Indigenous knowledge of soil fertility management in southwest...
Transcript of Indigenous knowledge of soil fertility management in southwest...
Indigenous knowledge of soil fertility
management in southwest Niger
Henny Osbahra,*, Christie Allanb
aTyndall Centre for Climate Change Research, School of Environmental Sciences, University of East Anglia,
Norwich NR4 7TJ, UKbDepartment of Social and Life Sciences, University of Surrey Roehampton, West Hill, London SW15 3SN, UK
Abstract
Agriculture in Niger is a complex and challenging operation. Farmers are faced with low-fertility
sandy soils, variable rainfall, changing social and political situations and an unfavourable economic
environment. Concerns about sustaining soil fertility have been voiced by agricultural scientists, who
view agriculture as the maintenance of soil nutrient capital. Many of the biological and economic
attributes of these farming systems have been documented, and are becoming better understood
through the growing body of agroecological literature. Although agroecology recognises social,
political and cultural interactions, much less is known about the specific details of farmers’ physical
and biological knowledge and how this knowledge is used tomakemanagement decisions. Research in
Fandou Beri village identified a local ethnopedological framework that had fundamental differences
from scientific systems. Farmers’ defined soils according to location, potential for production and
interaction with the wider ecological framework. They drew on varied ecological knowledge and
experiences to make complex and dynamic farm decisions, as at other Sahelian villages. Local soil
fertility management depends on individuals’ capabilities, perceptions of constraints and
opportunities, and their ability to mediate access to different types of resources. This research
suggests that there is a need to maximise the benefits of indigenous knowledge by integrating social
and natural science, for example to help ‘precision farming’, and to use it to understand diversity.
D 2002 Elsevier Science B.V. All rights reserved.
Keywords: Soil fertility; Ethnopedology; Indigenous knowledge; Niger; West Africa
1. Introduction
The Republic of Niger is a land-locked country in the West-African Sahel. It is one of
the world’s poorest countries in the UNDP indices on several accounts. The agricultural
0016-7061/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved.
PII: S0016 -7061 (02 )00277 -X
* Corresponding author. Tel.: +44-1603-593904; fax: +44-1603-593901.
E-mail address: [email protected] (H. Osbahr).
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Geoderma 111 (2003) 457–479
sector is the mainstay of the economy and farmers still rely largely on traditional farming
methods. Unreliable rainfall and poor soils create an unpredictable and harsh environment.
Niger suffered major droughts in the 1970s and 1980s and low rainfall years persisted into
the mid-1990s. Economic restructuring in 1994 pushed up prices for farming products and
cut subsidies for fertilisers; turbulent political and social conditions have created a sense of
insecurity. However, despite these and similar constraints elsewhere in the Sahel, more
people make a livelihood and with greater livestock densities than before the droughts in
the 1970s. This suggests that there is much to be learned from a better understanding of
Sahelian production systems.
This paper compares local and scientific understandings of soils in one village in Niger.
Firstly, Sahelian agriculture and the role of indigenous knowledge are outlined, and
secondly, local soil frameworks are analysed. Finally, local perceptions of soil fertility
change and the application of farmers’ agroecological knowledge to the management of
soil fertility are discussed.
1.1. Sahelian agriculture
Agriculture in dry Africa is undoubtedly suffering some serious environmental, socio-
economic and political problems (Benneh et al., 1996; Commins et al., 1996; Eswaran et
al., 1997; Raynaut, 1997; Barbier, 2000). Changes in soil fertility have been associated
with population growth, low inherent biological productivity, long-term rainfall decline,
inadequate infrastructure, inappropriate agricultural policies, unsustainable intensification,
international debt and unfavourable global market trends (Vierich and Stoop, 1990;
Sivakumar, 1992; Spath and Francis, 1994; Reenberg and Paarup-Laursen, 1996; Reardon
et al., 1997; Adedeji, 1999; Breman and Sissiko, 2000).
Much concern has been raised over low and declining nutrient capital (Stoorvogel and
Smaling, 1990; Smaling and Braun, 1996; Drechsel et al., 2001). Nutrient capital can be
defined as the stock of nitrogen, phosphorus and other essential elements that becomes
available to plants. All soils suffer depletion of that capital when brought into cultivation
as nutrients are removed in crops or lost through leaching, erosion, etc. Sandy low-fertility
soils, common throughout the drylands, are inherently more prone to this problem
(Buerkert and Hiernaux, 1998). Penning de Vries and Djiteye (1992) concluded that
nutrients were limiting in most of the agricultural areas of West Africa that had average
annual rainfalls of above 250 mm. However, the nutrient stocks of individual plots, within
farms and village territories, can differ considerably from the average, depending on
differences in soil texture, land use histories, rainfall variability and the individual
capabilities of the farmers involved.
The agronomic literature on soil fertility under such conditions in the Sahel is
extensive. Fertility is related to productivity and nutrient capital, and must include
reference to the chemical, biological and physical properties of the soil. It is also generally
agreed that fertility must be defined as the ability of the land to produce and reproduce; its
capacity to support the growth of plants over time, under given climate and other relevant
conditions (Ingram, 1990). Agronomic indicators of soil fertility include organic matter
content, microbial activity, soil air and water balance (which is related to soil depth,
texture and structure), and the availability of the most important nutrients (Finck, 1995;
H. Osbahr, C. Allan / Geoderma 111 (2003) 457–479458
Lal, 2000). The main sources of plant-available phosphorus, which is generally the
limiting nutrient in the Sahel (Bationo and Mokwunye, 1991; Mahamane et al., 1996), are
from the weathering of soil minerals, the mineralisation of soil organic matter, fertiliser
applications and organic inputs.
