We undertook a comparative analysis of (peri-)urban livestock production strategies across three West African cities. Using a semi-structured questionnaire, livestock-keeping households (HH) were interviewed in Kano/Nigeria (84 HH), Bobo Dioulasso/Burkina Faso (63 HH) and Sikasso/Mali (63 HH). Questions covered livestock species kept, herd sizes and structure, feeds used, manure management, livestock marketing and production constraints. Sheep and goats dominated ( p < 0.001) in Kano (76 and 75 % of HH) compared to Bobo Dioulasso (48 and 40 %) and Sikasso (28 and 40 %), while cattle and poultry were more frequent ( p < 0.001) in Bobo Dioulasso (82 and 69 % of HH) and Sikasso (65 and 79 %) than in Kano (29 and 20 %). Across cities, ruminant feeding relied on grazing and homestead supplementation with fresh grasses, crop residues, cereal brans and cottonseed cake; cereal grains and brans were major ingredients of poultry feeds. Cattle and sheep fetched highest prices in Kano, unit prices for goats and chicken were highest in Sikasso. Across cities there was little association of gardens and livestock, whereas field cropping and livestock were integrated. There was no relation between the education of the HH head and the adoption of improved management practices ( p > 0.05), but the proportion of HH heads with a long-term experience in UPA activities was higher in Kano and in Bobo Dioulasso than in Sikasso ( p < 0.001). We therefore postulate that the high illiteracy rate among (peri-)urban livestock keepers in West Africa does not threaten the acceptance of improved technologies and innovations supporting the sustainability of their livestock production.

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In large areas of sub-Saharan Africa crop production must cope with low soil fertility. To increase soil fertility, the application of biochar (charred biomass) has been suggested. In urban areas, untreated waste water is widely used for irrigation because it is a nutrient-rich year-round water source. Uncertainty exists regarding the interactions between soil properties, biochar, waste water and fertilization over time. The aims of this study were to determine these interactions in two typical sandy, soil organic carbon (SOC) and nutrient depleted soils under urban vegetable production in Tamale (Ghana) and Ouagadougou (Burkina Faso) over two years. The addition of biochar at 2 kg m−2 made from rice husks and corn cobs initially doubled SOC stocks but SOC losses of 35% occurred thereafter. Both biochar types had no effect on soil pH, phosphorous availability and effective cation exchange capacity (CEC) but rice husk biochar retained nitrogen (N). Irrigation with domestic waste water increased soil pH and exchangeable sodium over time. Inorganic fertilization alone acidified soils, increased available phosphorous and decreased base saturation. Organic fertilization increased SOC, N and CEC. The results from both locations demonstrate that the effects of biochar and waste water were less pronounced than reported elsewhere.

Urban and peri-urban agriculture (UPA) is an important livelihood strategy for the urban poor in sub-Saharan Africa and contributes to meeting increasing food demands in the rapidly growing cities. Although in recent years many research activities have been geared towards enhancing the productivity of this land-use system, little is known about turnover processes and nutrient efficiency of UPA. The aim of our study therefore was to determine horizontal fluxes of N, P, K, and C as well as gaseous N and C emissions in urban vegetable gardens of Bobo-Dioulasso, Burkina Faso. Two gardens referred to as "Kodéni" and "Kuinima" were selected as representative for urban and peri-urban systems classified as: (1) "commercial gardening + field crops and livestock system" and (2) "commercial gardening and semicommercial field crop system", respectively. A nutrient-balance approach was used to monitor matter fluxes from March 2008 to March 2009 in both gardens. Ammonia (NH 3 ), nitrous oxide (N 2 O) and carbon dioxide (CO 2 ) emissions from the respective soils were measured during the coolest and the hottest period of the day using a closed-chamber system. Annual partial balances amounted to 2056 kg N ha -1 , 615 kg P ha -1 , 1864 kg K ha -1 , and 33 893 kg C ha -1 at Kodéni and to 1752 kg N ha -1 , 446 kg P ha -1 , 1643 kg K ha -1 , and 21 021 kg C ha -1 at Kuinima. Emission rates were highest during the hot midday hours with peaks after fertilizer applications when fluxes of up to 1140 g NH 3 -N ha -1 h -1 , 154 g N 2 O-N ha -1 h -1 , 12 993 g CO 2 -C ha -1 h -1 were recorded for Kodéni and Kuinima. Estimated annual gaseous N (NH 3 -N + N 2 O-N) and C (CO 2 -C + CH 4 -C) losses reached 419 kg N ha -1 and 35 862 kg C ha -1 at Kodéni and 347 kg N ha -1 and 22 364 kg C ha -1 at Kuinima. For both gardens, this represented 20% and 106% of the N and C surpluses, respectively. Emissions of NH 3 , largely emitted after surface application of manure and mineral fertilizers, accounted for 73% and 77% of total estimated N losses for Kodéni and Kuinima. To mitigate N losses nutrient-management practices in UPA vegetable production of Bobo-Dioulasso would greatly benefit from better synchronizing nutrient-input rates with crop demands.

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This study reports and analyzes nutrient balances in experimental vegetable production systems of the two West African cities of Tamale (Ghana) and Ouagadougou (Burkina Faso) over a two‐year period comprising thirteen and eleven crops, respectively. Nutrient‐use efficiency was also calculated. In Tamale and Ouagadougou, up to 2% (8 and 80 kg N ha−1) of annually applied fertilizer nitrogen were leached. While biochar application or wastewater irrigation on fertilized plots did not influence N leaching in both cities, P and K leaching, as determined with ion‐absorbing resin cartridges, were reduced on biochar‐amended plots in Tamale. Annual nutrient balances amounted to +362 kg N ha−1, +217 kg P ha−1, and –125 kg K ha−1 in Tamale, while Ouagadougou had balances of up to +692 kg N ha−1, +166 kg P ha−1, and –175 kg K ha−1 y−1. Under farmers' practice of fertilization, agronomic nutrient‐use efficiencies were generally higher in Tamale than in Ouagadougou, but declined in both cities during the last season. This was the result of the higher nutrient inputs in Ouagadougou compared to Tamale and relatively lower outputs. The high N and P surpluses and K deficits call for adjustments in local fertilization practices to enhance nutrient‐use efficiency and prevent risks of eutrophication.

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