treatment plant is a viable option to minimize these external effects.

Shazia Iram, Iftikhar Ahmad, Doris Stüben · Pakistan Journal of Botany · Asia

Soil samples were collected from peri-urban agricultural land in Lahore, Pakistan, irrigated by industrial and sewerage waste from the Hudiara drain, and from mine waste soil in Wiesloch, Germany, and analyzed for heavy metals by X-ray fluorescence and ICP-MS and for fungal diversity and frequency by a soil dilution method. X-ray fluorescence found higher Zn, As and Pb in the German mine waste soil, and the more sensitive ICP-MS found higher Fe, Mn, Cu, As, Sr, Mo, Cd, Sb, Ti, Zn and Pb there as well; the Pakistani peri-urban soils had lower heavy metal concentrations than the German mine waste but higher overall fungal frequency and diversity. Testing radial growth of isolated Aspergillus niger, A. flavus and A. nodulans against CdCl2, CuSO4, NiCl2 and ZnCl2 at 1-40 ppm, all tested fungi tolerated ZnCl2 (25 ppm) and NiCl2 (12 ppm) but none tolerated CdCl2 or CuSO4.

Sophie Graefe, Eva Schlecht, Andreas Buerkert · Outlook on Agriculture · Niger (Niamey)

Semi-structured interviews with 130 households in Niamey, Niger, characterized urban and peri-urban agriculture (UPA) and assessed resource use. The study found high use of livestock manure and indiscriminate use of nutrient-loaded wastewater for irrigation, leading to significant nutrient surpluses in UPA gardens. Initial calculations suggested large gaseous emissions of nitrogenous compounds and and leaching of nitrogen, phosphorus, and potassium to groundwater.

Erastus K. Kang’ethe, Delia Grace, Thomas F. Randolph · East African Medical Journal · East Africa

This study synthesizes current knowledge on urban agriculture (UA) in East Africa, focusing on its human health impact. It identifies UA as an important source of food security, but notes that many zoonotic and food-borne diseases are associated with it, with a lack of evidence on human health impact and management. Major constraints include illegality and limited access to inputs and markets, indicating a need for more research to understand both positive and negative health impacts.

Bernard Keraita, Pay Drechsel, Flemming Konradsen · Water Science & Technology · Ghana (Kumasi)

A study in Kumasi, Ghana, assessed the use of on-farm ponds to reduce microbial contamination in wastewater-contaminated irrigation water, analyzing over 300 samples. It found that while ponds are common, their potential for pathogen removal via sedimentation is not fully optimized. Helminth eggs reduced by about 70% with careful water collection, but thermotolerant coliforms took six days in the dry season to meet WHO guidelines, indicating suboptimal performance for some pathogens.

Pay Drechsel, Olufunke Cofie, R. van Veenhuizen, Theophilus O. Larbi · Irrigation and Drainage · West Africa

Informal irrigation in urban and peri-urban agriculture (UPA) in West Africa offers benefits but is often hindered by water pollution, threatening public health. A multi-stakeholder process implemented since 2005 in six West African cities, including Accra, Ghana, aimed to integrate UPA into sustainable urban development. However, an internal lesson learned was that local partners may not prioritize every project, and capacity-building efforts might not provide expected incentives for commitment.

Euis Suryaningsih · Jurnal Hortikultura · Indonesia (Bandung)

From January to July 2001, a field experiment on vegetable disease control in a mosaic farming system in periurban agriculture was conducted at a farmer's field in Rancaekek, Bandung, Indonesia. Treatments included white plastic net cages, biorational pesticides, Bacillus subtilis, a mixture of Mancozeb and Bacillus subtilis, and an unsprayed control. All tested alternative control methods were very effective against major diseases of chili pepper, shallot, eggplant, beans, and cucumber, but the use of poisonous synthetic pesticides in periurban agriculture increases the likelihood of contaminating humans and the environment.

