Miombo woodland (MW) has several multi-purpose forest species, which are over-exploited for agriculture, charcoal and logging. Industrial plantations are among the promising solutions for sustainable management of MW, but high-yielding MW species are still lacking in the forestry sector. In this context, the present study assessed the growth of MW species, with respect to their early (ES) or late (LS) successional status. Seedling development was assessed for eight tree species, which were ES (Combretum collinum, Pterocarpus tinctorius) and LS (Brachystegia boehmii, B. longifolia, B. spiciformis, B. wangermeana, Julbernardia globiflora, J. paniculata), 1, 2 and 4 years after planting. Germination and survival varied in relation to ontogenetic traits of the species, but not the successional status, as was the case for growth and productivity. Seed germination was 60% to 88% for all species (except C. collinum). Seedling survivorship was greater than 70% for most species, except for J. paniculata (36%). ES species have greater growth compared to LS, due to the allocation of biomass to diameter and the length of the root, respectively, from the early stage of seedling development. These two strategies of biomass allocation are positively correlated with height. We further observed two distinct phases of seedling development (0–2 and 2–4 years) for all species. Growth differences among LS species were identified 4 years after planting. Based on seedling biomass, B. spiciformis, C. collinum and P. tinctorius are the most productive potential candidates for reforestation of degraded MW. We concluded that seedling growth and productivity varied according to strategies of biomass allocation that were related to successional status (ES (Chipya group) versus LS (Miombo group)) and to age following planting.

Doctoraten • Doctorates • Doctorats Systeme d'evaluation des terres a multiples echelles pour la determination de l'impact de la gestion agricole sur la securite alimentaire au Katanga, R.D. Congo

No abstract

Dans le but de soutenir la production du maïs sur un Arenosol, une étude a été conduite pendant la première campagne agricole 2016-2017 sur un Arenosol en République démocratique du Congo en vue d’évaluer les effets des feuilles de Tithonia diversifolia, du fumier de vache, de la chaux et des engrais inorganiques (NPK) sur le rendement de maïs et la rentabilité économique. L’essai a été conduit suivant un dispositif en bloc complet randomisé avec dix traitements : T0= témoin ; T1=Fumier de vache ; T2=Guano; T3=Feuilles de Tithonia diversifolia ; T4=Engrais NPK 17-17-17; T5= Feuilles de Tithonia diversifolia + Chaux; T6=Fumier de vache + chaux; T7=Guano + Chaux; T8=Engrais NPK 17-17-17 + Chaux et T9=Chaux. Des effets significatifs des traitements ont été observé sur la croissance des plants, le rendement grains et les marges bénéficiaires. Les traitements T3 et T5 ont donné les meilleurs rendements. Cependant, le traitement T3 révèle un bénéfice brut et l’indice d’acceptabilité (IA) les plus élevés et peut alors être proposé aux agriculteurs avec plus de chance d’adoption. In order to support the production of maize at an Arenosol a study was conducted during the first cropping season 2016-2017 on an Arenosol in the Democratic Republic of Congo to evaluate the effects of Tithonia diversifolia leaves, cow manure, lime and inorganic fertilizer (NPK) on maize yield and economic profitability. The trial was conducted in a randomized complete block design with ten treatments: T0 = Control; T1 = Cow manure; T2 = Guano; T3 = Tithonia diversifolia leaves; T4 = NPK fertilizer 17-17-17; T5 = Tithonia diversifolia leaves + Lime; T6 = Cow manure + Lime; T7 = Guano + Lime; T8=NPK fertilizer 17-17-17 + Lime and T9=Lime. Significant effects of treatments were observed on plant growth, grain yield and profit margins. Treatments T3 and T5 gave the best yields. However, the T3 treatment showed the highest gross profit and acceptability index (AI) and can then be proposed to farmers with more chance of adoption.

Le contrôle de l’érosion hydrique des sols est l’une des préoccupations importantes en agriculture pluviale, notamment sous les climats tropicaux. Dans la plaine de Lubumbashi, deux sites agricoles (ferme Kasapa et le périmètre agroforestier de Mukoma) ont été étudiés en vue d’y évaluer le risque d’érosion hydrique du sol. Des cartes thématiques des différents facteurs d’érosion, tels que décrits dans l’Équation universelle de pertes de sol, ont été intégrées dans un Système d’Information Géographique, permettant ainsi de : (1) démêler leur complexité et leur interdépendance dans l’analyse des risques d’érosion et (2) cerner l’impact et la contribution de chacun d’eux aux pertes en sol. Cette démarche a permis de : (1) hiérarchiser les différentes zones de sites étudiés selon leurs degrés de sensibilité à l’érosion et (2) déterminer le taux d’érosion par le ruissellement en nappe (30,8 t/ha/an en moyenne pour la ferme Kasapa et de 3,6 t/ha/an pour le site de Mukoma). Par ordre d’importance, les facteurs décisifs qui contrôlent l’érosion hydrique dans la plaine de Lubumbashi sont : la pente, l’érodibilité des sols et la couverture végétale. The control of soil erosion by water is one of the major concerns in rainfed agriculture, especially in tropical climates. In the plain of Lubumbashi, two agricultural sites (Kasapa farm and the agroforestry perimeter of Mukoma) have been studied to assess the risk of soil erosion. Thematic maps of the various erosion factors, as described in the Universal Soil Losses Equation, were integrated into a Geographic Information System to (1) unravel their complexity and interdependence in the analysis of erosion risks and (2) identify the impact and contribution of each of them to soil losses. This approach allowed us to (1) prioritize the different areas of the studied sites according to their degree of sensitivity to erosion and (2) determine the rate of sheet erosion by runoff (30.8 t/ha/year on average for the Kasapa farm and 3.6 t/ha/year for the Mukoma site). In order of importance, the decisive factors that control water erosion in the Lubumbashi plain are: slope, soil erodibility and vegetation cover.