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3 documents found tagged adventice [X]
  • Title
    Crop rotation and fertilization effects on weeds in rice based cropping systems in Madagascar
    Type
    Poster
    Description
    In the Mid-West region of Madagascar, yields in upland rice remain low due to both low soil fertility and high weed pressure in fields. Increasing managed biodiversity inside crop rotation may be an option to reduce weed pressure in cropping systems. The effect of managed biodiversity was studied in a field experiment carried out in Ivory (19°33’18.90”S, 46°24’53.08”E), with a randomized block design with four replications during two years. Three rainfed rice based rotations (Rice // Groundnut = RA, Rice // Sorghum + Vigna unguiculata =RSV, Rice//Mucuna cochinchinensis + Crotalaria spectabilis = RMC) combined with two levels of fertilization (Low Fertilization = manure vs. High Fertilization = manure + fertilizer) were compared to a rainfed rice monoculture. Each crop or crop mixture in the rotation was grown every year on plots measuring 45.9 m². Each year, weed and rice biomass were measured at each weeding date. Rice biomass was also measured at flowering and harvest. Rice yield and its components were measured at harvest. Weed flora was observed the second year to analyse potential change in weed communities according to fertilization and/or crop rotation. The first year, weed biomass and rice yield were higher in highly fertilized treatments than in lowly ones. In highly fertilized treatments, weeds did not affect yield and weed biomass was positively correlated to rice yield. On contrary, fertilization had no effect on weed biomass the second year. The highest and lowest weed biomass were observed on RA and RMC treatments respectively. Lowest rice yields were observed in RSV and RA treatments, in highly and lowly fertilized treatments respectively. In lowly fertilized treatments, weed biomass reduces significantly rice yield. Finally, rotation had more impact than fertilization on weed flora. Biodiversity may have positive effect on cropping systems performances but it depends largely on the introduced species.
    Attribution
    Ripoche A., Randriamampianina J.A., Christina M., Autfray P. Marnotte P.
  • Title
    Weed Control with a Cover Crop (Neonotonia wightii) in Mandarin Orchards in Guadeloupe (FWI)
    Type
    Miscellaneous
    Description
    Weed management is an important point of citrus production in Guadeloupe (French West Indies). Orchards are traditionally planted on sloping ground, and 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. The very first aim of cover crops is to control weeds, but benefits in terms of erosion and other services are also expected. This study consists in quantifying the effects of cover crop introduction on mandarin orchards (Citrus reticulata (‘Frémont’). The cover crop system is designed in order to obtain a perennial association and to limit chemical intervention as much as possible. Over the 3 years course of the study, two different modalities were compared: (i) farmer practice, mandarin orchard with herbicide (Glyphosate) every 2 months, and (ii) mandarin orchard in association with Neonotonia wightii. Despite some difficulties in setting up the system, N. wightii efficiently suppressed weeds after 6 months. No more herbicide was sprayed on the associated plot while the bare ground plot received 5 herbicides a year. Meanwhile, no significant difference in the predawn water potential of the soil has been revealed between N. wightii and bare ground conditions. This indicates that N. wightii use growth does not entail additional water supply. After 3 years of experimentation, no impact on the orchard performance of the field has been observed. Experimentation is still on-going to estimate the transfer of this new technique to the farmer.
    Attribution
    F. Le Bellec, O. Damas, G. Boullenger, R. Tournebize, H. Ozier Lafontaine, H. Vannière and M. Lesueur Jannoyer
  • Title
    La Lutte contre les mauvaises herbes tropicales
    Type
    Miscellaneous
    Description
    Texte synthétique sur les mauvaies herbes tropicales, l'identification et le raisonnement de la lutte
    Attribution
    Thomas Le Bourgeois et Pascal Marnotte (2002). Mémento de l'Agronome. Cirad-Gret Ministères des affaires étrangères : 663-683