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Agricultural success from Africa: the caseof fertilizer tree systems in southern Africa(Malawi, Tanzania, Mozambique, Zambia andZimbabwe)Oluyede Clifford Ajayi a , Frank Place b , Festus Kehinde Akinnifesi a &Gudeta Weldsesemayat Sileshi aa World Agroforestry Centre , PO Box 30978, Lilongwe 03, Malawib World Agroforestry Centre , PO Box 30677, Nairobi, KenyaPublished online: 08 Jun 2011.

To cite this article: Oluyede Clifford Ajayi , Frank Place , Festus Kehinde Akinnifesi & Gudeta WeldsesemayatSileshi (2011) Agricultural success from Africa: the case of fertilizer tree systems in southern Africa (Malawi,Tanzania, Mozambique, Zambia and Zimbabwe), International Journal of Agricultural Sustainability, 9:1,129-136

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Agricultural success from Africa: thecase of fertilizer tree systems in southernAfrica (Malawi, Tanzania, Mozambique,Zambia and Zimbabwe)Oluyede Clifford Ajayi1*, Frank Place2, Festus Kehinde Akinnifesi1 and Gudeta Weldsesemayat Sileshi1

1 World Agroforestry Centre, PO Box 30978, Lilongwe 03, Malawi2 World Agroforestry Centre, PO Box 30677, Nairobi, Kenya

In response to the declining soil fertility in southern Africa and the negative effects that this leads to, such as food

insecurity besides other developmental challenges, fertilizer tree systems (FTS) were developed as technological

innovation to help smallholder farmers to build soil organic matter and fertility in a sustainable manner. In this paper,

we trace the historical background and highlight the developmental phases and outcomes of the technology. The

synthesis shows that FTS are inexpensive technologies that significantly raise crop yields, reduce food insecurity

and enhance environmental services and resilience of agro-ecologies. Many of the achievements recorded with FTS

can be traced to some key factors: the availability of a suite of technological options that are appropriate in a range

of different household and ecological circumstances, partnership between multiple institutions and disciplines in the

development of the technology, active encouragement of farmer innovations in the adaptation process and

proactive engagement of several consortia of partner institutions to scale up the technology in farming communities.

It is recommended that smallholder farmers would benefit if rural development planners emphasize the merits of

different fertility replenishment approaches and taking advantage of the synergy between FTS and mineral fertilizers

rather than focusing on ‘organic vs. inorganic’ debates.

Keywords: agricultural innovation; agroforestry; development partnership; research for development; soil fertility;

southern Africa

Introduction

Background of the problem addressedby technological innovationLow soil fertility is widely recognized as a majorobstacle to improving agricultural productivity in sub-Saharan Africa (Sanchez, 2002). In most regions ofAfrica, soil fertility degradation is caused by threeinterlinked factors: (i) the breakdown of the traditionalfallow system as a result of an increase in humanpopulation and decreasing per-capita land availability,which forced farmers to crop continuously andencroach on marginal lands in search of more fertilelands; (ii) inadequate adoption of soil managementinvestments such as conservation or crop residue

incorporation; and (iii) sub-optimal use of fertilizersby a majority of smallholder farmers due to highcost and constraints to access them. The situationbecame more challenging after the removal of farminput subsidies and the collapse of para-state agricul-tural input marketing agencies beginning in the 1980s.For example, after the removal of fertilizer subsidiesin Zambia, the price ratio of nitrogen and maizewent up by 400 per cent, resulting in a 70 per centdecline in fertilizer use by smallholder farmers(Howard and Mungoma, 1996).

Given the strong linkage between soil fertility andfood insecurity, addressing the decline in soil fertilityremains an important challenge for those faced withformulating Africa’s development policy agenda

*Corresponding author. Email: [email protected]

INTERNATIONAL JOURNAL OF AGRICULTURAL SUSTAINABILITY 9(1) 2011

PAGES 129–136, doi:10.3763/ijas.2010.0554 # 2011 Earthscan. ISSN: 1473-5903 (print), 1747-762X (online). www.earthscan.co.uk/journals/ijas

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(NEPAD, 2003). There is a need for technologicaloptions that replenish soil fertility as quickly as poss-ible for a range of ecologies and agricultural systemsand that are suitable for different types of farm house-holds. Fertilizer tree systems (FTS) are one option thathas been developed to meet such challenges.

