MARTINA HAMMER, PETTER D. JENSSEN, TOR ARVID BRELAND
Agricultural University of Norway, Department of Plant and Environmental Science, Norway
The objectives of this study were to describe Havana's urban vegetable production, to analyse production constraints, and to explore the potential of ecological sanitation techniques (primarily greywater wetlands) for providing water, organic matter and nutrients. Onsite interviews were conducted at 10 gardens. The gardens were selected to include different forms of ownership, localities, and management practices. Additional information was collected from other stakeholders such as government officials, NGO representatives, and university researchers. Onsite measurements and discussions with stakeholders provided data on the supply of water and organic matter. Supply of nitrogen, phosphorous, and potassium was addressed through an experimental comparison of the nutrient uptake of lettuce plants grown in the gardens with a control group of plants provided with sufficient nutrients. Results showed that water supply was adequate in 7 of the 10 gardens, but there was a deficiency of nutrients and organic matter in all gardens. The average total nitrogen concentration of lettuce plants grown in the gardens was 2.0-2.3% compared to a target value of about 5.0% as determined in the control group of plants and from literature. Potassium and phosphorous deficiencies were less severe. This was due to a shortage of organic and inorganic fertilisers in the market and limited recycling through, for example, locally composted organic waste. Greywater wetlands would not relieve the deficiency of nutrients and organic matter. It is recommended to examine other ecological sanitation techniques, for example blackwater utilisation and improved composting of organic household waste. Further research and development involving gardeners and other stakeholders is needed particularly regarding blackwater utilisation.
Keywords: Ecological sanitation techniques, greywater wetlands, nutrient supply, organic matter supply, urban vegetable production, water supply