An e-publication by the World Agroforestry Centre
AGROFORESTRY IN THE HIGHLANDS OF EASTERN AND CENTRAL AFRICA
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An e-publication by the World Agroforestry Centre |
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AGROFORESTRY IN THE HIGHLANDS OF EASTERN AND CENTRAL AFRICA
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4. SUMMARIES OF TECHNICAL PRESENTATIONS 4.3 Wood and fruit production Alnus acuminata: A promising agroforestry species Alnus acuminata has been included in several agroforestry trials in Uganda. Results from two sites and a total of seven cropping seasons indicate that Alnus when planted and managed as either a contour hedgerow or as an upperstorey tree may give rise to an increase in production of beans and maize. At Makerere University Agricultural Research Institute, Kabanyolo (1200 m above sea level) near Kampala, a recently terminated trial lasting four years afforded the opportunity to compare the effect of eight upperstorey trees (including Alnus acuminata, Casuarina equisetifolia, Cordia abyssinica, Cupressus lusitanica, Markhamia lutea and Melia azedarach, and two provenances of Maesopsis eminii) and a control on the production of beans and maize. In the three final years of this trial, maize production in adjacent rows of crop averaged 19.3% more in plots with Alnus than in the control plots 2 while bean yields averaged 17.6% more. All of the other seven upperstorey species exhibited varying degrees of suppression on the crop yields averaging 33.3% and 38.4% respectively, for maize and beans. In a second trial at the Kachwekano District Farm Institute (2000 m above sea level) near Kabale in southwest Uganda, Alnus acuminata, along with a number of other species: Calliandra calothyrsus, Flemingia macrophylla, Leucaena diversifolia, Dodonaea viscosa and Guatemala grass (Tripsicum laxuni) were planted along the contours for the purpose of controlling run-off and soil erosion on steep slopes. During the first year of growth, bean production was nearly 50% higher in plots containing Alnus compared to control plots having no hedgerows. All other plots with either strips of Guatemala grass or hedgerows of other woody species exhibited a reduction in bean yield which averaged about 26%. In this period, the Alnus was not pruned and no differences in application of mulch were made. The AFRENA Project in Uganda will continue observing crop yields in the trial at Kachwekano and plans to undertake studies to identify the factors that have given rise to the apparent positive effect of Alnus on adjacent crops. If the foregoing observations can be verified, Alnus will likely become an important agroforestry species in East and Central Africa. Bio-economic analyses of banana, bean and tree intercropping in the
highlands of Burundi To meet their fruit and wood (timber, poles, fuelwood) needs, resource-poor farmers with only small land holdings are forced to mix trees in their food crop plots. For example, in the highlands of East and Central Africa, Grevillea robusta is mixed with food crops for wood products, Avocado (Persea americana) for fruit and the castor plant (Ricinus communis) for stakes to support bananas. While the presence of trees is appreciated, it is not always clear which tree to associate with the different crops. In this experiment the effect of nine tree species on the yield of bananas and beans and the wood production potential of the trees when intercropped were studied. In addition an economic analysis of the tree/banana/bean association was done. The experimental unit was a square plot of 16 m long and 16m wide. The bananas were spaced 4 m x 4 m, thus each plot had 16 banana stools. Within this plot were 2 rows of trees spaced 4 m within the row and 8 m between rows. Suckers of a local cultivar of banana (Musa sp), Igitsiri, were planted in the first week of January 1990 and each fertilized with 15 kg (wet weight) of cattle manure and 100 g of triple superphosphate. A further 10 kg of manure was applied per stool in October 1992. Beans (Phaseolus vulgaris) were undersown each season beginning in October 1990 except during the October 1992 to February 1993 season. Based on wood volume produced over the first three and one-half years, four distinct groups of trees are identifiable: those with volume less than 1 cu. m, those around 2 cu. m and 4 cu. m, and Grevillea with 5.8 cu. m of wood (table 18). Hitherto trees have had no influence on the yields of the bananas. Before the last cropping season none of the trees had a statistically significant impact on the yield of the undersown beans. During the May 1993 crop, compared to the control, Grevillea significantly reduced bean yield by 29%, Albizia by 34% and Leucaena by 36%. A partial budget, using the costs and benefits that change between the control and the treatments, was done. Trees were valued by farmers and carpenters, who were invited to the experimental station. Additional benefits of the tree plots, as compared to the control, included trees for poles and firewood, and prunings for firewood. Additional costs included seedlings, labour for planting seedlings, and reductions in bean yields.
