Sudano-Sahelian West Africa Research Articles

On- and non-farm adaptation in Senegal: understanding differentiation and drivers of farmer strategies

ABSTRACT Rainfed farmers in Sudano-Sahelian West Africa have long adapted to variable growing conditions. Today, in response to intersecting pressures from climate change, soil fertility loss, and socioeconomic change associated with globalization, these farmers are working to build more resilient livelihood systems. This study examines farmers' perceptions of environmental change and socioeconomic transition in Senegal and the drivers and constraints on their adaptive responses, with particular attention to the interplay of on- and non-farm livelihood strategies amid concerns about changing weather. Semi-structured interviews with 47 farmers provide insight into individual lived experiences while surveys and multinomial regression drawing data from approximately 500 farmers point to broader patterns in perceptions and adaptive strategies. The findings indicate that most Senegalese farmers perceive substantial environmental change that is amplifying ongoing processes of agrarian change, increasing reliance on non-farm livelihoods and youth migration in particular. While the most resource-constrained farmers rely primarily on prayer—likely an expression of limited alternative strategies—those most concerned about weather changes turn to diversified livelihood strategies. This study illustrates an evolving relationship between farmers and non-farm work amid environmental and socioeconomic change in rural Africa, with implications for development initiatives aimed at supporting farmer adaptation to climate change.

SLAUGHTER OF THE DROMEDARY (SINGLE-HUMPED) CAMEL (Camelus dromedarius) FOR MEAT IN A SEMI-ARID ENVIRONMENT OF NORTH-EASTERN NIGERIA

Monthly records on camels slaughtered for meat from 1982 to 1989 at the Maiduguri abattoir were collected and analysed to determine the seasonal and annual trends in slaughter and meat supply from the dromedary or single- humped camel (Camelus dromedarius). There were highly significant (P<.01) seasonal and yearly variations in the number of camels slaughtered. In any given year, greatest numbers were slaughtered by March-May Which resents the last stages of the long sahelian dry season. Lowest numbers were slaughtered towards the end of the rainy season. About equal numbers of males and females were slaughtered annually. In 1989 alone, up to 13% of the females slaughtered were pregnant. An average of 9,150 camels were slaughtered yearly giving an estimated carcass yield of about 2,596,397kg of camel meat per annum. Camels slaughtered within the three years of 1984/1986 represented about 61% of the total for the eight years. The period from 1983 to 1986 was another drought period in the sudano-sahelian West Africa. Attention should be given to our draught animals hitherto neglected so that their drought, meat, milk and other potentials could be exploited to the full benefit of our national economy.

New data on settlement and environment at the Pleistocene/Holocene boundary in Sudano-Sahelian West Africa: Interdisciplinary investigation at Fatandi V, Eastern Senegal.

The end of the Palaeolithic represents one of the least-known periods in the history of western Africa, both in terms of its chronology and the identification of cultural assemblages entities based on the typo-technical analyses of its industries. In this context, the site of Fatandi V offers new data to discuss the cultural pattern during the Late Stone Age in western Africa. Stratigraphic, taphonomical and sedimentological analyses show the succession of three sedimentary units. Several concentrations with rich lithic material were recognized. An in situ occupation, composed of bladelets, segments, and bladelet and flake cores, is confirmed while others concentrations of lithic materials have been more or less disturbed by erosion and pedogenic post-depositional processes. The sequence is well-dated from 12 convergent OSL dates. Thanks to the dating of the stratigraphic units and an OSL date from the layer (11,300–9,200 BCE [13.3–11.2 ka at 68%, 14.3–10.3 ka at 95%]), the artefacts are dated to the end of Pleistocene or Early Holocene. Palaeoenvironmental data suggest that the settlement took place within a mosaic environment and more precisely at the transition between the open landscape of savanna on the glacis and the plateau, and the increasingly densely-wooded alluvial corridor. These humid areas must have been particularly attractive during the dry season by virtue of their rich resources (raw materials, water, trees, and bushes). The Fatandi V site constitutes the first stratified site of the Pleistocene/Holocene boundary in Senegal with both precise geochronological and palaeoenvironmental data. It complements perfectly the data already obtained in Mali and in the rest of western Africa, and thus constitutes a reference point for this period. In any case, the assemblage of Fatandi V, with its bladelets and segments and in the absence of ceramics and grinding material, fits with a cultural group using exclusively geometric armatures which strongly differs from another group characterized by the production of bifacial armatures, accompanied in its initial phase by ceramics (or stoneware) and grinding material.

