Natural Resources Forum 31 (2007) 306–317
Adoption of renewable soil fertility replenishment technologies in the
southern African region: Lessons learnt and the way forward
Blackwell Publishing Ltd
Oluyede Clifford Ajayi, Festus K. Akinnifesi, Gudeta Sileshi and Sebastian Chakeredza
Abstract
Low soil fertility is one of the most important biophysical constraints to increasing agricultural productivity in sub-Saharan
Africa. Several renewable soil fertility replenishment (RSFR) technologies that are based on nutrient re-cycling principles
have been developed in southern Africa. Some success stories have been recorded (e.g. nitrogen-fixing legumes), but the
adoption of RSFR technologies has generally lagged behind scientific advances thereby reducing the potential impacts of
the technologies. This paper describes the major RSFR technologies being promoted in the region, synthesizes available
information regarding their adoption by farmers, and identifies the challenges, key lessons learnt and the way forward for
up-scaling RSFR technologies in the region. The review indicated that farmer uptake of RSFR technologies depends on
several factors that can be grouped into broad categories: technology-specific (e.g. soil type, management regime),
household-specific (e.g. farmer perceptions, resource endowment, household size), policy and institutions context within
which RSFR is disseminated (inputs and output prices, land tenure and property rights), and geo-spatial (performance
of species across different bio-physical conditions, location of village). Adoption of RSFR technologies can be enhanced
by targeting them to their biophysical and social niches, facilitating appropriate policy and institutional contexts for
dissemination, understanding the broader context and dynamics of the adoption process, a paradigm shift in the approach
to the dissemination of RSFR (e.g. expanding RSFR to high value crop systems, exploring synergy with inorganic fertilizer)
and, targeted incentive systems that encourage farmers to take cognizance of natural resource implications when making
agricultural production decisions.
Keywords: Agricultural productivity; Agricultural policy; Farm management; Natural resources management; Sustainable agriculture.
1. Introduction
Declining soil fertility and low macro-nutrient levels are
fundamental impediments to agricultural growth and a
major negative social externality in sub-Saharan Africa
(Vanlauwe and Giller, 2006; Sanchez, 2002). The soils in
sub-Saharan Africa are being depleted at annual rates of 22
kg/ha for nitrogen, 2.5 kg/ha for phosphorus, and 15 kg/ha
for potassium (Smaling et al., 1997). In addition, the organic
matter content of the soils is also declining. Apart from the
primary effects of declining per capita food production,
poor soil fertility triggers other side effects on-farm such
Oluyede Clifford Ajayi is an Agricultural Economist at ICRAF and is
based in Malawi. Email: [email protected].
F.K. Akinnifesi is a Senior Tree Scientist at ICRAF, based in Malawi.
Email: [email protected].
G. Sileshi is a Pest Management Specialist working at ICRAF Malawi.
Email: [email protected].
S. Chakeredza is a Senior Education Fellow at ICRAF Malawi. Email:
[email protected].
as lack of fodder for livestock production, reduction in
fuelwood and high deforestation rates (as farmers are
forced to abandon poor soils and encroach on forests which
are more fertile). These have the predictable consequence
of accelerating degradation of natural resources and offer
very little potential for sustainable agriculture.
The low soil fertility base arises due to two major factors.
First, with few exceptions, increases in human population
growth in much of the region have led to a reduction in
the per capita land availability and a breakdown of the
erstwhile traditional natural fallow system that used to be
the means of replenishing soil fertility. The methods used
to restore the fertility of soils and to sustain agricultural
productivity under traditional shifting agriculture have
become ineffective, and in some cases, they have
disappeared altogether. As high potential land becomes less
available and the rural human population increases,
farming is extending into more fragile lands, undermining
the natural resource capital base as well as undermining the
region’s continued ability to produce food for its people.
© 2007 The Authors. Journal compilation © 2007 United Nations.
Published by Blackwell Publishing Ltd., 9600 Garsington Road, Oxford, OX4 2DQ, UK and 350 Main Street, Malden MA 02148, USA.
Oluyede Clifford Ajayi et al. / Natural Resources Forum 31 (2007) 306–317
The second factor is that most smallholder farmers
continuously cultivate crops without using fertilizers or
they have drastically reduced the use of mineral fertilizer
after the elimination of farm inputs subsidies and the
collapse of government agencies that hitherto engaged in
agricultural inputs distribution. For example, in Zambia,
the ratio between the prices of nitrogen fertilizer and the
major crop (maize) increased fourfold after the elimination
of price subsidies on nitrogen fertilizer and this led to a
70% decline in fertilizer use by farmers (Howard and
Mungoma, 1996). Similar results were obtained elsewhere
in Africa (Honlonkou, 2004). While the government has
re-engaged in distributing fertilizer to certain categories of
smallholders and encouraged private traders to do the same,
only 20% of smallholder farmers in Zambia use fertilizer
(Govereh et al., 2002). The fertilizer market is further
constrained by the geographically landlocked nature of
many countries in the region, and the poor road
infrastructure which hinders access to agricultural inputs
at affordable costs to smallholder farmers. The cost of
inorganic nitrogen fertilizers at the farm gate is estimated
to be between two to six times higher in sub-Saharan
Africa than in Europe or North America (Sanchez, 2002;
Donavan, 1996). Improving soil fertility management in
African farming systems has therefore become a major
development policy issue (Scoones and Toulmin, 1999;
NEPAD, 2003). In a continent-wide survey to identify cases
of success in African agriculture, techniques for soil fertility
enhancement were most prominently mentioned (GabreMadhin and Haggblade, 2004).