All treatments had positive net benefits three and one-half years after planting (table 19). Cedrela serrulata and Calliandra calothyrsus were found to be the best trees to be intercropped in a banana/bean system. Monitoring of the trial continues, as the results may change with time.
Growth of Grevillea robusta at three densities and its influence on
intercropped bananas and beans - results of the first three years In the highlands of Kenya, Rwanda and Burundi, Grevillea robusta is certainly one, if not the most common tree species found, associated with crops because, according to farmers, it does not compete with crops and may even enhance yields. It is planted for shade, timber, poles and fuelwood. Its leaves are mixed with the soil or added to the compost heap. Estimates of the number of Grevillea trees found on a farm vary. This experiment was undertaken to: 1) determine the effect of three densities of Grevillea on the yields of beans and bananas and, 2) to quantify tree growth and wood production at the different densities. The densities of Grevillea, 208 trees/ha (4 m x 12 m), 312.5 trees/ha (4 m x 8 m) and 625 trees/ha (4 m x 4 m), were combined with three cropping systems - bananas, bean and banana/bean intercrop. The three cropping systems without trees served as controls. Plot size for the two highest tree densities and for the no tree plots were 256 m2 (16 m x 16 m) and for the lowest tree density was 448 m2 (28 m x 16 m). Randomised block design with three blocks was used. Tree seedlings were planted in March 1990. Suckers of a local cultivar of banana (Musa sp), Igitsiri, were planted in November, 1990. To limit shading "of the undersown beans, the lower branches of Grevillea were pruned in October 1991, in February and October 1992. Beans (Phaseolus vulgaris) were undersown each season beginning in October, 1990. The intercrop, not density of Grevillea, influenced height, basal diameter and diameter at breast height (table 20). Trees intercropped with beans had significantly higher values than those associated with bananas. Values for Grevillea interplanted with the banana/bean mixture were intermediate. Banana yields were not affected by the association with Grevillea at any density (table 20). The addition of beans improved banana production by about 21% due without doubt to the beneficial effect of the manure and the fertilizer applied to the beans.
In two out of five crops (May 1992 and January 1993) intercropping with Grevillea was beneficial to bean yield with optimal tree densities occurring at 340 trees/ha and 360 trees/ha. At the other three seasons, bean yields declined as the density of Grevillea increased. Beginning at the fourth cropping season banana depressed bean yields. The socio-economics of Grevillea robusta within the
Coffee-based land-use system of Kenya: Some preliminary results Grevillea robusta is a very important tree in the Coffee LUS of Kenya and East Africa. Previously, it has been shown to be present on 96% of the farms within the coffee and tea zones within Embu District and 97% of the farms just below the coffee zone in Kirinyaga District. In both places, it was found in great numbers (e.g. 40 per hectare in Embu UM1-3). This research is the natural follow-up to other ICRAF Grevillea activities, such as ICRAF's 1990 Grevillea workshop, two Grevillea robusta books, provenance trials, etc.. This research's goal is to provide the socio-economic understanding of the rapid spread of the Grevillea robusta by characterizing the adoption process and quantifying the impact of this adoption. The research area is in middle altitude area of the Kirinyaga District of Kenya, called "UM4". The area lies just "downhill" from Mt. Kenya's marginal coffee zone where the rainfall and altitude is slightly less than what is recommended for coffee production. The average rainfall is between 950 and 1200 mm per year. The altitude ranges from 1,280 to 1,340 metres asl. The land is privately held in small family farms where the vast majority of people are recent Kikuyu settlers from the upper slopes of the same district. The downhill settlement of the Kikuyu is spreading the Grevillea MPT boundary planting technology. Five small periphery surveys were conducted of key informants. These surveys included those of chiefs (n=3), timber and furniture shops (n=7), saw mills (n=5), tree nurseries (n=6) and interviews with the district forest department and forest plantation officials. Later, in August, 1993, a 90-farm survey was conducted and several trees were pruned and pollarded for biomass and profit measurements. Most of the results here are only from the five periphery surveys which were conducted between April and August, 1993. The Grevillea robusta is regulated much less than other major agricultural activities of the area, such as coffee, milk and maize, whose transport and prices are regulated. The cutting of Grevillea since the 1984 drought does require chiefs permission but it is