Climate variability and change are challenges for rainfed agriculture in the Sahel. The objective of this study was to identify and prioritize agroclimatic risks, their impacts and adaptive strategies through community perception and analysis of observed data. A survey of 361 household heads from 12 villages was conducted in the Sahelian and Sahelo-sudanian areas of Niger. Precipitation and wind data from 2 weather stations were analyzed. The results show that communities are aware of the existence of agro-climatic risks, including early cessation of the rainy season, early season sand winds, and dry spells that are the most frequent and most severe weather events. The perceptions on winds and dry spells agree with the results of the analysis of observed data, whereas in the case of early cessation of the rainy season, analysis of the observed data reveals a return to a better situation, which remains non-perceptible by the communities, due to the high intra- and inter-annual variability. The immediate impacts are loss of seedlings and crops and the development of crop pests. These impacts in turn lead to animal weakness and food insecurity. Although they develop adaptation strategies such as improved crop varieties and water conservation and soil protection/restoration techniques, communities seem to be overwhelmed by the phenomenon. In the short term, the proposed adaptation strategies to the risks identified by the communities will help to cope with the effects of variability and climate change on rainfed agriculture in the Sahel.

The small rainfall recovery observed over the Sahel, concomitant with a regional climate warming, conceals some drought features that exacerbate food security. The new rainfall features include false start and early cessation of rainy seasons, increased frequency of intense daily rainfall, increasing number of hot nights and warm days and a decreasing trend in diurnal temperature range. Here, we explain these mixed dry/wet seasonal rainfall features which are called hybrid rainy seasons by delving into observed data consensus on the reduction in rainfall amount, its spatial coverage, timing and erratic distribution of events, and other atmospheric variables crucial in agro-climatic monitoring and seasonal forecasting. Further composite investigations of seasonal droughts, oceans warming and the regional atmospheric circulation nexus reveal that the low-to-mid-level atmospheric winds pattern, often stationary relative to either strong or neutral El-Niño-Southern-Oscillations drought patterns, associates to basin warmings in the North Atlantic and the Mediterranean Sea to trigger hybrid rainy seasons in the Sahel. More challenging to rain-fed farming systems, our results suggest that these new rainfall conditions will most likely be sustained by global warming, reshaping thereby our understanding of food insecurity in this region.

Estimation of the response of rainfed crops to heat stress and water stress must adequately account for the uncertainty in climatic and non-climatic factors that affect impact assessments. The objective of this research was to narrow the range of values characterizing the limits within which estimates are expected to fall in the diagnostics of agroclimatic risks. Assessments were made by analyzing historical observations and evaluating the influence of heat stress and rainfall variability on crop water demand, biomass and grain yields of short-cycle cultivars of pearl millet and maize. We used a wide range of consistent and practical sets of crop model ensemble analyses (based on crop management practices such as plant density, fertilization levels, early/late sowing dates and soil types) and climate model ensembles from 2 climate change hypothesis (A1b and RCP8.5) over the West African Sudan-Sahel. Recent rainfall developments show that hazardous intra-seasonal rainfall distribution affects crop productivity, with increased frequency and intensity of daily rainfall, false start and early cessation of the rainy season and decreasing diurnal temperature range. In 2011-2050 perspectives, relative to the 1981-2010 baseline, a slight in crease in temperature (i.e. + 0.6 to + 0.8 degrees C) combined with a stationary to moderate decrease in precipitation leads to a 10 to 15% (8 to 15%) decrease in aboveground biomass production (grain yield). When the warming is moderate (i.e. + 1.4 to 1.8 degrees C), the decline in grain yield worsens (10 to 20%), despite a slight increase in rainfall projections. At these rates of loss in crop production, resilience can be reinforced. However, it will require that climate-smart crop management practices be embedded in sub-seasonal and interannual monitoring and early warning systems.

Cette étude a été menée en serre pour évaluer l’effet de deux types d’insecticides sur la mycorhization et le développement de deux variétés de pomme de terre (Aïda et Atlas). Les insecticides carbofuran et chlorpyriphos-éthyl, respectivement systémiques et contacts, ont été appliqués au sol à différentes stades d’inoculation du champignon Glomus mosseae. Le pourcentage de mycorhization, la biomasse aérienne, lenombre et le calibre des minitubercules ont été évalués après 60 jours de culture. L’application du carbofuran ou du chlorpyriphos-éthyl 21 jours avant ou après l’inoculation du champignon induit une diminution significative du pourcentage de colonisation mycorhizienne chez toutes les deux variétés. Cependant, cette baisse est plus importante avec les traitements de l’insecticide de contact après inoculation et de l’insecticidesystémique effectué avant inoculation. Cette tendance s’est répercutée sur la biomasse aérienne et le nombre des minitubercules. Le calibre des minitubercules présente une variabilité de réponse selon la variété de pomme de terre et le type d’insecticide. Ce travail a permis de déterminer le moment compatible de l’inoculation de Glomus mosseae avec l’application des insecticides au sol chez les variétés Aïda et Atlas de la pomme de terre.© 2013 International Formulae Group. All rights reserved.Mots clés: Glomus mosseae, carbofuran, chlorpyriphos-éthyl, Aïda, Atlas.

