Promising high-yielding tetraploid plantain-bred hybrids in west Africa

Open Access Journal; Published online: 21 April 2019The devastating threat of black leaf streak disease caused by Pseudocercospora fijiensis on plantain production in West Africa spurred the development of resistant hybrids. The goal of this research and development (R&D) undertaken was assessing the development and dissemination of two plantain hybrids PITA 3 and FHIA 21 bred in the 1980s by the International Institute of Tropical Agriculture (IITA, Nigeria) and the Fundación Hondureña de Investigación Agrícola (FHIA, Honduras), respectively. In Côte d’Ivoire, plantain growers selected PITA 3 and FHIA 21 based on their improved agronomic characteristics and, between 2012 and 2016, they were massively propagated and distributed to farmers in Benin, Burkina Faso, Côte d’Ivoire, and Togo under the West Africa Agricultural Productivity Program (WAAAP) coordinated by the West and Central Africa Council for Agricultural Research and Development (CORAF). In 2016, the Centre National de Recherche Agronomique in Côte d’Ivoire included the hybrids in the improved cultivar directory. This R&D activity illustrates how three decades of crossbreeding, selection, and distribution led to local acceptance. It also highlights how a CORAF-led partnership harnessed CGIAR research for development. The dissemination and acceptance of these plantain hybrids will enhance the sustainable intensification in plantain-based farming systems across the humid lowlands of West and Central Africa

Carbone des sols en Afrique

Les sols sont une ressource essentielle à préserver pour la production d’aliments, de fibres, de biomasse, pour la filtration de l’eau, la préservation de la biodiversité et le stockage du carbone. En tant que réservoirs de carbone, les sols sont par ailleurs appelés à jouer un rôle primordial dans la lutte contre l’augmentation de la concentration de gaz à effet de serre. Ils sont ainsi au centre des objectifs de développement durable (ODD) des Nations unies, notamment les ODD 2 « Faim zéro », 13 « Lutte contre le changement climatique », 15 « Vie terrestre », 12 « Consommation et production responsables » ou encore 1 « Pas de pauvreté ». Cet ouvrage présente un état des lieux des sols africains dans toute leur diversité, mais au-delà, il documente les capacités de stockage de carbone selon les types de sols et leurs usages en Afrique. Il propose également des recommandations autour de l’acquisition et de l’interprétation des données, ainsi que des options pour préserver, voire augmenter les stocks de carbone dans les sols. Tous les chercheurs et acteurs du développement impliqués dans les recherches sur le rôle du carbone des sols sont concernés par cette synthèse collective. Fruit d’une collaboration entre chercheurs africains et européens, ce livre insiste sur la nécessité de prendre en compte la grande variété des contextes agricoles et forestiers africains pour améliorer nos connaissances sur les capacités de stockage de carbone des sols et lutter contre le changement climatique

Dynamique de Fer ferreux (FeO) du sol de bas-fond en fonction de la répartition de l’eau selon la toposéquence au sud du Bénin: Phénomène de la toxicité ferreuse et production du riz

