The following indicative summaries and case-specific examples of ideotype specifications are presented for illustrative purposes only and should not be used as recipes or substitutes for diligent site-specific design work. Since this body of material reflects work in progress to systematize and develop a multidisciplinary perspective on tree and technology specifications, no attempt has been made to impose a premature standardization on the specifications given here. They are presented here in order to illustrate the range of considerations that enter into the derivation tree specifications for a particular application and have been recorded with a minimum of editorial modification in order to convey a feeling for the nature of the exercise.
The sample ideotype specifications presented here come from the reports of diagnostic and design exercises undertaken by ICRAF in collaboration with various national and international research partners during the planning phase of agroforestry research projects in a wide range of environments. The specifications represent an idealized conception of the kind of tree that would best suit the needs of the technology design concept developed by the D&D team.
It should be emphasized that these specifications are intended for use in
agroforestry research projects which are mandated to explore and develop promising agroforestry technologies. Although the basic relevance of the suggested technologies is established by the D&D process, the technical efficacy of some of the newer agroforestry technologies is still hypothetical. Just as there is no prior guarantee that the original design concept will work without modification in the intended environment, there is also no guarantee that the ideal tree exists. The tree specifications are used to guide the researchers in screening a wide range of trees for the desired attributes. This leads into tree management trials and, eventually, into trials of prototype technology designs with the intended land users. The astute reader will note the unevenness in the treatment of the specifications for different technologies. Obviously, the writing of tree specifications, like other design skills, is an art. As more is learned from the research which is now underway about agroforestry design principles and about the attributes of trees in the context of these new technologies, no doubt the standard of specification writing will also improve.
In accordance with the third principle of our selection strategy, all specifications should be regarded as hypothetical until validated by experience. If a given set of initial specifications proves too ambitious or optimistic, it is an error that will be corrected in the course of the search and screening process. Perhaps it is better to err on the side of optimism during the R&D phase of a tree growing technology and on the side of caution in the active dissemination phase.
The following key to the listing of tree specifications by technology in Table 25 classifies tree planting practices by arrangement of the tree/shrub and other components:
ARRANGEMENT IN SPACE
MIXED ARRANGEMENTS
1. Mixed intercropping
2. Dispersed trees in grazing land
3. Homegardens
ZONAL ARRANGEMENTS
4. Woodlots
5. Orchards
6. Fodder banks
7. Tree crops on boundaries (including paths, roadways, field borders, etc.)
8. Trees on paddy bunds
9. Living fences
10. Tree crops on conservation structures
11. Hedgerow intercropping
ARRANGEMENT IN TIME
12. Enriched fallows
13. Leys
14. Taungya
1. MIXED INTERCROPPING
(Synonym: dispersed trees in cropland, agrosilvicultural systems )
For supplementary production with minimal yield reduction, or net yield increase, of associated crops
General specifications
climatically suitable edaphically suitable vigorous growth
pest & disease resistance
ease of establishment (especially if proposed as low labour alternative to hedgerow intercropping)
direct seeding vegetative propagation
High yield and quality of desired product
For timber:
vigorous vegetative growth straight stems wood strength wood quality
For poles:
vigorous vegetative growth straight stems coppiceable
For fruit:
high fruit yield
early maturation & fruiting
off-season fruit production desirable (for marketing or for labour spreading)
ease of acquisition/management of propagation material
low perishability (if far from market)
For industrial processing:
high yield of valuable part
tolerant of handling or easily processed locally (may depend on availability of simple technology)
ease of storage
high value/weight ratio of processed product (if far from market)
For fodder:
dry season pods or good quality herbage (Tanzania)
For cash:
marketable products
Comuatibility with associated crops
Non-competitive with crops
non-allelopathic
deep rooting (minimal lateral spread) light canopy or
leafless during cropping season (e.g. A. albida ) fast-growing with high canopy self-pruning desirable (to reduce labour)
Soil benefits
N-fixing or other nutrient cycling ability high leafy biomass production
coppicing, pollarding, or otherwise prunable to provide mulch (if labour available)
abundant litter
seasonally deciduous (reduced labour for pruning)
nutrient-rich leaves (for nutrient input)
slowly decomposing leaves for organic matter buildup
rapidly decomposing leaves for nutrient flush at critical times of cropping season
Microclimatic benefits
canopy providing appropriate or otherwise manageable shade, shelter, etc.
