Estimations du parametre fractionnaire de memoire d : applications aux prix du coton par tonnes pour les cas des pays Benin, Burkina-Faso et Mali

L’objet de cet article est d’utiliser la caractéristique de mémoire longue de certaines séries de prix du coton par tonnes à des fins prévisionnelles. Cet article propose ainsi de mener des prévisions au moyen de processus ARFIMA des prix du coton par tonnes du Bénin, du Burkina-Faso et du Mali. Les résultats obtenus suggèrent que les prix du coton par tonnes du Bénin ont suivi un processus stationnaire à mémoire longue (d = 0.2567772), avec les autocorrélations positives et diminuent hyperboliquement vers zéro lorsque le retard augmente et la densité spectrale concentrée autour des faibles fréquences et tendait vers l’infini lorsque la fréquence tend vers zéro. Par contre les paramètres de mémoires (d) des deux autres pays le Burkina-Faso (d = -0.155915 et le Mali (d = -0.0172887) sont négatifs. Les paramètres de mémoire (d) des deux pays ont suivi donc des processus anti-persistants: les autocorrélations ont diminué hyperboliquement vers zéro et la densité spectrale dominée par les composantes de hautes fréquences (elle tend vers zéro lorsque la fréquence tend vers zéro). La présence de mémoire longue est en outre directement liée à la question d’efficience des politiques de prix agricoles, par contre les processus anti-persistants induisent des prévisions avec des effets naïfs et inefficaces pour une politique de prix agricoles.Mots clés: Mémoire longue, anti-persistance, paramètre d de mémoire longue, prix du cotonEnglish Title: Evaluations of the fractional parameter of d memory: applications to the prices of cotton by tons for the case of Benin, Burkina-Faso and MaliEnglish AbstractThe objective of this research is to use the characteristic of long memory of some sets of cotton price by tons to estimable ends. Thus it proposes to lead some fore castings by means of ARFIMA process of the cotton prices by tons of Benin, the Burkina-Faso and Mali. The gotten results suggest that the prices of cotton by tons of Benin follow a stationary process to long memory (d = 0.2567772), with the positive autocorrelation and decrease hyperbolically toward zero when the delay increases and the spectral density concentrated around the weak frequencies and stretches toward the infinity when the  frequency stretches toward zero. On the other hand the parameters of d memorials of the two other countries the Burkina-Faso (d = -0.155915 and Mali (d = -0.0172887) are negative. The parameters of d memory of the two countries follow anti-obstinate processes therefore : the autocorrelation decreases hyperbolically toward zero and the spectral density dominated by the components of high frequencies (she/it stretches toward zero when the frequency stretches toward zero). The long memory presences besides bound directly to the question of efficiency of the policies of agricultural prices, on the other hand the anti-obstinate processes lead some fore castings with naive and inefficient effects for a politics of agricultural prices.Keywords: long memory, anti-persistence, d parameter of long memory, price of cotto

Effet comparé de la fertilisation à base de biochar, engrais organique et engrais chimique sur les éléments minéraux et la production de l’oignon (Allium cepa L.)

