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We compared four oil palm (Elaeis guineensis Jacq.) progenies’ morphological growth characteristics to reveal genotypic differences in plant growth and assess their adaptability in Nigeria’s environment in response to different levels of potassium chloride (KCl) and kieserite fertilizer applications. The studied progenies (C1, C2 and C3 of Deli × La Mé origin and C4 of Deli × Yangambi origin) represent a wide genetic diversity of oil palm and have shown among a population of 116 different progenies, a contrasting K and Mg leaflet concentrations that covered the extreme ranges of leaflet concentrations in these minerals. The trial consisted of a completely randomized split-plot factorial design with six replicates, where progenies, considered as sub-factor were treated with combinations of 3 levels of potassium chloride (0, 1.5, 3.0 kg of KCl palm−1 year−1) and kieserite (0, 0.75, 1.5 kg of MgSO4 palm−1 year−1) fertilizers (main factor), respectively. Growth characteristics differed significantly among progenies, but not in all studied years. In all progenies, KCl treatments significantly increased the average annual collar girth increment and projected canopy area. Adding 3.0 kg palm−1 year−1 of KCl significantly increased the total leaf area of progeny C4. Kieserite applications did not have an effect on progenies’ growth characteristics whereas potassium showed to be the main mineral needed for oil palm growth. It was shown that with equal amounts of fertilizers applied, progeny C3 had better morphological traits than the other progenies, suggesting that the effective nutrient requirements should be assessed for each individual progeny and that fertilization should be adapted accordingly.

Oil palm fertilizer requirements are based on leaflet mineral concentrations. Four oil palm progenies representing a wide genetic diversity of Elaeis guineensis species and with contrasting K and Mg leaflet concentrations were tested in Indonesia and Nigeria, environments which differ predominantly in climate. During 5 years, we compared oil palm progenies’ leaflet mineral concentrations between both countries under abundant fertilizer applications to investigate the extent to which they depend on the environment. In the two studied environments, leaflet concentrations significantly differed between progenies for K, Mg and Ca, but the country effect was not found significant (p = 0.352) for any leaflet mineral’s concentration. In both countries, progenies ranked similarly in their mineral categories (lowest and highest cation concentrations within the 4 progenies population), indicating that leaflet mineral concentrations in the tested oil palm progenies are mainly determined by their genetic background. For each progeny, with abundant fertilization, K, Mg and Ca proportions to total leaf cation charge (TLCC) were similar, irrespective of the environments in which the palms were cultivated. We have strong indications that foliar concentrations of K, Mg and Ca are determined by genetic factors which dominate the environmental effect. However, it remains uncertain whether differences in oil palm foliar concentrations between different oil palm progenies imply that they require specific fertilizer amounts to attain an optimal production.

L’étude aborde la dynamique de l’utilisation des terres à travers l’évolution des emblavures et de la production des principales cultures, puis l’impact des activités agricoles sur l’environnement et les conditions de vie des populations. Objectif : L’objectif global de l’étude était d’évaluer les impacts socio-environnementaux des activités agricoles dans les Communes de Natitingou, Boukombé, Tanguiéta et Toucountouna en zone de montagnes au nord-ouest de l’Atacora au Bénin. Méthodologie et résultats : Les méthodes utilisées étaient les enquêtes exploratoires, les diagnostics participatifs, les sondages d’opinion et les analyses statistiques tels que la variance suivant le test de Tukey et le test de corrélation. Au total, 400 agriculteurs sont sélectionnés au hasard et interrogés dans huit villages des quatre communes à l'aide d'un questionnaire structuré pour obtenir des données relatives aux nombres de cultures produites sur une même parcelle, aux différentes pratiques agricoles, à l'utilisation des engrais minéraux, à l’adoption des techniques endogènes et exogènes de gestion et de conservation de la fertilité des sols dans le milieu. Les résultats ont montré que les systèmes de productions agricoles étaient encore de type extensif et itinérant sur brûlis. Les cultures étaient mises en place en pure et en associations entre avril et décembre avec une prééminence des céréales qui ont occupé environ 52 % des superficies emblavées. Les productions étaient plus en fonction des superficies que de l’intensification agricole. Les causes de dégradation des sols, la production, ont été collectées lors des entretiens collectifs et individuels. Les impacts de la production agricole se traduisaient surtout entre autres, par la disparition du couvert végétal, la baisse de la fertilité des sols et la pollution de certains cours d’eau aux bords desquels se réalisaient des activités à dominance agricole. Conclusion et application des résultats : Certaines activités telles que l’utilisation des engrais chimiques et les feux de végétation ont résolu d’une manière ponctuelle certains problèmes comme l’amélioration des rendements agricoles et l’augmentation des revenus, mais elles n’ont pas duré dans le temps. Au fil des années, ces activités ont eu un impact négatif sur le milieu et les conditions de vie des populations. L’intensification agricole basée sur la vulgarisation et l’adoption des technologies plus productives et respectueuses de l’environnement, efficientes, facilement applicables par les producteurs, demeure l’une des stratégies pour garantir une utilisation durable des ressources naturelles. Mots clés: Bénin, Atacora, activités agricoles, impacts socio-environnementaux et dégradation des sols ABSTRACT The study approaches the dynamics of the land use through the evolution of cultivated area and the production of the principal crops, then the impacts of the agricultural activities on the environment and the living conditions of the population. Objective: The total objective of the study was to evaluate the socio-environmental impacts of the agricultural activities in the Communes of Natitingou, Boukombe, Tanguieta and Toucountouna in mountainous area in the North-Western of Atacora in Benin. Methodology and Results: The methods used were the exploratory investigations, the participative diagnoses, the opinion polls and statistical analyses such as the variance according to the test of Tukey and the test of correlation. On the whole, 400 farmers were selected randomly and questioned in eight villages of the four communes using a structured questionnaire to obtain relative data with the numbers of cultures produced on the same piece, with various husbandries, with the use of mineral manures, the adoption of the endogenous and exogenous technical of management and conservation of the fertility of the grounds in the medium. The results showed that agricultural production systems were still extensive and itinerant on slash-and-burn. Crops were established in pure and association between April and December with a pre-eminence of cereals, which accounted for about 52% of the area. Productions were more based on acreage than agricultural intensification. The causes of soil degradation, production, were collected during collective and individual interviews. The impacts of agricultural production were mainly reflected in the disappearance of vegetation cover, the decline in soil fertility and the pollution of certain rivers along which agricultural-dominated activities were carried out. Conclusion and application of results: Some activities such as the use of chemical fertilizers and wildfires have solved problems such as improving agricultural yields and increasing incomes on an ad hoc basis, but they didn’t last. Over the years, these activities have negatively affected the environment and living conditions of the population. The agricultural intensification based on the popularization and the adoption of more productive and environment friendly technologies, easily applicable by the producers, remains one of the strategies to guarantee a durable use of the natural resources. Keywords: Benin, Atacora, agricultural activities, socio-environmental impacts and impoverishment of the soil