In response to the challenges highlighted above, a number
of international research and development institutions have
collaborated with national partners and farmers to introduce
renewable and integrated soil fertility management
technologies in the region in the previous two decades.
These institutions include the Conservation Farming Unit
of the Zambia Farmers Union, Golden Valley Agricultural
Research Trust (GART) of Zambia, Tropical Soil Biology
and Fertility Programme (TSBF) of the International Centre
for Tropical Agriculture (CIAT), the World Agroforestry
Centre (ICRAF), African Conservation and Tillage, and the
International Centre for Maize and Wheat Research
(CIMMYT). In addition, networks such as the Soil Fertility
Management and Policy Network for the Maize-based
Farming Systems of Southern Africa (SoilFertNet) were
created to deal with the challenges of developing and testing
alternative soil fertility management technology options.
SoilFertNet now called Soil Fertility Consortium for
Southern Africa (SOFECSA) developed and promoted
renewable soil fertility management technologies through
widespread participatory research and testing in Malawi,
Zimbabwe, Zambia and Mozambique. The primary goal of
these initiatives is to develop renewable soil fertility
replenishment (RSFR) technologies that are suitable for
different types of resource-poor farm households. In addition
to improving soil fertility, some of these technologies
© 2007 The Authors. Journal compilation © 2007 United Nations.
307
enhance the biological and physical properties of soil and
thus contribute to reduced soil erosion.
Despite their potential, apart from a few cases of exceptional
success, some of which have been cited as examples of
“successes in African agriculture” (Gabre-Madhin and
Haggblade, 2004), the adoption and diffusion of RSFR
among smallholder farmers in the region has generally lagged
behind scientific and technological advances thereby reducing
their impact (Ajayi et al., 2007; Ajayi and Kwesiga, 2003;
Franzel and Scherr, 2002; Waddington et al., 1998). Similar
challenges regarding adoption of RSFR have been reported
in other parts of Africa.1 The low adoption of RSFR
necessitates a thorough analysis of the biophysical, economic,
social, and cultural constraints which have been barriers to
using these promising and renewable technologies. This
paper undertakes this analysis by synthesizing available
information for the southern Africa region. First, it provides
an overview of key RSFR technologies that have been
developed and promoted in the region. Second, it discusses
the key lessons learnt from various studies regarding the
adoption of RSFR by smallholder farmers and third, it
identifies the way forward for scaling up RSFR among
smallholder farmers in the southern Africa region.
2. Renewable soil fertility replenishment
technologies in southern Africa
Among the RSFR technologies being tested and promoted
by the various research and development institutions in the
region are nitrogen-fixing trees (also known as “fertilizer
tree” systems), nitrogen-fixing food and dual-purpose
legumes, green manure legumes and integrated soil nutrient
management. Some of these key RSFR technologies are
described briefly below
2.1. Description of RSFR technologies
2.1.1. Nitrogen fixing trees and shrubs (known as
“fertilizer tree systems”)
The “fertilizer tree” system2 is an agroforestry technology in
which leguminous trees or woody shrubs are grown and the
biomass used to replenish the fertility of soils. Based on
nutrient re-cycling principles, the technology takes advantage
of the knowledge that, though nitrogen is the most limiting
macro nutrient in the soil, it is highly abundant in the
1
As examples, the rate of adoption of mucuna-based soil fertility
management fallows in Benin Republic was just 7% of farmers
(Honlonkou, 2004). Lal (2007) found that zero-tillage farming is practiced
on 6% of the global cropland area despite the great successes achieved in
the biophysical performance of the technology.
2
“Fertilizer tree systems” do not provide all the major nutrients. They fix
only N which is the major nutrient most limiting in the soil. They can
recycle the soil’s phosphorus (P) and potassium (K) that exist in the soil,
but these two macro nutrients need to be applied if they are completely
depleted from the soil e.g. by adding rock phosphates.
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Oluyede Clifford Ajayi et al. / Natural Resources Forum 31 (2007) 306–317
atmosphere. The planted leguminous species replenish soil
fertility by transforming atmospheric nitrogen and making
it available in the soil. The cycle begins by planting tree
species as a pure stand (fallow) or intercropped with food
crops in the first year. The trees are allowed to grow for
about two years after which they are cut and the biomass
incorporated into the soil during land preparation. The
trees’ leaf and root biomass decomposes and releases
nutrients for crops planted in the plot over the next two to
three years. Fertilizer tree systems help farmers to produce
plant nutrients by substituting land and labour for cash,
which most farmers lack. The most common species used
in “fertilizer tree systems” are Sesbania sesban, Gliricidia
sepium, Tephrosia vogelli, Tephrosia candida and pigeon
pea. In the quest to meet the requirements of different types
of farm households, variants of fertilizer tree systems
have been developed. These include improved fallows
which are short-term managed fallows that allow for rapid
replenishment of soil fertility within one to two years only,
compared to more than ten years required under traditional
fallow systems. The tree/crop intercropping system is more
appropriate for locations where per capita land holding size
is small and the possibility of leaving part of the farm
fallow is low because of high human population density. In
annual relay cropping systems, shrubs are planted after the
crop is well established and trees are left to grow during
the dry-season, while in biomass transfer systems,
leguminous trees and shrubs are planted and managed on
a separate field from where the leaf biomass is used.
Farmers are required to choose a system and legume
species that are suited to their agro-ecological zones and
soil conditions. Further details of these systems have been
documented (Akinnifesi et al., 2007; Akinnifesi et al.,
2006; Chirwa et al., 2003; Kwesiga et al., 1999).