The chemical composition of calyces and seeds of three ecotypes of Roselle from Niger was compared. The results indicate that calcium (Ca), potassium (K), sodium (Na), magnesium (Mg) and protein contents in calyces are significantly different (P<0.005) among ecotypes. The highest concentrations of K, Na, Mg and protein in calyces were recorded for ecotype E7 (35.66, 3.40, 6.01 and 101 mg/g d.w., respectively). Ecotype E9 had the highest Ca content in calyces (34.41 mg/g d.w.); while E3 and E7 had similar and lower contents. The protein content in calyces for E9 (52 mg/g d.w.) was approximately halved compared to those of E3 and E7. For all ecotypes, the concentrations of Ca, K, Mn, Na and Fe in the calyces were higher compared to those in the seeds. In contrast, P content was higher in seeds. The highest K, Na, Mg and P concentrations in seeds were registered for E7 and the lowest ones for E9. Ecotypes E3 and E9 recorded higher and similar Cu, Fe and Mn contents in calyces and in seeds compared to E7. The highest Zn concentrations in seeds were obtained for E3 and E7. Keywords : Niger, Roselle, seeds, calyces, protein, composition, micronutrients, macronutrients African Journal of Biotechnology Vol. 12(26), pp. 4174-4178

Dans le contexte actuel de changement climatique, la veille agro-hydro-meteorologique des regions semi-arides doit etre amelioree et renforcee. L’objectif de ce travail est d’utiliser des donnees observees en station pour identifier l’evolution spatio-temporelle des risques agroclimatiques associes aux grandes tendances du regime pluviometrique dans la bande soudano-sahelienne elargie aux parties nord de certains pays cotiers de l’Afrique de l’Ouest (Benin, Togo, Nigeria). Les resultats montrent que sur la periode 1950-2010, l’evolution du regime pluviometrique est en trois phases quasi identiques sur les cumuls (Cum), l’intensite du cumul sur trois jours consecutifs (Px3), et les longueurs de saison culturale (LSC) par rapport a la normale 1961-1990. A savoir : i) une periode d’excedents de Cum et Px3 avec des LSC plus importantes (1950-1969) ; ii) une periode de deficits de Cum et Px3 avec des LSC plus courtes (1970-1990) ; et iii) la periode recente dont les Cum, Px3 et LSC sont tres variables (1991-2010). Cependant, les dates de demarrage des saisons montrent une tendance quasi stationnaire, de 1970 a 2010. Les risques agroclimatiques de resemis, de stress post-floraison et d’occurrence de faux departs et de fins precoces des saisons des pluies sont lies aux periodes de secheresse historique, en particulier pendant les deux dernieres decennies. L’occurrence des faux departs et des fins precoces de la saison des pluies rend la distribution des evenements pluvieux peu profitable a la croissance des cultures. En effet, cette distribution est bien correlee aux deficits pluviometriques observes dans la region. Ces resultats statistiquement significatifs permettent de poser deux hypotheses majeures dans le contexte du changement du regime des pluies : i) les risques agroclimatiques de la periode 1991-2010 sont restes similaires a ceux de la periode de secheresse historique 1970-1990 ; ii) les annees humides sont associees a des vagues d’evenements de faux departs observes de maniere precoce dans la premiere decade de juin ou avant. A chaque fois que des faux departs (fins precoces) sont observes au-dela de la premiere decade de juin (avant fin septembre), le cumul de cette saison sera tres probablement inferieur aux normales 1961-1990 et 1981-2010. Ces hypotheses peuvent servir d’elements de renforcement des techniques utilisees dans la prevision saisonniere de la pluie et la veille agroclimatique dans la region.

Climate variability and change affect most socioeconomic sectors in West Africa. It is now admitted that the variability of climate has increased since the 1950s mainly because of the increased concentration of anthropogenic greenhouse gases in the atmosphere. In this study, we analyze the evolution of some extreme temperature and precipitation indices over a large area of West Africa spanning from latitudes 10–25°N and longitudes 17°W–15°E. The results show a general warming trend throughout the region during the period from 1960 to 2010, namely through a negative trend in the number of cool nights, and more frequent warm days and warm spells. This was the case not only for locations inside the continent, but also for those in coastal areas. Trends in rainfall related indices are not as uniform as the ones in temperatures. Nevertheless, a general tendency of decreased annual total rainfall and maximum number of consecutive wet days characterizes the study period. The cumulated rainfall of extremely wet days shows a positive trend in most locations. As for the maximum number of consecutive wet days, it shows an overall decreasing trend from 1960 to the mid 1980s, but starting from the late 1980s, an increasing trend is observed in several locations, indicating that extreme rainfall events have become more frequent in the West African Sahel during the last decade, compared to the 1961–1990 period. Policy implications of these observed trends may include investment and promotion of low cost and environmentally friendly energy production systems, the redesign of infrastructure and production systems to account for higher risks of losses due to floods and/or droughts, and the promotion of research for more heat tolerant crop/animal species and cultivars/breeds.

