Organic substrates recycling in the sub-urban agriculture of Ouagadougou (Burkina Faso) for soils fertilization: description of the different actors and their practices

Organic substrates recycling in the sub-urban agriculture of Ouagadougou (Burkina Faso) for soils fertilization: description of the different actors and their practices. This study aimed to establish an overview of the main actors of the sub-urban agriculture of Ouagadougou, their practices and expectations, and to characterize the used organic substrates (OS). For that, a farm survey was carried out on the most representative sites with 64 persons (cereal farmers, truckers and nurserymen) randomly chosen. OS were sampled with each actor, when available. Thus, 27 samples were taken and characterized through chemical analyses and laboratory incubations to follow organic carbon mineralization. The results highlighted that 35% of cereal farmers, 69% of truckers and 95% of nurserymen were 20 to 40 years old, that a large proportion of cereal farmers and truckers were not sent to school while 70% of nurserymen had at least primary education. Sub-urban agriculture was the only activity for 43% of farmers, 83% of truckers and 91% of nurserymen. Moreover, 71% of cereal farmers and 73% of nurserymen used municipal wastes as source of organic matter against only 17% of truckers, the majority of them using animal manures. The main criterion of choice of OS was their availability without any other consideration. Even if a large majority of the actors think that composts of OS were better than brut OS, a minority of them used currently composts. The best ways for an adoption and utilization of OS composts were to facilitate their accessibility and to promote these composts, composting techniques and their interests through advertising in mass media. Chemical analyses and laboratory incubations showed a great variability of the SUW, both in the same group and actors' groups. However, in case of total organic carbon, total nitrogen and total phosphorous contents, the following tendencies were observed: Content(truckers) > Content(farmers) > Content(nurserymen). For the sum of major elements Ca, K, Mg, Na (SME), it was observed that SME(truckers) approximate to SME(farmers) > SME(nurserymen). In addition, except a few atypical substrates, OS used by nurserymen were largely stabilized compared to those of cereal farmers and truckers.