Assessment through socioecological abstraction: The case of nutrient management models in Sudano-Sahelian West Africa

The sustainability of smallholder agriculture in the drylands of West Africa is a topic of long-lasting concern. This paper is focused on the scientific assessment of nutrient (mis)management affecting the long-term productivity of cropland. “Nutrient mining” is seen as a major mechanism for land degradation in the region. Two models will be the focus: that tied to the rangeland-to-cropland metric and the nutrient balance model. These tools of assessment follow a long history of environmental assessment and modeling that purposefully abstracts from the heterogeneity of the same farming practices that modeling efforts seek to assess. Abstraction is always part of modeling but the form of abstraction described here ignores any detailed understanding of farming practices and in so doing, demands very little information about farming practices. In this way, models serve as both the symptom and cause of continued ignorance of farming practices by most agronomists and soil scientists working in the region. The variables used in these models will be described and how these same variables are strongly influenced by the variation of farmers’ practices will be discussed. In addition, it will be shown that needless model abstraction results in research outcomes that provide very little insights to guide land policy formulation and agricultural extension. In short, these models point to the ultimate resource limits of the regional agricultural system but provide few insights of what could be changed to reduce rates of land degradation. The paper concludes by presenting alternative approaches that through their engagement with the diverse positionalities of farmers, provides insights useful for the development of effective land policies.

The dividing of fields in Sudano-Sahelian West Africa: The roles of soil fertility variation and legal doctrine

The distribution of agricultural land is strongly shaped by field divisions that occur as rural households split in Sudano-Sahelian West Africa. Still, there remains very little empirical work focused on how fields are divided. Under local interpretations of Islamic law, parcels resulting from division should be of equal size. Complicating this is the potential for within-field variation in soil fertility which may result in parcels of unequal fertility. Research was conducted in western Niger to understand how these considerations affect the placing of boundaries when fields are divided. In two adjoining village territories, a random sample of farmers were interviewed about soil quality variation in their fields and how their management may vary within these fields. Interviews were conducted with those who oversee the division of fields: village chiefs and Islamic clergy. The divisions of 92 fields resulting from 43 household splits over a twenty-one-year period were analyzed. Group interviews of the parties to these splits were conducted and for 54 of the divided fields, soil quality variation was mapped. This information was used to assess the equality of the parcels resulting from division in terms of area and fertility. Unequal divisions were also accessed for bias toward the eldest party to the division. We find that soil fertility variation is an important consideration in the placement of boundaries and requirements for equal parcel size is not significant impediment to creating parcels of comparable fertility. Still, a significant fraction of field divisions is unequal, resulting in parcels of unequal fertility and/or unequal size. Unequal divisions are not significantly biased toward the eldest party. Factors in addition to parcel size and fertility affect field division decisions.

Plant species associated with different levels of species richness and of vegetation cover as indicators of desertification in Burkina Faso (West Africa)

Desertification is a major problem in Sudano-sahelian West Africa, including the loss of biodiversity and vegetation cover. The loss of related ecosystem services is having a severe impact on human wellbeing. To facilitate assessments of these aspects of desertification, we decided to find plant species suitable as indicators. Based on a large database of vegetation plot data for Burkina Faso, we identified species associated with high or low levels of species richness and vegetation cover by calculating average values of these measures from vegetation plots on which they occur. To account for the differences between the dry Sahel and the more humid Sudan, we separated the plots of our study area in three vegetation zones (Sahel, North Sudan, South Sudan). Furthermore, herbs and woody plants were analysed separately, as they were usually represented in different plot sizes in the primary data. For each combination of species richness or vegetation cover, vegetation zone and growth form we identified ten species indicating low and another ten species indicating high values and assigned indicator values based on the average values of these species in the relevés.