XU Yong-xian, Biao Huang · Soils · China

A study of a small-scale vegetable farming system in peri-urban Nanjing, China, monitored heavy metal balances and pollution potential from July 2003 to July 2004. Heavy metals entered the soil mainly through fertilization and irrigation, with organic manure application accounting for more than 98% of inputs. Annual heavy metal input in the area was significantly higher than in European farmland, while annual output was very low, under 10% of input, leading to accumulation of heavy metals in the plots; long-term vegetable cultivation had already caused heavy metal buildup in the soils. Copper, lead, zinc, and cadmium concentrations in vegetables and soil were still below national safety standard limits, so the vegetable farming system was assessed as currently safe. However, an evaluation that incorporated atmospheric deposition showed the region carries a high risk of copper, zinc, and cadmium contamination, and the study concludes that intensive vegetable cultivation will aggravate soil heavy metal pollution, potentially pushing the soil to Second Grade of the National Soil Environment Quality Standard within several decades.

Do Thuy Trang, Kåre Mølbak, Phung Dac Cam, Anders Dalsgaard · Tropical Medicine & International Health · Vietnam (Hanoi)

A cross-sectional study in a peri-urban area of Hanoi, Vietnam, surveyed 400 agricultural households and examined 807 stool samples from 620 adults and 187 children for helminth infections. The study found that 39% of samples were infected with helminths, with Ascaris sp. at 21.6%, Trichuris sp. at 9.8%, and hookworm at 21.8%. Wastewater exposure was not a major risk, but lack of sanitation facilities and use of fresh or inadequately composted human excreta in agriculture were important risk factors for infection.

Stephanie Buechler, Gayathri Devi Mekala, B. Keraita · Victoria University Research Repository (Victoria University) · Global

This 2006 global study from Victoria University discusses wastewater use in urban and peri-urban agriculture for crop production and aquaculture, noting its role in generating livelihoods and providing cheap produce. However, the study emphasizes that clear policy guidelines and careful research are needed to prevent potential negative impacts on human health and the environment from wastewater reuse.

Tony Binns, Roy Maconachie, Adamu Idris Tanko · Land Degradation and Development · Nigeria (Kano)

This paper examines health and environmental concerns associated with urban and peri-urban agriculture (UPA) in Kano, Nigeria. Empirical evidence indicates that industrial and domestic toxins are reaching dangerously high levels, leading to significant pollution of soils and water channels. This raises serious questions about the sustainability of UPA and the long-term health implications of toxin exposure.

Ogunyemi Awodoyin, Taliat Opadeji · Emirates Journal of Food and Agriculture · Nigeria (Ibadan)

A 2003 study in Ibadan, Nigeria, investigated heavy metal contamination of Amaranthus cruentus L. grown on domestic refuse landfill soils. Lead (Pb) and Cadmium (Cd) concentrations in soils from four landfill sites and a control site ranged from 110.5 to 678.5ppm for Pb and 2.01 to 3.20ppm for Cd. Metal accumulation in Amaranthus cruentus L. tissues was proportionate to soil Pb concentrations, while Cd levels in crop tissues exceeded soil levels. Crop growth and yield were significantly reduced due to Pb and Cd contamination, leading to the conclusion that Ibadan landfills are unsafe for Amaranthus cruentus cultivation, with heavy metal concentrations in the vegetable tissues much higher than FAO/WHO dietary allowances.

Bernard Keraita, Pay Drechsel, Philip Amoah · Environment and Urbanization · Ghana (Kumasi)

This study in Kumasi, Ghana, investigated the influence of urban wastewater on stream water quality and peri-urban agriculture through interviews and water quality assessments. It found that population increase and underinvestment in sanitation facilities led to large volumes of untreated wastewater entering streams. High levels of faecal coliform were recorded in the city's streams, downstream areas, and on vegetables sold in Kumasi’s markets due to contaminated wastewater.