However, this scientific approach to soil fertility management fails to include the
complexity of agricultural practice. First, while technical appraisal does emphasise the role
of rainfall and bioproductivity constraints, analysis tends to use ‘typical’ models of
farmers’ responses, and, in the varied cultural and natural environment of the Sahel, it has
been claimed that this is inadequate (Guyer and Peters, 1987; Vierich and Stoop, 1990).
For example, negative nutrient balances do not always justify recommendations to farmers
for the immediate use of mineral fertilisers. This is because farm households very often
have short-term objectives that run counter to that advice, but which fit prevalent socio-
economic, ecological, public policy and international agricultural circumstances. Cases of
these circumstances are well-documented (Sikana, 1993; McIntire and Powell, 1995;
Scoones and Toulmin, 1999a). Second, scientific systems attempt to be generic in nature,
whereas indigenous knowledge systems are specific, interactive and allow heterogeneity
(Tabor, 1990; Davis, 1996). There needs to be greater integration between social and
natural science discourse and farming practice.
1.2. Changes in agroecological thought and the role of farmer knowledge
The notion of progressive decline in dryland agricultural production, which is
prevalent in the agronomic community (Powell et al., 1999; Breman et al., 2001) is
being challenged (Howorth and O’Keefe, 1999; Mazzucato and Niemeijer, 2000;
Mortimore and Adams, 2001). Soil fertility is no longer merely seen as just a physical
or environmental process. There is a greater appreciation of the multiplicity of
situations and complex interactions between society and nature, making generalisations
inappropriate (Raynaut, 1997).
To deal with the emerging complexity, research approaches have evolved, shifting from
farming systems research into production research and currently focusing the broad notion
of sustainable production. While many hailed ‘Farmer First’ thinking as a step in the right
direction, the ‘Populist’ strategies it promoted have now been said to fail to integrate fully
with local systems, or to translate the socio-cultural and political economic dimensions of
knowledge creation, transmission and use into a usable framework (Scoones and
Thompson, 1993; Chambers, 1997; Neefjes, 2000). The challenge is to listen and learn
from farmers’ own knowledge, and this is not easy. There is still a concern about the
analytical dichotomy between scientific and indigenous knowledge systems in relation to
West African farming (Richards, 1985; Leach and Fairhead, 2000). Simpson (1999)
pointed out that while many of the biological and economic attributes of traditional
farming systems have been documented (Brokensha et al., 1980; Warren et al., 1995), and
are becoming better understood through the growing body of agroecological literature
(Altieri, 1998), much less is known about the specific details of farmers’ physical and
biological knowledge and how this knowledge is used in making key management
decisions. Raynaut (1997) contended that a full understanding of the complexities
demanded a closer engagement at the microscale than most studies had achieved.
H. Osbahr, C. Allan / Geoderma 111 (2003) 457–479 459
Mortimore and Adams (1999) also believed that the major deficiency in the dominant
international research discourse was its lack of concern for the local.
Agroecological approaches to understanding local-level farming systems have had a
large influence in the debate. Agroecology is a combination of agricultural science,
ecology and elements of anthropology (Hecht, 1998). As well as the agroecology
itself, it addresses the social system within which farmers work and legitimates
farmers’ knowledge. The underlying analytic framework owes much to theoretical
and practical attempts to integrate the numerous factors that affect agriculture,
including indigenous ethnoecology (McCorkle, 1994; Gray, 1997; Rain, 1999; Maz-
zucato and Niemeijer, 2000). Using this approach, specific management decisions
cannot be divorced from economy or culture and are embedded in this wholeness or
integrity (Reenberg, 1996).
Part of the agroecological approach has been greater attention to local soil knowledge
(Tabor, 1990; Osunade, 1992; and as reflected in the papers in this collection). There have
been several studies in the Sahel, which have examined ethnopedologies as part of wider
investigations into local land management (Dialla, 1993; Reenberg, 1996; Hopkins et al.,
1995; Baidu-Forson, 1999). Studies of the ethnopedologies of the Djerma (Taylor-Powell
et al., 1991; Manu et al., 1991, 1996; de Groot, 1995; Allan, 1997) and Fulani (Lamers and
Feil, 1995; Krogh and Paarup-Laursen, 1997) have found many common terms within the
separate traditions (not common to both).
Following a focus on indigenous knowledge, many researchers have shown the
ability of smallholders to adapt (Harris, 1999; Ellis, 2000; Abdoulaye and Lowenberg-
DeBoer, 2000; Mortimore and Adams, 2001), while others have demonstrated the
importance of understanding the strategies of differentiated social actors in soil
management (Osbahr, 2001; Scoones, 2001; Scoones and Wolmer, 2002). The themes
from new agroecological thought, in relation to soil fertility management and local
ethnopedological knowledge, are explored further using the following Sahelian village
as a case study.