spreading canopy (e.g. for shade or protection from hail or heavy rainfall)
pollarding (to regulate shade for coffee; e.g. coffee/erythrina in Costa Rica)
Other management requirements
thornless (to prevent injury to barefoot farmers)
Situationally linked attributes
fire resistant tolerant of browsing
tolerant of periodic waterlogging (dimba) tolerant of drought stress requiring few purchased inputs
able to compete with natural fallow vegetation (if in rotational system)
Source: Summarized from ICRAF t 1 (1982), ICRAF et al (1984), ICRAF and ICAR (1984), ICRAF and ICAR (1986), Minae and Akyeampong (1988), Djimde and Hoekstra (1988), Kwesiga and Kamau (1988), Djimde and Rainsree (1989).
2. DISPERSED TREES IN GRAZING LAND (Synonym: silvopastoral systems)
To increase supply of wood products &fodder (grass as well as tree leaves)
For all species
climatically suitable
edaphically suitable (pay attention to shallowness of soils in steep grazing land)
N-fixation desirable
vigorous growth compatibility with grasses For timberfpoles straight stems coppiceable (poles) browse resistant light canopy
For fodder
leaves/pods palatable & nutritious pollardable
Source: Djimde and Hoekstra (1988)
For sylvopastoral systems combining tree products (timber, fruits, fodder, etc.) with grazing
compatibility with lower storey plants
not densely shading
no smothering litter
not allelopathic
tolerant of browsing or lopping
productive of by-products for cottage industry and/or gathering by labourers
provide some shade for animals fodder production in dry season Source: ICRAF and ICAR (1986)
3. HOMEGARDENS
(Synonyms: homestead or compound trees)
For banana-based homegardens
For all species (reeardless of role) climatically & edaphically suitable deep rooting
minimal competition with annual, coffee & bananas
N-fixing desirable
vigorous growth nutrient rich litter
For timberhDole production
quick growth in shaded environment straight stem
coppiceable (for poles) For fruit trees
disease & pest free (not host to diseases affecting bananas, coffee & annuals)
single stem or little branching nutrient rich leaf litter
Source: Djimde and Hoekstra (1988)
4. WOODLOTS
Multipurpose woodlots on very steep slopes
Tree/shrub ideotvne
Variable, depending on which products are desired from the woodlot mix. General requirements are for: capability to provide high yields of desired products (fuelwood, fodder, industrial materials, etc.) ease of establishment
rapid growth
adaptability to climatic and edaphic conditions of the site
effectiveness in controlling erosion
compatibility with other trees in managed associations
Plant arraneement and management
Other understorey economic plants or cover crops might also be included in the mix to control erosion during the establishment phase and/or to diversify the economic value of the plantation. The optimal spacing for different species needs to be worked out and establishment methods need to be evaluated with a view toward identification of low labour-requiring techniques.
Source: Minae (1989)
Multipurpose woodlots in Kenya
Recommendation domain: All land use systems, particularly for farmers in zones of wood products scarcity, and those close to major markets for these products. As demand for wood products increases with population in the high-potential highlands, such products may become economically competitive with [agricultural] crops for farmland. This will especially be tree for marginal lands, but near active timber/pole/fuelwood markets such products may be competitive even with [agricultural crops on] cropland. Development of multipurpose woodlots is proposed to achieve farm self-sufficiency in wood products, and to generate cash income through commercial sales. As woodlot technology at standard spacing for largeholders has already been developed for the high-potential highlands, we concentrate on high-density mini-woodlots which are attractive to smallholders.
MPT specifications
climatically and edaphically suitable
high growth rates at high density spacing
high quality wood for fuelwood and poles
growth habit appropriate for harvest as fuelwood and poles
Source: Minae and Akyeampong (1988)
5. ORCHARDS
Fruit orchards in Kenya
Recommendation domain: Larger farms of the tea-based and maize-based farming systems in the highlands Tree specifications
climatically and edaphically suitable
high fruit production
off-season fruit production (if possible)
early maturity and fruiting
ease of acquisition of planting material
pest and disease resistance both pre- and post-harvest
Source: Minae and Akyeampong (1988)
6. FODDER BANKS
Intensive fodder banks with MPTS in Kenya; conceived as a mixture of woody and herbaceous species, densely planted and intensively managed.
