Nutrient flows in urban and peri-urban agroecosystems in three West African cities

A. Abdulkadir

Research output: Thesisinternal PhD, WU

Abstract

Key words: Sustainability, CATPCA, two-step cluster analysis, farm types, nutrient balances, West Africa, gross margin, NUTMON/MONQI.

Urban and peri-urban agriculture (UPA) is defined as the cultivation of crops and keeping livestock within and around cities. In addition to providing the cities’ demand of fresh vegetables, crops and livestock products, it plays an important role in the livelihoods of the urban farmers. With the rapid urbanization in sub-Saharan Africa, UPA provides food and jobs for many urban dwellers. UPA makes use of a diverse range of urban resources such as labour, waste and wastewater to produce food and raise livestock, and it is characterized by large nutrient imports into farms or gardens, often accompanied by environmental and human health risks. In view of the complexity and diversity of the UPA systems, there is a need to understand the socio-economic characteristics of UPA as drivers to farm management practices. This research was conducted in three secondary West African cities with important UPA activities: Kano (Nigeria), Bobo Dioulasso (Burkina Faso) and Sikasso (Mali). From principal component analysis of categorical variables (CATPCA) and two-step cluster analysis, six major farm types were identified based on production systems and market orientation, of which three are common in the three cities and one farm type is unique to each city. The six farm types are commercial gardening plus field crop-livestock (cGCL); commercial gardening plus semi-commercial cropping (cGscC); commercial livestock plus subsistence field cropping (cLsC); commercial gardening plus semi-commercial livestock (cGscL); commercial cropping (cC); and commercial gardening (cG). The former three are common for the three cities, the latter three farm types are unique for one city, each. The diverse activities in these farm types contributed differently to household income. Nutrient balance studies are useful indicators to assess the sustainability of farming systems. From the identified farm types, in-depth assessment of nutrient flows and balances as well as the economic performance of the different production systems was conducted in Kano (Nigeria) using the nutrient monitoring toolbox (NUTMON/MONQI). Farm nitrogen (N) balance was positive at 56.6, 67.4 and 56.4 kg farm−1 yr−1 for cGCL, cGscL and cLsC farm types, respectively. The same trend was observed for phosphorus (P) and potassium (K) in all the farm types except for cGCL where an annual negative K balance of 16 kg farm−1 was found. Commercially-oriented livestock keeping (cLsC) was economically more viable than the other farm types with average annual positive gross margin (GM) and net cash flow (NCF) of 033 and 35, respectively. Cropping activities within cGCL and cGscL had positive GMs (059 and 94) and NCFs (57 and 06), but livestock activities in both farm types incurred financial losses. Using the same MONQI approach across vegetable production systems of the three cities, large amounts of nutrients were observed to be applied with large positive nutrient balances. Average annual N balances were positive for all gardens in the three cities: 279, 1127 and 74 kg N ha–1 in Kano, Bobo Dioulassoand Sikasso, respectively. Phosphorus balance was positive in all cities except annual K deficits of 222 and 187 kg ha–1 in Kano and Sikasso, respectively. Efficiencies were 63%, 51% and 87% for N; with poor P use efficiencies due to excess application in all three cities. K efficiency of 85% was observed in Bobo Dioulassowhile in Kano and Sikasso’s gardens, it was 120% and 110% respectively, indicating K mining. The average annual gross margins/benefits from gardening indicate a higher return of .83 m–2 in Bobo Dioulasso and differs statistically (P<0.05) from returns obtained in Kano (conv2.info.92 m–2) and Sikasso (.37 m–2). Results show that UPA is an important economic livelihood strategy for urban and peri-urban farmers because of positive economic returns but with huge environmental trade-offs as a consequence of excess nutrient application. Efforts to better integrate resource management with measures to improve environmental and food safety are required of UPA stakeholders. Achieving this will require the formal recognition of the UPA sector by city officials, along with formulating realistic strategies for effective nutrient and water management for a more sustainable UPA operation in West Africa. The consistent and replicable typology developed in this study provides a basis to target system-specific technologies and appropriate recommendations to improve use efficiencies of resources as a whole.

 

 

Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • van Keulen, Herman, Promotor
  • Agbenin, J.O., Co-promotor, External person
  • Leffelaar, Peter, Co-promotor
Award date14 Nov 2012
Place of Publication[S.l.]
Print ISBNs9789461730039
Publication statusPublished - 2012

Keywords

  • nitrogen cycle
  • cycling
  • nutrients
  • urban agriculture
  • farming systems
  • west africa

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