2. Fandou Beri
The case study is of Fandou Beri (13j31.8039N, 2j33.4486E) (Fig. 1), already the
focus of various scientific and development projects.1 It is a small (population of
about 750–800), but regionally important settlement in the hinterland of Niamey in
1 1996–1998 Project Social and Environmental Relations in Dryland Agriculture (SERIDA), a collaboration
between University College London, the International Institute for Crop Research in Semi-Arid Tropics
(ICRISAT-Niger), the Institute of Hydrology and Brunel University (Batterbury et al., 1999; Warren et al.,
2001a,b). Additional research has been carried out in the village on ecology, indigenous knowledge, hydrology,
erosion and gender (Chappell, 1995; Longbottom, 1996; Osbahr, 1997; Allan, 1997; Piper, 1998; Matthews,
1998). The study village is in the IGPB-SALT site and ‘East-Central’ site of HAPEX-Sahel (The NASA
Hydrologic–Atmospheric Pilot Experiment) (Goutorbe et al., 1997), and soil maps are available (Legger, 1993;
Manu et al., 1991). The nearby village of Banizoumbou has been intensively monitored as part of the HAPEX and
ORSTOM programmes for several years and, along with another nearby site, is currently being used by the
international centres of ICRISAT and ILRI.
H. Osbahr, C. Allan / Geoderma 111 (2003) 457–479460
southwest Niger. The village territory is approximately 37 km2. The landscape is an
open savanna parkland mosaic of farmland, degraded land, and rangeland. Most of the
arable land is in a wide, shallow valley, filled with now stabilised Late-Pleistocene
dune sands, which thin out northward onto an uncultivable, ferricrete plateau, used
only for grazing and wood fuel. The sandy soils of the valley are poor and acidic, and
as such, are susceptible to rapid leaching, P-fixation and contain free Al. Some of
these sandy acid soils have complex patterns of erosion, exposed hardpans and are
dissected with dry abandoned channels, in which there are soils with higher clay
content. The rains come in a well-defined season from April to September, giving a
mean annual rainfall of about 550 mm. Early-season storms bring high intensity rains
and high winds, which cause erosion and consequent dust storms. There is an
appreciable input to soils of far-travelled dust in the Harmattan season between
November and February, and this appears to replace the calcium and potassium
removed by crops, but not phosphorus (Warren et al., this collection). Villagers come
from Djerma and Fulani ethnic groups and are mostly farmers who practice rainfed
subsistence agriculture and rear small ruminants. The Fulani families farm loaned
fields, but some remain almost wholly pastoral. The agricultural system is focused on
cereals such as millet and sorghum that are intercropped with cowpea, groundnut and
hibiscus in low-density patterns. Farmers have only basic equipment (using hoes rather
than ploughs), rarely use mineral fertiliser because of its expense and apply only
limited amounts of organic fertilisers, relying on short-fallow rotation (averaging 3
years) for nutrient replacement. Many rely on off-farm income to supplement their
household cash flow, made easier by the good access to roads and the capital. There
Fig. 1. Location of study village.
H. Osbahr, C. Allan / Geoderma 111 (2003) 457–479 461
are four primary constraints for the farming community: the unreliable rainfall (above
all), low soil bioproductivity, limited capital and limited labour.
Most farms are dependent on family labour, but farming suffers a shortage of
labour, even at a population density of about 20 people per square km. Nevertheless,
the area of cultivation increased from 11% in 1950 to 23% in 1992 (Batterbury et al.,
1999). This kind of extensification is shared with villages elsewhere in the region
(Heasley and Delehanty, 1996; Amissah-Arthur et al., 2000) and can be partly
attributed to changes in tenure law (Lund, 1998). There have been changes in the
crops grown. Cotton has not been grown since the droughts of the 1980s and farmers
have had to look to the sale of the remaining crops for additional income. The loss of
vegetation on common land and increased harvest of crop residues for household use
appears to have been one of the factors behind the reduction in the numbers of herds
passing through the village, once important sources of manure.
3. Methods
Studying farmers’ knowledge of soil is methodologically demanding because of the high
variability in ecological, cultural and socio-economic factors. The study used a multi-
disciplinary approach, incorporating Grounded Theory (Strauss and Corbin, 1990), partic-
ipatory methods (Guijt and van Veldhuizen, 1998) and soil science to build an understanding
of soil knowledge andmanagement on 20 farms (households were selected through stratified
proportional sampling). The research was conducted during the 1997 and 1998 agricultural
seasons (April–August). The rainy season was chosen because migrant workers have
returned to their farms by April and make the most farm management decisions during this
time. Trained Djerma and Fulfude translators were used to conduct focus groups, transect
walks, farm visits, qualitative interviews and semi-structured questionnaires (including the
household heads, male village elders andwomen). Through a process of participatory review
and repeat visits, information was cross-checked and organised at three scales: field, farm
and village territory.
3.1. Developing local narrative through visualisation
Visualisation techniques were used to develop soil maps of the village territory. Each
member of the group was asked to indicate and describe the location and soil type of their
current fields. After discussing the soil types found in the territory, the group was asked to
draw a map showing the distribution of the soil types. Individuals and groups were
presented with photographs and samples of the different soil types and asked to identify the
soil type. This gave insights into the role of intrinsic physical characteristics and spatial
locations in the classification framework. Farmers were asked about perceived changes in
soils, soil management, and the meanings of the soil and land use terms recorded by
previous studies (Taylor-Powell et al., 1991; de Groot, 1995). Individuals were also asked
to create network diagrams to convey everyday experiences, common knowledge and
practice by representing their individual perceptions of the choices and priorities that
influence resource allocation and investment.