Description of the technological innovationFTS [The term ‘fertilizer tree system’ does not implythat the trees provide all the major nutrients: they arecapable of fixing only N, which is the most limitingmajor soil nutrient. The trees can recycle the soil’sphosphorus (P), calcium (Ca), magnesium (Mg) andpotassium (K), but these macronutrients must besourced externally when they are highly depletedfrom the soil.] involve the planting or regenerationof fast-growing nitrogen-fixing trees or woodyshrubs that produce high-quality leaf biomass, andare adapted to the local climatic and soil conditions(Kwesiga and Coe, 1994; Akinnifesi et al., 2008).The principle underlining the concept of FTS comesfrom the fact that although nitrogen is the most limit-ing macronutrient in the soil, it is highly abundant inthe atmosphere. Through biological nitrogen fixation,trees replenish the soil fertility by transforming atmos-pheric nitrogen and making it available in the soil.Depending on the species, trees grow for one ormore years, after which they are cut down and thebiomass gets incorporated into the soil. When thetree biomass decomposes, it releases nitrogen forcrops’ use, thus replenishing the soil fertility andimproving crop productivity. FTS help farmers toproduce the needed plant nutrients by using landand labour instead of cash, which most farmers lack.

Over the years, different types of FTS havebeen developed including sequential fallows,semi-permanent tree/crop intercropping, annualrelay cropping and biomass transfer. To ensure sub-stantial contribution in terms of amount of nitrogenfixed and biomass production, the choice of FTS pro-moted in a given area takes cognisance ofagro-ecology and soil conditions. Technical detailsof FTS have been documented elsewhere (Mafongoyaet al., 2006; Akinnifesi et al., 2010).

Processes

Who developed the technological orinstitutional innovation?Diagnostic research identified the key obstacles toagricultural production and farming systems in theregion. In particular, nitrogen was identified as the

most important missing nutrient and this lack of nitro-gen is responsible for low yields of maize, the stapleand politically strategic food crop in the region.Given that farmers in the region do not traditionallyplant trees to improve soil fertility, an ethno-botanicalsurvey was carried out to establish an inventory ofindigenous tree species that grow quickly to amasssufficient biomass, tolerate periodic droughts orwaterlogging and survive under nitrogen-limitingconditions. The initial attempts to fertilize soilsusing trees through the alley cropping techniquewere discontinued because the technology did nottechnically fit in parts of the region (Ong, 1994).Efforts were then directed to research on improvedtree fallows and modification of the alley croppingconcept to improve the performance of nitrogen-fixing trees in a semi-permanent intercroppingsystem. Research on FTS was initiated in the late1980s through the collaboration of researchers fromthe World Agroforestry Centre (ICRAF) and nationalagricultural and forestry institutions in four southernAfrican countries: Malawi, Tanzania, Zambia andZimbabwe. Improved (sequential) fallows weredeveloped and first tested in Zambia (Kwesiga andCoe, 1994). Annual relay fallows and Gliricidia–maize intercropping were both developed and werefirst tested on-station and on-farm in southernMalawi (Akinnifesi et al., 2008).

FTS on-station experiments conducted in the early1990s showed promising results of increasing cropyield through Sesbania sesban with or without the appli-cation of mineral fertilizers (Kwesiga and Coe, 1994).To avoid the potential genetic risk associated withusing only one plant species and to diversify optionsto meet the preference of different typologies of house-holds, other plant species and provenances were evalu-ated alongside Sesbania. These include Cajanus cajan,Tephrosia vogelii and Tephrosia candida, which aredirectly sown and hence save labour inputs on nurseryestablishment and transplanting. The others are Glirici-dia sepium, Leucaena spp., Calliandra calothyrsus andAcacia spp. The work on a tree–crop intercrop systemusing G. sepium was developed by ICRAF in southernMalawi to address small landholding size (Akinnifesiet al., 2010). It is a modification to address key short-comings that affected crop performance, includingeliminating the ‘hedge competition effect’. It allowsconcurrent cultivation of trees with crops during farmseasons and fallow during off-season up to 20 yearswithout replanting (Akinnifesi et al., 2008). It is cur-rently the fertilizer tree species most preferred by small-holder farmers in Malawi.