2.1.2. Conservation farming
Conservation farming (CF) systems involve four key
elements: (i) preparation of land using minimum tillage
methods during dry-season; (ii) retention of crop residues
from the prior harvest rather than burning them; (iii) targeted
planting and application of farm inputs in restricted fixed
locations; and (iv) encouraging farmers to practice crop
rotations using nitrogen-fixing plant species. Among
others, the advantages of the system include the following:
enables farmers to plant seeds early (as land preparation
would have been done in the dry season), improves water
infiltration and reduces erosion, inputs are applied as close
as possible to crops and, it encourages nutrient recycling
and improves the organic matter content of the soil
(Haggblade et al., 2004; Haggblade and Tembo, 2003).
Studies from Zambia suggest that due to variations in
weather and annual rainfall pattern, the effectiveness of
conservation farming varies across regions, crops and over
time. The benefits of the technology such as improved
soil physical properties, gains from nitrogen-fixing, crop
rotations and reduction in the labour demand for land
preparation, occur incrementally over time (Haggblade and
Tembo, 2003).
2.1.3. Green manure and dual purpose legumes
Since colonial times, green manure legumes have been
widely tested in many parts of southern Africa as soil
amendment and a nutrient source for crops (Davy, 1925).
A number of green manure species including legumes from
the genus Crotalaria, Mucuna, Macroptilium, Sesbania,
Tephrosia have been tested in southern Africa (Cherr et al.,
2006; Mekuria and Waddington, 2004). In Malawi, Davy
(1925) regarded Mucuna as “the finest green manuring
plant for Nyasaland”.
Some dual-purpose legumes have special attraction in
the agricultural systems of southern Africa, improving soil
fertility, providing human food as a vegetable or pulse crop
and feeds for the small number of animals present. The
legume species used include cowpea and lablab. Cowpea is
one of the most important tropical dual-purpose legumes,
being used for vegetables (for example, the leaves are used
as vegetables in some parts of Malawi and Zambia ), grain,
as fresh cut-and-carry forage, and for hay and silage. The
grain of cowpea is used widely for human nutrition.
Cowpea and lablab also have high potential as a green
manure. When incorporated into the soil, they can provide
the equivalent of up to 80 kg N/ha to a subsequent crop.
Many fast-growing leguminous crops such as mucuna,
soybeans and phaseolus species are grown as green manures
and cover crops for erosion control, weed suppression and
for soil fertility restoration.
2.1.4. Organic manure
Organic manure can be animal manure (cattle, sheep, goats,
chicken etc) or compost (crop residues, natural vegetation,
kitchen refuse etc). Well-decomposed organic matter will
release the necessary nutrients for plant growth and will
also help improve the soil structure, and hence improve
aeration and water retention. In some parts of southern
Africa, mixed farming is commonly practiced. Under this
system, manure is used as the fertilizer for crops and the
crop residues and by-products are part of the animal feed.
Many international institutions and NGOs actively promote
use of animal manure in such areas.
2.2. Biophysical and socio-economic performance of
RSFR technologies
Unlike synthetic fertilizers, renewable soil fertility
replenishment technologies represent sources for on-farm,
biologically fixed nitrogen and may also add large amounts
of organic matter to cropping systems (Giller et al., 1997).
Biological nitrogen-fixation can contribute as much as 300
kg N/ha in a season through grain legumes or legume green
manures and exceptionally 600 kg N/ha in a year through
tree legumes (Giller, 2001). However, this depends on the
legume species and site conditions. The slow release of N
© 2007 The Authors. Journal compilation © 2007 United Nations.
Oluyede Clifford Ajayi et al. / Natural Resources Forum 31 (2007) 306–317
from decomposing green manure residues may be better
synchronized with plant uptake than sources of inorganic
N, possibly increasing N-uptake efficiency and crop yield
while reducing N leaching losses (Cherr et al., 2006).
Legumes also drive long-term increases of soil organic
matter and microbial biomass, further improving nutrient
retention and N-uptake efficiency. When used in place of
traditional fallows, well-chosen green manure cover crops
and fertilizer tree systems reduce erosion and nutrient loss and
suppress weeds and specific crop pests (Sileshi et al., 2006;
Sileshi, Kuntashula and Mafongoya, 2006; Sileshi et al.,
2005). Green manures may also offer habitat or resources
for beneficial organisms. They allow farmers to produce
nutrients with little direct cash expenditure relative to
inorganic fertilizers that are often less accessible to
smallholder farmers since they require high cash
transactions or credit (Akinnifesi et al., 2006; Mafongoya
et al., 2006; Mekuria and Waddington, 2004; Waddington
et al., 2004; Haggblade and Tembo, 2003; Kwesiga et al.,
2003; Waddington et al., 1998; Kumwenda et al., 1996).
Legumes also improve soil physical properties through
tree root activities and the biomass incorporated into the
Table 1. Percentage yield increase (over unfertilized maize)
using various soil fertility management technologies in
southern African countries
Soil fertility
technology
Malawi
Fertilizer
Coppicing fallow
Non-coppicing fallow
Green manure
Natural fallow
327.9
340.1
110.4
115.8
29.9
Tanzania
(39) 71.3 (23)
(27) 10.3 (16)
(15) 145.1 (39)
(32) 51.4 (8)
(11) 55.2 (28)
Zambia
855.5
271.5
242.3
134.3
61.0
Zimbabwe
(115) 443.1 (187)
(29)
35.6 (36)
(39) 349.6 (124)
(14)
58.8 (16)
(13)
93.3 (24)
Source: Adapted from Sileshi et al. (2007).
Note: (i) Figures in parentheses are standard errors of means;
(ii) The yield increases are recorded on a plot (farm) level.
309
soil. In Zambia, Phiri et al., (2003) observed an enhanced
water infiltration into the soil where S. sesban was planted.