H. Osbahr, C. Allan / Geoderma 111 (2003) 457–479462
3.2. Methods for eliciting understandings of soil fertility
Farmers were asked to rank the soil types by texture, colour and fertility and to rank
their fields by fertility for 1996 and 1997. Fertility was ranked for both ‘good rain’ years
and ‘poor rain’ years (locally defined). Since not all groups used the same number of soil
types, rankings were scaled by dividing by the total number of soil types ranked. A
modified proportional piling technique was used to quantify the fertility differences
between soil classes. Farmers were asked to use the local boko measure (bundle of millet)
to indicate comparative yields for the different soil classes and fields represented by
identical circles. For comparison, the field with the most fertile soil (as identified by each
group) was said to be producing 100 boko.
3.3. Comparative soil sampling and laboratory analysis
Available ammonium and nitrate in the four locally defined soil types of five fallow
fields was measured from nine duplicate soil samples in each site (10 g of each soil was
shaken in 25 ml 1 M KCl for 1 h, the sediment allowed to settle and the supernatant
decanted). The nutrient content was determined using standard methods described for
ammonium (Rowland, 1983; Gentry and Willis, 1988), nitrate (Dorich and Nelson, 1983;
Tel and Heseltine, 1990), phosphate (Bray and Kurtz, 1945) and organic matter content
(Tiessen et al., 1991). Soil pH (H2O) was measured with a pH meter in a 1:1 solution.
Grain size was measured using a set of soil sieves of 1000, 500, 250 and 45 Am mesh size.
4. Ethnopedological framework
Table 1 gives the local classification for soils in Fandou Beri. The seven groups of
farmers consistently divided the soils into two major soil classes, hard soils (locally known
as botogo and gangani) and sandy soils (tassi). The hard soils were further divided by
perceived fertility, the botogo soils being considered more fertile than the gangani. A
fourth type of soil (korabanda) was identified by a characteristic black surface. Farmers’
opinions differed as to whether korabanda occurred only on hard or sandy soils (it was
observed on both during the survey) and approximately one-third of farmers interviewed
Table 1
The main soil types identified by farmers in Fandou Beri and their distinguishing characteristics (from: Allan,
1997)
Soil name Texture Colour Fertility
Botogo hard; compacted and heavy to work dark brown most fertile but dependent on rain
Gangani hard; highly compacted, needs
animal traction for cultivation
red fertile but dependent on rain
Tassi loose and sandy red, white or black least fertile but still productive in
low rainfall years
Korabanda skin on hard or sandy soil black skin over
any colour soil
fertile in low and high rain years
H. Osbahr, C. Allan / Geoderma 111 (2003) 457–479 463
did not describe korabanda as a separate soil type, whereas all groups described the other
three soil types as distinctly different.
This summary gives a conceptual framework. The division is primarily texture-based
and has two exclusive classes. There is a secondary division in one of these classes based
on fertility, this being characterised by a colour difference. Here again there are two
exclusive classes. Thus, there are a total of three distinct classes of soil (tassi, botogo and
gangani) and a floating class defined by a soil crust (korabanda) that can occur on any of
the other three soils.
4.1. Comparing soil identification characteristics
Despite giving texture and colour as important identifying characteristics, farmers were
unable to distinguish each soil type by these characters alone. When presented with
photographs of each soil type, most farmers could identify the korabanda soils from the
distinctive black surface markings, but were unable to identify, or frequently wrongly
identified the others; this was despite relatively good photographic reproduction. Farmers
invariably asked where they had come from, suggesting the need to use a spatial reference
as the primary method of soil identification.
The mapping exercises were used both to elicit a range of information about the local
ethnopedology and for triangulation, whereby the descriptions of the soil types and
location of the fields farmed by each informant were compared to the soil distribution map
drawn up by each informant at the start of the session. The high degree of agreement
created a local soil distribution map (Fig. 2), although two fields of korabanda soil were
located outside the ‘korabanda area’.
These exercises highlight an important difference between how soils are identified
and differentiated in the local ethnopedological framework and a scientific framework.
Fig. 2. Farmers’ map of soil types (from: Allan, 1997).
H. Osbahr, C. Allan / Geoderma 111 (2003) 457–479464
Indigenous soil knowledge contained a wealth of information, and direct comparison
with scientific soil classifications is not always straightforward. In common with other
ethnopedologies (Osunade, 1992), colour and texture were used as the primary
characteristics. However, they could not be used to identify soil samples removed
from their physical location with the history attached to that piece of land. In contrast,
a soil scientist often identifies soils from samples far removed from their site and uses
characteristics, including colour and texture, intrinsic to the soil samples to differ-
entiate them. The scientific study of the soils in the territory, conducted during the
NASA HAPEX-Sahel experiment (Legger, 1993), roughly correspond to the three
zones described by the farmers. However, in the scientific survey they are categorised
into units, such as Arenosols or Podzols, that can be separated out from context and
still retain distinguishing characteristics. This is not the case with the local soil
framework.
4.2. Comparing soil fertility
The relative fertility of the different soil types was perceived by the farmers in terms of
crop production. In a year with adequate and evenly distributed rainfall (a ‘good’ rain
year), the groups consistently ranked hard soils (botogo and gangani) as more fertile than
the sandy soils, and all but one group ranked botogo as more fertile than gangani (Table
2). The modified proportional piling exercise was used to produce values that were
comparable for both rainfall regimes. The number (N) is given for each average value in
Fig. 3. Notwithstanding, Fig. 3 does suggest a picture of the relative productivity of the
soil types as perceived by the farmer groups.