O. C. Ajayi et al.130

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What partnerships helped?The development of FTS was based on multi-institutional and cross-disciplinary partnership andcollaboration between researchers and farmers. Overtime, researchers placed increasing emphasis ontesting FTS under the realities of farmers’ fields andincreasing the involvement of farmers as key partnersto refine and develop the technology further.Researchers began to test the technologies on-farmand involve farmers as partners in the process insouthern Africa in the late 1980s. The first set ofon-farm testing was designed and wholly managedby researchers (Type 1 trials). The second stage ofon-farm testing of FTS was designed by researchersbut managed by farmers (Type 2 trials). In the thirdstage, on-farm testing was wholly designed andfully managed by farmers (Type 3 trials).

At national and sub-national levels, two major part-nerships were formed in the course of development ofthe technology. One was the ‘adaptive participatorytrial’, which focused primarily on ensuring collabor-ation with farmers in on-farm trials of FTS. Theother partnership was a network of key stakeholdersinvolved in FTS drawn from government and non-government institutions. These were christened as‘Consultative Forum on Agroforestry’ in Zambia,‘National Agroforestry Research and DevelopmentForum’ in Malawi and ‘National Agroforestry Steer-ing Committee’ in Tanzania and Zimbabwe.Members of the network met once a year to reviewactivities from the preceding year, share researchresults and experiences regarding field performancesof FTS, and plan for the coming year.

More recently, through the Agroforestry FoodSecurity Programme (AFSP) currently beingimplemented in Malawi, ICRAF has been scaling upthe testing and dissemination of fertilizer trees withmore than 20 Research for Development stakeholdersin Malawi since 2007. In this scaling-up approach,stakeholders undertake annual joint planning andbudgeting and implementation in 13 agricultural dis-tricts. ICRAF provides research and science backstop-ping, training and information, and ensures qualitygermplasm provision.

To what extent was social capitaldevelopment a part of the project?Following one cycle of researcher-managed exper-imentation, a constructivist approach was adopted,that is, farmers were encouraged to experiment andshare their experiences with the technology. Muchof the training and planning took place through

farmer groups, which were important for colla-borative nursery management. From research andfarmer findings, it became apparent that efforts mustbe focused on shortening fallow period, identifyingcheaper methods of plant establishment and encoura-ging wider farmer participation in technology devel-opment and adaptation. As a result, farmers madeseveral modifications and adaptations based on theirexperiences (Kwesiga et al., 2003; Akinnifesi et al.,2008), including

† intercropping maize with trees during the first yearof tree establishment to reduce the waiting periodbefore trees start to impact on soil fertility;

† using bare-rooted seedlings instead of the rec-ommended potted seedlings, to reduce labourinputs; and

† pruning Gliricidia simultaneously with weedingrather than performing these two operationsseparately.

The details of these innovations have been documen-ted elsewhere (Katanga et al., 2007). In addition, inrecent years, studies have been carried out to obtainsystematic feedback about FTS through a betterunderstanding of farmers’ knowledge, attitude andpractices on soil fertility FTS (Ajayi, 2007).

Outcomes

The number of farmers adoptingThe early years of the development of FTS weredevoted to technology generation, while adoptionand scaling up of the technology among farmerswere increasingly emphasized in recent years. In acontinent-wide survey carried out among a panelof science and development experts in Africa, FTSwere cited as an example of ‘successes in African agri-culture’ (Gabre-Madhin and Haggblade, 2004).

The end of the project report of Zambezi BasinAgroforestry Project revealed that about two-thirdsof the roughly 400,000 smallholder farmers hadadopted FTS in the five countries Malawi, Tanzania,Mozambique, Zambia and Zimbabwe. The Zambiadata are presented below as a case study as it dis-aggregated agroforestry adoption by gender and theextension approach used (Table 1). From only 12farmers who participated in the initial on-farmtesting in the early 1990s, the number of plantersof FTS increased steadily, especially from 2000onwards, to about 66,000 farmers in Zambia as at2006. (The initial research and development of FTS

Agricultural success from Southern Africa region 131


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were supported mainly by funding from the CanadianInternational Development Agency, RockefellerFoundation and Swedish International DevelopmentAgency.)

