Coffee farming and soil management in Rwanda
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Coffee farming and soil management in Rwanda Innocent Nzeyimana, Alfred E. Hartemink and Jan de Graaff Abstract: Agriculture is the cornerstone of Rwanda’s economy. The authors review how the sector has changed and specifically what soil management practices are now being implemented to enhance coffee production. Coffee covers around 2.3% of total cultivated arable land, and is grown mainly by smallholder farmers on plots of less than one hectare. Rwanda produces high-quality speciality or fully washed coffee, which is intercropped with annual crops due to land scarcity to enable farmers to achieve a better combination of food and cash crops. Most of the agricultural soils have a pH of < 5.2 and are highly deficient in phosphorus. Reduced land fragmentation, increased organic and inorganic fertilizer applications and mulching are all needed to boost yields. These practices will also help to improve the soils’ chemical and physical properties and control erosion on the steep cultivated slopes. Keywords: coffee; soil fertility; mulching; erosion; soil conservation; inorganic fertilizers Innocent Nzeyimana (corresponding author) is with the Soil Science Centre, Land Degradation and Development Group, Wageningen University, The Netherlands, and the Faculty of Agriculture, National University of Rwanda, PO Box 56, Butare, Rwanda. E-mail: inzeyimana@nur.ac.rw. Alfred E. Hartemink is with the University of Wisconsin – Madison, Department of Soil Science, F.D. Hole Soils Lab, 1525 Observatory Drive, Madison, WI 53706, USA. E-mail: hartemink@wisc.edu. Jan de Graaff is with the Soil Science Centre, Land Degradation and Development Group, Wageningen University, PO Box 47, 6700 AA, The Netherlands. Coffee was introduced into Rwanda by German 26,000 ha, which then increased to 33,000 ha by 2010 missionaries in 1904 and was cultivated mainly for the (NBR, 2010). Most of the suitable land for coffee is located colonial administration. Production gradually increased on the borders of Lake Kivu (Figure 2). In 2010, coffee over time, reaching a peak in the mid-1980s. In 1987, production covered 2.3% of total cultivated land and 43,000 tons of semi-washed coffee was produced produced 19,320 tons (NAEB, 2011). The price of coffee (Figure 1). During subsequent years, production dropped cherries paid to farmers increased from RwF250 to 1,200 to an annual average of 26,000 tons, mainly due to ageing kg–1 between 2000 and 2010 (Figure 3). Rwanda used to coffee trees, a decline in soil fertility, low coffee prices to produce semi-washed or semi-processed and ordinary the farmers, and the 1994 genocide. coffee of low quality, which was then sold at a lower price From 2000, the Rwandan coffee sector started to receive than speciality coffee and was subject to less price increased interest internationally; thus, in 2002 the fluctuation. With low prices being paid for coffee, growers Government of Rwanda issued a National Coffee Strategy lacked the necessary finance to reinvest in farming to promote the cultivation and production of high-quality improvements. However, with the implementation of a coffee. Between 2002 and 2011, production increased by new coffee strategy, the government started to promote 20%, but coffee exports increased by 150% (Figure 1) new higher-yielding varieties to increase production of (NAEB, 2011). Over the same period, coffee production higher-quality coffee. This then influenced the way the increases of 20% and 8% per year respectively were crop was cultivated, with changes in soil management reported in Vietnam and Brazil (D’Haeze et al, 2005). practices being critical in improving coffee production In 2005, the total extent of coffee production was about and quality. Outlook on AGRICULTURE Vol 42, No 1, 2013, pp 47–52 doi: 10.5367/oa.2013.0118 47
Coffee farming in Rwanda
50,000
Coffee production Coffee export value
70 production on these soils is limited by increasing
Coffee export value (US$ million)
45,000
60
depletion of N, P, Ca and Mg, high P adsorption (1,500 to
Coffee production (tons)
40,000
3,000 mg kg–1 of soil), low permanent charges (–0.5 to
35,000 50 –2.45 cmol+ kg–1) and Al toxicity. Generally, soil organic
30,000
30,000 40 carbon is low, with the exception of soils in the valley
25,000 swamps and forests where C concentrations may exceed
30
20,000 10%. Most volcanic soils and soils under natural forests
15,000 20 (for example, Nyungwe and Gishwati forests) are high in
10,000
10 N; soils with N deficiency are mostly found in the central
5,000 and southern parts of the country. Phosphorus is the main
0 0
element that limits crop yield in most soils, but
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particularly in the soils derived from volcanic deposits.