Fertility was related both to intrinsic soil properties and critically the amount of
rainfall in a given year (Table 2 and Fig. 3). Few groups ranked the fertility of
korabanda, but of those that did, half ranked it higher in fertility than gangani and
half ranked it lower. This resulted in a similar average fertility rank for the two
classes. In years when rainfall was low or poorly distributed (temporally or spatially)
(a ‘bad’ rain year), tassi soils were given the highest fertility rank (although still only
attaining 70% of hard soil fertility levels in ‘good’ rain years, Fig. 3), while botogo
and gangani were equally low; notably, korabanda retained its relatively high position
in the rankings in these years (Table 2 and Fig. 3). Gangani soils were believed to be
unproductive in a ‘bad rain year’. The pattern of ranks for the sample fields in the
years of survey most closely resembled the ‘good rain year’ ranking pattern. It is clear
from the fertility rankings that soil fertility is not perceived as an intrinsic property of
Table 2
Average scaled soil rank (number of groups who ranked each type given in square brackets) (from: Allan, 1997)
Soil types Good rain year Bad rain year Sample fields
Botogo 0.98 [7] 0.46 [7] 1.00 [7]
Gangani 0.66 [7] 0.43 [7] 0.80 [7]
Korabanda 0.62 [5] 0.79 [5] 0.53 [7]
Tassi 0.28 [7] 0.98 [7] 0.33 [7]
H. Osbahr, C. Allan / Geoderma 111 (2003) 457–479 465
the soil, but rather as an interaction between a combination of soil characteristics
(encompassing nutrient content and texture) and rainfall.
Discussion with the groups provided qualitative evidence to support the relationships
represented in Fig. 3. Farmers described a complex situation, one in which the productivity
of any given field in any given year is difficult to predict with high spatial variability in
rainfall. In previous studies of both Djerma and Fulani, rainfall was also found to be central
to local perceptions of soil productivity (Manu et al., 1991; Krogh and Paarup-Laursen,
1997). Manu et al. (1991) reported that in ‘good’ rain years, crops would be sufficient
regardless of soil nutrients, while in years of lower or more erratic rainfall, low soil fertility
became the more important limiting factor. This study found that it was both the temporal
and spatial (on a field-by-field scale) distribution of rainfall during the growing season that
determined the relative productivity of the soils. It is the soil characteristics that affect
productivity in relation to rainfall that are most important in the local division of soil types.
The ethnopedological framework is evidently based around perceptions of how soil qualities
interact with rainfall to affect productivity, and this suggests that farmers seek to manage
ecological uncertainties to maintain yield even in ‘bad’ rain years.
4.3. Results of laboratory tests
The levels of nutrients measured in all the soils were low and variation between soil
samples within and between grids was high, making patterns of inter-soil type nutrient
availability difficult to distinguish (Table 3). However, tassi soils did have discernibly lower
nitrate values, while botogo, korabanda and gangani had similar values for ammonium. The
highest values of available phosphate and nitrate were found in soil from korabanda.
Inter-site patterns of soil organic matter content and pH did not correspond to observed
patterns in nutrient availability, but grain size did differ slightly between the soil types
(Table 3). Organic matter levels were extremely low in all soil types, not one site having
levels exceeding 0.8%, and inter-soil type differences showed no clear pattern. Average
soil pH was between 5.2 and 5.5. The soils were sandy with generally very low silt
Fig. 3. Comparative expected yields (average number of boko or bundles of millet estimated by each group)—N
for each average is given in square brackets under each soil type in the form [N ‘good’ rain year, N ‘bad’ rain
year] (from: Allan, 1997).
H. Osbahr, C. Allan / Geoderma 111 (2003) 457–479466
Table 3
Results of scientific soil analysis (from: Allan, 1997)
Code Soil type Fallow age
(years)
NH4–N
(Ag/g) averageNO3–N
(Ag/g) averagePO4–P
(Ag/g) averageOrganic matter
(% dry weight)
pH (H2O)
average S.E.
Grain size
(% dry weight in each size class)
(S.E.) (N= 9) (S.E.) (N= 9) (S.E.) (N = 9) average (S.E.)
(N= 9)
(N= 9)< 0.25
mm
0.5–0.25
mm
>0.5
mm
F13 B Botogo 4 7.7 (1.0) 2.1 (0.9) 2.4 (1.1) 0.1 (0.1) 5.4 (0.1) 40.9 47.0 12.1
F7 2A Gangani 2 8.2 (2.3) 2.3 (1.6) 3.6 (1.2) 0.1 (0.1) 5.5 (0.1) 50.0 37.3 12.7
F7 2B Gangani 2 7.2 (1.6) 1.5 (0.8) 2.5 (0.8) 0.5 (0.1) 5.2 (0.1) 42.3 48.4 9.3
F7 4A Gangani 4 7.5 (1.0) 1.4 (0.7) 3.8 (1.9) 0.7 (0.1) 5.4 (0.1) 56.4 36.1 7.5
F7 4B Gangani 4 9.4 (2.0) 3.5 (1.5) 2.7 (0.5) 0.3 (0.2) 5.4 (0.1) 57.0 34.6 8.3
F1 A2 Korabanda–
tassi
6 9.1 (1.6) 5.3 (0.4) 10.9 (2.1) 0.2 (0.2) 5.4 (0.1) 45.8 41.7 11.8
F1 A3 Korabanda–
tassi
6 7.8 (3.4) 1.5 (0.5) 3.6 (1.3) 0.7 (0.1) 5.3 (0.1) 41.6 48.9 9.5
F5 A Tassi 1 6.5 (1.6) 1.7 (0.3) 4.0 (1.7) 0.3 (0.3) 5.5 (0.1) 34.0 58.7 7.3
F5 B Tassi 1 6.8 (2.0) 3.1 (0.9) 2.9 (1.6) 0.3 (0.2) 5.5 (0.1) 35.7 56.9 7.4
F8 2B Tassi 2 5.4 (0.5) 1.9 (1.2) 4.2 (1.9) 0.7 (0.1) 5.3 (0.1) 29.5 65.4 5.2
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contents. The hard (botogo and gangani) soils had a higher percentage of the finest grains
( < 0.25 mm), which included clay. The tassi soils (including korabanda on tassi) had a
correspondingly higher percentage of the medium sized grains (0.5–0.25 mm).