MPT specifications
climatically & edaphically suitable
minimally competitive with associated grasses/herbaceous legumes
vigorous regrowth after coppicing
fodder material palatable & nutritious for animals
high protein content in fodder material
high rates of production for fodder material (leaf/pods)
continued production of fodder material during dry season
Source: Minae and Akyeampong (1988)
As a store of cut-and-carry fodder to be used as a supplement during the dry season in Uganda
MPT specifications
climatically and edaphically suitable palatable & nutritious coppiceable/pollardable vigorous growth/high leafy biomass Source: Djimde and Hoekstra (1988)
As supplementary fodder supply for more intensive management of calves & work animals. A small plot
protected by live fence, enclosing a fodder orchard consisting of a mixture of pod producing trees and leaf fodder producing perennial which can be intercropped with pasture legumes.
MPT specifications
palatable fodder (leaves & pods)
fodder available during the dry season
relatively fast growing
drought tolerant
Source: Minae (1989)
For fodder orchards in Tanzania
On sandy upland soils
legume producing palatable pods with digestible seeds during the late dry season
relatively fast growing
drought tolerant
On hvdromorphic soils (including vertisols)
legume producing palatable pods with digestible seeds during the late dry season OR
capable of producing leaves & twigs high in protein, low in phenolic compounds (limiting digest)
tolerant of temporary waterlogging (up to 2 months) tolerant of long dry seasons tolerant of cracking vertisols relatively fast growing
Source: Kamau and Odra (1988)
7. TREE CROPS ON BOUNDARIES
(Synonym: boundary planting)
General specifications climatically suitable edaphically suitable fast growing
pest & disease resistance
easy to establish
easy to manage
non-weedy (non-spreading)
early maturity (for desired product) high value products
High yield and quality of desired products: timber
poles fuelwood fodder
fruits, nuts, oilseeds fuelwood
industrial raw materials
marketable cash crops (with of without processing)
For cash crops in marginal lands (drvland or acid soils) distant from markets:
easy to establish
fast-growing
early maturity of desired product Compatibility with other crop plants non-allelopathic
deep rooting
compatibility with trees in managed hedgerow association
able to grow in relatively close association with other trees
minimal competition with nearby crops
non-spreading roots
non-spreading crown
not harbouring birds, other pests & diseases
Sources: Summarized from Kwesiga and Kamau (1988) and Minae and Akyeampong (1988)
8. TREES ON PADDY BUNDS
Line plantings on bunds of rice paddies for green manure/mulch/fodder N-fixing
rapid growth
ease of establishment
light or easily management canopy for shade control
nutrient recycling capability through leaf shedding or pruning tolerant of waterlogging
tolerant of cracking soils
suitable as supplementary fodder during dry season (nutritious, palatable) Source: Kwesiga and Kamau (1988)
9. LIVING FENCES
Living fences for pioneer cattle ranching system in Peru MPT specifications
ease of establishment
survival and rapid growth rate at close in-row spacing short time lag before achieving functional effectiveness non-competitiveness with adjacent pasture non-toxicity to livestock
fire resistance
yield additional by-products Source: ICRAF et ál (1982)
iving fences for cereal-cotton-cattle system in Uganda MPT specifications
able to grow in hedges
thorny
useful by-product
Source: Djimde and Hoekstra (1988)
10. TREE CROPS ON CONSERVATION STRUCTURES
For integration of production with conservation functions stabilization of soil & water management structures in the Bijapur watershed of Karanataka, India (RR = resource rich; RP= resource poor) MPTS on water catchment bunds for timber. fruits. fodder edaphic suitability (vertisols: waterlogging, cracking)
climatic suitability (drought tolerant) limited competition with adjacent crops suitable phenology
limited root spread
light canopy
limited height (can be taller on E-W rather than N-S bunds) not encourage birds to perch or nest good soil stabilizing features
ease of establishment
minimal protection problems not harbour crop pests or weeds no root suckering
good soil micro-site enrichment characteristics high levels of plant N, P, K, Ca, Mg good litter turnover
For timber, (RR)
local marketability/utility little branched
straight grained
self-pruning (if possible)
could be slower growing than fruit or fodder variants For fruit (RR & RP)
nutritious, marketable, storable
local processing potential (cottage or small village industry) early bearing
regular bearing
short harvest season (other systems may require long bearing season) free from pests & diseases
For leaf fodder (RP)
palatable
nutritious
good digestibility
low toxicity (& low in anti-metabolites)
available during needed seasons (Oct, April-June) quick regeneration after cutting/browsing coppiceable
non-thorny
For pod fodder (RP)
high harvest index (large proportion of annual dry matter increment goes into pods) free from pests & diseases
regular & reliable pod yields Source: ICRAF and ICAR (1986)
Trees on terrace risers in Bhaitan watershed in the outer Himalayas of Uttar Pradesh ease of propagation
fast growth
low shade
small stature (multistemmed?)
