Search

Increasing vegetable production to meet the growing urban demand is essential in developing countries. This article proposes a new model to analyse farm land use for market gardening in tropical urban agriculture and to evaluate the capacity of farmers to increase their vegetable surface area. It is based on a decision model simulating crop sequences and crop location initially validated for temperate arable and vegetable productions. In this study, the leafy vegetables land use model (LYLU) was first adapted to suit the specificities of urban leafy vegetable production: short crop cycles; wide crop diversity; instability of the cultivated area during a season, in our case due to flood recession; manual labour and close relationships with retailers. The output variables of the model were then compared to observations collected on an 11 farms sample. The model estimates the surface area for each leafy vegetable, depending on plant species requirements, farm resources and relations with retailers. This is the first model that simulates the spatial and temporal variation of the farm land and the exploitable surface areas over the cropping season depending on the dynamics of water availability and labour force. In some cases, up to half of the surface remained uncultivated because of slow fields' drainage at the end of the rainy season and/or lack of water in the wells in the dry season. Moreover, the available labour force on farm and the way vegetables were sold greatly affected the intercrop period, which in turn contributed to reducing the cultivated area. Finally the model was used to quantify farmers' room for manoeuvre in order to increase their vegetable cultivation area. Opportunities to overcome them were discussed both at farm and territorial levels. This is an innovative approach that could be useful to face the growing urban demand in developing as well as in Western countries. [ABSTRACT FROM AUTHOR]

Abstract: The rapid urbanization in developing countries implies an increasing pressure on urban agriculture for production. As most perishable food products come from this agriculture in close proximity to population concentrations, we analysed from an agronomic point of view how market-garden farmers can meet this increasing urban demand. This work took place in the case of Mahajanga, a secondary city with high increasing demographic rate on the Northwest coast of Madagascar. Based on preliminary surveys to characterize the farming systems (on a sample of 91 farms), 11 market-garden farmers chosen in the three main agricultural zones of the urban area were surveyed during two years. Surveys aimed at understanding their decision rules in crop choices, crop allocation to land and resource management, and to estimate their room for manoeuvre to increase their leafy vegetable areas under cultivation. The wholesalers and retailers who buy the farmers’ produce were also surveyed. A previous model of decision rules regarding crop location on farm territory was used to analyse the on-farm surveys and cartographic methods (GIS and on-farm manual representations) were used to quantify the land use. We highlight the following major points. (1) The leafy vegetable production in the surveyed farms already intensively uses land: farmers have complex decision rules largely depending on the water dynamics in the two main environments (lowlands and lakesides) where leafy vegetables are cultivated during the dry season. (2) The scarcity of farmers’ resources (labour money and water) leads to very little internal room for manoeuvre to increase the leafy vegetable production in the farms. (3) At territorial level however, some land reserve exist in one of the lowlands, but not on lakesides. The water availability for agriculture must be better informed through specialized hydrologic studies, as one of the main constraints nowadays to extend the agricultural area. An extrapolation to other cases of urban agriculture is then discussed as well as the role of agronomy to help urban planners to consider the place of agriculture in the urban development. [Copyright &y& Elsevier]