Of all the factors measured, grain size had the closest correlation to local divisions of
soil types, indicating the importance of water-holding capacity on soil productivity.
Available moisture increases with increasing proportion of fines, sandy soil having the
lowest water holding capacity. Thus, botogo and gangani would be expected to have the
highest available moisture when there is sufficient rain. However, these soils also have the
highest clay content. Although clay was not measured in this study, Taylor-Powell et al.
(1991) recorded clay contents of 2–8%, with the highest values in the soils near the
plateau (i.e. botogo and gangani) and the lowest values in the valley soils (i.e. tassi). Even
small differences in clay content can make a great difference to the hard-setting tendency,
which affects workability, especially under hoe cultivation. It is possible that in bad rain
years or during intense rainfall events, the rain falling on the higher altitude areas of
botogo and gangani would run off towards the tassi areas. This has two effects: erosion
and the transport of water towards the higher tassi soils.
The farmers’ perceptions of fertility were based around an interaction between soil
characteristics and climatic factors, which produced a distinctive pattern of soil fertility
that the scientific soil tests used in this study, were unable to discern. A study that
measured available nutrients over several entire growing seasons may better detect the
patterns perceived by the farmers. However, since intrinsic soil characteristics composed
only part of farmers’ perceptions of fertility, there may be no direct relationship between
measurable soil characteristics and local fertility ratings. The farmers’ ethnopedological
framework relates to a complex management system that incorporates social and cultural
as well as environmental considerations and it is these factors in combination which
dictate the productivity of the land, not soil characteristics alone.
5. Perceptions of change in soil fertility
The majority of the farmers (80%) reported declining soil fertility and crop yields on
sandy soils. They had noticed a lighter colour and coarser texture for soils near the village,
indicating a decrease in organic matter. Farmers attributed these changes to the increase in
the area of permanent cultivation, the decrease in the area of long-term fallow (over 3
years), the limited inputs of manure from livestock, and to low rainfall. Elders believed
that there were fewer areas of black sandy soils (tassi biri), that is those soils with high
organic matter content, and more areas of red or white sandy soils (tassi kirey and tassi
kware), which have lower organic matter contents. This is consistent with previous studies
in the village (Batterbury et al., 1999). Only 10% of the farmers felt that there had been a
decline in fertility of the hard soils and all of them believed that the restricted areas of
tombo had lost little fertility (these soils gain their fertility from inputs near or on
household compounds). In contrast to the beliefs of the Djerma, the Fulani groups reported
no such declines in soil fertility on their fields, which they attributed to their constantly
high inputs. The process of declining soil fertility during cultivation was reflected in the
naming of stages of the rotation system. Farmers describe how one piece of land
H. Osbahr, C. Allan / Geoderma 111 (2003) 457–479468
progresses from fertile cleared sacara in the first year of cultivation to lalibanda the year
after, to kwar kwari (white sand with less organic matter) in the third season and finally to
boulouga (degraded land) after 5 years. After cropping for 5 years, farmers observe that
some of the field will need to be rested as fallow (farezenon), or nutrients have to be added
or, if particularly degraded, abandoned to long-term bush until the farmer has the ability to
add enough inputs. Under farezenon farmers noticed the development of darker soil
colours and korobanda.
6. Using local knowledge to manage soil fertility
Farmers hold complex ecological knowledge or berey (local knowledge), as the
ethnopedological framework presented in this paper has shown. There is great variation
in the kinds and depth of such knowledge. The choices made by individual farmers
depends on their capacity to enact successful agricultural performances and to exploit an
evolving range of opportunities, and these in turn are based on the use of their local
knowledge, as well as on their communication and creative capacities. The knowledge,
here as elsewhere (Pawluk et al., 1992; Stoller, 1989), becomes intertwined with the belief
and value systems that underlie culture (for example, in the use of metaphoric linkages).
On an individual basis, knowledge is acquired through personal experiences and over-
lapping communication pathways, both of which are influenced by social factors,
including age, gender and family ties. Uncertainties arise because any one farmer’s
knowledge is incomplete and incapable of dealing with risks outside of their partial
perspective and this creates a plurality of perspectives (as discussed by Mehta et al., 1999).
For example, an overlapping set of influences affects knowledge distribution and
communication. One of this set is familial status, based on lineage and traditional
divisions. Family ties can allow access to specialised spheres of knowledge and sources
of income. The traditional belief system and its associated practices is not equally spread,
and appears to be eroding in importance in many locations, especially amongst the young
who chose to enter new professions.