This evidently increases the soil water storage capacity.
Chirwa et al. (2003) observed improved cumulative water
intake and reduced run-off as a result of increased water
stable aggregates in improved fallows. The addition of
above-ground biomass from the planted species probably
enhanced microbial activity which contributed to improved
soil aggregation. Green manure and fertilizer tree systems
involving leguminous species significantly increase crop
yields as compared to the natural fallows and continuously
cropped unfertilized fields (Table 1).
We compiled data from a large number of independent
studies conducted on-station and on-farm in Malawi,
Tanzania, Zambia and Zimbabwe and conducted a metaanalysis (Sileshi et al., 2007), the results of which are
summarized in Table 1.
The importance of RSFR technologies from agricultural,
environmental and social perspectives as potential sources
of income for smallholder farmers (Kuntashula et al.,
2004) have been documented (Ajayi et al., 2007; Franzel
and Scherr, 2002; Ayuk, 2001). This is summarized in
Table 2.
3. Adoption of renewable soil fertility replenishment
technologies
Studies conducted in the region revealed that tree-based
RSFR technologies are financially more profitable than the
conventional farmers’ practice of continuous crop production without external fertilization (Ajayi et al., 2007;
Kuntashula et al., 2004; Franzel, 2004; Place et al., 2002).
Similar results were obtained for mucuna and other green
manure systems in Zimbabwe and Malawi which revealed
that these RSFR technologies were profitable for both land
constrained and land adequate smallholder farmers
(Waddington et al., 2004; Mekuria and Waddington, 2004).
Table 2. Types of benefits from RSFR technologies
Benefit
Private
Social
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Between 2– 4 fold increase in yield
Potential for higher price premium for farm produce
Stakes for tobacco curing
Fuel wood — available in field, and so reduces
time spent searching for wood
Has multi-purpose functions — food, soil nutrition
Fodder for livestock
Used as bio-pesticide (e.g. Tephrosia vogelii)
Suppresses the growth of noxious weeds
Improved soil infiltration and reduced run-off
Potential to mitigate the effects of drought
spells during maize season
Social equity — availability is not dependent on political
connection or social standing
Diversification of farm production (e.g. mushrooms)
© 2007 The Authors. Journal compilation © 2007 United Nations.
Potential for carbon sequestration
Suppression of noxious weeds
Improved soil infiltration and reduced run-off on the slopes
Potential to mitigate the effects of drought spells during maize season
Enhanced biodiversity
Diversification of income opportunities in the community
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The adoption of RSFR has, however, been affected by
several factors including the biophysical characteristics of
the technologies themselves, the individual and household
conditions of farmers, and the institutional context within
which the adoption of RSFR technologies takes place.
3.1. Biophysical and technological factors affecting
adoption of RSFR technologies
It has been long known that organic manure (animal or
compost) improves soil fertility. However, it is difficult for
most small-scale farmers in southern Africa to produce and
transport the 10–20 t per ha of organic matter necessary to
fertilize their fields. In many cases, most of what is
available is used on high value crops rather than the
subsistence food crops. Animal manure is also becoming
scarcer because most farmers have too few animals to
produce adequate quantities of manure. Transport problems
for the huge quantities of manure required, and poor
treatment of manure resulting in low quality may limit its
utilization (Kuntashula et al., 2004). The major factors that
positively influence the farmers’ decision to use manure are
availability of manure, herd size, farmers’ experience in
farming and the availability of extension services. Other
important considerations include labour and transport
requirements for handling manure, lack of technical
information on the fertilizer value and management of
manure, increased growth of weeds and bad odour. The
tropics, where green manures have achieved spontaneous
diffusion in smallholder agriculture, are invariably where
labour savings have resulted due to the suppression of
pernicious weeds (Vanlauwe and Giller, 2006; Giller, 2001).
However, soil fertility improvement and weed control
alone, did not suffice to convince the majority of farmers
to adopt green manure legumes (Schulz et al., 2003;
Douthwaite et al., 2002). In contrast, most farmers would
be willing to grow mucuna if the grain could be consumed
or sold (Schulz et al., 2003). In some places, farmers were
reluctant to adopt mucuna because it took land out of
production that could otherwise be used for growing food
or cash crops (Schulz et al., 2003). The same problems are
raised in other fallow and green manure species that do not
offer marketable products, while this is not the case with
pigeon pea or dual purpose grain legumes. Where the soil
is not suitable for the growth of certain nitrogen-fixing
plant species, they may not grow well and the amount of
biomass produced to fertilise the soil may be compromised.
3.2. Individual and household factors affecting adoption
of RSFR technologies
Several studies have investigated the adoption of RSFR
technologies in southern Africa by assessing the effect of
household and farm variables on farmers’ decision-making
(Ajayi et al., 2006; Phiri et al., 2004; Ajayi et al., 2003;
Keil et al., 2005; Thangata and Alavalapati, 2003; Franzel
and Scherr, 2002; Gladwin et al., 2002; Place et al., 2002).
Results suggest that constraints to successful adoption of
RSFR are rarely just technical or economic in nature. The
studies revealed that adoption of RSFR does not have a
simple direct relationship with technological characteristics
alone, but it is a matrix of several hierarchies of different
factors including household-specific characteristics,
community-level factors, and institutional arrangements
and policies (Ajayi et al., 2003). When making decisions
to adopt a technology or not, farmers are influenced not
only by its biophysical and economic profitability alone,
but by key attitudinal issues such as the perceived
usefulness (extent to which a person believes that using a
particular technology will enhance their job) and perceived
ease of use, i.e. user’s perception of the ease or difficulty
of learning and using a technology (Ajayi, 2007; Flett
et al., 2004). Thus, while economic considerations and
short-term profitability of RSFR generally increase the
probability of adoption (Haggblade et al., 2004; Ayuk,
1997), economic models alone do not fully explain
farmers’ adoption behaviour regarding these technologies.