Financial performance of fertilization strategies for sustainable soil fertility management in Sudano–Sahelian West Africa. 2: Profitability of long-term capital investments in rockphosphate

Phosphorus (P) deficiency is a major impediment to securing crop productivity on the acid, sandy soils of Sudano-Sahelian West Africa (SSWA). However, given the low profitability of many annually applied fertilization strategies with imported P, the effects of yield-enhancing, alternative P-sources, such as rockphosphate (RP), should be considered. Therefore, the financial performance of 14 strategies—including 2 annual and 11 long-term fertilization strategies plus 1 farmers’ practice—were compared in three rainfall zones in SSWA. The comparison comprised the net present value, the annuity, the internal rate of return, and a risk analysis. Agronomic data came from a four-year, five-location trial complemented by information on farming systems, labor demands, and input–output prices. Compared with farmers’ practices, none of the P-fertilization strategies examined were financially superior at all locations. The financial performance of medium-term RP-strategies tended to increase with rainfall, but remained highly variable. Net returns to land with high rates of RP were often superior to annual inputs of mineral-P, but never the best alternatives. In most cases, the most profitable strategies comprised medium-level RP-applications with or without supplementary hill-placed NPK-fertilizer (also known as “micro-dosing”). The financial performance of medium quantities of RP sometimes increased and sometimes decreased with supplementary nitrogen (N) additions. The combination of hill-placed NPK and broadcast RP as well as N-applications with broadcast RP are alternatives to the use of RP alone. Our results can assist researchers and development institutions in advocating and implementing more effective strategies to enhance agricultural production in SSWA.

Financial performance of fertilisation strategies for sustainable soil fertility management in Sudano-Sahelian West Africa 1: profitability of annual fertilisation strategies

Low concentrations of phosphorus (P) also limit crop production on the acid, sandy soils in Sudano-Sahelian West Africa (SSWA). An increased P-use is thus a key leverage for enhancing food security and alleviating poverty. Therefore, P-imports into the predominating agro-pastoral farming systems are indispensable, but most smallholders are cash-poor and risk averse, face labor-constraints, and P-fertiliser responses are site-specific. Key to the adoption of any new technology is a high financial performance with low risk levels of failure, low demands of labor and cash, and adaptation to the prevailing farming systems. Financial performances were assessed from nine, annually applied fertilising practices during 4 years in five SSWA zones. Information about the farming systems, labor demands, and input–output prices stem from secondary sources. The profitability largely depended on rainfall and location-specific soil conditions, but those of annually repeated mineral and organic P-strategies increased over time. Several P-fertilisations were profitable on a per land unit basis, but could not compete with farmers’ practices on a per labor unit basis. Mulching with and without P (13 kg P ha−1) were not financially superior, but the broadcast application of 13 kg P ha−1 became profitable over time. Hill-placed P (4 kg P ha−1), also known as micro-dosing, was a profitable alternative to farmers’ practices particularly in the intermediate rainfall zone. The results showed the importance of recommendations following rainfall zones, which are of interest across a spectrum of users including policy makers, land use practitioners, private firms, NGOs and research for development implementers.

Agricultural innovations in small-scale farming systems of Sudano-Sahelian West Africa: Some prerequisites for success

L’intensification agricole qui conduit a une reduction des jacheres, une sur-utilisation des residus de recolte et des especes perennes pour l’alimentation du betail et la construction, et le surpâturage temporaire dans certaines regions presentent un scenario catastrophe pour la zone soudano-sahelienne. Alors que les phenomenes qui sont decrits contribuent sans nul doute au declin de la productivite des sols dans les grandes etendues des systemes agropastoraux a base de mil et sorgho, quelques innovations, largement ignorees, ont pourtant contribue a augmenter la productivite a travers plusieurs contextes ecologiques et socio-economiques. Celles-ci valent la peine d’etre analysees pour comprendre comment des contraintes bien connues a l’investissement dans des systemes de production durable peuvent etre depassees. Des innovations couvertes de succes, aussi simple qu’une charrette tiree par un âne, ou bien la culture d’oignons en contre-saison, ont transforme l’agriculture du Niger depuis 1970. Plus recemment, l’utilisation de petites quantites de fertilisant phosphate (plus connu sous le nom de ‘microdose’) pour le mil et le sorgho, un usage grandissant des surfaces agricoles periurbaines et urbaines pour la culture maraichere, des cultures specialisees, et parfois la production de lait, ou encore l’engraissage des petits ruminants avant les jours de fete sont autant de strategies d’amelioration du niveau de vie, favorisant l’independance alimentaire, et cela souvent sans avoir a passer par les services de dissemination. Les facteurs qui semblent etre derriere le succes de ces approches sont: i) leur capacite a ameliorer l’acces aux marches (pour assurer un revenu monetaire) ; ii) la possibilite d’adopter une innovation sans grand besoin en investissement (faible cout d’entree) ; iii) un risque d’echec limite en depit de la haute variabilite saisonniere (retour sur investissement assure). Ces facteurs s’ajoutent au recent developpement de l’information en temps reel sur la demande des consommateurs et les prix des biens agricoles dans la region, resultant essentiellement de la revolution de la telephonie mobile en Afrique.