always granted when the farmer demonstrates his willingness to replant replacement trees, which farmers are almost always glad to do. Old mandates regarding coffee, except the one that states that nothing should be grown within the coffee trees, have been forgotten within administrative memory. The Grevillea has been the tree of choice by the government since the 1970s within the research area, while Eucalyptus spp. have been frowned upon as a "water drinkers". The Kikuyu have a strong boundary planting tradition which pre-dates colonial history. In general, people involved in timber yards and furniture shops have little knowledge and experience with Grevillea timber. Only about 2% of their work is with Grevillea: demand for Grevillea timber is very weak. In general, they do not know how to work with it and they believe it is inferior in all respects. They especially feel it is very susceptible to insect attack. In contrast to the timber yards and furniture shops, the saw millers feel Grevillea timber is under-rated and misunderstood by the public. Five of the six mills surveyed showed that only about 2 percent of their business is in Grevillea and all of this is through special order only. These orders are occasionally by farmers providing their own trees for home construction; occasionally industries in Nairobi will order 2x2s for the construction of knife, machete (panga), and broom handles, cutting boards and rolling pins. The timber is also used to make local oxcarts and lorry walls. The Grevillea serves well in products which must not split when frequently wet. Consequently, Grevillea is sometimes used to make dhows (traditional boats) at Kenya's coast. One of the six mills was intentionally visited because it was known for using Grevillea as its major business.. Three-fourth of its Grevillea was used to make coffee driers which must withstand the rains of the region. The following market share table ignores this mill because there is no other like it in the district.
The Grevillea saw mill recommended the following for Grevillea timber treatment to prevent insect attack. One should rub paraffin into the base of the felled tree so that the paraffin is sucked up into the wood. After the wood is split no varnish nor wood preservatives are needed. If the paraffin is not used, timber should not be stored long to dry and season, as other woods are. Insects will attack the wood. One should quickly put the timber into use and varnish timber used in furniture and oil planks used in household construction. To prevent warping, timber should always be stacked. The supply of pine and cypress, which come mostly from forest plantations, is quickly diminishing mostly because re-growth is very poor since the end of the "shamba" ("tangewai") management system in the mid-1980s. The exact supply figures are available but not yet compiled but it is clear that on-farm forestry will be the major supplier of tree products in the near future. Although Mt. Kenya Forest has been closed, on and off, for several years, there is still some illegal harvesting of indigenous trees, especially camphor. Seedlings for boundary planting are by far the major sellers in the district. There is also very much planting of boundary material from cuttings, which is not reflected in the nursery research. It is obvious, from the seedling figures, that the future of on-farm biomass is the Grevillea, with about 60% of all seedlings being for Grevillea. Cypress sales have done poorly in the last few years because of the aphid and Eucalyptus has been frowned upon since the 1970s. Nonetheless, these two trees are the only two close exotic competitors to the Grevillea, and they make poor competitors at that. The nurseries sell only a very small number of indigenous trees and mostly for ornamental and ceremonial purposes. 1992 Seedling sales
Kei apple (Dovyalis caffra) is a common thorny shrub used exclusively for inner- and outer-boundaries. Grevillea is also mostly used on boundaries. Thus, in private nurseries, boundary plants make up over 96 percent of all seedlings sold! This possibly more than anything else shows the importance of the Kikuyu boundary planting traditions in this recently settled UM4 research domain. It also shows that the biomass on inner- and outer-boundaries are a key area for future agroforestry focus. To ascertain possible social variables which effect Grevillea adoption, the nursery managers were asked to characterize Grevillea buyers. A small portion of the results follow:
