DÉCHET URBAIN-AGRICULTURE-ENVIRONNEMENT (DUAE): USING WASTE AS A RESOURCE FOR AGRICULTURE

Increasing agricultural production sustainably implies the use of organic fertilizer. Urban wastes in developing countries are rich in recyclable organic matter and they increase as urbanization increases. A recent project carried out in Dakar analyzed the potential contribution of urban organic waste (OW) to urban horticultural production. A research project was conducted in order to 1) carry out farm surveys to understand local fertilization practices; 2) identify and characterize locally available organic wastes chemically; and 3) carry out experiments with these wastes in greenhouses and farms to evaluate their agronomic potentialities and their implementation in local farmers’ practices. Horse and poultry manure are the main OW used by farmers around Dakar; however, these may become less available and/or more expensive in the future. The OW obtained after sifting through other sources of urban wastes (i.e., compost) could provide an alternative and unlimited source of organic matter. However, chemical analyses of this compost show that organic matter and nitrogen levels are weak compared to manure. Experiments were therefore conducted in greenhouses with the two representative soils of the region, a sandy-clay soil (Deck) and a sandy soil (Dior): these showed no significant effect of compost on the early growth of tomatoes compared to treatment without compost, but rather a light-positive effect at the end of the tomato-growth cycle, consistent with the analytical properties of the product. The fertilizing value of this compost is low and will require the addition of other fertilizing inputs. On-farm tests have been carried out on tomato in the same soils, where the agronomic values of treatments combining compost, manure and other local organic inputs are compared. The initial results are now under study (available December 2010).