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Afin d’assurer la préservation et la valorisation des écosystèmes aquatiques menacés par la jacinthe d’eau Eichhornia crassipes, des méthodes basées sur le chlorure de sodium NaCl ont été mises au point pour lutter contre la prolifération de cette macrophyte envahissante. Cette étude évalue l’impact de la technique mise au point sur la qualité physico-chimique de l’eau et présente l’état physico-chimique de l’eau d’un écosystème semi-artificiel (étang) suite à la pulvérisation des plantes de jacinthe à base de solution chlorure de sodium (NaCl). Le but de l’étude est de préserver les risques écologiques d’une telle méthode de lutte en milieu réel. L’expérience a été réalisée dans un étang de 11 mètres de long et de 3 mètres de large, couvrant une surface de 33 mètres carrés. La partie occupée par les plantes de jacinthe représente les 2/3 de la surface de l’étang. L’étang contenait au départ un volume d’eau estimé à 34,1 mètres cubes. L’eau de mer a été utilisée pour pulvériser les plantes de jacinthe. Cette pulvérisation a été réalisée en une seule journée et le volume de solvant pulvérisé au mètre carré était de 11,32 litres. Les paramètres physico-chimiques de l’eau de même que les substances chimiques eutrophisantes ont été mesurés au début (avant pulvérisation), aussitôt après la pulvérisation et ceci tous les cinq jours après pulvérisation sur une période de 25 jours. Au terme de l’étude, la salinité est passée de 0,10 à 0,27 gramme par litre pour un volume final d’eau de 13,6 mètres cubes. La concentration du milieu en sels nutritifs a significativement augmenté. Il en résulte une augmentation significative de la conductivité de l’eau, conséquence de l’augmentation des sels minéraux issus de la décomposition et de la minéralisation des feuilles mortes des plantes de jacinthe dans le milieu. In order to ensure the preservation and enhancement of aquatic ecosystems threatened by the water hyacinth Eichhornia crassipes, methods based on sodium chloride NaCl have been developed to combat the proliferation of this invasive plant. This study presents the physico-chemical state of the water in a semi-artificial ecosystem following spraying of hyacinth plants based on sodium chloride (NaCl) solution and aims to preserve the ecological risks of a such a method of struggle in a real environment. The experiment was carried out in a pond 11m long and 3m wide, covering an area of 33m2. Part occupied by hyacinth plants represents 2/3 of the surface of the pond. The pond initially contained a volume of water estimated at 34,1m3. Seawater was used to spray hyacinth plants. This spraying was done in one day and the volume of solvent sprayed per m2 was 11.32L. The physico-chemical parameters of the water as well as the eutrophying chemicals were measured at the beginning (before spraying), immediately after the spraying and this every five days after spraying over a period of twenty-five days (25 days). At the end of the study, the salinity increased from 0,10 to 0,27g/L for a final volume of 13,6 m3. The concentration of nutrients in the medium increased significantly. This results in a significant increase in the conductivity of the water; consequence of the increase of the mineral salts resulting from the decomposition and the mineralization of the dead leaves of the hyacinth plants in the medium.

Recent studies reported the important contribution of animal dejections as organic manure for crop production but, little is known on the decomposition rate and nutrient release pattern in wetland of the manure of pigs nourished with diet enriched with Azolla filiculoides. A litter bag study was carried out under full control during 6 weeks in pots containing 25 liters of tap water and 15g of pigs’ dejection in each decomposition bag. The experimental design was a completely randomized block design with three replications. The treatments consisted of dejections of pigs nourished with : T1 (recommended diet composition) consisted of 15% Azolla + 55% provender + 5% coconut copra + 5% oil palm + 5% soybean bran + 10% rice bran + 5% kitchen waste ; T2 (partially improved diet with Azolla) consisted of 30% Azolla + 65% rice bran + 5% oil palm ; T3 (improved diet with Azolla) consisted of 47.5% Azolla + 47.5% rice bran + 5% oil palm; and T4 (improved diet with cereal bran) consisted of 15% Azolla + 40% rice bran + 40% wheat bran + 5% oil palm). Four pigs per diet were considered leading to 16 white landrace pigs of six months age. Decomposition rates in water were significantly (P < 0.05) fast during the first week and became very slow during the following weeks. After the six weeks of experiment, 58.2 % of manure from treatments T1 and T4 were decomposed against 47.2 % for T2 and T3. However, 40.1, 53.3, 67.4 and 57.1% of total N content in treatments T1, T2, T3 and T4 respectively were released. As consequence, manure from improved diet with Azolla (T3 and T2) are suggested for integrated rice and fish production system. Nevertheless, decomposition and nutrients (P, K, Ca and Mg) release patterns had significantly (P < 0.05) increased in water in treatments T1 and T4 compared with the two treatments containing more Azolla in the diet (T2 and T3).