Farmers’ decisions often appear to be guided by the level
of household resource endowment and the prevailing social
context such as customs, obligations, and beliefs.
3.3. Policy and institutional factors affecting adoption of
RSFR
Fiscal policies such as subsidies and institutional support
for certain soil fertility management options may have
considerable indirect influence in shaping farmers’ decisions
on RSFR. Studies carried out in Zambia to compare the net
benefits of RSFR technologies with fertilizer and farmers’
practice (maize production without use of external fertilizer)
showed that nitrogen-fixing soil fertility technologies are
more profitable than farmers’ practices of continuous
maize production without external fertility inputs, but it is
less profitable than the use of subsidized fertilizer (Franzel,
2004). The nitrogen-fixing options have a higher benefit
cost ratio (BCR) than the mineral fertilizer option implying
that there is a higher return per unit investment made on
the nutrient cycling options (Ajayi et al., 2007). Price and
other factors affect the financial profitability of the different
soil fertility options that were studied. In general, the
prevailing price of the staple crop (maize), cost of capital
(interest rate), cost and level of subsidy on fertilizer, and
wage rate of labour are key determinants of the relative
financial attractiveness and the potential adoptability of the
different soil fertility options (Ajayi et al, 2007). Most
smallholder farmers do not have direct control over these
important factors, but will often respond to them when
making choices concerning soil fertility.
Similar studies in West Africa found that when inorganic
fertilizer prices were not subsidized, the social profitability
of RSFR technology relative to fertilizers increases and,
this is expected to lead to an increased interest by farmers
© 2007 The Authors. Journal compilation © 2007 United Nations.
Oluyede Clifford Ajayi et al. / Natural Resources Forum 31 (2007) 306–317
311
and policy makers in RSFR technology (Adesina and
Coulibaly, 1998). Several years ago, the RSFR technology
was considered impractical or less economically rational to
use in Nigeria because nitrogen fertilizers were a cheaper
option at that time (Sanchez, 1999). Apart from the
technological attributes, economic and social factors are
important for the adoption of RSFR as they are reflected
in the discount rate, risk, information and prices of inputs
and outputs and influence farmers’ choices (Honlonkou,
2004). Drawing on their study on conservation agriculture
in Zambia, Haggblade et al. (2004) noted that the adoption
of conservation agriculture technologies depends on the
financial incentives and risk decisions facing individual
households, particularly in the first year of adoption, even
though the effects of the technology occur through time
both on a single farmer’s land and across a landscape.
Some local customary practices in the region, especially
the incidence of bush fires and browsing by livestock
during the dry season, limit the widespread uptake of
specific types of RSFR (Ajayi and Kwesiga, 2003). For
example, the promotion of pigeon pea (Cajanus cajan) as
a soil fertility option was discontinued in eastern Zambia
due to extensive browsing by livestock (Franzel et al., 2002).
The adoption of certain RSFR technologies is affected by
land tenure and inheritance rights especially where there is
considerable time lag between initial investment and
accrual of benefits, e.g. tree-based RSFR technologies.
Unruh (2001) reports that in Mozambique certain groups
such as women, tenants and migrants are customarily
restricted from planting trees (because they are the most
common forms of customary evidence for claiming
ownership of land). Such customary arrangements prevent
longer-term investment in soil fertility improvement and
affect farmer adoption of tree-based RSFR. There is,
however, no consensus yet on the extent to which land
tenure rights influence the adoption of RSFR. Some studies
reported that the adoption of RSFR is definitely constrained
by insecurity of tenure and absence of private property
rights on land (Honlonkou, 2004; Unruh, 2001; Ayuk, 2001;
Sturmheit, 1990) while other studies reported that land
security issues do not necessarily constrain adoption of
RSFR (Place et al., 2002; Adesina et al., 2000). These
suggest that the relationship between land tenure and
farmer adoption and investment in RSFR improvement
may not be straightforward. It also suggests that the
influence of land tenure on adoption of RSFR varies by
geographical location, type of culture and type of RSFR
technology, i.e., whether it is tree-based or annual
leguminous shrubs.
Policy documents in several countries in the region
emphasize the need to enhance food production while
maintaining the agricultural resource base. This is a goal
that most RSFR technologies can readily meet if they are
implemented by farmers. In addition, RSFR technologies
are consistent with three of the four cardinal thrusts for
improving Africa’s agriculture as outlined in the
Comprehensive Africa Agriculture Development Program
(CAADP) of the New Partnership for African Development
(NEPAD) to which the region subscribes. A number of
lessons could be drawn from the studies that were reviewed
which would be helpful in further research and
development and in efforts to realize the potential benefits
of the RSFR technologies in the region.
4. Key lessons learnt from adoption studies and way
forward to scale-up RSFR in southern Africa
4.2. Policy and institutional context is vital for the
dissemination and adoption of RSFR technologies
Opportunities exist to increase farm level adoption of
RSFR in the region. For example, National Agricultural
Farmers’ adoption decisions are strongly influenced by the
policy and institutional context within which technologies
© 2007 The Authors. Journal compilation © 2007 United Nations.