Climate change trends and projections based on observation and climate models were reviewed in West Africa (WA). Historically, the region has experienced decades of severe drought along with cycles of above average rainfall which have greatly affected agricultural production. Future projections indicate decreased rainfall over the Sahel coastline. Observations already indicate an average increase in temperature of between 0.2 and 0.8 °C; when projected, this increases further to between 3.0 and 4.0 °C. Of greater concern, however, is the late onset, early cessation dates of rainfall and reduction of length of growing period (LGP) which are now locally negatively impacting agriculture in the region. Furthermore, projections indicate a 20% reduction of LGP in 2050. These results represent essential input for accelerating agricultural adaptation to climate change. Copyright © 2012 Royal Meteorological Society

Au Burkina Faso, le maïs est cultivé dans les zones soudaniennes et soudano-sahéliennes où les conditions pluviométriques sont plus favorables. La culture est sensible aux aléas climatiques liés à la variabilité et aux extrêmes pluviométriques. L'objectif de l'étude est d'identifier les risques climatiques pour la culture du maïs. A partir des données météorologiques journalières, une analyse agroclimatique a été réalisée sur la période 1979-2008 sur six stations synoptiques. A l'aide du logiciel Instat+ v 3.036, la variabilité des précipitations et des paramètres clés de la saison agricole dont les dates de démarrage, de fin, la longueur de la saison, les occurrences de séquences sèches et la satisfaction des besoins en eau ont été analysés en termes de risques d'apparition. Les résultats ont montré que le maïs est confronté à deux risques agroclimatiques majeurs. Il s'agit, dans la zone soudano-sahélienne, des déficits hydriques imputables à des séquences sèches au cours du développement du maïs. Tandis que les excès d'eau liés à des fortes pluies ou des successions d'épisodes secs et d'excès d'eau constituent les risques en zone soudanienne. La période d'installation, le cumul pluviométrique, la longueur de la saison ne semblent pas constituer de risques agroclimatiques majeurs pour le maïs.Keywords: Maïs pluvial, variabilité pluviométrique, paramètres saison agricole, déficit hydrique, excès d'eau

De toutes les activites humaines, l’agriculture reste le secteur le plus influence par le climat et ses variations. Or, l’intensification et la frequence des evenements extremes dues au changement climatique auront de plus en plus des consequences desastreuses sur la production agricole et les revenus des paysans. Dans ce contexte, l’assurance agricole climatique est de plus en plus consideree comme un outil d’adaptation au changement climatique. Pour indemniser les agriculteurs en cas de pertes de recoltes dues aux aleas climatiques, l’estimation des degâts peut etre faite indirectement par le biais d’indicateurs appeles indices climatiques. Des valeurs seuils des ces indices climatiques sont utilisees pour declencher les indemnisations des producteurs sinistres. Cet article fait une synthese des indices climatiques bases sur la pluie, le bilan hydrique, les indices de vegetation, utilises ou pouvant etre utilises dans les systemes d’assurances agricoles indicielles. Il presente egalement leurs atouts et leurs faiblesses.

Roselle (Hibiscus sabdariffa L.) has considerable economic importance in the western Sahel because of its nutritional and medical properties. In order to obtain information on variability, a study of yield and some related characters (number of branches/plant, number of capsules/plant, number of seeds/fruit, hundred seed weight) using nine ecotypes of Roselle was undertaken during the rainy season (from July to September) in 2004 at the experimental station of the Agrhymet Regional Centre in Niamey (Niger). Results indicated considerable variability among ecotypes for most of the measured parameters. Seed yield ranged from 292 +/- 8.80 kg/ha (ecotypes E8) to 497 +/- 8.91 kg/ha (E4). Calyx yield varied significantly (P < 0.01), from 123 +/- 8.26 kg/ha (E1) to 766 +/- 36.81 kg/ha (E9). The ecotypes which produced the highest seed yield also had high leaf yield but low calyx yield. There was also a significant (P < 0.05) difference among ecotypes in yield components such as hundred seed weight, number of branches/plant, number of capsules/plant and number of seeds/fruit. Ecotypes with higher calyx yield had lower hundred seed weight and shorter plants. Results indicated the possibility to increase calyx yield and consequently farmer's income through selection programs.

