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Weed control with a cover crop (Neonotonia wightii) in mandarin orchards in Guadeloupe (FWI)

Le Bellec F., Damas O., Boullenger G., Vannière H., Jannoyer-Lesueur M., Tournebize R., Ozier Lafontaine H.. 2012. In : Albrigo L.G. (ed.), Wünsche J.N. (ed.). Proceedings of the International Symposium on citrus, bananas and other tropical fruits under subtropical conditions : Proceedings of the XXVIII International Horticultural Congress on Science and Horticulture for People (IHC 2010), Lisbon, Portugal, Augu. Louvain : ISHS [Belgique], p. 359-366. (Acta Horticulturae, 928). International Horticultural Congress on Science and Horticulture for People. 28, 2010-08-22/2010-08-27, Lisbonne (Portugal).

Weed management is an important point of the citrus production in tropical wet area. Thus, the use of herbicides regularly sprayed on the whole farm is the most common practice. Such a practice impacts the environment and the production benefits. Introduction of cover crops on these orchards is an interesting alternative. A multi criteria evaluation grid was built to select an "optimal" cover crop. Specific criteria were first defined related to local climate, plant biology and seed availability in the island. Specific features were then determined according to the agronomic potential and ecological services for an optimal cover crop. The very first aim of cover crops is to control weeds, but benefits in reduced erosion and other environmental services are also expected. This study consists in quantifying the effects of a cover crop introduction on 3 years old mandarin orchards. In our conditions, the cover crop system is designed in order to obtain a perennial association and to limit as much as possible the number of chemical interventions. For 3 years two modalities have been compared: (i) farmer practice, mandarin orchard with herbicide (Glyphosate) every 2 months, and (ii) mandarin orchard in association with Neonotonia wightii. No more herbicide was sprayed on the associated plot while the bare ground plot received 6 herbicides a year. We measured the cover crop - tree water competition and the environmental impacts through Indigo® indicators. Despite some difficulties in setting up the system N. wightii suppressed efficiently weeds after 6 months. Meanwhile, no significant difference in the predawn water potential of the soil has been revealed between the two modalities. So water stress is not induced by the cover crop in our citrus orchard. After 3 years of experimentation, no impact on the performance of the field has been observed. Experimentation continues to estimate the transfer of this new practice to the farmer. (Texte intégral)

Mots-clés : citrus; désherbage; culture sous couvert végétal; neonotonia wightii; culture fruitière; guadeloupe; france

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