4.1. Target RSFR technologies to their biophysical and
socio-cultural niches
One of the lessons learnt is that there is a spatial dimension
to the adoption of RSFR technologies in southern Africa,
i.e. the performance and potential for farmer uptake of
the technologies varies with location. Not all RSFR
technologies perform equally well in all locations. Rather,
the performance of the technologies varies across regions,
crops and over time (Haggblade et al., 2004). The emphasis
should therefore be to establish proper targeting of the
technologies to geographic and social niches to ensure that
they create the desired impact among smallholder farmers.
One approach to doing this is to use Geographical
Information System (GIS) techniques to establish
“suitability maps” for the major RSFR technologies. First,
boundary limits for the biophysical performance of each
key RSFR technology (taking cognizance of a range of
major factors such as soil type, rainfall, slope, etc.) should
be established and mapped out. A similar map based on
socio-economic criteria (e.g. population density, road
network, market access, property rights arrangements, etc)
should be constructed. The delineation of the niches should
consider the farmers’ perception of need for the
technologies. The two maps would then be overlaid to
identify “hot spots” where a given RSFR technology could
be most suitable in terms of biophysical performance and
ensure socio-cultural relevance. The dissemination and
promotion of each technology could then be done within a
given suitable geographical area and thus ensure that
technologies are targeted to specific locations where they
are most relevant and may make the greatest impact. The
scale of the map may be national or at a finer resolution
depending on availability of data and resources for the
mapping exercise.
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are disseminated to potential users. Programmes to scale
up RSFR technologies will be more successful when
farmer training and other dissemination activities at the
farm level are complemented by active engagement of
policy makers and shapers (advocates) to facilitate policy
incentives and regulations that are conducive to and
encourage smallholder farmers to adopt RSFR technologies.
Such engagements will need to highlight the relevance of
and gains from RSFR technologies to individual farmers in
the short run, and also emphasize the contributions of
the technologies to sustainable crop production and the
protection of the natural resource capital base for the
society in the long run. Availability of relevant information
based on sound and rigorous studies is an important ingredient
to facilitate policies to promote RSFR technologies among
policy makers and shapers. It is important, however, that
efforts to facilitate favourable policies in relation to RSFR
should be done in a concerted manner including close
integration with related technologies (e.g. rain water
harvesting, minimum tillage and other renewable farming
technologies) that are being promoted by several
development organizations in the region.
As part of the effort towards “getting the policy right”,
there is a need to evaluate existing national and regional
policies to determine whether they have inadvertently
created direct and/or indirect (dis)incentives to the adoption
of RSFR. Farmers’ decisions to adopt RSFR often depend
on broader incentives created by market and non-market
institutions. National policies and international trade
policies may impact on the incentives for smallholder farm
households to manage their soil resources in a sustainable
manner, such as modifying the relative (private) profitability
and net returns from land use systems and altering the
attractiveness and potential adoptability of soil fertility
management practices. Such appraisal requires effective
institutional arrangements and forums to appropriately
inform on public policy. This requires the participation of
a wider range of different public stakeholders because policies
emerge from policy processes that are themselves embedded
in political processes, and the political feasibility of
expected institutional changes.
A review of the impact of institutions and policies to support
the adoption of soil fertility technologies in Zambia and
Zimbabwe indicated that the low producer pricing policies
adopted by several governments in the region heavily tax
smallholders in favour of urban consumers, thus reducing
the financial ability of farmers to invest in soil fertility
management technologies (Mekuria and Waddington, 2004).
A study in southern Zambia revealed that state agricultural
extension services and education curricula had little or no
content on such topics as RSFR technologies, erosion
control and composting (Sturmheit, 1990) due probably to
low confidence in handling such topics. Given the degradation
of the extension services and delivery systems in most parts
of Africa, strong links with NGOs and other developmentoriented institutions are important in the efforts to scale up
the technology and achieve widespread impact. Programmes
to build sufficient capacity of government agricultural
extension and delivery departments in various countries are
essential to enhance support for and institutionalize the
dissemination of RSFR technologies.
The extent to which local and national policy-making
processes accept and institutionalize RSFR (e.g. through
specific policy documents and budgetary allocations) plays
an important role in smallholder farmers’ adoption of these
technologies. Given that most RSFR technologies in the region
are incipient technologies, there is the need for a stronger
science-policy linkage to enhance the institutionalization of
RSFR into the agricultural and natural resource management
programmes in various countries. The extent to which local
and national policy-making processes accept and
institutionalize RSFR (e.g. through specific budgetary
allocations) plays an important role in sustaining the
adoption of RSFR on a continuous basis.
4.3. An understanding of the broad context and dynamics
of adoption of RSFR matters
The adoption of technologies by farmers is a process that
begins with acquisition of information, testing and eventual
adoption (or continuous use) of a technology. According to
Ajayi et al. (2006), the factors that initially influence
farmers’ decisions to test a RSFR newly disseminated in a
geographical area (i.e. “testing phase”) may be different
from or exert a different level of influence compared with
the factors that affect the decision to continue using the
technology on an expanded, long term basis (i.e. “adoption
phase”). During the testing phase, factors relating to
availability of information and training, and incentives that
are associated with the dissemination of the technology
play important roles. Over time, however, issues of
institutional constraints (Ajayi and Katanga, 2005; Ajayi
and Kwesiga, 2003), availability and cost of alternatives,
land size and tenure (Place, 1995), national policies (Place
and Dewees, 1999) and compatibility with other operations
in the farming systems become important. Development
programmes to enhance the adoption of RSFR must
recognize the key factors that influence farmers’ decisions
and how these factors and their influence change over time.
A number of the studies investigating the adoption of
RSFR in southern Africa have focused mainly on assessing
the effect of household and farm variables and household
characteristics on farmers’ adoption decision-making.