Network mapping can capture some of the farmers’ everyday experiences and
‘common’ knowledge (assumed knowledge held within a culture). Such diagrams
identify the links that exist in soil fertility maintenance practices and the conceptual
arrangement of knowledge or differences in management between individuals. The
varying levels of complexity in the diagrams represent the opportunities and constraints
for individuals. These opportunities and constraints are defined by the household’s
livelihood portfolio or predominance of particular types of ‘capital assets’ (see Carney,
1998; Scoones, 1998; Bebbington, 1999). Hence, the conceptual importance attached to
soil fertility investment for farmers with poor soils and little access to livestock or labour
is defined by constraints, whereas for farmers with exogenous knowledge or with higher
social status, it is defined by opportunities. Thus, each ‘map’ becomes a statement about
the way each individual views farm management, but also a reflection of their status,
power, skills, identity and fears. The example given in Fig. 4 reflects the social and
financial ‘asset’ opportunities open to a Djerma farmer with status in the village (a
marabout and old family lineage).
H. Osbahr, C. Allan / Geoderma 111 (2003) 457–479 469
Furthermore, at the local level, the inherent temporal and spatial heterogeneity of
natural resources is paralleled by equally variable household productive capacity (includ-
ing knowledge, family labour and social networks, livestock, tenure, cash, and ability to
Fig. 4. Conceptual network diagram of soil fertility management (from: Osbahr, 2001).
Table 4
Soil fertility practices used in 1998 (from: Osbahr, 2001)
Soil fertility practice 1998
% Farmers,
n= 20
% Fields,
n= 58
% Tassia,
n= 41
% Gangania,
n= 8
% Botogoa,
n= 9
Fallow: 85 48 60 13 30
(a) Short (1–3 years) 80 38 50 13 0
(b) Long (4 years+) 30 10 10 0 30
Inputs from livestock: 80 34 38 13 30
(a) Corralling or grazing 55 19 25 0 10
(b) Manure transported
from homestead
65 24 30 13 30
Mineral fertilisers 0 0 0 0 0
Nitrogen-fixing crops 100 72 85 38 40
Ash from burning 40 19 23 0 20
Protecting trees 80 69 75 50 80
Laying of millet stalks 100 100 100 100 100
Recycling and
composting organic
materials
90 84 90 70 52
a Although the local soil type is variable with all fields, values are given for the primary soil type found in the
field.
H. Osbahr, C. Allan / Geoderma 111 (2003) 457–479470
enact resource entitlements) (Osbahr, 2001). There are many constraints to productive
capacity for farmers in Fandou Beri. Table 4 shows that only 21% of the survey
households used labour intensive methods (such as compost or hand-distributed applica-
tions of inputs), while most farmers were dependent on fallow rotation and a variety of low
labour intensive methods. In other circumstances, farmers relied on their local knowledge
of soil characteristics and plant indicators to focus effort in ‘precision farming’ methods, in
which they target their planting strategies and additions of nutrients to specific places and
soil types, with the aim of maximising nutrient recycling (Osbahr, 1997). For example,
farmers value fertile niches around Faidherbia albida, termite mounds, old livestock pens
Box 1. One farmer’s agricultural season in 1998 (from Osbahr, 2001).
Amadou Abdoullaye2 is a middle-aged Djerma farmer. He had inherited three
fields of different soil types but considered the largest, nearest to the homestead, to
have low soil fertility because it had been cultivated continuously for over 50 years.
Below-average annual income meant he relied on help from his family to run the
farm. His family needed to produce an annual minimum of 330 boko for subsistence.
However, in 1997 grasshopper swarms caused much of the farm to be abandoned,
producing a harvest of 146 boko, and presenting him with constraints in essential
resources, such as seed, manure and labour for 1998. Mr. Abdoullaye worked as a
migrant farm labourer in the Ivory Coast from November to February to earn cash to
buy seed. With the lack of early 1998 rains, experience told him that the sandy soils
would be more productive and he decided to clear a 3-year fallow on his large tassi
field and mulch and burn the other fields. He put his household animals on the
closest field but carried manure to the distant gangani field because he had not been
able to pay local Fulani for grazing (7000 F CFA for 2 months). He and his family
planted the millet seed on the tassi parts of the large field 3 days after the first rains at
the end of April. Unfortunately, he misjudged his labour management as the result of
a conflict with neighbours and missed seeding after the next rains, forcing him to
plant a fast growing cultivar. Different crops were planted on the different soils
reflecting the fertility and moisture-retention capability (Fig. 5). He partitioned his
mid-season labour, preferentially weeding the tassi plots. Improved late-season rains
allowed him to redirect work to botogo and gangani areas, which were additionally
able to support sorghum, sorrel and hibiscus (planted at the same time as the millet)
and he planted peanut on these soils 15 days later. However, much of the farm’s
botogo soils had not been prepared and he was restricted to cultivating only those
parts ready. High levels of weed growth, including Striga varieties, developed with
the better rains and several parts were abandoned. Overall, 1998 brought more
sustained late-season rains but his limited labour resources made prioritising action
for soil fertility management and farm tasks especially difficult, making him
vulnerable to unpredictable rainfall patterns (Fig. 6).
2 Name has been changed.
H. Osbahr, C. Allan / Geoderma 111 (2003) 457–479 471
Fig. 5. Seeding pattern used in 1998 (from: Osbahr, 2001).