Reason and formula for widespread adoption: Strong boundary planting tradition: - boundary volatility The tradition of clan land right establishment is called "kuuna githaka" in Kirinyaga Kikuyu and "runo" in kiEmbu. In UM4 Kirinyaga, 91 percent of farmers had Grevillea on the outer boundary. At UM4 nurseries, 96 percent of seedlings are for boundaries. The Haugerud anthropological study as well as others speak of the high level of land disputes in this high population density area of Kenya. The population growth rate is 3.2 percent and population densities range from 500 to 600 people per square hectare "uphill". This means that land portions are now too small (about 1.0 to 1.2 hectares) to subdivide and thus people fight over what little land there is if they lack the funds to buy land "downhill". All people surveyed came from uphill and still 48 percent mentioned land/tree tenure problems ranging from neighbours burning or uprooting trees to adult children not planting trees because of family disagreements about impending land subdivisions. Area chiefs also reaffirmed the problem of land disputes. The following three most critical rating comparisons show that Grevillea is "outstanding" among competing trees. Ratings are from 1 to 4 from the 90-farm survey. There was no single favourite indigenous tree so an average was taken.
Competitive interactions of multi-storeyed linear agroforestry
systems In 1989, three trials were established at two sites in Uganda to study the interactions of two multipurpose upperstorey trees (Casuarina equisetifolia and Grevillea robusta), two understorey fodder species (Calliandra calothyrsus and Pennisetum purpureum or Napier grass) and crops. Upperstorey treatment levels included control plots without any upperstorey trees and plots with intra-row spacing of 1, 3 and 5 m. These were combined or interplanted with understorey treatments of control plots without understorey or plots with either Napier or Calliandra. Upperstorey trees were monitored for growth after every 3 months and understorey biomass production was measured. Crop yields were estimated every season. At Kabanyolo (1200 masl) after 36 months, Casuarina height was greatest in plots having no understorey. Similarly, height differences in Grevillea were observed during the first year, but these subsequently disappeared. At Kachwekano (2000 masl) height difference were not consistent. Generally, upperstorey trees not associated with any understorey were taller than those associated with an understorey. Intra-row spacing had no significant effect on the growth of either Casuarina or Grevillea. Root collar diameters were highest in treatments with no understorey and lowest in those with napier. Biomass of prunings from upperstorey trees were greater in plots without understorey and also in those where the upperstorey was widely spaced. Crown diameters also followed the same trend, except with Grevillea at Kabanyolo, which showed no differences among the understorey types. There were no differences in Calliandra production associated with intra-row spacing of Casuarina and Grevillea at Kabanyolo. Napier grass production tended to decrease with increasing intra-row spacing of Casuarina but not with Grevillea. At Kachwekano, Calliandra yield was significantly reduced with wider spacing of Grevillea. Crop yields were highly affected by the understorey. Napier suppressed crop yield more than Calliandra while intra-row spacing of the upperstorey showed no influence on crop yield. Wood supply and use model for food crop-based land-use system
of Western Kenya Poles and firewood are among the most important tree products in rural areas of Western Kenya. Firewood provides nearly all the fuel and poles are critical for house construction and for earning cash. The objective of this study is to develop a model that quantifies the farmers use of poles and firewood and the number of trees required to meet the needs. The study was conducted in Siaya and Kisumu districts. Five farm household's use of firewood was monitored for four days. An informal survey of house construction including 18 houses was used to estimate pole use in construction. Twenty farmers were interviewed to estimate house construction frequency. Five farmers were interviewed concerning the number of trees required to supply the needed poles for constructing a house. Firewood consumption is estimated at about 8.2 kg dry/household/day. Firewood use accounts for about 80% of total fuel consumption; therefore firewood use is about 2400 kg (3.4 m3) per year. About two-thirds of this quantity comes from the farm itself; the rest is collected from off the farm or is purchased. Fuelwood from the farm is assumed to come from the 240 trees and 290 m of hedges that are found on the farm (Scherr and Alitsi, 1991). Five different kinds of poles are required in house construction. A house with an iron-sheet roof (mabati) requires about 228 poles whereas a thatched house needs about 281 poles. The quantity of wood required is 2.2 m3 for a mabati house and 1.6 m3 for thatched. Mabati houses require more wood because the poles must be longer and bigger in diameter. Poles would cost about KShs 3000 for a mabati house and KShs 2220 for grass thatched house. An average household builds a house (or its equivalent) every 8.4 years. Kitchens, latrines, stores and bachelors' houses are also included in the analysis by computing their equivalent pole use as compared to a main house. The number of poles required and the time and trees required to supply them depends on species and management practices. In our analysis, we assumed that all poles come from Eucalyptus (the most common tree used), and all are from a woodlot. Trees are coppiced after 5 years and 4 coppices are left to grow. Using these assumptions, 23 coppiced trees and 8 newly planted trees would be required for constructing a house at the end of an 8.4 year period. Comparative performance of seventeen upperstorey trees associated