Use of MODIS NDVI to evaluate changing latitudinal gradients of rangeland phenology in Sudano-Sahelian West Africa

Abstract This study is concerned with the implications of changing latitudinal gradients in vegetative phenology (green-up, senescence, and length of growing season) for the management of long-distance seasonal movements of livestock herds in Sudano-Sahelian West Africa. For a study area covering much of the southern half of Mali, phenological parameters were estimated using a double-logistic function fitted to seasonal NDVI trajectories for 1 km 2 MODIS data over the period 2000–2010. Green-up dates, senescence dates and length of growing season were all found to more strongly vary by latitude (+ 9 days/degree, − 5 days/degree and − 14 days/degree, respectively) than across years (+ 0.42 days/year, + 0.86 days/year and + 0.44 days/year respectively). Interannual and spatial variability of these parameters are highest at lower latitudes within the study area. The slopes of the relationship of phenological parameters with latitude change across the latitudinal range studied. Breakpoint analysis of annual green-up versus latitude curves identifies a mean inflection point of 13° north latitude above which the positive slope declines significantly. This previously-undescribed pattern is consistent with recent work on monsoonal dynamics showing rainfall onset being associated with an abrupt shift in the location of the ITCZ (monsoon onset) at latitudes north of 13° north latitude. The effects of the observed variation in latitudinal gradients of phenological variables on the direction and timing of regional livestock movements are discussed.

Exploring the diversity of urban and peri-urban agricultural systems in Sudano-Sahelian West Africa: An attempt towards a regional typology

Developing appropriate and innovative technologies and policies to respond to the challenges that urban and peri-urban agriculture (UPA) faces in West Africa requires a better understanding of the existing production systems. Although there is an increasing recognition of the importance of UPA in the region, its extent, forms and related practices may vary across countries and cities because of different socio-economic conditions and urbanization patterns. A systematic classification of the regional UPA systems is lacking but is necessary to allow for meaningful comparisons between cities and avoid misleading generalizations. The purpose of this study was to develop a typology of UPA households across three selected West African cities. Survey data from 318 UPA households (Kano: 99, Bobo Dioulasso: 111, Sikasso: 108) were submitted to principal components analysis for categorical variables (CATPCA). Next, the Two-Step cluster method was used to classify the households using object scores obtained from the CATPCA. Diversification of farm activities, farm resource endowment and production orientation were the major discriminating variables. In each city, four distinct UPA systems were identified, of which three were common to Kano, Bobo Dioulasso and Sikasso: commercial gardening plus field crops and livestock (59%, 18%, and 37%), commercial livestock plus subsistence field cropping (14%, 41%, and 7%), and commercial gardening plus semi-commercial field cropping (14%, 28%, and 30%). The fourth group was different at each location and was characterized as follows: commercial gardening plus semi-commercial livestock in Kano (13%), commercial field cropping in Bobo Dioulasso (13%) and commercial gardening in Sikasso (26%).

Hydrosedimentary records and Holocene environmental dynamics in the Yamé Valley (Mali, Sudano-Sahelian West Africa)

Research conducted in the Yamé Valley (Dogon Country, Mali) provides valuable information about the river systems and their Holocene evolution in Sudano-Sahelian West Africa. Past research in the region has relied primarily on marine and lacustrine records. The new results confirm correlation between palaeoclimatic fluctuations recorded in both the river system and in tropical African lakes. They offer a new continental milestone for understanding of the environmental repercussions of Holocene monsoon oscillations. These studies demonstrate the value of river systems as a palaeoenvironmental record and the role of palaeoclimatic and anthropogenic factors in the Holocene dynamics of Sudano-Sahelian hydrosystems.

