Previous - Next
This is the old United Nations University website. Visit the new site at http://unu.edu
Intercropping of tree crops/woody perennials
with commercial or subsistence ground or tree crops
Planting of timber, fuel wood, and
general-purpose trees in relation to agroforestry and agriculture
Grazing with commercial tree cropping and
silviculture
The future of institutional agroforestry in the
Pacific
The agroforestry systems so far described in this volume have been informal, often traditional systems that were developed on the basis of empirical, non-quantitative experimentation by local practitioners. We turn now to institutional agroforestry in the Pacific Islands, by which we mean those agroforestry activities that are promoted by governments, quasi-government organizations, private agencies, companies, and aid donors and that involve external funding, formal training, agronomic research, and extension services. Because the activities that fall under the rubric "institutional agroforestry" are becoming so many and varied, we provide here only a summary review rather than attempt a comprehensive survey. Other reviews of the topic are the paper by Vergara and Nair (1985) and the reports given by country representatives at a meeting on agroforestry held in 1987 at the University of the South Pacific's School of Agriculture in Western Samoa (Clements 1988).
Inasmuch as plantation agriculture is the core of much institutional agroforestry in the modern Pacific, it can be said that institutionalized activities were first promoted by colonial governments when they encouraged the plantation production of products for export in order to finance government expenditure and to provide cash income to local populations. Agroforestry projects are encouraged today for similar reasons as well as to meet local demand for forest products, to bring grass-fern "wastelands" to greater productive use, and to reduce the adverse environmental effects of rapid deforestation. A major emphasis of recent agroforestry programmes has been the promotion of increased productivity through multiple use, although multiple use is often defined solely with regard to the commodities derived from some mix of commercial crops, livestock, or timber, rather than in terms of the traditional context wherein an agroforested landscape showed increased multi-purpose utility and stability.
Table 10 Categories and examples of institutional agroforestry in the Pacific Islands
Intercropping of tree crops/woody perennials with commercial or subsistence ground or tree crops - Coconuts intercropped with ground and tree crops
Planting timber, fuel wood, and general-purpose trees in relation to agroforestry and agriculture
Grazing with commercial tree cropping and silviculture (silvipastoral or agrosilvipastoral systems)
Most modern agroforestry projects fall into one of three categories:
Table 10 provides examples of the kinds of activities that are practised under each category.
In the first category, the focus has been on monocultural production, with limited intercropping, of major export crops such as coconuts (for copra and oil), cocoa, bananas, coffee, rubber, and oil from oil palms, and, to a lesser extent, Citrus fruit, papaya, mango, kava (Piper methysticum), and vanilla (which requires support, or mother, trees). Although most of the species in this category have been promoted on the basis of large-scale, often foreign-owned, plantations or estates, they have also been actively promoted for smallholder production by colonial and independent governments and aid agencies.
Since the early nineteenth century and until recently, most of the islands in the Pacific basin have been characterized as plantation economies dependent on the production of coconuts, cocoa, and to a lesser extent coffee or bananas. On the atolls and smaller isolated islands, the coconut, which was an integral component of subsistence agroforestry systems, became the main source of terrestrial-based cash income. For some of the atolls of Micronesia, the introduction of the "tin can copra economy" led to abandonment of Cyrtosperma chamissonis taro pits and the erosion of self-sufficiency (Farrell 1972). The cultivation of subsistence crops was replaced by the cultivation of coconuts for copra and coconut oil to earn a cash income. On the larger islands, the establishment of coconut plantations was soon followed by the development of intercropping systems that included cattle and later cocoa under the coconut palms.
Because of the economic significance of plantation crops, especially coconuts, to many of the islands, systems of raising cocoa, cattle, or coffee under coconuts and other trees have been the subject of concern by island departments of agriculture and regional and global development organizations. Most of the plantation crops have been characterized by fluctuating demand and prices, determined largely by metropolitan countries and larger producers, an uncertainty that has motivated many countries in the Pacific to investigate alternative export crops such as ginger and vanilla.