Given that adoption is a dynamic process, several factors
(e.g. age, household size, wealth ranking, farm size, etc)
presumed to be independent are, in fact, likely to influence
one another, hence they should not be treated in isolation,
ignoring their mutual interdependencies and reducing the
adoption-decision to a zero-sum game. If individual household
and farm characteristics are singled out, a certain
characteristic considered to have a positive influence on
adoption in one study may be viewed as having a negative
© 2007 The Authors. Journal compilation © 2007 United Nations.
Oluyede Clifford Ajayi et al. / Natural Resources Forum 31 (2007) 306–317
313
influence in another. These differences can often be
clarified from the institutional and social contexts and
through an understanding of the dynamics of the adoption
processes of the respective study areas.
There is also the need for a systematic documentation of
farmer innovations and adaptations of RSFR as these provide
useful hints for their implementation and/or modification.
Such an approach to technology dissemination, which
allows farmers to assess options offered to them by
development institutions, and actively encourages them to
make several modifications and adaptations based on their
experiences working with the technologies, helps to ensure
that they are continuously relevant and appropriate to farmers’
changing needs and preferences over time (Douthwaite et
al., 2002). In addition, feedback from farmers provides an
opportunity for development workers and researchers to
identify key issues that require further investigation in the
effort to scale up RSFR technologies.
(e.g. paprika, cotton, sunflower) should also be considered
in the continuous process of the development and
promotion of RSFR technologies in the region. This will
help to widen the domain of applicability of RSFR to
different organizations that promote other crops apart from
maize and, enhance the adoption of the technologies among
different types of farmers. In Zambia, the promoters of
conservation agriculture explored the use of the technology
in cotton fields and worked in collaboration with cotton
companies. As a result, the two major cotton companies in
Zambia — Dunavant and Clark cotton — which account
for 75% of all cotton production in the country are currently
promoting the use of conservation farming among their
collaborating farmers, estimated at over 85,000 farmers
nationwide (Tschirley et al., 2004). This demonstrated
relevance of conservation agriculture to cotton crop in
addition to the crop (maize), has contributed greatly to
enhancing its adoption by farmers.
4.4. A shift in paradigm in the approach to the
dissemination and adoption of RSFR technologies matters
4.5. Targeted support systems to enhance private
investment in RSFR technologies
Plant nutrient requirements can be met either through
mineralization from purchased inorganic fertilizers or
relying on biological processes through nutrient cycling.
Several authors have argued that there is potential for these
two sources to complement each other and take advantage
of the synergies between them (Akinnifesi et al., 2007;
Haggblade and Tembo, 2003; Ajayi et al., 2003; Palm et
al., 1997; Kumwenda et al., 1996). The synergy arises from
the combination of mineral fertilizers with organic
fertilizers which helps to improve soil structure and the
soil’s water-holding capacity. In some cases, combined use
may reduce the total cost of improving soil fertility. Plants
(and development agencies) should care much more about
the quantity, timing of availability, access and quality of
nutrients that are available than the source(s) where the
nutrients come from. Given that the biomass required for
RSFR may not always be available in the sufficiently large
quantity required for sole application, increasing emphasis
should be placed on identifying appropriate combinations
and mixes that are best suited to different types of farming
households. Given the central role of soil fertility in raising
agricultural productivity in the subcontinent, complementary
initiatives are needed across the continent, at all scales and
levels of activity. The debate on organic versus inorganic
source of nutrients to meet food requirements in the region
is less helpful than emphasizing the potential synergy
between organic and inorganic nutrients.
Part of the paradigm shift should include widening the
relevance of RSFR to other crops beyond maize. Most of
the research carried out on RSFR in the region has almost
exclusively focused on maize. While maize is most likely
to maintain its strategic importance in the near future, in
terms of food security, it is important that the use of RSFR
technologies in the cropping systems for high value crops
There is a need for targeted policy and incentive mechanisms
to support the promotion of private investment in soil
fertility replenishment, in general, and the adoption of
RSFR technology, in particular. The rationale for such
support is based on two related reasons: (i) to bridge the
gap between the costs and benefits of investment in
renewable soil fertility from the private and public
perspectives and, (ii) to recognize and reward the adopters
of RSFR technologies for the positive accrual of the
technologies beyond the farm.
First, it is important to note that the private and social
costs of soil fertility depletion and the private and social
benefits of investments in soil fertility improvements differ
from the perspective of individual farmers and that of
society as a whole. The divergence between private and
social costs and benefits is primarily due to the fact that
individual farmers most often tend to under-estimate the
real user-cost of soil depletion. As a result, individuals
systematically tend to discount future costs and benefits at
a higher rate than that which the social policy makers,
acting on the behalf of the society, would use. This situation
leads to higher current rates of soil depletion which from
the individual’s (private) perspective is rational, since
farmers would prefer to defer costs to the future, but not
necessarily so from the public perspective (Izac, 1997).
Several reasons may account for the higher levels of
individual discount rate, e.g. insecure rights to land; higher
levels of poverty, and/or lack of access to credit. The effect
of this is a lower than optimal level of investment for soil
fertility replenishment. Efforts to address these constraints
could be an entry point for policy intervention to ensure
that the gap in soil fertility investment is bridged.
Second, a number of RSFR technologies produce
multiple outputs, i.e. in addition to improving soil fertility
© 2007 The Authors. Journal compilation © 2007 United Nations.