with crops in the highlands of Uganda Trials were established at three sites in Uganda to test the suitability of multipurpose trees (MPTs) as upperstorey in crop lands. The MPTs are expected to provide poles and small timber as final products, while the prunings obtained from them can be used as fuel wood. They were planted in single rows at intra spacing of two metres and each plot contained seven or nine trees. On both sides of the tree row, crops were raised. Data on crop yields were collected every season, while data on the growth of the trees were collected four times each year. In terms of tree growth, Grevillea robusta, Casuarina cunninghamiana and Alnus acuminata, performed well at the high elevation site of Kachwekano, while at the mid-elevation site of Bushenyi, Grevillea robusta, Casuarina junghuhniana, Cupressus lusitanica and Cedrela serrulata, had better growth rates. At Kabanyolo (low elevation), Melia azedarach, Cassia siamea, Jacaranda mimosifolia, Grevillea robusta and Maesopsis eminii, performed best. Crop yields were affected by the presence of the MPTs, with Maesopsis eminii having the greatest negative effect. The crop rows which were nearest to the tree line were most affected. Only Alnus acuminata had a positive effect on crop yields. The installation of a root mesh to reduce tree root competition for nutrients and water increased yields in plots with MPTs by 5% (Melia azedarach) to 152% (Maesopsis eminii). Despite these increases, the control plot still had significantly higher bean yields, suggesting that bean suppression may not be due to root competition alone but also as a result of shading. In the case of maize, suppression seems to be due mainly to root competition because after eliminating this competition, maize yields in the MPT plots did not differ significantly from those of the control. The negative influence of the MPTs could be minimized by pruning the tree crowns and roots. A diagnostic study of tree-crop associations in Kigulu County, Iganda
District, Uganda A diagnostic survey was conducted among randomly selected farmers in Kigulu County, Iganga District, with the objectives of documenting the existing tree species and agroforestry practices, identifying on-farm tree related constraints, and determining possible agroforestry interventions for the area. The study area was found to have a wide range of tree species, but suitable agroforestry species were few. The common multipurpose trees found in the area include Chlorophora exelsia, Markhamia lutea, Spathodea campanulata, Cassia siamea, Cassia spectabilis and at least six species of Ficus, notably Ficus natalensis and Ficus mucosa. The most common fruit trees were Artocarpus heterophyllus, Persea americana, Mangifera indica, Carica papaya and Citrus spp. Farmers are solely dependent on Ficus natalensis for fodder, in addition to having a limited choice of suitable upperstorey trees (Ficus natalensis and Ficus mucosa) for bananas. Detailed study is required to establish the scientific basis for the reported favourable effects of these two species on banana production. Due to increasing population pressure, tree cover in the area has generally declined. The majority of farmers generally think that trees can play a significant role in checking the deteriorating biological potential of their area; however, analyses of the data indicated that lack of knowledge about suitable agroforestry tree species and lack of tree seedlings were major constraints to on-farm tree planting. Possible agroforestry interventions for the area are suggested in the light of results arising out of current on-station agroforestry research in Uganda. Potential fruit and nut trees in agroforestry-based ecosystems