About 87% of soils have a pH < 5.2 and are P-deficient
Figure 1. Coffee production and export value in Rwanda between (P < 30 mg kg-1 of soil) (Mukuralinda, 2007).
1980 and 2010. Soils under coffee farming systems are characterized by
Source: NAEB, 2011. very low pH values (< 5.0) with high soil aluminium
toxicity (> 30%), very low Ca (< 30%), Mg (< 10%),
N (< 0.16%), P (< 20 ppm), K (< 5.8%), S (< 20 ppm),
Zn (< 1 ppm) and Bo (< 0.8 ppm) (Cordingley, 2009). A
Soils and soil fertility high aluminium toxicity level reduces root development
In Rwanda, there is a reasonable body of existing and limits crop yield through reduced nutrient and water
knowledge on soil and soil fertility (Mbonigaba et al, uptake. Calcium and magnesium deficiencies are common
2009). Soils in Rwanda are mainly derived from in most coffee farming systems throughout the country
Precambrian and Quaternary parent materials. Plinthite due to high aluminium toxicity in acid soils. Moreover,
and ironstone are found in the strongly weathered soils of removal of crop residues after harvest is a common
the eastern part of the country. About 75% of soils are farming practice and a major cause of nutrient loss. Crop
acidic, with a pH below 5.5 (Beenart, 1999). Soil acidity residues are mostly high in K and grains are high in P. By
includes high exchangeable aluminium (Al) and possible removing residues, K and P deficiencies gradually
Al toxicity for sensitive crops. Plant growth and develop (Yamoah et al, 1990).
Agroecological zone
Water bodies
National Parks
Kilometres
Figure 2. Spatial distribution of coffee trees in production zones and by agroecological zone in Rwanda.
Source: Data collected from the National Export Board (NAEB) using the 2005 database.
48 Outlook on AGRICULTURE Vol 42, No 1Coffee farming in Rwanda
Table 1. Average yield of mono- and intercropped coffee (tons of
1,400 300 green bean ha–1 yr–1) and banana (tons of fresh fruit ha–1 yr –1).
Price of cherries (RwF/kg)
1,200 250 Cropping system Yield
Dry coffee
1,000 Arabica coffee Banana
200
Parchment
800 Coffee monocrops 1.23 ± 0.88a –
150 Coffee–banana intercrops 1.18 ± 0.99a 20.19 ± 10.25a
600
Banana monocrops – 14.82 ± 8.10ba
100
400
Note: For each parameter, values in the same column with the
200 50 same letter are not statistically different.
Source: After Van Asten et al, 2011.
0 0
1995 1998 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Figure 3. Price of parchment coffee and cherries to the farmer in used in Rwanda, in contrast to Uganda and Kenya where
Rwanda between 1995 and 2010.
it is a primary food and cash crop. Banana interplanted
Notes: Cherries are fresh coffee with the outer red pulp, while
parchments are coffee beans from which the outer pulp has been with coffee has been reported to increase coffee yields,
removed using a pulping machine. with no significant yield differences between
RwF = Rwandan francs. monocropped and coffee–banana intercropping systems
Source: NAEB, 2011. (Van Asten et al, 2011) (Table 1).
