Conventional agriculture is based on a high level of chemical inputs such as pesticides and fertilisers, leading to serious environmental impacts, health risks and loss of biodiversity. Pesticide reduction is a priority for intensive agricultural systems such as orchards. Reintroducing biodiversity in single crop systems can enhance biological regulations, and contribute to reduce the use of chemicals and to provide additional services such as run-off and erosion control. In tropical wet areas, weed control is difficult to manage without herbicides especially when orchards are not located in easily mechanised areas and when labour force is costly. Cover plants can be easily introduced in orchards and could be efficient in weed control and other functions. Based on this assumption, we developed a specific approach for the choice of adapted cover plants in single crop orchards to control weeds and provide additional ecological services. The approach was undertaken on citrus orchards in the French West Indies.

A multicriteria evaluation grid was built to select an “optimal” cover crop. In both Martinique and Guadeloupe, 202 species were first selected in the local flora, and tested on vegetative characteristics. Specific criteria were secondly defined relating to seed availability (limitation of alien species introduction), farm constraints and regulations (no invasive species). Specific features were then determined according to the agronomic potential and ecological services for an optimal cover plant. Criteria included weed control, the ability to control runoff and erosion, water and nutrient competition, pests and natural enemies hosting capacity. The whole evaluation grid combines data from literature, expert assessment and experimental measurements.

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Magalie Lesueur Jannoyera, Fabrice Le Bellecb, Christian Lavignea, Raphaël Achard & Eric Malézieux