for the highlands species and research needs Fruit or nut trees are important components in the farming system of the highlands of Eastern and Central Africa. The edible fruits/nuts which are consumed fresh or in processed form are cultivated for local or export markets. They are also important in that they supplement starch staples by providing additional carbohydrates, proteins and fats. Most of the fruits/nuts produced also contain large quantities of vitamins A and C (Rice et al, 1991). Since most of the fruits are sweet and easily palatable they are often consumed in large quantities this contributing markedly to nutrient intake. Various fruit/nut producing trees and shrubs are important components of many agroforestry systems which include home gardens, forestry gardens, plantations and bush-fallow systems. Huxley, (1988) indicated that many agroforestry systems could be enriched by inclusion of fruit/nut trees. But due to limitation of land sizes in the highlands, fruit/nut trees are grown together with other crops and to a lesser extent in small plantations (Aiyelaagbe, 1992). In subsistence farmer condition, the fruit/nut trees have a distinct advantage over other woody species in that they form a source of income to the farmer as they can be harvested periodically or in a staggered manner, in addition to other crops growing under them. They also produce various products of immense nutritive value in addition to their environmental protection role. This has led to greater diversification in the farming systems (Nair, 1985). Studies elsewhere have indicated that communities like in tropical forests are more stable than simple communities with less diversity (Trenbath, 1976). Agroforestry has been practised in many parts of the of the world especially in India (Aiyer, 1949) where fruit trees of separate age groups are planted together with food crops. A desire to provide fruit/nut for the family is one motive. Fruit/or nut trees have a crucial role to play in food production systems. One of their most important roles is as a source of fruits/or nuts which provide a substantial proportion of nutritive and energy requirements of the local diet. Fruit/or nut tree cultivation also generate diversified income and off-farm employment opportunities. It is also regarded as a relatively stable form of land-use for small farms in a highly populated area. Farmers are also aware that tree crops improve micro-climate around the homesteads. The economy of the Eastern and Central African highlands is based on agriculture, which provides a livelihood for about 80% of the population (Anon., 1987). Farmers develop most of farming systems in response to their subsistence needs and the agroecological situations in which they live. Fruits/nuts are considered economically important since they give good yields in small areas and yet sell for high prices when compared to field crops. This combination of high yields and high prices means that in heavily populated areas, farmers can make good incomes even from small farms; including generation of substantial employment opportunities especially in production and processing enterprises. It is worthy noting, however, that at peak periods over production may occur and contribute to lower prices and fruit deterioration. Industrialization and urbanization can alleviate this in addition to diversifying the species with varying production cycles to ensure continuous production throughout the year. It has been indicated that fruit/nut growing could be used to foster integrated rural development especially in improvement and contribution to sustainable land-use systems (Aiyelaagbe, 1989). Fruit/or nut growing in the highlands of the Eastern and Central region of Africa has potential to compliment agricultural productivity and contribute to diversification and increase in farm incomes. The potential of suitable fruit/nut tree species in agroforestry-based systems lies on the fact that most of the farmers in the region are subsistence who already practice intercropping. In general, there has not been any guiding principle in the choice of different species/cultivars for planting in the small holdings except to a certain extent the home needs of the family. Due to wrong choices of species/or cultivars, (eg. the local mangoes which have a shading effect to other crops due to their big sizes and the number of fruits realized is small) the return from such gardens is extremely low. The conditions in the region seem favourable for the successful implementation of fruit/or nut trees interaction in agroforestry systems. There are indication that farmers are becoming familiar with the vegetatively propagated fruit/nut trees which are suitable for mixed cropping without affecting food crops (Murithi, 1993 unpublished). There are many different fruits/nuts, varying in flavour and in seasonal availability but the characteristics of desirable species/cultivars depend on environmental factors and the needs of the farmer. Some of the potential fruit/nut tree species have been identified for the highlands which are suitable for some parts of the region (Beniest et al, 1979; Gachanja and Ilg, 1979?) are shown in table 21. Surveys carried out in some parts of the region identified the farmers growing almost similar fruit/nut species (Aiyelaagbe, 1992; Murithi, 1993 unpublished). Among the most popular fruit/or nut trees grown by farmers in the highlands are:- avocadoes, mangoes, passion fruits, tree tomatoes, macadamia, guavas, custard apples etc.. Table 21 also shows some of the most essential environmental requirements for fruit/or nut growing (e.g. climate, soils, rainfall).
