Constitution des systèmes de culture maraîchers à proximité d'une ville : quelles marges de manœuvre des agriculteurs pour répondre à une augmentation de la demande ? Cas des systèmes de culture à base de légumes feuilles dans l'espace périurbain de Mahajanga (Madagascar)

摘要

The rapid urbanization of developing countries in developing countries implies a growing demand for food that raises the problem of securing urban food and nutritional supplies. The market-gardening systems contributes strongly in the food supply of perishable produce. This includes frequently a large proportion of leafy vegetables. Faced with this urban growth the development of the vegetable production, notably leafy vegetables, plays a major role. Increasing the vegetable production on farms may be obtained by increasing yields per surface and/or increasing the cultivated surface areas. This latter possibility, which is the focus of our research, is an important issue in urban agriculture where access to certain resources, one of these resources being surface areas, becomes particularly difficult because there is potential competition with urban uses. One must analyse how the agricultural land is currently used for the different agricultural products in the different farms: firstly by understanding how farmers decide where to locate crops over their farm territory, then by evaluating their room for manoeuvre to possibly increase these areas. This study was carried out on the market-gardening systems in the case of Mahajanga, a secondary town with high increasing demographic rate, on the North-West coast of Madagascar. To respond to this research question, we used previously established conceptual models of decision rules regarding crop location on farm territory. We chose three agricultural zones where 11 market-gardeners were surveyed during two years, to understand their decision rules in crop choices, crop allocation to land, resource management, and to estimate their room for manœuvre to meet growing urban demand, revealed by the retailers. From a theoretical point of view, we formalized a conceptual model of decision rules regarding leafy-vegetable location on farm territory. We extended and enriched certain variables used in pre-established models, purposing new variables and new determinants. We show that the relationships between farmers and retailers influences certain decisions in the management of cultivated surface areas of leafy vegetables. From an operational point of view, we diagnose these limiting factors to extend the cultivated surface areas on leafy vegetables in this case study. Here we demonstrate that the room for manoeuvre to increase the cultivated area resides mainly in a modification of the productive resources like appropriated land but also water and labour and in an a organisational modification of the supply chain. We were able to show different levels of room for manœuvre to extend cultivated areas between farms. Although the room for manoeuvre at the farm level to extend cultivated surfaces remains limited, we demonstrate that it is by using the farm scale that one can understand issues posed at the territorial scale and farmers' opportunities and constraints to adopt proposals made at that level. The obtained results discussed with regard to the literature and the limits of the study, result in new theoretical and operational perspectives. Beyond this local study, our research posture seems to us complementary of the methods used by urban planners. The major interest of this study is to help in a precise identification of the limiting factors and the room for manoeuvre at farm and territorial level to extend the cultivated surface areas.