Being an incipient technology, efforts to enhancethe uptake of FTS have focused on some key areas:creating awareness about the technology, the trainingof farmers about integration and management of treeson farm and the development of sustainable germ-plasm supply systems. Several scaling-up approacheswere tested and a four-pronged scaling-up conceptwas developed. These dissemination prongs are (i)the direct training of farmer trainers by project staff;(ii) the training of partner staff as farmer trainers;(iii) facilitating direct farmer-to-farmer training and(iv) providing support to national extension pro-grammes. Experiences in Zambia indicate that themost cost-effective way to reach farmers wasthrough the training of staff of development organiz-ations, that is, prong 2. Based on the training of trai-ners principle, the prong facilitates the provision ofappropriate information about the technologies tofield staff of development organizations, who in turnproceed to train farmers in their respective projectlocations. This approach builds on the comparativeadvantage of the various organizations and enhancessynergy among them. Almost two-thirds of thefarmers who planted agroforestry trees were reachedthrough this approach (Table 1). With the onset oftime, support to national extension systems and

sensitizing the policy makers are becoming increas-ingly important in the dissemination of FTS, asscaling-up efforts move from the local to the nationallevel.

Not all the farmers who tested FTS eventuallyadopted it. The responses are mixed depending onregion. Empirical research in Zambia found that 75per cent of farmers who initially tested the technologyeventually adopted it (Keil et al., 2005). But inWestern Kenya, where improved fallows were lesssuited to the small farms, studies showed that manyfarmers dropped out after withdrawal of a majorproject (Kiptot et al., 2007).

In Malawi, rather than improved fallows, emphasishas been on relay and intercrop FTS due to small farmsizes. The number of farmers who have establishedFTS plots has increased because of a number ofinitiatives carried out to promote the technology. Itis estimated that currently over 145,000 farmershave established FTS plots in Malawi through theongoing AFSP (Table 2). With explicit but modestefforts, scaling-up approaches have been used toreach female farmers and assist them to benefit fromfertilizer trees in the country.

The number of hectares covered by newtechnologies or practicesIn addition to increases in the number of farmers prac-tising fertilizer trees, the field measurement carriedout in 2003 in eastern Zambia showed that theaverage size of plots has also increased from anaverage 0.07ha recorded in the mid-1990s to 0.20haper farmer in 2003 (the field size ranges widelyfrom 0.01 to 0.78ha in 2003). This translates toabout 13,300ha in Zambia alone.

Table 1 | Approach for reaching farmers withagroforestry technologies in Zambia

Training methods used todisseminate agroforestry

Male Female Total

Prong 1: Direct training offarmer trainers and localchange teams

7,373 8,773 16,146

Prong 2: Training ofcollaborating partnerinstitutions’ staff, that is,training of trainers

23,532 16,190 39,722

Prong 4: Support to thenational extension systemto promote agroforestry

7,446 3,165 10,611

Total 38,351 28,128 66,479

Note: The figure for farmers reached through Prong 3 (which involved

farmer-to-farmer exchange) was not assessed.

Source: Zambia ICRAF Agroforestry Project report for 2005, Chipata,

Zambia.

Table 2 | The number of farmers who establishedongoing FTS plots through AFSP in Malawi

Region of Malawi Male Female Total

Northern region 15,206 17,409 32,615

Central region 26,945 27,712 54,657

Southern region 28,628 30,917 59,545

Total 70,779 76,038 146,817

Note: The figures reported in this table are exclusively farmers that were

reached under the auspices of the AFSP funded by Irish Aid. Beyond

this figure, many more farmers have been reached through other

initiatives such as the Malawi Agroforestry Extension Programme,

Total Land Care Programme and other organizations.

Source: AFSP annual report, 2010.



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Predicted trends for both farmers andhectares into the futureSeveral factors affect the level of uptake of fertilizertrees. A recent review showed that the adoption of fer-tilizer trees in southern Africa is affected by a matrixof factors (Ajayi et al., 2007a). These factors, whichwill determine the future trend of hectares under agro-forestry, may be classified into four broad categories:(i) the prevailing policy such as the price of nutrientsand other farm inputs and outputs; (ii) technology-specific factors such as management regime requiredto integrate trees and crops in the same field, theperiod of time trees take to produce a noticeableeffect on biomass and crop yield; (iii) household-specific factors such as the effective number ofpeople available for farm work in the household, thetrend of landholding size per capita; and (iv)geo-spatial factors such as future trend of climateand soil conditions that support tree establishment.