314
Oluyede Clifford Ajayi et al. / Natural Resources Forum 31 (2007) 306–317
and crop production, they also generate ecosystem services
and conserve natural resource capital in several ways, e.g.
enhancing soil animal biodiversity (Sileshi and Mafongoya,
2006), sequestering large quantities of carbon in soil and
biomass (Makumba et al., 2007), improving soil moisture
conservation, reducing water runoff and soil erosion through
enhanced water infiltration and water holding (Phiri et al.,
2003). Where such benefits from the adoption of a given
RSFR technology spill over to other fields, the resulting
beneficial impact represents positive externality to the
public (who benefits without necessarily sharing in the cost
of adoption of the technology). Where such positive
externalities exist, and there is no incentives system to
reward individual farmers (investors), then the level of
investment (in this context, the level of adoption of RSFR
by farmers) will be less than optimal (FAO, 2001; Ajayi
and Matakala, 2006). This is illustrated in a conceptual
framework (Figure 1). In general, externalities can
overstate (understate) gains from a given technology if
some costs (benefits) are not counted.
The cost of adopting a soil fertility technology is
represented by the “cost” curve in Figure 1. For a
technology that enhances the soil to produce a single
product (e.g. maize yield only), the benefit to the farmer in
terms of the value of crop produced is represented by the
“individual benefit” line. At Point A, the marginal cost is
equal to the marginal revenue for individual (private
farmers) as illustrated by the slopes of the total cost and
total (private) revenue/benefits which are the same at this
point. The optimum level of food production is further
increased to point B when the extra environmental benefits
are taken into consideration. Assuming that potential
adopters (farmers) take rational economic decisions, the
level of adoption can be increased if environmental benefits
are recognized and rewarded.
Economically rational limits of adoption of RSFR under
different rewards systems.
Source: Modified from Ajayi and Matakala (2006).
Figure 1.
For RSFR technologies that generate environmental
services, the benefits of adopting them increase from
“individual benefit” to “social benefit”. The magnitude of
the shift is dependent on the value of the environmental
services produced as “public” which accrues to the society
as a whole. As a result, the economically rational level of
adoption increases to “B”. For adoption of multi-output
RSFR to move from “A” to “B”, some facilitation and
incentive supports through a public support system may be
required. This is because the farmers’ objective of
satisfying basic household needs in the immediate period
may not necessarily coincide with long-term sustainability
goals of society (Ajayi and Matakala, 2006; Izac, 1997).
Part of this incentive may include helping farmers get
access to niche markets where the produce from renewable
land use systems can fetch higher prices, enhance profit
and incite farmers’ interest in adopting them. Initiatives
that offer an incentive mechanism to assist smallholder
farmers to adopt RSFR and contribute to the generation of
global public environmental services should be
encouraged. Such initiatives are particularly important for
specific RSFR technologies where the cost of adoption is
incurred upfront, and separated from benefits by a long
time interval, that is often longer than the “waiting period”
for annual crop technologies. Land use innovations such
as RSFR technologies that enhance or conserve the soil
resource base may also not provide immediate benefits
to land users (Ayuk, 2001; Shiferaw and Holden, 1998).
There is, therefore, a need to identify options that align
smallholder farmers’ incentives with those of society and
encourage farmers to take cognizance of natural resources
in making their agricultural production decisions.
5. Conclusion
The need to enhance food production while maintaining the
agricultural resource base and the resilience of the agroecosystem will be an increasingly important topic in
discussions on the development of the southern Africa
region in the foreseeable future.
This paper identifies RSFR technologies as an option to
meet the short-term needs of smallholder farmers for
adequate food and income, while addressing the long-term
considerations of sustainable resource management. A
number of inferences can be drawn from the key
determinants of, and the challenges facing the adoption of,
RSFR by smallholder farmers that must be addressed to
ensure actualization of the potential benefits of RSFR.
First, beyond technological characteristics, farmer adoption
of RSFR technologies is affected by a matrix of factors
including technology-specific factors, household-specific
factors, institutional and policy context within which the
technologies are disseminated to farmers, and geo-spatial
factors. Second, RSFR technologies do not perform equally
well in all locations as their performance varies across
© 2007 The Authors. Journal compilation © 2007 United Nations.
Oluyede Clifford Ajayi et al. / Natural Resources Forum 31 (2007) 306–317
regions and over time. Specific RSFR technologies should
therefore be targeted to their biophysical niches (to ensure
that they perform well in the field) and their socio-cultural
niches (to ensure that resources are committed to
disseminating technologies that are most relevant to the
needs of farmers and can make the greatest impact in given
locations). Third, given the important role of government
policies on farmers’ adoption of RSFR, a more effective
scaling up of the technologies will be achieved when
farmer training and other dissemination activities at the
farm level are complemented by active engagement with
policy makers (and policy shapers). Among others, such
engagement should seek to institutionalize RSFR into the
mainstream agricultural and natural resource development
agenda, reduce policy and institutional constraints to wider
adoption of RSFR and facilitate appropriate policy for
incentives and options that encourage smallholder farmers
to take cognizance of natural resources in making their
food production decisions. Fourth, the dissemination of
RSFR should be done in a broader context recognizing the
dynamics of the adoption process, and the key variables
that influence farmers’ adoption decision over time, and the
influence of mutual interdependencies of variables on
adoption. Finally, the scope of the approach to the
dissemination of RSFR technologies should be expanded
to take advantage of well documented synergy with mineral
fertilizer and concentrate less effort on debates regarding
organic versus inorganic sources of soil fertilization.
Similarly, the relevance of RSFR should be widened
beyond just maize crop alone, to include other high value
crop systems (e.g. paprika, cotton).
Acknowledgment
The authors are grateful to the anonymous reviewers for
helpful comments on an earlier draft of this paper. This
work was partially funded by the core financial support
given to World Agroforestry Centre by the Rockefeller
Foundation, the Governments of Canada and Sweden. The
usual disclaimer applies.
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