Rwandan coffee is mainly cultivated without shade, in
contrast to other regions, notably in Central America (Van
Oijen et al, 2010). Coffee production without shade can be
as high as in shaded systems, provided inorganic
Coffee farming systems fertilizers are applied (De Souza et al, 2012). In Mexico,
Coffee is grown mainly by smallholders, with farming small-scale coffee farmers prefer the shade system because
systems characterized by land fragmentation and many it also provides them with timber, firewood and fruit
small plots scattered on hillsides. Depending on the (Peeters et al, 2003). It is often assumed that a coffee tree-
number of trees per plot, farmers generally own between shade system is beneficial ecologically as well as
two and six plots. The scattered plots and the distance economically (Borkhataria et al, 2012). However, a
from home to the plots reduce the frequency of plant and significant decrease in coffee yield has been reported in a
land management practices. The Ministry of Agriculture high shade-tree density. Shade may be beneficial to reduce
and Animal Resources is implementing a land extremes in temperatures and rainfall and regulate fruit
consolidation policy to reorganize land use patterns. bearing, but in general it gives lower yields (De Graaff,
Although coffee farmers are encouraged to adopt a 1986). Coffee without shade trees produces higher yields
monoculture farming system, intercropping is mostly only if land and crop management systems, varieties,
used because of land scarcity and land pressure. A coffee altitude and climatic conditions are considered. Unshaded
field often contains food and cash crops such as banana, coffee is more susceptible to failing harvests.
sweet potato, taro, cassava, yam, beans, cowpea and horse
grams. Cultivation of these crops between rows of coffee
plants enables farmers to achieve a better combination of
Soil fertility management
food and cash crops. However, it also results in
competition for water, nutrients and light, leading to Mulching
reduced coffee growth and low coffee yields. Mulches used in coffee farming include Eucalyptus
In Burundi, Uganda, Tanzania, western Kenya and the branches, Grevillea branches, sorghum thatches, Panicum
eastern Democratic Republic of Congo (DRC), coffee is spp., Cymbopogon spp., sugar cane leaves, banana leaves
sometimes grown in association with agroforestry (AF) and mixed residues. Looking at the steep landscape of the
tree species. The AF species for coffee include Leucaena country, mulching is adopted in coffee farming to protect
leucocephala, Calliandra calothyrsus, Tephrosia vogerii and the soil surface from the kinetic energy of the raindrops.
banana (Boffa et al, 2009). The N-fixing trees that are Furthermore, mulching is usually used as a soil
intercropped with coffee are pruned regularly to moderate conservation measure. According to Romero et al (2002),
the shade levels and maintain adequate coffee the increased nutrient concentrations in soils with
productivity. The use of N-fixing trees can also increase mulches occur through direct leaching or decomposition.
litter decomposition and N availability and may increase N and K can be provided to the soil directly by mulching
soil organic matter through tree biomass, which helps to and/or organic fertilization. About 10 to 25 tons of mulch
stabilize soils against erosion, reduce soil disturbance and per ha (a layer of ± 10 cm) can be used in coffee farming
improve soil chemical and physical properties (Mulumba to provide 110 kg of N, 1,200 kg of K, 18 kg of Ca and
and Lal, 2007). As many of the soils used for coffee in 30 kg of Mg per ha, depending on the type of mulch
Rwanda are characterized by N deficiency and high Al (Coste, 1989). Foshee et al (1999) reported that straw
toxicity, farmers could benefit by adopting agroforestry mulch markedly increased K concentrations in tree
coffee farming systems to improve coffee productivity. farming. Hay mulch used as ground cover in orchards
Banana as a shade tree in coffee farming is not widely increased topsoil nitrate (NO3), K and Mg concentrations
Outlook on AGRICULTURE Vol 42, No 1 49Coffee farming in Rwanda
(Merwin et al, 1995). The application of mulch in coffee Measurements on run-off plots have shown that sheet and
farming systems increases the content of soil organic rill erosion can reach 300 to 700 tons ha–1 yr–1 on 20 to 60%
matter and soil aggregate stability. Mulch availability is slopes with the regional rainfall erosivity factor (R)
limited, but improvements in coffee production have been varying between 250 and 700, and the soil erodibility
reported when applying it. Most farmers know about the factor (K) varying between 0.001 and 0.20 (Roose and
benefits of applying mulch, but apply low quantities Ndayizigiye, 1997). These values are very high and are
because of cost and labour constraints. found in fields without soil conservation techniques such
as mulching and/or terracing.
