Remineralization of a Dystric Ferralsol Using Basalt and Tephra Dusts, Effective Microorganisms Manure and NPK 20-10-10 for Radish (Raphanus sativus) Production in Bamougoum (Cameroon Western Highlands)

This paper studies the effect of basalt and tephra dusts, as alternatives to chemical fertilizers, on soil fertility and Radish (Raphanus sativus) production. The experiment was conducted in the field and in the laboratory in the years 2017 and 2018 on two separate plots so as to annul residual effects of fertilizers). The experimental design in the field was a randomized complete block design (56 m2 ), including five treatments and three replications: control (T0), basalt dust (T1), tephra dust (T2), effective micro-organism (EM) fertilizer (T3) and NPK 20-10-10 (T4). The main results show the following decreasing trend based on yield: T1>T3>T0>T4>T2. The best yields appear in T1 and T3 probably because they supplied the highest levels of soil nutrients to match the needs of the crops. Although T2 plants performed poorly, soil properties like pH.H2O (6.14 to 6.49), sum of exchangeable bases, base saturation, available phosphorus and cation balance were improved after tephra treatment. T2 plants might have performed poorly due to intrinsic properties of the tephra dust like low availability of trace elements compared to T1 and T3. T4 plants show the highest number of leaves, leaf area index and plant height. The Fe, Mn, Cu and Zn levels in bulbs and leaves will not pose danger of toxicity to human upon consumption and could serve as nutrient supplement for children and expectant mothers. The most profitable treatment is T1 permitting to recommend the popularization of basalt dust for radish cultivation as an alternative to chemical fertilizers

Biogeochemistry of Iron, Aluminium and Silicon in Humid Tropical Mountainous Soils (Bambouto Mountain, West Cameroon)

International audienceHumid tropical mountainous soils of the Bambouto volcanic mountain (West Cameroon) have been studied mainly from a chemical view point. The aim of the study was firstly to study the behaviour of iron, aluminium and silicon during pedogenesis, and to determine the forms of the three main elements. Global balance of iron is negative; it is the result of slight illuviation at the base of the profile, and moderate eluviation in the upper horizons. Selective extractions show that iron is mainly in the 'resistant' form, more moderately in the crystallized forms, while the amorphous forms are negligible, with a quasi-absence of organic amorphous forms. Silicon is highly evacuated in all horizons. Aluminium, characterized by high accumulation at the base of the profile and moderate evacuation in the upper part, presents an excess global balance. Otherwise, contrary to iron, organic amorphous forms of aluminium are well represented in these soils, which the occurrence of aluminium permits to assimilate to Aluandosols. Humid tropical mountainous soils show pedological evolution mainly dominated by the behaviour of silicon and aluminium, with iron appearing to have a negligible role. However, contrary to the temperate soils, in which bisiallitisation is the predominant process, in mountainous soils, characterized by high evacuation of silica concomitantly to notable accumulations of aluminium, allitisation predominates. This is associated with moderate andosolisation, due to the presence of a volcanic parent rock

Évaluation des pertes en terres en région de montagne tropicale humide (cas du massif volcanique des Bambouto - Ouest Cameroun)

Le massif volcanique des Bambouto dans l’Ouest Cameroun, est un écosystème de montagne tropicale humide particulièrement exposé à la dégradation des sols en raison de son relief très accidenté, de la forte pluviosité et de la faible densité de son couvert végétal. Sur un tout autre plan, les sols de la région, réputés fertiles, attirent les populations et cette pression anthropique sur le milieu accroît encore la vulnérabilité de cet environnement de montagne tropicale, avec pour conséquence une intense érosion des sols.Afin d’évaluer l’ampleur de ce phénomène dans la région, l’Equation Universelle des Pertes en Terre (USLE) de Wischmeier et Smith (1978) a été mise à contribution pour la quantification des taux d’érosion, estimée à 674 t ha-1 an-1 ; et l’intégration des paramètres de cette équation dans un système d’information Géographique a permis d’y spatialiser et d’hiérarchiser les pertes en terre.Au vue de la vitesse de dégradation du couvert végétal naturel dans la région, les taux d’érosion devraient croitre avec le temps et conduire à moyen terme à une situation de crise alimentaire dans ce secteur peuplé à 90 % d’agriculteur Bamiléké.The Bambouto volcanic mountains in the western Cameroon is an ecosystem of humid tropical mountain particularly exposed to the degradation of soils because of its accidented relief, high rainfall and the low vegetation cover. On the other hand, the soils of the region with known fertility, attracts the population whose anthropic pressure on the milieu increases the vulnerability of its environment with remarkable degradation of soils through erosion.In order to evaluate the rate of erosion in the region, the Universal Soil Loss Equation (USLE) of Wischmeier and Smith (1978) was used for the estimation of total soil losses due to erosion ; evaluated at 674 t/ha-1 yr-1.Considering the rate of degradation of the natural vegetal cover, the erosion rate would rise and the fall in soil fertility demonstrated through severe reduction in agricultural production, and in the medium term to a severe food shortage in this sector populated to 90 % by Bamileke farmers

