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.

No abstract

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.

The decline in yam productivity due to the lack of arable land and impoverished soils forces farmers to use fertiliser. The fertilisers used are mineral, organic or organo-mineral. A study of these fertilisers has been carried out to propose to the farmers a dose or combination that can improve their yield. Thirteen (13) fertilisers obtained from the combination of mineral fertiliser (NPK 15-15-15) and composted cow or poultry manure were tested on the yam variety Krengle in a 3 replicate randomized complete block design. The experiment was conducted over two (2) campaigns at Bouake in Central of Côte d’Ivoire. The results show that high dose mineral fertilisation (NPK 15-15-15, 300 kg/ha) negatively influenced the growth and yield parameters of the yam variety Krengle. High doses of organic fertilisers (Cow manure (CM) 20 t/ha and poultry manure (PM) 20 t/ha) have a positive effect on vegetative growth. While the medium-high doses of organic fertiliser (CM 15 t/ha and PM 15 t/ha) gave better tuber yield (13.5 t/ha) and allowed an increase in tuber yield from 17 to 18%. Organo-mineral fertilisation combining a small dose of organic fertiliser (5 t/ha) with a medium dose of mineral fertiliser (200 kg/ha) gave also fairly good yield (13.3 and 14.42 t/ha) with an increase of 15 to 25%. Thus, 200 kg/ha of NPK 15-15-15 associated with 5 t/ha of poultry or cow manure can be recommended for the cultivation of the yam variety Krengle at Bouake.