Organic and chemical fertilizers With little natural mulch formed by litter, considerable
Both organic and chemical fertilizers are used in coffee soil erosion losses have been observed in coffee
farming; organic fertilizers are usually prepared by plantations (Hartemink, 2005). Ataroff and Monasterio
mixing grasses, crop residues and/or animal manure in (1997) reported larger soil erosion losses in unshaded
compost. Inorganic fertilizers include NPK (20-10-10) coffee plantations (1.57 tons ha–1 yr–1) compared with
applied at 400 g per tree per year, or NPK (17-17-17) at shaded coffee (0.73 t ha–1 yr–1). Studies in Colombia,
120 g per tree per year, plus urea (46% of N) at 75 g per Venezuela and Indonesia on run-off plots measured soil
tree per year. These are applied in two doses (March and losses ranging from 0.2 to 8.9 t ha–1yr–1 in established
September) and at half the dose to reduce the potential for coffee plantations (Iijima et al, 2003). Assuming a crop
leaching loss (Minagri, 2010). factor (C = 0.415 for coffee) and using the USLE model,
Depending on the coffee variety (Mibilizi, Catuai, Angima et al (2003) reported soil losses of 112 to 290 tons
Catimor, BM, Barrar, Jackson, Baraka), agroecological ha–1 yr–1 under coffee. These values are much lower
conditions and soil and plant management, coffee yields compared with the actual erosion rates in Rwanda.
can vary between 0.8 and 2.8 tons ha–1 of dry coffee beans Mulching significantly reduces soil erosion (Lewis, 1988).
(Loveridge and Nyarwaya, 2003). Yields above 2.8 t ha–1 In Rwanda, with 20 tons ha–1 yr–1 of mulch in coffee
for dry coffee are rare. In the western part of the plantations, erosion can be reduced to less than 1 ton ha–1
country, soils are highly suitable for coffee and yields vary yr–1 (Roose and Ndayizigiye, 1997).
between 1.1 and 1.6 tons ha –1. The central and southern Soil erosion also leads to nutrient loss. Table 2 indicates
areas are moderately suited, with yields varying between the nutrients lost in one production year from coffee
0.8 and 1.2 tons ha–1. Coffee yield in the eastern region is fields in Rwanda, assuming a soil erosion rate of 15 tons
low (average 1.0 t ha–1 y–1). Potassium deficiency impacts ha–1 yr–1. This will lead to a deficit of nutrients and
on coffee yield, especially berry size. Potassium deficiency decrease in yield. Soil erosion accounts for up to 50% of
is mainly observed in acidic soils developed on shale all nutrient losses (Stoorvogel and Smaling, 1990).
parent material (Cordingley, 2009). Nitrogen deficiency is Soil conservation includes erosion control measures
often observed on degraded and poorly managed soils. N (for example, bench terraces, sloping or progressive
deficiency in coffee farming has the largest influence on terraces, and ditches) and soil management such as
vegetative development, leading to reduced application of organic fertilizers (manure and compost),
photosynthetic potential (Cordingley, 2009). Phosphorus application of inorganic fertilizers, liming, mulching,
(P) is required in smaller amounts compared with N and agroforestry and crop rotations. The physical measures
K. Both P and K are required to stimulate coffee growth in include using trenches or ditches, progressive terraces
young trees. In mature trees, P is required to play a role in (PT) using grass or vegetation strips, soil bunds, bench or
flower development, and thus improve yield. Low levels radical terraces and narrow bench terraces. Radical/bench
of P can affect the size of coffee beans (Cordingley, 2009). terraces have been shown to improve water retention and
The use of fertilizers is not always effective when the soil nutrients and to increase yield (Fleskens, 2007).
soil is low in organic matter. In the southern part of However, farmers often mention the high labour cost
Rwanda on the gravelly Oxisols (low in organic matter required to maintain them (Bizoza and de Graaff, 2012).
content) the use of NPK (20-10-10) yielded around 0.32 kg
of dry beans per tree per year (0.8 ton ha–1) (Mukashema,
2003). Organic fertilizers are applied in order to increase
Discussion and conclusions
the physical properties of the soil and its nutrient-holding Coffee is important for the Rwandan economy and for the
capacity. On the very acid soils of Rwanda, Ca and Mg are livelihoods of its many farmers. Government policies have
added every three years by applying 1 kg of lime/ helped stimulate more efficient and higher-yielding coffee
travertine per tree to decrease soil acidity (Minagri, 2010). production. But these policies only become effective if soil
resources and management are taken into account.