Soil Water Characteristics of Gleysols in the Bamenda (Cameroon) Wetlands and Implications for Agricultural Management Strategies

Water budgeting in agriculture requires local soil moisture information as crops depend mainly on moisture available at root level. The present paper aims to evaluate the soil moisture characteristics of Gleysols in the Bamenda (Cameroon) wetlands and to evaluate the link between soil moisture content and selected soil characteristics affecting crop production. The work was conducted in the field and laboratory, and data were analyzed by simple descriptive statistics. The main results showed that the soils had a silty clayey to clayey texture, high bulk density, high soil organic carbon content, and high soil organic carbon stocks. The big difference between moisture contents at wilting point and at field capacity testified to very high plant-available water content. Also, the soils displayed very high contents of readily available water and water storage contents. The soil moisture characteristics give sigmoid curves and enabled noting that the Gleysols attain their full water saturation at a range of 57.68 to 91.70% of dry soil. Clay and SOC contents show a significant positive correlation with most of the soil moisture characteristics, indicating that these soil properties are important for soil water retention. Particle density, coarse fragments, and sand contents correlated negatively with the soil moisture characteristics, suggesting that they decrease soil water-holding capacity. The principal component analysis (PCA) enabled reducing 17 variables described to only three principal components (PCs) explaining 73.73% of the total variance; the first PC alone expressed 45.12% of the total variance, associating clay, SOC, and six soil moisture characteristics, thus portraying a deep correlation between these eight variables. Construction of contoured ditches, deep tillage, and raised ridges management techniques during the rainy season while channeling water from nearby water bodies into the farmland, opportunity cropping, and usage of water cans and other irrigation strategies are used during the dry season to combat water constraints

Growth promotion potential of Bacillus spp. isolates on two tomato (Solanum lycopersicum L.) varieties in the West region of Cameroon

Inoculation of plants with plant growth-promoting bacteria (PGPB) is an ecological approach to improve plants growth and yield. The objective of this study was to screen native PGPBs in tomato root rhizosphere and evaluate their performance in germination and growth of seedlings in the greenhouse in the western region of Cameroon. Isolates were selected based on their ability to solubilize phosphate, produce indole-3-acetic acid, and improve seed germination and seedling growth under laboratory conditions. Following this screening, eight bacteria were selected (S1, S4, S13, S14, S16, B9, B11, and B15) to assess their performance on seedling growth in greenhouse. Seeds of two tomato varieties (one improved, Raja, and the local one, Foolewouh) were used in this study. The experiment was performed in sterilized and non-sterilized soils. Phylogenetic analysis of the 16S rRNA sequence showed that these bacteria belong to the genus Bacillus, including B. thuringiensis, B. cereus, B. pacificus, and B. aerius. The bacterial performance depended on the variety and conditions of soil treatment. Isolates improved seed germination (up to 31.93%) and seeding strength (up to 78.59%) in vitro. In greenhouse, inoculation with PGPB significantly increased stem height, root length, and weight of fresh and dry stems and roots. Raja variety was more sensitive to bacteria and performed better than the Foolewouh variety. Bacterial isolates on sterilized soil allowed to better seedling growth compared to non-sterilized soil. The study showed that B. thuringiensis (strain B9), B. pacificus (strain B11), and Bacillus sp. (strain B15) can be used as inoculant formulations to improve seedling growth of tomato plant

Lutte antiérosive

Face à la pression démographique et foncière dans les pays en développement, la productivité des terres connaît actuellement une forte baisse dans de nombreuses régions tropicales. Par ailleurs, la succession rapprochée des tempêtes cycloniques entraîne l'appauvrissement extrême de certaines populations du fait de la dégradation des terres et des inondations des plaines où se développent les principales agglomérations. Telles sont les problématiques étudiées par l'IRD et le réseau Érosion de l'AUF dont ce CD présente les derniers travaux. Initialement réunies dans la perspective d'un colloque à Haïti (annulé suite au séisme de 2010), les contributions publiées ici portent sur des études de cas à Haïti, mais aussi à Madagascar, au Maghreb ou au Vietnam, soit au total une soixantaine de communications et une série de documents récents issus des réflexions des experts. Structuré en six thèmes, ce CD constitue ainsi une source bibliographique précieuse pour les décideurs, les experts, les ONG, les acteurs de la société civile et les chercheurs concernés par la gestion durable de l'eau et la restauration de la productivité des sols (GCES)