Coconut intercropping
Coconut agroforestry is the most widespread and important form of commercial and government-promoted agroforestry in the Pacific Islands. Although most smallholders have intercropped coconuts with ground crops and other tree crops or protected trees as part of the traditional polycultural agroforestry systems, many governments in the region continue to encourage the intercropping of ground crops and some tree crops with coconuts. In many cases, this effort has taken the form of the systematic planting or replanting in existing garden areas of regularly-spaced palms, which can then be under cropped. Alternatively, undercropping in existing commercial groves of coconut palms has been systematically encouraged.
Very early on in Papua New Guinea, "it was advocated that plantations could be virtually self-supporting with regard to the provision of food for labour" by intercropping subsistence foods between coconuts; "if grown in correct rotation, the fertility of the soil will not only be maintained, but improved" (Gallasch 1976). However, apart from the widespread intercropping of coconuts with cocoa and pasture, and to a lesser extent, with Robusta coffee, interplanting with food crops was actively discouraged by the Department of Agriculture, Stock and Fisheries. In the early 1970s, however, experiments conducted on the intercropping of coconuts with selected forage grasses and legumes, taro, sweet potatoes, corn, and peanuts indicated that a variety of food crops could be grown successfully between coconuts, and that the effect of intercropping tended to be beneficial in terms of reduced weeding and maintenance of all crops, and that such intensive use of scarce land yielded substantially greater returns than coconut monoculture (Gallasch 1976).
Similar experiments have been conducted in Vanuatu, Fiji, Tonga, and Western Samoa. For instance, in Tonga, a succession of coconut replanting schemes over the past two decades has encouraged the replanting of coconuts on smallholder agricultural allotments, and has actively encouraged intercropping with ground crops, a practice that would probably continue regardless of official support. Maude (1965) found that on some of the smaller islands of Ha'apai, where land is scarce, there were few allotments without full coconut coverage, under which ground-cropping was practiced. Thaman (1976) reported that the median coconut coverage on the main island of Tongatapu was 50 per cent, with over 50 per cent of all allotments having recently planted coconuts, most of which were undercropped at least partially with staple ground crops and supplementary crops. A wide range of cultivated and protected tree species also grow throughout the coconut groves. The normal spacing was 30 feet between rows and 20-30 feet within rows. Because of the increase in plough cultivation and the interest in intercropping, there have been moves to increase the between-row distance and to decrease the within-row distance to as little as 10 feet in order to maintain copra yields, while at the same time making cultivation easier and maximizing both subsistence and commercial intercropping between rows.
As Watt (1980, 303) argues, for most island groups and many small islands within groups, institutionalized coconut intercropping and re habilitation is of utmost importance since coconuts constitute the only sizeable wood resource: "only in the case of Papua New Guinea is the size of the coconut resource dwarfed by the commercial timber resource." The development of a successful coconut-milling industry for overmature stems in Tonga and other areas has not only made use of a resource that had been wasted or destroyed, but also has facilitated the improvement of coconut production by removing overmature trees so that effective replanting could take place. This process is facilitated in Tonga by coupling the well developed and ongoing coconut replanting scheme with a chain-saw service to remove overmature palms for milling (MAFF 1985, 41).
Cocoa intercropping
There are numerous examples of the intercropping of cocoa, or cacao, with food crops or with other tree species, many of which serve as shade plants. In the Tolai areas of the Gazelle Peninsula of New Britain in Papua New Guinea, large-scale planting of cocoa, which began in the 1950s, has either displaced food gardens or has resulted in significant changes to the traditional food systems, including the development of cocoa-intercropping systems. The system that operated in the mid-1970s consisted of clearing forest fallow and then planting root crops and bananas. After the root crops were harvested, cocoa was planted under the shade of the bananas, together with Leucaena leucocephala and/or coconuts, so that the food garden became a regularlyspaced cocoa plantation under Leucaena or a cocoa-coconut-Leucaena mixture (Bourke 1976).