capacity to be pruned
restricted root competition
not to encourage pests
Source: ICRAF and ICAR (1984)
11. HEDGEROW INTERCROPPING
(Synonyms: alley cropping, alley farming; see also 10)
General specifications
climatic suitability edaphic suitability
easy establishment (direct seeding or cuttings if possible)
high leafy biomass production under heavy pruning (providing sufficient mulch without undue shading of
of adjacent crops)
large, broad, slowly decomposing leaves for organic matter, weed control & water conservation
insect-repelling leaf mulch (desirable)
deep-rooting for drought tolerance, recycling of leached nutrients, minimal surface root competition with
adjacent crops
nitrogen-fixing or other nutrient cycling capability no allelopathic effects
thornless to avoid injury to farmers
ability to provide useful by-products (fodder, fuelwood, poles)
For fodder vroduction
palatable nutritious digestible
For rotational alley crooning
able to develop broad canopy cover during fallow period browse tolerant
able to produce useful by-products
straight stems for poles
good fuelwood quality
For tobacco farmine system (Tanzania) nematicidal or nematode-repelling properties not harbouring other pests For cotton farming system (Tanzania) insecticidal or insect-repelling properties not harbouring other pests
Source: Summarized from ICRAF et al (1982), Vonk (1983), ICRAF _e gá(1984), Minae and Akyeampong (1988), Djimde and Hoekstra (1988), Kwesiga and Kamau (1988), Min" (1988), Djimde (1988), Kwesiga and Sabas(1989)
12. ENRICHED FALLOWS
Enriched fallow for the Chitemene, Maize-Cattle, Maize-small stock systems in Zambia
Recommendation domain: In transitional areas using hoe cultivation, where grass or bush fallow continues to be used for enriching the soil in the cropland, biologically and economically enriched fallows could be introduced. This is an agroforestry practice in which land that is not being cropped reverts to an improved
fallow which serves simultaneously for feed, fuelwood, or production of other tree products. There are two basic variants, the first being a hedgerow layout of coppicing fallow trees, appropriate where the system is expected to intensify into a continuous cropping system based on hedgerow intercropping, or where ox-ploughs may be used.... The second variant is broadcast planting of scattered fallow trees, an approach which has very low labour requirements, and could potentially be utilized when fallow periods are still rather long. MPT specifications
climatic & edaphic suitability
easily established by direct seeding or vegetative propagation
very rapid growth rate (to outcompete weeds)
N-fixing or other nutrient cycling ability superior to natural fallow (quicker regeneration) easily removed at end of fallow period (does not resprout if cut)
quick root decomposition after cutting (residual fertility effect)
effective weed suppression
yield of useful by-products
For tobacco crooning systems
nematocidal or nematode-repelling capability
high yield of fuelwood at end of fallow cycle (for flue curing of tobacco crop) If retained in crooland after fallow for mixed intercropping
compatible with crops
beneficial to crop growth
yield of useful by-products from side pruning for shade management Source: Kwesiga and Kamau (1988) & Kamau and Odra (1988)
13. LEYS
Technology description: Regulated leys are cultivated pastures established on croplands to provide fodder for a production oriented livestock system and restore soil fertility and structure. An efficient utilization of such pastures requires the introduction of fencing to control grazing. Agroforestry can contribute to this ley farming technology through the introduction of leguminous shrubs mixed with grasses in the pasture and through the development of living fences. In addition to the accepted benefits of N-fixing legumes on soil fertility, leguminous shrubs could facilitate pasture management, as their erect architecture enables them to avoid the problem of competition between grasses and legumes that is common to mixtures based on prostrate herbaceous legumes. If planted along contours, shrubs could also improve the erosion control property of pastures. In addition, such an arrangement would make it possible to have hedges as a permanent feature in the rotation cycle. When combined with maize stover they could improve the quality of the diet of cattle grazing crop residues. j)esmodium spp. are good candidates for these roles. The basic idea is that when the land is not being cropped it reverts to an improved fallow which serves simultaneously as a source of feed for grazing/browsing animals in a regulated ley system.