Roselle is an important part of the human diet in many countries, particularly in the Sahel zone of West Africa. The leaves of Roselle are consumed as a green vegetable and in sauce. Nevertheless, little attention has been paid to their nutrient composition at different stages of plant growth. Therefore, the experiment was carried out under rainfall conditions from July to September 2006 at the experimental station of the Agrhymet Regional Centre in Niamey (Niger). The contents of Ca, K, Mg, P and protein in leaves of three ecotypes (A3, A7 and A9) were determined at stages I, II and III, corresponding, respectively to vegetative, flowering and mature stages. The experimental design was a randomized complete block with four replicates and one variable (ecotype). For ecotype A7, the protein content of the leaves decreased significantly (p

In the western Sahel, leaves of Roselle ( Hibiscus sabdariffa ) have considerable economic importance because of their nutritional and medical uses. These plant organs are used to supplement nutrients provided by cereals such as millet and sorghum. However, there is a lack of information on the nutrient composition of these plant organs of Roselle at different growth stages. Therefore, the experiment was carried out under rainfall conditions during the 2006 rainy season (from July to September) at the experimental station of the Agrhymet Regional Centre in Niamey (Niger). The content of the micronutrients Fe, Mn, Cu and Zn in leaves of three ecotypes of Roselle (A3, A7 and A9) at three growth stages, vegetative (stage I), flowering (stage II), and mature (stage III) was determined. The experimental design was a randomized complete block with four replicates and one variable (ecotype). Results indicated that at stage I, ecotype A3 had higher Fe content in leaves. In addition, A3 had also the highest Zn content in leaves at stage I. For all three ecotypes, Fe and Zn content in the leaves decreased significantly (p<0.05) from stage I to stage II, then remained constant until stage III. For Fe, the decrease between stage I and II was 37% for A3 and 50%, respectively for A7 and A9. The corresponding decrease of Zn content was 30% for A7 and 50%, respectively, for A3 and A9. The Mn content in the leaves of Roselle was similar for the three ecotypes at stage I, thereafter increased continuously during plant growth. From stage I to II, the increase was about 90%, 70% and 50%, respectively for A9, A7 and A3. From stage II to III, the increase in Mn content in the leaves was significantly (p<0.05) higher for A3 and A7, respectively 180% and 80%. At stages I and II, the highest Cu content was recorded for A3 and the lowest one for A7. During the whole cycle of plant growth, the Cu content in the leaves was relatively constant for A9. In contrast, Cu content in the leaves decreased for the remaining ecotypes. Therefore the vegetative stage corresponding to 25 days after sowing is the recommended optimal harvest time of Roselle to maximise on the nutrients.

Although nitrogen application could improve growth and yield of roselle, fertilizer recommendations for Niger are lacking. The objective of this study was to evaluate the effects of two treatments of nitrogen (N1=50 kg N,ha−1 and N2=100 kg N.ha−1) on yields and yield components in three ecotypes of Roselle (A3, A7 and A9). An increase in nitrogen was associated with an increase in leaf yield in every ecotype. However, there was no significant difference in yields between N1 and N2. Compared with the control plants (N0), the increase was about 181% for A3, 70% for A7 and 95% for A9 at N2. This level of nitrogen significantly decreased seed yield by 30% for A3 and 48%, respectively for A7 and A9. Nitrogen treatment had no effect on calyx yield which was approximately identical for the three ecotype (420 kg ha−1). With the exception of the number of branches/plant, yield components were not affected by nitrogen application. Therefore, N1 could be considered as the optimum fertilization for leaf yield.

Scientific validation of pharmacological actions of 7 Senegalese plants used in traditional medicine for the treatment of respiratory illness was carried out. Changes in contractility of isolated rat trachea were assessed in organ chambers. Rings were allowed to equilibrate for 60 min before experiments were carried out, during which time the resting tension was adjusted, as required. Rings were first exposed to methanolic plants extracts (10-2 and 10-1 mg/ml) or solvent. After a 30 min incubation period, they were contracted with acetylcholine in a cumulative manner (10-9 to 10-3M). Extracts from leaves of Guiera senegalensis, Melaleuca leucodendron and Hymenocardia acida elicited a significant dose-dependant inhibition of the contractile agonist, suggesting further investigations on its chemical composition, the underlying mechanisms involvedand its potential health value. However, in rings pre-incubated with extracts fromCymbopogon giganteus leaves and Salvadora persica roots, effect of the contractile agonist was not affected. Moreover, a hypereactivity was observed with extracts from Gossypium barbadense leaves and Cassia occidentalisseeds. These results provide evidence that Senegalese herbals may be of interest as valuable source of information for the selection of plants for focused screening programmes and for therapeutically useful products.   Key words: Tracheal contractility, medicinal plants, respiratory illness.