Effects on food production or productivity(either yields or total production)?Fertilizer trees have been widely documentedand known to substantially increase the yield ofmaize compared with continuous maize productionwithout fertilizer, which is de facto farmers’ practice.A recent meta-analysis conducted across severalregions in Africa found that FTS doubled yields ofmaize relative to the control (maize without fertilizer)in most cases, especially in sites with low-to-mediumpotential and under good management (Sileshi et al.,2008). The analysis also suggests that organic inputsfrom legumes have synergetic effects with mineralfertilizer and that legume rotations can play an impor-tant role in raising crop productivity without relyingfully on expensive mineral fertilizers. One way toassess the impact of the higher yield in terms offood security is by determining the number ofadditional days of food provided. Using Zambia asan example, with an average tree plot area of0.20ha, FTS generate between 57 and 114 extraperson days of maize consumption per year (Ajayiet al., 2007b). A multi-country study conductedamong households in Malawi, Mozambique, Tanza-nia, Zambia and Zimbabwe shows that FTS have posi-tive impacts on household food security among otherimpacts (Schuller et al., 2005). Details are presentedin Table 3.

In terms of economic performance, field studiesperformed in Zambia show that FTS perform muchbetter than continuous maize production withoutfertilizer (Franzel et al., 2002; Franzel, 2004; Ajayi

et al., 2007, 2009). Over a five-year cycle, the netprofit from unfertilized maize was US$130 perhectare compared to US$269 and US$309 formaize grown with Gliricidia or Sesbania, respect-ively. With respect to returns per investment, FTSperformed better with a benefit-to-cost ratioranging between 2.77 and 3.13 in contrast to 2.65in (subsidized) fertilizer fields, 1.77 in (non-subsidized) fertilizer fields and 2.01 in non-fertilizedfields (Ajayi et al., 2009).

Effects on environmental services (e.g.standing and soil carbon, biodiversity, waterand soils)Fertilizer trees improve soil physical propertiesthrough the addition of litter fall, root biomass, rootactivity, biological activities, and roots leaving macro-pores in the soil following their decomposition. Thetrees also improve soil aggregation, thereby enhan-cing water filtration (Chirwa et al., 2007), whichreduces water runoff and soil erosion relative to pro-duction systems where maize was continuously culti-vated without planting trees (Phiri et al., 2003).

Table 3 | Qualitative assessment of the impact ofagroforestry adoption on livelihoods of farmers insouthern Africa

Impact indicator Proportion of householdsinterviewed (%)

Malawi(n 5 31)

Zambia(n 5 184)

Mozambique(n 5 57)

Increase in areaunder agroforestry

55 87 65

Increase in maizeyield (quarter todouble)

70 90 71

Improvement infood security(greater than twomonths of hungerreduction)

94 84 54

Increase in income 58 68 53

Increase in savings 87 94 71

Increase in wealth 77 84 77

Strong reductionin Striga spp.

90 93 88

Soil improvement 84 82 59

Source: Schuller et al. (2005).



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Improved tree fallows enhance soil biodiversity byincreasing soil invertebrates, which perform impor-tant ecosystem functions that can affect plantgrowth. A long-term study concluded that the technol-ogy also has a positive impact on biodiversity,enhances the ecosystem services rendered by soilinvertebrates (Sileshi and Mafongoya, 2006), sup-presses weeds (Sileshi et al., 2006) and sequesterscarbon (Makumba et al., 2007).

Organic inputs from tree legumes can supplyenough nitrogen for crops but may not supply suffi-cient phosphorus and potassium to support cropyields over time. An eight-year nutrient balance trialconducted showed that unfertilized maize had thelowest N and P balances even though maize grainand stubble yields were very low over time(Mafongoya et al., 2005). The tree-based fallows hada positive nitrogen balance due to biological nitrogenfixation and capture of nitrogen from depth, but thenitrogen balance became very small in the secondyear of cropping. Most of the maize productionsystems showed a positive phosphorus balance due tolow uptake of phosphorus in maize grain yield andstubble (relative to nitrogen), and increased mycorrhi-zal populations in the soil. Most maize productionsystems showed a negative balance for potassium.The largest negative potassium balance was obtainedin fully fertilized maize fields due to higher maizeand stubble yields, which extract a lot of potassium(Table 4). Similarly, soil pH was lower in continuouslycropped, fully fertilized maize compared with maizegrown in FTS in eastern Zambia (Chintu et al., 2004)and Malawi (Akinnifesi et al., 2007). This is in agree-ment with reports from elsewhere that show that appli-cation of organic residues can mitigate soil acidity tosome extent (Haynes and Mokolobate, 2001),especially due to nutrient recycling from deeper soillayers by tree roots (Akinnifesi et al., 2004). Neverthe-less, the long-term impact of biological nitrogen