Recommendation domain: Regulated leys are a fairly sophisticated management approach to a stable mixed livestock/ cropping systems. It is appropriate only where intensive management is desirable and where tenure conditions permit fencing of cropland and controlled access to grazing land. MPT specifications
compatibility with grasses, herbaceous legumes & other fodder species pod production, leaf fall or other fodder production (during dry season) not harbouring important pests of the crops in the rotation
high biomass production of desired parts (leaves, pods)
ease of removal for subsequent cultivation
Additional specification for high rainfall upland sands
id tolerance, termite resistance
Addictional specification for low rainfall upland sands
drought tolerance
Source: Kamau and Odra (1988), Kwesiga and Kamau (1988)
14. TAUNGYA
For Bijapur, Karnataka, India
Recommendation domain: These specifications must be understood in the context of the highly stratified social system of the area, where the D&D team felt it was important to give special attention to the needs of the resource poor (landless labourers, gatherers, etc.), This technology is recommended for resource rich land users with sufficient land and for resource poor land users if land can be leased to them or otherwise made available. Tree specifications
growth and stature of woody species should allow intercropping for first 1 or 2 years trees and crops should be as compatible as possible trees should be multipurpose if possible, yielding raw materials for cottage industries, with some low value by-product for gatherers in the system main labour input requirements for management should occur outside the peak season Source: ICRAF and ICAR (1986)
Experimental cassava-based taungya system for the Sukuma agropastoral system in Tanzania Comment on the proposed intervention
More than the other lines of research, this one addresses a "socially" oriented intervention, i.e. how to develop
a socially acceptable way of growing trees in areas where tree planting is severely threatened by livestock damage. Ultimately the decision whether or not to adopt such a system will depend on a) whether, in the farmer's judgment, it represents an advantageous use of scarce cropland, and b) whether the customary respect shown by livestock herders for standing cassava fields can be used to protect trees through the establishment phase. A study should be conducted to determine the viability of this system and establish its recommendation domain before attempting dissemination. This does not necessarily mean that a biologically viable prototype should not first be developed, since realistic farmer assessments may not be possible until after they have seen a demonstration of a high-performance prototype.
Although successful systems of this type have been developed for the humid tropics, this is an experimental approach for drier environments like this one, and research should first validate the appropriateness of specific designs before commencing trials with farmers. Ultimately the decision whether or not to adopt this system would depend on the farmer's judgment that it represented an advantageous use of scarce land. Nevertheless, if a viable system of this type could be developed, it could have a major impact on tree production in areas where this is made difficult by extreme grazing pressure.
Technolo¢v description
Two fundamentally different approaches are possible, each requiring different tree selection and agronomic strategies: a) where the purpose of the system is mainly to grow trees under protected conditions (and, thus, where the yield of the intercropped cassava is of secondary importance and need not be maximized)--under such conditions the compatibility requirement might not be so stringent and a wider range of tree species might be used; b) where the yield of cassava is considered at least as important as the yield of tree products and the two must both be optimized, tree selection should be restricted to the least competitive/ most beneficial species. In either case, it should not automatically be assumed that the net effect of the trees will be a reduction in cassava yield on a per plant basis. Whether or not an LER > 1 is possible is an experimental question that depends on species selection, plant spacing, and management.
Tree ideotvne
capable of providing high yields of locally valued products (fuelwood, building poles, dry season fodder) relatively rapid growth with intercropped cassava (minimally must reach height at which it is no longer threatened by browsing within period of cassava cropping)
relatively low competition to intercropped cassava
deep rather than shallow-rooting
light or easily managed canopy for shade control
Adapted from Kamau and Odra (1988)