Generally, coffee is cultivated as a pure-stand commercial
Soil erosion and soil conservation crop or monoculture farming. Intercropping is common
Rwanda has many high mountains and steep-sloped hills, because of limited cultivable land for annual cropping.
with much of the farmland suffering from moderate to Coffee intercropping with food crops can increase
severe soil erosion. Maximum soil loss has been estimated competition for nutrients, light and water, and thus affects
at 557 tons ha–1 yr–1 (Republic of Rwanda, 2003). In the yield. Although intercropping practices do not leave the
southern province of Butare, on a 28% to 55% slope where soil surface bare, they may contribute to controlling
traditional agricultural practices were used, soil losses erosion, mainly for coffee cultivated on marginal land
were reported to be about 250 tons ha –1 yr–1 (König, 1992). such as steep slopes of upper hillsides. Crop residues that
Lewis and Nyamulinda (1996) reported values of up to are removed, together with coffee litter, can be used as a
270 tons ha –1 yr–1 on a 60% slope without any vegetation. mulch to control water erosion, but also to improve the
50 Outlook on AGRICULTURE Vol 42, No 1Coffee farming in Rwanda
Table 2. N, P2O5 and K2O balance in two different settings in Rwanda.
Deposition Fixation Production Residues Leaching Gaseous losses Erosion Total
(+) (+) (–) (–) (–) (–) (–) (kg/ha)
1 (N)* 4 2 28 0 2 7 5 –36
2 (N)* 5 5 28 1 4 14 30 –67
1 (P 2O5) 2 0 5 1 0 0 2 –6
2 (P 2O5) 2 0 5 1 0 0 11 –15
1 (K2O) 3 0 16 1 1 0 4 –19
2 (K 2O) 4 0 16 2 6 0 23 –43
Note: 1 = no fertilizer, no manure, residue removal of 10% and erosion of 5 tons ha –1 yr –1; 2 = no fertilizer, no manure, residue removal of
20% and erosion of 15 tons ha–1 yr–1.
Source: Stoorvogel and Smaling, 1990.
soil physical and chemical properties. In addition, to References
control water erosion, coffee farmers use various manage-
ment practices, including mechanical man-made trenches, Angima, A.D., Stott, D.E., O’Nell, M.K., Ong, C.K., and Weesies,
hedgerows, mulching, or a combination of the mechanical G.A. (2003), ‘Soil erosion prediction using RUSLE for central
and biological methods. Mulching remains the dominant Kenyan Highland conditions’, Agriculture, Ecosystems and
Environment, Vol 97, pp 295–308.
management practice to control erosion and weeds. In Ataroff, M., and Monasterio, M. (1997), ‘Soil erosion under
addition to the use of sustainable land management different management of coffee plantations in the Venezuelan
technologies, considerable focus should be directed Andes’, Soil Technology, Vol 11, No 1, pp 95–108.
towards farmers’ training and awareness raising through Beenart, F.R. (1999), Feasibility Study of Production of Lime and/or
participatory extension methods, such as farmer field Ground Travertine for the Management of Acid Soils in Rwanda,
schools (FFS). Pro-Inter Project Consultants, Brussels.
Bizoza, A.R., and de Graaff, J. (2012), ‘Financial cost–benefit
Organic fertilization (with manure, composted coffee
analysis of bench terraces in Rwanda’, Land Degradation and
pulp and lime) should be promoted on a large scale as this Development, Vol 23, No 2, pp 103–115.
is at the heart of sustainable soil management. Such Boffa, J.M., Turyomurugyendo, L., Barnekow-Lilleso, J.P., and
applications can help maintain and build soil carbon Kindt, R. (2009), ‘Enhancing farm tree diversity as a means of
levels and supply nutrients in a well balanced ratio. conserving landscape-based biodiversity’, Mountain Research
Liming will ensure that the soil pH is within the optimum and Development, Vol 25, pp 212–217.
