Essai de phytostabilisation des sites contaminés par les éléments traces métalliques dans la région de Lubumbashi (RD. Congo) : Gamme de tolérance de Jatropha curcas au sulfate de cuivre.

Problématique : Les activités industrielles notamment la métallurgie dans la ville de Lubumbashi, ont engendré via leurs rejets atmosphériques (canalisés et diffus) une forte contamination des sols aux alentours des usines. Cependant, les sols à usages divers (forestiers, agricoles ou résidentiels), leur pollution par les éléments traces métalliques (ETM) constitue un danger plus ou moins sévère pour l’environnement et pour les populations.Objectif : Cette étude a été menée pour évaluer la croissance et le potentiel de phytostabilisation de Jatropha curcas installé sur un substrat contaminé à différentes doses de sulfate de cuivre.Méthodologie et résultats: Deux essais ont été conduits simultanément au champ expérimental de la faculté des Sciences Agronomiques de l’Université de Lubumbashi (FSA/Unilu), suivant un dispositif complètement randomisé comprenant 4 répétitions de 7 traitements constitués par des doses croissantes de sulfate de cuivre apportées artificiellement au sol normal sous forme de poudre. Les résultats relatifs aux paramètres végétatifs notamment le taux de reprise, le taux de levée, le taux de survie, la taille et le diamètre au collet des plantes ont été soumis à l’analyse de la variance (ANOVA) et au test de Tukey. Les résultats d’analyse chimique dans les sols et dans les plantes ont été comparés aux normes internationales. Les résultats obtenus montrent que Jatropha curcas s’est montré vigoureux sur les traitements ayant reçu des faibles doses de sulfate de cuivre (CuSO4) (250 ; 500 et 1000 mg.kg-1 de sulfate de cuivre (CuSO4), tandisque des fortes doses (4000 et 8000 mg.kg-1 de sulfate de cuivre (CuSO4) ont induit des mortalités maximales des plantules (100%). Par ailleurs, les calculs de bioaccumulation et translocation montrent des taux élevés de bioaccumulation du sulfate de cuivre de Cuivre dans les racines et des faibles taux de translocation en sulfate de cuivre de Cuivre des plantes de Jatropha curcas vers les parties aériennes.Conclusion et application des résultats : La phytostabilisation des sols contaminés en ETMs avec l’espèce Jatropha curcas est possible dans la région de Lubumbashi, du faite que cette espèce est tolérante jusqu’à des doses allant jusqu’à 2000 ppm par semis indirecte et minimise les risques de transfert d’ETM vers les autres compartiments de l’environnement.Mots-clés : Phytostabilisation, Jatropha curcas, ETMs, Lubumbashi

Impact of Organic Amendments and Mineral Fertilizers on the Growth of Vitroplants of the Great Dwarf Cultivar of Banana ( Musa sp ) Installed on a Ferralsol

peer reviewedIn the Democratic Republic of Congo, banana is the third largest source of starch after cassava and maize and is the primary fruit crop. However, its cultivation remains secondary due to its high mineral demand, the infertility of tropical soils (ferralsol) and the low income of farmers. The dynamics of mineral elements and the understanding of its influence on crop growth are a necessity for a better use of fertilizers and an optimal crop production. The objective of this study was to evaluate the influence of organo-mineral amendment inputs on banana growth and improvement of soil chemical properties. The experiment was set up in a randomised complete block design with 9 treatments spotted 6 times. The treatments consisted of T0 (unfertilized control) ; T1 : 250g NPK (10-20-10) +187.5g urea (46%) ; T2 : 500g NPK (10-20-10) + 375g urea (46%); T3 : 750g NPK (10-20-10) +562.5g urea (46%) ; T4 : 1000g NPK compound fertilizer (10-20-10) +750g urea (46%), T5 : 12 kg (chicken droppings) ; T6 : 18 kg (chicken droppings) ; T7 : 24 kg (chicken droppings) and T8 : 30 kg (chicken droppings) per plant. The vitroplant banana of the great dwarf cultivar were planted and vegetative parameters were observed. Before and during the trial, soil samples were taken from the surface layer for chemical analysis. The results show that the different doses applied to the soil significantly decreased the sodium content (p=0.008) after the trial. On the other hand, similar effects were observed on the other chemical parameters (K+, Mg2+, Ca2+, Total C and Organic N) before and during the experiment. On the crop, the results show positive effects of organic amendments and mineral fertilization on the development of banana vitroplants. The mineral fertilizer treatments showed a high performance on the crop followed by the manure treatments compared to the control treatment which showed a low performance. However, positive relationships were obtained on soil mineral elements with some crop parameters. Based on these results, it should be noted that the use of organo-mineral amendments contributes to the growth of banana and the reduction of sodium in the soil through the presence of organic matter

In Vitro Regeneration Protocol for <i>Securidaca longepedunculata</i> Fresen., a Threatened Medicinal Plant within the Region of Lubumbashi (Democratic Republic of the Congo)

Securidaca longepedunculata Fresen. is an overexploited forest species in the Lubumbashi region (south-eastern DR Congo), as its roots are highly valued in traditional medicine. Conventional propagation of this species is affected by seed dormancy and a high mortality rate during early seedling development. To improve on existing methods, we developed an in vitro seed germination protocol. After observing the germination rates, the effects of different doses (0.5, 1, 1.5, and 2 mg/L) of cytokinins (6-benzylaminopurine, kinetin, and meta-topolin) on S. longepedunculata seedling development were compared. Our results showed that soaking for 10 min in NaOCl (10%) followed by 5 min in ethanol (70%) effectively reduced the death rate of seeds while increasing the germination rate to almost 77%. The addition of cytokinins improved plantlet growth: a 12.2× increase in the number of plantlets was obtained with 1.5 mg/L meta-topolin, while only a single stem was obtained from the control. The effects of different auxin types on rhizogenesis did not differ significantly. The best recovery and rooting were noted with microcuttings from the basal parts of S. longepedunculata plantlets. Finally, the seedlings produced survived during the acclimatisation phase regardless of the type of substrate used. The established protocol provides a means for large-scale production of S. longepedunculata plantlets for the restoration of degraded landscapes and agroforestry