Objectif: La présente étude évalue la dynamique de la teneur du sol en (FeO) dans le bas-fond, mesure les conditions de développement du riz sur des sols immergés et établit les relations qui existent entre les paramètres de production et l’évolution de l’accumulation du (FeO) en fonction des répartitions de l’eau selon la toposéquence dans les casiers rizicoles.Méthodologie et résultats: Trois traitements ont été testés sur les parcelles : Écoulement naturelle de l’eau, inondation suivie de drainage, inondation permanente. Le prélèvement du sol est fait aux profondeurs 0-10 cm, 10-20 cm et 20-30 cm. Des échantillons composites ont été constitués par profondeur et un total de 504 échantillons de sol ont été analysés pour l'étude Les mesures du potentiel redox (Eh) et du pH sont réalisées sur le site par le pH letter pc228 mais l’évaluation de la teneur du sol en (FeO) et son dosage, sont réalisés au laboratoire au spectromètre à absorption atomique. Le rendement du riz est calculé en rapportant la production de riz paddy à l’ha. Une analyse de la variance à trois facteurs est effectuée, au moyen du logiciel SAS version 9.2. Le potentiel redox a varié entre 32,25±13,69 et 199,78±13,45 mv avec un pH allant de 4,56±0,16 à 7,79±0,32. La quantité de FeO a varié de 3132±534 à 498±96 ppm et les rendements de 2103±180 à 2854 ±174kg/ha au poids sec.Conclusions et application des résultats: Le bas-fond présente deux types d’hydromorphie : l’hydromorphie moyennement réductrice et l’hydromorphie très réductrice. L’effet conjugué des conditions de réduction et de la dynamique de la teneur du sol en fer ferreux a permis d’apprécier et de mesurer leurs impacts sur les paramètres de production du riz. Il existe une relation statistiquement significative (p<.0, 05) et inversement proportionnelle entre les paramètres Eh, Fer ferreux et pH. On constate que plus la valeur de Eh ne diminue, plus les valeurs du pH et du Fer ferreux ne sont élevées. Le traitement d’inondation suivie de drainage présente un fort tallage avec un taux de fertilité de 86,5% des talles et un meilleur rendement en grain de riz (2854kg/ha) est le plus recommandable pour la valorisation du bas-fond par la production rizicoleMots clés: dynamique, toxicité ferreuse, bas-fond, BéninEnglish AbstractObjectives: This study assesses the dynamics of soil content in FeO of the shallows, measure the rice growth conditions in submerged soils and establishes the relationship between production parameters and the FeO accumulation‘s evolution.Methodology and Results: Three treatments were tested on the plots. Composite samples were made by depth and a total of 504 soil samples were analyzed for the study. The redox potential (Eh) and pH measurements are carried out at the site by pH letter pc228; The evaluation of the FeO content and its determination are carried out in the laboratory using an atomic absorption spectrometer. The statistical analysis is performed using the software SAS 9.2. The redox potential varies between 32, 25±13, 69 and 199, 78±13, 45 mv with a pH from 4, 56±0, 16 to 7, 79±0, 32. FeO’s amount varies from 3132±534 to 498±96 ppm and the yields from 210±18 à 285±17 g/m2Conclusions and application of the results: The shallow presents two types of water logging : One slightly reductive and the second very reductive. The reduction conditions and the dynamics of the soil’s content in ferrous iron were used to measure and evaluate the effect of irrigation scheme on rice’s growth parameters. There is a statistically significant (p <0, 05), inversely proportional relationship between the parameters Eh, ferrous iron and the pH. It is found that more the value of Eh decreases, more the pH values and ferrous iron increase. This is confirmed by the Pearson’s correlation coefficient R, -0.8757 and -0.8830 indicating a strong relation between the three variables. The flooding treatment followed by drainage showed strong tillering with a fertility rate of 86.5% of tillers and performance (2854kg/ha) is the more recommended scheme in the shallow.Keywords: dynamic, iron toxicity, shallow, Beni

Allometric equations for estimating oil palm stem biomass in the ecological context of Benin, West Africa [+ Corrigendum 2019, vol. 33, no 1, p. 315]

Key messageThe models we developed used palm stem diameter at 1.5m, stem density measured by core sampling at 1.5m, and the height of the palm to estimate palm stem biomass.AbstractAllometric equations based on non-destructive methods were developed to estimate palm stem biomass. Twenty mature palms of different ages were subject to destructive and non-destructive measurements: stem height from the collar to the bottom of the frond at the 33rd position in the crown (frond 33), dry weight, the diameter and thickness of cylindrical slices sectioned at different heights along the stem, and the dry weight of samples of stem tissue taken from the core of each slice. The densities of the stem slices obtained using the destructive method (D-true) and the non-destructive method (D-core) were linearly correlated: D-true=1.062xD(core) (R-2=0.99) independently of the height, age and genetic origin of the palm. Stem density varied with height, reaching its maximum at around 1.5m, after which it remained more or less constant to the top of the stem. Stem linear density (SLD) estimated from the product of the density and the section of the stem fell to a threshold value that remained more or less constant above 1.5m. SLD between observed slices was estimated by interpolation based on a hyperbolic model to compute the true biomass of each palm. An equation derived from the integral of the hyperbolic model was fitted to estimate palm stem biomass as a function of wood density observed by non-destructive sampling at 1.5m on the stem and of the diameter at the same height. With this equation, palm stem biomass can be estimated with an error of 5%