Changing Access to Labor, Pastures, and Knowledge: The Extensification of Grazing Management in Sudano-Sahelian West Africa

The broader ecological and social contexts within which livestock husbandry of Sudano-Sahelian West Africa operates have changed significantly over the past thirty years. This study concerns how: (1) these broader trends have affected the quantity and quality of labor investments into livestock herding; and (2) the ecological and animal nutritional implications of observed variation in labor investments into herding. The study was conducted in a 500 km2 area of western Niger using a combination of qualitative interviews of herders and herd managers, household composition surveys, herd composition monitoring, grazing management monitoring and georeferenced vegetation and livestock grazing itinerary data. Statistical analyses were performed using a two-staged approach: (1) analysis of the factors affecting the allocation of labor to herding at the level of the managing household; and (2) analysis of the effect of herd characteristics, season, microgeography and herders’ social position on herders’ effort and the nutritional and ecological impacts of these efforts. The results of these analyses support the conclusion that the changing regional context of livestock husbandry leads to a reduction in labor (quantity and quality) investment or an “extensification” of herding with significant implications for livestock productivity and the environment.

A critical analysis of challenges and opportunities for soil fertility restoration in Sudano-Sahelian West Africa

Since the 1970s, research throughout West Africa showed that low soil organic matter and limited availability of plant nutrients, in particular phosphorus and nitrogen, are major bottlenecks to agricultural productivity, which is further hampered by substantial topsoil losses through wind and water erosion. A few widely recognized publications pointing to massive nutrient mining of the existing crop–livestock production systems triggered numerous studies on a wide array of management strategies and policies suited to improve soil fertility. Throughout Sudano-Sahelian West Africa, the application of crop residue mulch, animal manure, rockphosphates and soluble mineral fertilizers have been shown to enhance crop yields, whereby yield increases varied with the agro-ecological setting and the rates of amendments applied. In more humid areas of Western Africa, the intercropping of cereals with herbaceous or ligneous leguminous species, the installation of fodder banks for increased livestock and manure production, and composting of organic material also proved beneficial to crop production. However, there is evidence that the low adoption of improved management strategies and the lack of long-term investments in soil fertility can be ascribed to low product prices for agricultural commodities, immediate cash needs, risk aversion and labour shortage of small-scale farmers across the region. The wealth of knowledge gathered during several decades of on-station and on-farm experimentation calls for an integration of these data into a database to serve as input variables for models geared towards ex-ante assessment of the suitability of technologies and policies at the scale of farms, communities and regions. Several modelling approaches exist that can be exploited in this sense. Yet, they have to be improved in their ability to account for agro-ecological and socio-economic differences at various geographical scales and for residual effects of management options, thereby allowing scenario analysis and guiding further fundamental and participatory research, extension and political counselling.

Modeling of sorghum response to photoperiod: a threshold–hyperbolic approach

High photoperiod sensitivity is a singular trait for adaptation of sorghum to environmental constraints in sudano-sahelian West Africa. Difficulties encountered by selected models such as CERES-sorghum and STICS to simulate crop development may result from the representation of sorghum response to daylength during the photoperiod inductive phase. Four modeling approaches combining two temperature and photoperiod responses (linear, hyperbolic) and two calculation methods for development rates (cumulative, threshold) were evaluated to simulate time to panicle initiation (PI) in highly photoperiod sensitive Guinea sorghum variety CSM388. In the cumulative method, development rates were computed as summations of daily photothermal ratios, whereas in the threshold method accumulated degree days were tested against thermal time requirement to PI modulated by current photoperiod. Each model was calibrated based on observations from a Sotuba, Mali (12°39′N) planting date experiment spanning a 2-month period in 1996. Observed time from emergence to PI decreased from 54 to 22 days for a 20 min variation in daylength. Apparent higher performance by threshold methods was further tested against a 1994 independent dataset featuring three latitudes and a much wider range of sowing dates extending from February to September. Results validate the superiority of threshold over cumulative methods and confirm the better fit of a hyperbolic temperature and photoperiod response. A threshold–hyperbolic modeling approach is believed to be more consistent with crop physiology as it associates cumulative (temperature) processes and trigger (photoperiod) events that better reflect the concepts of quantitative plant growth and qualitative plant development. Its mathematical form and computational simplicity should ensure wide applicability for varietal screening over a large range of photoperiod sensitivities including neutral cultivars, and easy implementation into existing models.