It is envisaged that most of these fruit/or nut species/or cultivars would be adaptable in other highlands within the region which have similar environmental factors. It is worthy, however, to consider that all quarantine regulations are strictly observed during transferring of the planting material for farmers adoption. It has been shown that agroforestry has biological advantages over mono culture; however, in reality planting of fruit/nut trees has an economic advantage which drives the farmers towards selections of the right species/cultivars to plant in the specific highland regions. If the possible advantages of agroforestry are to be realized, localized research is required. This is because, growing of fruit/nut trees is limited by constraints, namely: poor management practices, pest and diseases management, lack of post-harvest technology and poor marketing channels (Beniest et al, 1979; Gachanja and Ilg, 1990). It is therefore, imperative that research should be designed to assist the farmer in choosing the most appropriate fruit/nut tree species that, when mixed with food crops systems, is biologically advantageous. Considering that most of the land in the highlands is sloppy, the potentiality of increasing the practice of contour planting should be exploited. There is also need to determine optimum densities as well as planting patterns and structural growth of fruit/or nut trees that would not affect other crops. Other aspects which need to be investigated include:- interactions between the fruit/or nut trees and field crops with respect to shade, rooting patterns, competition for moisture, optimum nutrient requirements in mixed cropping systems, etc.. Improvement of popular multipurpose fruit/or nut trees by developing appropriate agronomic packages in regard to adequate management practices in mixed cropping systems, will help to enhance their acceptability in agroforestry interventions.
Acland, J.D. (1973). East African Crops. F.A.O. Longman group, Ltd. London. Aiyelaagbe, I.O.O. (1989). The role of fruit production in integrated rural development in Nigeria, NIHORT Occasional Paper N°19 Aiyelaagbe, I.O.O. (1992). Fruit crops in Agroforestry - Final project report of study commissioned by ICRAF/GTZ. Nairobi, Kenya. Aiyer, A.K.Y.N. (1949). Mixed cropping in India. Indian Journal of Science 19: 439-543. Anon. (1987). International Fruit World, Agro Press Ltd 2. Beniest, J., Gachanja, S.P. and Njoroge, S.M. (1979). Fruit Tree Nurseries in Kenya. AG: DP/KEN/75/028 Working Document M. Nairobi, Kenya. Gachanja, S.P. and Ilg, P. (1990). Fruit Tree Nurseries. Ministry of Agriculture Soil & Water conservation Branch, Nairobi Kenya. Huxley, P. (1988). Fruit crops in agroforestry. Chronica Horticulture 28(3) Nair, P.K.R. (1985). Fruit Trees in Tropical Agroforestry Systems. Working Paper N°32. Environment and Policy Institute East West Centre 1777, Honolulu, Hawaii, 96848. Rice, R.P., Rice, L.W. and Tindall, H.D. (1991). Fruit and vegetable production in warm climates. Macmillan Education Ltd., London and Basingsoore. Sturmhiet, P. (1990). Agroforestry and Soil Conservation needs of small holders in Southern Zambia. Agroforestry Systems 0(3) pp.265. Trenbath, B.R. (1976). Diversify or be damned. Ecology 5:76-83 |