Effet de la gestion des feuilles d'élagage du palmier à huile sur le stock de carbone et les propriétés physico-chimiques du sol dans les palmeraies villageoises du Bénin

Description of the subject: In Benin, oil palm plantations are widely managed by smallholder farmers. The study addresses the impact on soil properties of the recycling of pruned fronds from these trees. Objectives: The study aims to assess the effect of two modes of management of pruned fronds on the carbon stock and physico-chemical properties of soil. Method. Six oil palm plantations were selected to represent two age classes (7-12 years and 13-24 years) in southeastern Benin. They were used to compare the soil properties of two areas: the areas of total recycling of pruned fronds (TR) and the areas of no recycling of the fronds (NR), which represented the control. In each plantation, soil samples were collected under the two treatments, from holes of up to 50 cm depth, near six oil palm trees. The soil properties were determined using conventional laboratory methods and near-infrared spectroscopy method. Results: Carbon and nitrogen stocks under TR of adult plantations were 58 Mg.ha(-1) and 4.3 Mg.ha(-1), respectively, and were significantly higher than the stocks in all other treatments (34.6 Mg C.ha(-1) and 2.9 Mg N.ha(-1)). Recycling of pruned fronds improved soil fertility at a depth of up to 20 cm in the adult plantations. The porosity and bulk density of the soil were also improved. Conclusions: The management of the pruned fronds in the smallholders' oil palm plantations modified the soil properties, which were significantly improved in the top soil after 10 years of frond recycling

Quantification of soil organic carbon in particle size fractions using a near-infrared spectral library in West Africa

International audienceParticle size fractionation enables a better understanding of soil organic carbon (C) dynamics since it separates fractions that differ in composition, residence time and function. However, this method is time-consuming and tedious; thus, its use has been greatly limited. Our objective was to evaluate the ability of an existing soil spectral library (SSL) from different regions of West Africa to predict the C amount in the fractions (gC kg-1 soil) of the samples in a new target set from Benin. The SSL included 181 samples from five countries, and the target set included 94 samples (depth ≤ 40 cm), most of which were coarse-textured; near-infrared reflectance (NIR) spectra were collected for 2 mm sieved samples (non-fractionated samples). The predicted variables were the C amounts in the non-fractionated soil and in the 50 μm fractions (F50, respectively). Different methods were tested to optimize the predictions: (i) SSL enrichment with 10 or 15 samples selected from the target set (spiking) and replicated six times (i.e. extra-weighted); (ii) locally weighted (local) partial least squares regression (PLSR), which is calibration by the spectral neighbours with the highest weights attributed to closest neighbours, and was compared to “global” (i.e., common) PLSR, where all calibration samples equally contribute; and (iii) spectrum pretreatments (e.g., smoothing, centring, derivatization). In addition, the intermediate precision of the conventional data (standard error of laboratory; SELint) was estimated through triplicate fractionation of three samples carried out by three operators (one per replicate). When the SSL alone was used for calibration, the predictions were inaccurate for the C amounts in the nonfractionated soil and in F50, with minimal benefit from the local PLSR over the global PLSR in general. For the non-fractionated soil, F50, the ratios of performance to the interquartile range in the validation set, RPIQVAL, were 1.6–1.8, 1.6–1.7, 1.9 and 1.9–2.1, respectively. Calibration with SSL spiked (i.e., completed with spiking samples) yielded an increase in RPIQVAL from 33 to 56% for the C amount in the non-fractionated soil and F50 (RPIQVAL reached 2.4–2.5, 2.2–2.3, 1.9–2.0 and 2.1–2.3, respectively), and the benefit of local PLSR was still limited. The SELint was based on a few samples and thus only provided a rough estimation; this estimate represented at least 65% of the prediction error for the C amounts in the fractions. Therefore, the SELint needs to be determined more extensively to both improve the model accuracy and refine the interpretation of the predictions based on NIR spectra. This library should be enriched with samples from other sites to represent other soil types