Cereal/legume rotation effects on cereal growth in Sudano-Sahelian West Africa: soil mineral nitrogen, mycorrhizae and nematodes.

Yield increases of cereals following legumes in rotation have been previously reported for West Africa, but little progress has been made to explain the mechanisms involved. At four sites in Niger and Burkina Faso, field trials with pearl millet (Pennisetum glaucum (L.) R. Br.), cowpea (Vigna unguiculata (L.) Walp), sorghum (Sorghum bicolor (L.) Moench) and groundnut (Arachis hypogaea L.) were conducted from 1996 to 1998 to investigate the role of soil mineral nitrogen (Nmin), native arbuscular mycorrhizae (AM) and nematodes in cereal/legume rotations. Grain and total dry matter yields of cereals at harvest were increased by legume/cereal rotations at all sites. Soil Nmin levels in the topsoil were consistently higher in cereal plots previously sown with legumes (rotation cereals) compared with plots under continuous cereal cultivation. However, these rotation effects on Nmin were much larger with groundnut than with cowpea. Roots of rotation cereals also had higher early AM infection rates compared to continuous cereals. The dominant plant-parasitic nematodes found in all experiment fields were Helicotylenchus sp., Rotylenchus sp. and Pratylenchus sp. In sorghum/groundnut cropping systems, nematode densities were consistently lower in rotation sorghum compared to continuous sorghum. Continuous groundnut had the lowest nematode densities indicating that groundnut was a poor host for the three nematode groups. In millet/cowpea cropping systems with inherently high nematode densities, crop rotations barely affected nematode densities indicating that both crops were good hosts. These results suggest that on the nutrient poor Sudano-Sahelian soils of our study, total dry matter increases of rotation cereals compared with continuous cereals can be explained by higher Nmin and AM infection levels early in the season. The site-specific magnitude of these effects may be related to the efficiency of the legume species to suppress nematode populations and increase plant available N through N2-fixation.

Root-induced increases in soil pH and nutrient availability to field-grown cereals and legumes on acid sandy soils of Sudano-Sahelian West Africa.

A field experiment with millet (Pennisetum glaucum L.), sorghum [Sorghum bicolor (L.) Moench], cowpea (Vigna unguiculata L.) and groundnut (Arachnis hypogeae L.) was conducted on severely P-deficient acid sandy soils of Niger, Mali and Burkina Faso to measure changes in pH and nutrient availability as affected by distance from the root surface and by mineral fertiliser application. Treatments included three rates of phosphorus (P) and four levels of nitrogen (N) application. Bulk, rhizosphere and rhizoplane soils were sampled at 35, 45 and 75 DAS in 1997 and at 55 and 65 DAS in 1998. Regardless of the cropping system and level of mineral fertiliser applied, soil pH consistently increased between 0.7 and two units from the bulk soil to the rhizoplane of millet. Similar pH gradients were observed in cowpea, but pH changes were much smaller in sorghum with a difference of only 0.3 units. Shifts in pH led to large increases in nutrient availability close to the roots. Compared with the bulk soil, available P in the rhizoplane was between 190 and 270% higher for P-Bray and between 360 and 600% higher for P-water. Exchangeable calcium (Ca) and magnesium (Mg) levels were also higher in the millet rhizoplane than in the bulk soil, whereas exchangeable aluminium (Al) levels decreased with increasing pH close to the root surface. The results suggest an important role of root-induced pH increases for crops to cope with acidity-induced nutrient deficiency and Al stress of soils in the Sudano-Sahelian zone of West Africa.

Transitions Between Cultivation and Pastoralism in Sub-Saharan Africa [and Comments and Reply

This paper presents a dynamic optimality model of herding and farming as long-term survival strategies. The model can be used to predict which modes of subsistence will be associated with different ecological and economic conditions and therefore to examine under what circumstances people might change from one mode of subsistence to another. It predicts that the shift into pastoralism is associated, principally, with increasing wealth, and examples from recent history support his. It also explains such counter-intuitive b haviour as pastoralists' taking up cultivation in an area although farmers are moving out.