Borkhataria, R., Collazo, J.A., and Groom, M.J. (2012), ‘Species
range for soil microbial activity, which will correct the
abundance and potential biological control services in shade vs.
high aluminium toxicity and thus improve the efficiency sun coffee in Puerto Rico’, Agriculture, Ecosystems and
of nutrient uptake. In most Rwandan soils, a supply of Environment, Vol 151, pp 1–5.
50–60% Ca and 10–16% Mg is recommended to stimulate Cordingley, J. (2009), Soil Fertility Survey of Rwandan Coffee Sector,
soil biological activity (Cordingley, 2009). The adoption of Crop Nutrition Laboratory Services, Nairobi.
organic and liming applications could reduce the input of Coste, R. (1989), Caféier et Cafés. Techniques et productions tropicales,
mineral fertilizers required to achieve higher coffee yields. Editions Maisonneuve et Larose, Paris.
de Graaff, J. (1986), ‘The economics of coffee’, Economics of Crops
In order to promote organic fertilizer use, the in Developing Countries, Pudoc, Wageningen.
government has invested in the sensitization and De Souza, H.N., De Goede, R.G.M., Brussaard, L., Cardoso, I.M.,
mobilization of farmers. In 2011, 3,055 tons of organic Duarte, E.M.G., Fernandes, R.B.A., Gomes, L.C., and Pulleman,
fertilizers were applied to 11,000 ha of coffee (Minagri, M.M. (2012), ‘Protective shade, tree diversity and soil proper-
2012). The application of mineral fertilizers in coffee ties in coffee agroforestry systems in the Atlantic rainforest
farming is practised, but a lack of sufficient farmer biome’, Agriculture, Ecosystems and Environment, Vol 146,
pp 179–196.
awareness of the value of applying mineral fertilizers
D’Haeze, D., Deckers, J., Raes, D., Phong, T.A., and Loi, H.V.
limits coffee productivity. NPK fertilizer is widely used at (2005), ‘Environmental and socio-economic impacts of
the 20-10-10 ratio, but it is essential to apply fertilizers institutional reforms on the agricultural sector of Vietnam:
closer to a 1:1 ratio for N:K in soils with a low K content land suitability assessment for Robusta coffee in the Dak Gan
(Cordingley, 2009). In 2012, the government targeted 4,000 region’, Agriculture, Ecosystems and Environment, Vol 105,
tons of mineral fertilizers at 35,000 ha of planted coffee, pp 59–76.
Fleskens, L. (2007), Prioritizing Rural Public Works Interventions in
with an investment cost of US$2.9 million (NAEB, 2012).
Support of Agricultural Intensification, Report for IFDC and
This investment cost could only be recovered if current Helpage, Kigali.
coffee productivity increased to 7.5 tons ha–1 (NAEB, Foshee, W.G., Goff, W.D., Patterson, M.G., Tilt, K.M., Dozier,
2012). W.A., Tucker, L.S., and Bannon, J.S. (1999), ‘Organic mulches
Finally, the government is also encouraging farmers to affect soil and leaf nutrient levels of young pecan trees’, Journal
join the land consolidation programme, whereby coffee of Arboriculture, Vol 25, No 2.
can even be cultivated as ‘Ibiterane’, meaning larger coffee Hartemink, A.E. (2005), ‘Plantation agriculture in the tropics:
environmental issues’, Outlook on Agriculture, Vol 34, No 1,
plantations. This programme aims to aggregate pp 11–21.
smalholder farms into larger landholding units to make Iijima, M., Izumi, Y., Yuliadi, E., Sunyoto, A., and Utomo, M.
