Impact De La Variabilité Pluviométrique Sur La Saison Culturale Dans La Zone De Production Cotonnière En Côte d’Ivoire

In Côte d’Ivoire, agriculture is mostly rain-fed. As a result, changes and variations of climate have considerable impacts on crops production including cotton production. This paper focuses on analyzing the effects of rainfall variations on the cropping season (useful rain season) of cotton in cotton production area of Côte d’Ivoire. A set of stationarity tests was applied to the Nicholson index using rainfall data of the period 1950-2000. Then, from a frequency analyses, the variability of rainfall and characteristic parameters of the cropping season was evaluated in terms of risks. The result shows a general downward trend of rainfall in the cotton growing area with years of breaks between 1964 and 1975. Moreover, spatial evolution of the cropping season parameters is a function of latitude. After the years of breaks, the beginning and the end of the cotton cropping season, which became respectively later and earlier, indicated that the length of useful rain season became shorter. The deficits of seasonal rainfall accumulations vary up to 60%. It is therefore necessary to update the crop calendar by taking into account variability of parameters of the useful rain season

Variabilité des descripteurs pluviométriques intrasaisonniers à impact agricole dans le bassin cotonnier de Côte d’Ivoire : cas des zones de Boundiali, Korhogo et Ouangolodougou

Objectif: Cette étude vise à caractériser l’évolution des descripteurs pluviométriques intrasaisonniers à impact agricole durant la saison culturale dans le bassin cotonnier ivoirien. A cet effet,Méthodologie et résultats: dix descripteurs pluviométriques intrasaisonniers susceptibles d’influencer l’agriculture ont été analysés à partir des données pluviométriques couvrant les périodes 1951-2000 et 2011-2016 et provenant des bases de données de la Société de Développement et d’Exploitation Aéroportuaire, Aéronautique et Météorologique et du Centre National de Recherche Agronomique. Les tests de tendance (Mann-Kendall) et de stationnarité (Pettitt) et une comparaison des périodes ont été appliqués aux variables déterminées. L’analyse des cumuls pluviométriques saisonniers, du nombre de jours de pluie et des précipitations moyennes journalières a mis en évidence une tendance significative à la baisse de ces paramètres sur la période 1951-2000. Les fins et les longueurs de la saison des pluies ont présenté respectivement une tendance significative à la précocité et au raccourcissement. Les autres descripteurs intrasaisonniers ont peu varié. En revanche, des ruptures statistiquement significatives ont été observées entre 1968 et 1979. La comparaison des périodes indique une dégradation des conditions climatiques pendant la période sèche (1971-2000). Ces dégradations se sont accentuées dans la période actuelle (2011-2016).Conclusion et application: Les nouvelles conditions climatiques observées dans le bassin cotonnier traduites par une variabilité des descripteurs intrasaisonniers rendent de plus en plus difficile la planification agricole. Dès lors, l’actualisation des calendriers culturaux dans le bassin cotonnier devient nécessaire.Mots-clés: Descripteurs intrasaisonniers, pluviométrie, agriculture, bassin cotonnier, Côte d’IvoireEnglish AbstractObjective: This study aims to characterize the evolution of agricultural impact intra-seasonal descriptors during the growing season in cotton production area of Côte d’Ivoire. For this purpose...Methodology and results: ten intraseasonal descriptors likely to influence agriculture were determined from rainfall data covering the periods 1951-2000 and 2011-2016 from the Airport, Aeronautical and Meteorological Development and Operations Company and the National Agronomic Research Center. Trend (Mann-Kendall) and stationarity (Pettitt) tests and an inter-period comparison were applied to the identified variables. Analysis of seasonal rainfall accumulations, number of rainy days and average daily rainfall amounts showed a significant downward trend over the period 1951-2000. The cessation and length of the rainy season showed a significant trend towards early onset and shortening respectively. Other intraseasonal descriptors do not varied significantly. In contrast, statistically significant breaks were observed between 1968 and 1979. The period comparison indicated a deterioration in conditions during the dry period (1971-2000). The comparison of the periods indicates a deterioration of the climatic conditions during the dry period (1971-2000). These degradations have increased in the current period (2011-2016).Conclusion and application: New climatic conditions observed in the cotton production area translated by a variability of intraseasonal descriptors are making agricultural planning increasingly difficult. It is therefore necessary to update the crop calendars in the cotton production area.Keywords: Intraseasonal descriptors, rainfall, agriculture, cotton production area, Côte d'Ivoir

Caractérisation Des Paramètres Agroclimatiques Clés De La Saison Culturale En Zone De Contact ForêtSavane De Côte-d’Ivoire

In the Central region of Côte d’Ivoire, contact area between the South forest estate and savanna’s area in the North, the climate is a major concern for people. Since the late 1960s, the constant changes in rainfall amounts make it difficult for the various agricultural operations in the area. Before the natural instability of the rainfall regime and the extreme variability of agro-climatic parameters, farmers are no longer able to detect the probable dates of start and end of the rainy seasons that are essential to optimize agricultural production. From the descriptive statistical analysis of rainfall data from the stations of Bouaké, Béoumi, Katiola and Dabakala over the period 1961-2000, this study focuses on assessing the dynamics of agro-climatic key factors of the growing season in this transition zone. The results show an earlier start and a later end of the rainy season in Bouaké and Béoumi. On the contrary, the seasons started later and ended earlier in the localities of Katiola and Dabakala, and the dry sequences, during the rainy seasons, are longer in these localities

Impact of Local Global Warming on Rainfall and Annual Cocoa Water Requirements in the Regions of Lôh-Djiboua and Gôh in West-central Côte d'Ivoire

Aims: To understand the role of the interannual variability of cumulative rainfall and maximum dry sequences in cocoa production in the Centre-Ouest, one of the cocoa basins in Côte d'Ivoire, in order to propose technical routes more adapted to current rainfall conditions. Study Design: Collection, analysis and processing of daily rainfall data collected by the rain gauges at Divo and Gagnoa stations. Location and Duration of Studies: Divo Cocoa Research Station of the National Center for Agricultural Research, between January 2017 and June 2019. Methodology: The rainfall regime of each locality was determined to assess the impact of rainfall changes on the seasonality of rainfall. The interannual variability of rainfall was studied from the reduced centred rainfall indices. The break years in the time series were detected at both stations from the Khrono Stat software. The interannual cumulative rainfall were analysed for each station and compared to the minimum threshold allowed for cocoa trees. The means of the maximum interannual dry sequences and their probabilities of occurrence were determined using the agrometeorological software called Instat + Version 3.37. Results: The rainfall regime in the area studied (west-central Côte d'Ivoire) has not been modified by the post-rupture rainfall recession as is the case in other parts of the country; it remains a bimodal system characterized by two rainy seasons and two dries during the year. The Divo and Gagnoa regions have been facing a general recession in rainfall since 1966 in Gagnoa and 1972 in Divo. However, the locality of Gagnoa has experienced an increase in rainfall since 2000. Most of the rupture detection tests identified rainfall rupture dates identical to those indicated by the interannual variability highlighted by the rainfall indices. In Gagnoa and Divo, the interannual cumulative rainfalls after the years of rainfall break are reduced compared to those before these rainfall accidents. This situation has led to an increase in the maximum interannual dry sequences in the departments studied. Conclusion: Local climate change has created difficult rainfall conditions after years of rainfall break for cocoa trees as their water needs are increasingly reduced, especially in Divo in Lôh-Djiboua where the downward trend in rainfall has been continuous since 1972. In Gagnoa since the beginning of this century, there has been a new wet period that allows rainfall to adequately meet the cocoa tree's water requirements