fixation and net crop export on the soil resource is animportant area that requires further research.

Social outcomes – who are the keybeneficiaries? Who are the losers?Studies from Zambia found that wealthier farmers weremore likely to test the technology, but less likely to con-tinue with FTS compared with other social groups (Keilet al., 2005) because poorer farmers are less able to pur-chase fertilizer. Whether this pattern continues now thatfertilizer prices are partly subsidized has not yet beenstudied. Several studies (e.g. Gladwin et al., 2002;Keil et al., 2005) found no significant differencesbetween the proportions of female- and male-headedhouseholds planting improved tree fallows. Otherstudies found that men in the region control manyhousehold decisions including those involving cashtransactions and hence, although women may beusing the technology as commonly as men, they maynot be benefiting from it as much.

Another social outcome of FTS is that with theestablishment of trees, fields that hitherto were‘common property’ on which livestock may freelygraze have become more privatized even duringthe dry season. This sometimes leads to conflictsbecause it limits fodder availability for livestock orresults in extra labour being deployed in herdinganimals. This has triggered changes in traditional cus-tomary practices on livestock rearing and use of bushfires to hunt for mice (local delicacies) during the dryseason. Details of these social impacts have beendescribed elsewhere (Ajayi and Kwesiga, 2003).

How could the technology or practicebe spread to other agro-ecological zones orcountries?Given the increasing awareness at national and inter-national levels of the need to maintain the agriculturalresource base in food production strategies, there are

Table 4 | Nutrient budgets for different maize production systems in two-year fallows (0–60cm of soil)

Land-use system Nitrogen Phosphorus Potassium

1998 1999 2002 1998 1999 2002 1998 1999 2002

Cajanus fallow 44 17 84 21 8 33 37 9 27

Sesbania fallow 47 19 110 39 24 32 220 225 220

Fertilized maize 70 54 48 14 12 12 256 252 265

Unfertilized maize 220 217 222 22 21 22 231 230 238

Source: Mafongoya et al. (2005).



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good prospects for spreading fertilizer trees to otherzones. FTS do not perform equally well in alleco-regions and different types are more appropriatefor different household conditions. Specific fertilizertrees should be targeted to their biophysical niches(to ensure that they perform well in the field) andtheir socio-cultural niches (to ensure that resourcesare committed to disseminating technologies that aremost relevant to the needs of farmers and can makethe greatest impacts in given locations). Due to theimportant influence of policies on farmers’ adoptionof the technology, a scaling-up strategy shouldcombine farmer training and dissemination activitiesat the farm level with active engagement with policymakers. Local and national policy-making processesneed to institutionalize sustainable agricultural pro-duction (e.g. through specific policy documentsand budgetary allocations, and implementation ofvarious governmental declarations on sustainableagricultural production systems).

The well-documented synergy between fertilizertrees and mineral fertilizer should be emphasizedrather than focusing on ‘organic vs. inorganic’

debates. Indeed, there is a need for African farmersto increase the use of a range of soil fertility manage-ment practices. There is also a need to expand the useof FTS on high-value crops as most research carriedout on the technology to date has focused almostexclusively on maize.

Conclusion

Experiences with FTS in southern Africa demonstratethat inexpensive technologies are available to signifi-cantly raise crop yields, reduce food insecurity andenhance environmental services in ways that helpensure the long-term productive capacity of thesoils. Hundreds of thousands of poor farmers are cur-rently using the technologies in Malawi and Zambia.The key obstacles to its wider use, which is thesame that confronts other agricultural technologies(e.g. improved seed and fertilizer), include policyand institutional changes and the generally lowreturns on investments in rainfed smallholder agricul-ture in sub-Saharan Africa.

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