them more suited to monoculture farming. (2003), ‘Erosion control on a steep sloped coffee field in
Outlook on AGRICULTURE Vol 42, No 1 51Coffee farming in Rwanda Indonesia with alley cropping, intercropped vegetables, and NBR (2010), Rwanda Export Statistics Report, National Bank of no-tillage’, Plant Production Science, Vol 6, No 3, pp 224–229. Rwanda, Minecofin, Kigali. König, D. (1992), ‘The potential of agroforestry methods for NAEB (2011), Annual Report 2010, National Agricultural and erosion control in Rwanda’, Soil Technology, Vol 5, pp 167–176. Export Board, Republic of Rwanda, Minagri, Kigali. Lewis, L.A. (1988), ‘Measurement and assessment of soil loss in NAEB (2012), Action Plan for 2012–2013 Fiscal Year, National Rwanda’, Catena Supplement, Vol 12, pp 151–165. Agricultural and Export Board, Republic of Rwanda, Minagri, Lewis, L.A., and Nyamulinda, V. (1996), ‘The critical role of Kigali. human activities in land degradation in Rwanda’, Land Peeters, L.Y.K., Soto-Pinto, L., Perales, H., Montoya, G., and Degradation and Development, Vol 7, pp 47–55. Ishiki, M. (2003), ‘Coffee production, timber, and firewood in Loveridge, S., and Nyarwaya, J.B. (2003), ‘Decaffeinated? traditional and Inga-shaded plantations in Southern Situation, trends and prospects for smallholder coffee Mexico’, Agriculture, Ecosystems and Environment, Vol 95, production in Rwanda – analysis of a rural household survey – pp 481–493. 2002’, in Ministry of Agriculture, ed, Research Report, Policy Republic of Rwanda (2003), National Strategy and Action Plan for Synthesis, Food Security Research Project (FSRP) & Division of the Conservation of Biodiversity in Rwanda, Minitere, Kigali. Agricultural Statistics (DSA), Republic of Rwanda, Kigali, pp 9– Romero, Y.A., Pinto, L.S., García-Barrios, L., and Barrera-Gaytán, 81. J.F. (2002), ‘Coffee yields and soil nutrients under the shades of Mbonigaba, J.J., Nzeyimana, I., Bucagu, C., and Culot, M. (2009), Inga sp. vs. multiple species in Chiapas, Mexico’, Agroforestry ‘Caractérisation physique, chimique et microbiologique de trois Systems, Vol 54, pp 215–224. sols acides tropicaux du Rwanda sous jachères naturelles et Roose, E., and Ndayizigiye, F. (1997), ‘Agroforestry, water and contraintes à leur productivité’, Biotechnologie, Agronomie, soil fertility management to fight erosion in tropical mountains Société et Environnement, Vol 13, No 4, pp 545–558. of Rwanda’, Soil Technology, Vol 11, No 1, pp 109–119. Merwin, I.A., Rosenberger, D.A., Engle, C.A., Rist, D.L., and Stoorvogel, J.J., and Smaling, E.M. (1990), Assessment of Soil Fargione, M. (1995), ‘Comparing mulches, herbicides, and Nutrient Depletion in Sub-Sahara Africa, Report No 28, Winand cultivation as orchard groundcover management systems’, Staring Centre, Wageningen. Horticulture Technology, Vol 5, pp 151–158. Van Asten, P.J.A., Wairegi, L.W.I., Mukasa, D., and Uringi, N.O. Minagri (2010), ‘Agenda Agricole du Rwanda’, Minagri, Kigali. (2011), ‘Agronomic and economic benefits of coffee–banana Minagri (2012), Annual Report 2011, Minagri, Kigali. intercropping in Uganda’s smallholder farming systems’, Mukashema, A. (2003), Evaluation de la fertilité des sols et son impact Agricultural Systems, Vol 104, pp 326–334. sur la production du caféier Arabica dans le district de Maraba. Van Oijen, M., Dauzat, J., Harmand, J.M., Gerry, L., and Vaast, P. Mémoire – Facagro, UNR, Butare. (2010), ‘Coffee agroforestry systems in Central America: II. Mukuralinda, A. (2007), ‘Influence of phosphorus resources on Development of a simple process-based model and soil phosphorus dynamics and crop productivity in Rwanda’, preliminary results’, Agroforestry Systems, Vol 80, pp 361–378. PhD thesis, Makerere University, Kampala. Yamoah, C.F., Burleigh, J.R., and Mayfield, R.M. (1990), Mulumba, L.N., and Lal, R. (2007), ‘Mulching effects on selected ‘Application of expert systems to study of acid soils in soil physical properties’, Soil and Tillage Research, Vol 98, No 1, Rwanda’, Agriculture, Ecosystems and Environment, Vol 30, pp 106–111. pp 203–218. 52 Outlook on AGRICULTURE Vol 42, No 1
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