H.Osbahr,C.Alla
n/Geoderm
a111
(2003)457–479
472
and target applications of green manures, livestock grazing and burning. The importance
of these practices has been widely qualified in numerous scientific studies (Juo and Manu,
1996; Brouwer and Bouma, 1997; Payne et al., 1998; Hiernaux et al., 1999; Wezel et al.,
2000; Esse et al., 2001).
To work with environmental microdiversity, farmers have developed an understanding
that allows them to manage dynamic social, economic and environmental resources, and
this knowledge may often appear to run counter to the understandings of conventional
agricultural science. Their perspective essentially incorporates the ephemerality of soil
status, the historical dynamics of soil fertility and the need for soil fertility maintenance to
reflect natural variability. In the context of annual crop production, the convergence of
these physical and social forces is possibly best conceived as a dynamic performance
(Richards, 1989). It is more accurately a set of linked performances, through which
individuals respond to the evolving set of physical and social conditions within each year,
and from one year to the next (Box 1, Figs. 5 and 6). The general nature of these
performances, as summarised by Moris (1991), applies very well to the situation at
Fandou Beri. Risk and uncertainty dominate farmers’ lives; they must respond to an
unfolding scenario of opportunities and constraints (for example, wet or dry years, early
or late onset of the rains, pest outbreaks in a particular crop, unplanned labour shortages,
and so forth). Farmers are able to bring to their farming an accustomed ‘script’, modified
as the season develops. This does not preclude strategic natural resource management
plans and indeed the process in adaptive strategies operating at different scales and over
different timeframes has been well documented (Reij et al., 1996). Thus, local soil fertility
management is the result of a combination of responses to unforeseen events, planned
management, land use history and the farmer’s own particular knowledge. These form the
basis of a household’s strategy at a particular time, in a specific place, whereby local
knowledge is employed in an array of methods to manage soil fertility depending on
labour and capital.
Fig. 6. Household farm labour and rainfall in 1998 (from: Osbahr, 2001).
H. Osbahr, C. Allan / Geoderma 111 (2003) 457–479 473
7. Conclusions
Our findings show that the local framework for understanding soil types was part of a
wider conceptualisation of the local ecology. The soil classification was based on an
understanding of the interactions of different environmental and social factors, as they
affect the productivity of a particular field. The awareness of differing soil potentials under
variable rainfall or anthropogenic inputs supported an essentially flexible and responsive
management strategy, which may well be better at coping with the inherent and increasing
variability in Sahelian systems than those suggested by orthodox agricultural science. It is
clearly important for research into ethnopedologies to avoid easy comparisons of super-
ficial similarities that may overlay a deeper divergence of perspectives.
The comparison of agricultural science and local knowledge is not straightforward. The
results of the soil chemical analysis, which showed low nutrients levels in all soil types,
indicate that orthodox soil analysis may not distinguish the subtle differences in soil
productivity represented in the local ethnopedology (although more thorough analysis
might detect these). There were fundamental differences between local and scientific
systems for defining and describing soil properties. Whereas scientific frameworks tend to
be based on intrinsic soil characteristics that can be quantified independently of the
context, the local framework defines the important distinguishing characteristics of soils in
terms of factors such as location, potential and interaction in the wider ecology and history.
Risk-aversion and dynamic soil use (responsive to rainfall, household labour, capital and
ability to increase nutrient inputs) are more important in the local framework than are
absolute soil fertility and crop production. Critically, the local knowledge is pluralistic,
locally and historically embedded and socially constructed, factors that are not included in
scientific soil frameworks.
The local ethnopedological framework only represents one part of the farmers’
strategy for managing soil fertility. They draw upon varied ecological knowledge to
make complex and dynamic management decisions. This research has shown that as well
as biophysical, economic and social variability, local perceptions of the environment
heavily influence soil fertility management. The local approach, incorporates measure-
ments of crop yield, integrates complex soil–water relations and allows for inter-annual
rainfall variability. Each household responds to these influences according to its
capabilities, constraints and opportunities and ability to mediate access to resources.
The strategies at Fandou Beri are similar to patterns in other Sahelian villages (Reenberg
and Paarup-Laursen, 1996; Scoones and Toulmin, 1999b; Mortimore and Adams, 1999;
Scoones, 2001).
There is an urgent need for further studies to discover, develop and maximise the
benefits of indigenous knowledge, such as is used in ‘precision farming’ techniques.
They are particularly important where labour and capital are constraining. However,
despite the local capabilities, it is acknowledged that many of the constraints on the use
of technologies to improve soil fertility, such as the scarcity of inputs, labour, land,
capital, and to some extent knowledge, can only be overcome by intervention at the
policy level. In particular, there needs to be greater access to credit and economic
rewards for farmers before investment in soil fertility matches local aspirations and
knowledge.
H. Osbahr, C. Allan / Geoderma 111 (2003) 457–479474
Acknowledgements
This paper draws on separate research carried out in Niger by the authors during the
1997 and 1998 agricultural seasons. It was funded by awards from the Economic and
Social Research Council and Natural Environment Research Council, Royal Geographical
Society, University College London Research and Travel Committee and the Eric Brown
Geographical Trust. We would like to extend our thanks to the villagers of Fandou Beri, to
our research assistants and local collaborators, and the SERIDA Project. We are grateful
for comments from Katherine Homewood, Andrew Warren, John Pearson, Simon
Batterbury and two referees.
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