Au cours des dernières décennies, il y a de plus en plus des études universitaires sur l'importance du biochar. Ce dernier constitue un moyen efficace pour la valorisation des déchets agricoles et forestiers. Cette étude qui s’inscrit dans le même contexte a pour objectif principal de déterminer les effets combinés du fumier de chèvre (FC, 5 t ha-1) et de son biochar (BC 10 t ha-1) sur l'efficacité d'utilisation des engrais chimiques (EC) sous différents ratios (100%, 50% et 0%), avec la variété d’oignon Metan 88. Pour ce faire, des essais ont été conduits en plein champ, dans le Centre de Recherche Horticole (CRH Ayas) de l’Université d'Ankara. En effet, le dispositif expérimental est un bloc complet randomisé comportant douze (12) traitements en quatre (4) répétitions, soit quarante-huit (48) parcelles. Les différentes mesures et analyses effectuées ont permis la détermination des paramètres tels que ; le poids frais et sec, le rendement total, la chlorophylle relative, l’acide ascorbique, ainsi que les concentrations des N, P, K, Ca, Mg, Fe, Zn, Cu et Mn. Les résultats obtenus ont montré que le rendement total de l'oignon a augmenté de manière significative avec l'application du biochar, du fumier ainsi que leur combinaison. Tous les traitements d'engrais organiques et inorganiques ont considérablement augmenté les concentrations en N, P et K respectivement 38,8, 2,81 et 42,2 g Kg-1 par rapport aux témoins 33,8, 2,32 et 35,6 g Kg-1. Les  concentrations en Ca et Mg respectivement 7,31 et 6,69 g kg-1 ont été augmentées avec l'engrais organique par rapport aux témoins 6,43 et 5,10 g kg-1. Le Biochar et le fumier ont donné la concentration la plus élevée de chlorophylle relative avec 297 et 294 respectivement. En conclusion , la combinaison du BC+FC a permis d’obtenir une croissance optimale de l’oignon.   In recent decades, numerous academic studies were carried out in order to determine the importance of biochar. The latter constitutes an effective means for valuing the agricultural and forestry waste. The main objective of the present study was to determine the combined effects of goat manure (GM, 5 t ha-1) and its biochar (BC 10 t ha-1) on use efficiency of chemical fertilizers (CF) in different ratios (100%, 50% and 0%), in the Metan 88 variety of onion.  The , trials were carried out in the open field at the Horticultural Research Center at Ankara University. The experimental device is a complete randomized block comprising twelve (12) treatments in four (4) repetitions, forty-eight (48) plots. The various measurements and analyses carried out allowed the determination of parameters such as fresh and dry weight, total yield, relative chlorophyll, ascorbic acid, the concentrations of N, P, K, Ca, Mg, Fe, Zn, Cu and Mn, as well  . The obtained results  showed that the total yield of onion increased significantly with biochar, manure as well as their combination. All organic and inorganic fertilizer treatments significantly increased N, P and K concentrations 38.8, 2.81 and 42.2 g Kg-1 respectively compared to controls 33.8, 2.32 and 35, 6g Kg-1. As for the concentrations of Ca and Mg 7.31 and 6.69 g kg-1 they were increased with the organic fertilizer compared to the controls 6.43 and 5.10 g kg-1 respectively.. Biochar and manure gave the highest concentration of relative chlorophyll with 297 and 294 respectively. Inconclusion , the combination of BC + CF resulted in optimal onion growth

Genetic diversity of Oryza species in Niger ; screening and breeding for resistance to rice yellow mottle virus (RYMV)

Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.Rice is a staple food in many West African countries, including Niger. However, both regional and national rice production have failed to meet demand due to several constraints, among which is the Rice yellow mottle virus (RYMV). Moreover, attempted intensification of rice cultivation and the introduction of modern cultivars are encouraging farmers towards abandoning local landraces for high yielding, but often susceptible varieties. The study was primarily oriented towards rice pre-breeding, and identifying priorities for rice breeding in Niger in relation to farmers' preferences and their environment. A secondary aim was the development and evaluation (for release at the regional level) of new breeding lines with resistance to RYMV. This study aimed to: 1) Establish farmers' perception of rice varieties as well as the main constraints on rice production in Niger and particularly those posed by RYMV; 2) Create a collection of rice species from Niger for ex- situ conservation, and to determine the phenotypic variability within this collection; 3) Determine the genetic diversity and population structure of the collection; 4) Screen the collection for resistance to RYMV, so that new sources of resistance could be detected; 5) Improve five elite varieties from West Africa for resistance to RYMV using marker-assisted selection (MAS). The germplasm collection and PRA of this study were conducted in 2008 and 2009 in Niger, while the field and the laboratory researches were conducted in 2008 and 2009 at the Africa Rice Center (AfricaRice) in Benin. For the PRA, data was obtained from a semi-structured group discussion carried out in 14 villages, individual questioning of 153 farmers and visits to farmers' field and storage facilities. The local farmers' union was the only formal seed dissemination system. Seed exchanges between farmers and the use of seeds from previous harvests were important. The RYMV and the bacterial leaf blight (BLB) were cited as the prevalent biotic stresses in the irrigated agrosystem, where the varieties IR1529-680-3 and Waihidjo were found to be the most popular. Flood, birds and hippopotamus were the most damaging agents in the lowland cropping system, and the landrace Degaulle/ D5237 was the preferred variety. Apart from the yield, farmers preferred varieties with good grain quality (milling quality and good taste), high market value, stress tolerance (drought, flood, disease, birds, rodents), and those recommended by the local farmers' association. These findings should be included in breeding goals, seed production and dissemination systems. During collection, a total of 270 rice accessions were assembled, comprising the two cultivated rice species Oryza sativa L. and O. glaberrima Steud. and its two wild relatives Oryza barthii A. Chev. and O. longistaminata Chev. et Roehr. The region of the Niger River and its tributary (the Dallol Maouri) provided the majority (80.7%) of the accessions. Apart from a few wild O. barthii accessions, the accessions found around Lake Chad and the Komadougou river (South-East) were also collected in the Niger River area. Farmers' naming and ecological classification of rice varieties was generally consistent. Three major phenotypic groups were found during the field trials, and the overall phenotypic variability of the collection (as measured by the Shannon-Weaver Diversity Index) was relatively high. There was no significant difference in diversity between the main eco-geographical zones of collection, as well as between the identified phenotypic groups, suggesting a high level of germplasm exchange between the regions in Niger. From the collection, 264 accessions were genotyped from the collection using 18 well distributed SSR markers and two main genetic compartments were detected, comprising O. sativa subsp. indica varieties and O. glaberrima and its wild relative O. barthii and O. longistaminata. The O. sativa group in Niger was divided into irrigated and floating rice, bound by lowland rice. The wild progenitor O. barthii was widespread but without any clear genetic differentiation from O. glaberrima, probably due to the presence of admixtures within the collected samples of O. barthii. Allelic diversity was relatively high, despite the geographical distance from the centre of domestication of African rice, and the points of entry of Asian rice to Africa. The findings reflect the underuse of Niger's rice landraces genetic potential for rice breeding, given that all the "improved" varieties released during the last 25 years in Niger were clustered together on the dendrogram. The response of a set of the rice collected from Niger and some accessions from Mali to inoculation by RYMV was evaluated using five different virus isolates from Niger (3), Benin (1) and Burkina Faso (1). All rice varieties were susceptible to the disease. However, depending on the virus strain, a few O. glaberrima accessions displayed partial resistance, similar to the highly resistant TOG5681. Allelic research based on primers derived from the RYMV1 gene revealed one accession with allele rymv1-3, and two accessions with allele rymv1-4, and one accession with a different resistance gene. The implications of the finding were discussed and a strategy proposed for breeding varieties with a comprehensive resistance to RYMV. After three generations of backcrossing, the major resistance gene of the variety Gigante was successfully introgressed into five elite rice varieties of West Africa by Marker-Assisted Backcross (MABC). The newly developed BC3F3 progenies were screened for resistance to RYMV in farmers' fields in Guinea and Mali and also under controlled conditions in a screenhouse in Benin. As shown by low virus content and level of disease incidence, low tiller number and plant height reduction, the transferred gene was fully functional in the new genetic background. Moreover, some lines also displayed a high level of resistance to rice blast (Pyricularia oryzae) and stem borer infestation in Guinea. Four of those lines are in the second year of multi-location trial in seven West African countries. Therefore, effective deployment of the newly developed varieties, coupled with good cultural practices, should reduce the damaging effects of RYMV in lowland and irrigated rice cropping systems and thereby increase the income of small scale farmers from rice cultivation

ESTIMATIONS DE TYPE RAVAILLON DE L’ANALYSE DE L’EFFICIENCE DES MARCHES AGRICOLES DE MAÏS AU BENIN

This article aims to assess the spatial integration and transmission of maize prices in eight markets in Benin. The results of the econometric tests and the Ravallion (1986) model show that maize prices in the markets (7) are integrated to that of the market of Parakou (reference). The long-run transmission elasticity appears to be important. The Ravallion type model reveals an asymmetric transmission, the magnitude of which differs according to the nature of the shocks in the eight markets. Fluctuations in maize prices are more rapidly transmitted to Beninese markets close to Nigeria (Parakou, Nikki, Pobé and Dantokpa). These results can be explained by the market power of people living the borders of Benin with Nigeria. These markets are frequently operated by commercial intermediaries, mainly from Nigeria. Transport costs, prohibitive taxes and, above all, the ransoming of Customs administrative agents, strongly influence informal trade. In the context of cross-border trade benefits to traders in Benin and Nigeria, government intervention mechanisms in the free movement of goods is necessary in order to efficiently absorb the functioning and integration of agricultural markets in the African space