In other places in the Pacific, several other intercropping combinations with cocoa have been developed. For example, in the Solomon Islands, cocoa has been intercropped with chillies, ginger, and tumeric; and Leucaena leucocephala and Gliricidia septum have been used as shade trees (Walton 1988, personal communication). In Vanuatu, the joint-venture Metenesel Estates Cocoa Project, covering 1,700 ha, has officially encouraged intercropping and the preservation of buffer zones of alternate 10-ha blocks of uncleared indigenous forest between cocoa planting, with Gliricidia septum as temporary shade. Most of the cocoa in Vanuatu is cultivated under the shade of coconuts or thinned natural bush or forest, although some areas have been formally planted under Gliricidia septum, Leucaena leucocephala, and Erythrina variegate (Jacovelli and Neil 1984, 6). In Fiji, cocoa is commonly intercropped with tannia (Xanthosoma sagitti folium)under Erythrina variegate as a shade tree. The Ministry of Primary Industries has recommended the planting of cocoa under coconuts, taro, bananas, cassava, and kava (Piper methysticum) (MAF 1974).
Coffee intercropping and agroforestry
Like cocoa, commercial coffee plantations are planted under shade trees and/or with wind-breaks. The major species used in Papua New Guinea for such purposes are Leucaena leucocephala, Casuarina spp., Albizia stipulate, and Erythrina variegate. Coffee has also been interplanted under coconuts in coastal Papua New Guinea, Vanuatu, and New Caledonia (Brookfield with Hart 1971, 157). In the Sepik district of lowland Papua New Guinea, Allen (1985, 227) reports that Robusta coffee, grown in permanent blocks, has been integrated into the traditional diversified shifting agricultural system, with food crops being planted during the establishment stage and bananas and Xanthosoma taro being retained in mature gardens, with Leucaena leucocephala serving as the shade tree.
On Tanna, in Vanuatu, intercropping and agroforestry strategies have been actively promoted on a 450-ha Arabica coffee nucleus estate and on a projected 250 ha of associated smallholder plots (of which 50 ha had been established at the end of 1987). The intercrops included peanuts and maize (root cropping is discouraged). Various models have been tried to protect the coffee from wind damage; these included leaving strips of indigenous forest between coffee blocks and planting casuarina shelter-belts. There is also a major French-sponsored research project on Santo, where experiments are being conducted on the intercropping of cocoa and coffee with coconuts and other species such as kava, black pepper (Piper nigrum), and vanilla, using Erythrina and Cyathea spp. (tree fern) trunks as nurse plants/climbing poles for pepper and Gliricidia for vanilla (Barrance 1988).
Apart from the almost universal planting of shade or wind-break trees, very few countries have actively and systematically promoted the intercropping of coffee with food crops. Many have actually discouraged it, even though, as noted above, studies by Carrad (1982) in the Papua New Guinea highlands showed that intercropping of root crops, bananas, and other crops with coffee, in a 15-year cycle, gave smallholder farmers almost twice the real income obtained from coffee monocropping.
Citrus with shelter-belts and intercropping
The Fiji Sugar Corporation (FSC) and its predecessor, the Colonial Sugar Refining Company (CSR), in conjunction the Agricultural Department, have, at various times, officially promoted the establishment of small mixed citrus orchards on smallholder sugarcane farms throughout Fiji. Such orchards are now common, and do provide some cane-farm families with an additional source of income through local sales, often at fresh produce markets in the main towns. In most cases, however, such efforts have met with only limited success beyond satisfying on-farm subsistence needs.
Perhaps most notable was the proposal for the eventual development of a system of 90 ha of smallholder citrus holdings, each of 2.5 ha, to supplement production from 162 ha of monocultural production at the Batiri Citrus Scheme, established on the island of Vanua Levu in 1978, funded by foreign and local investors and the Fiji Development Bank (FDB). Additionally, 200-500 ha of West Indian limes were to be established in nearby Seaqaqa and Bua to generate additional income and employment on Vanua Levu and to extend the processing season at the factory (C.P.O. 1980, 110). As early as 1984, it was suggested that the Batiri Citrus Scheme would not be feasible as a "stand-alone" orange-processing project, given the high costs of operations, inadequate financing, low long-term production levels, delayed investments in other aspects of the project, and the underutilization of land (McGregor 1984).
To achieve fuller utilization of the project, which has been hampered by the very short processing season of the oranges, diversification into pineapples, mangoes, guavas, and passion-fruit was recommended. Various intercropping trials were carried out, but, unfortunately, this highly export-oriented and capital-intensive project ran into major financial difficulties in 1988 and has subsequently been taken over by the National Marketing Authority (NMA). The smallholder "outfarm" Stage II component was never developed, although a few smallholder farmers did plant improved citrus cultivars, and surrounding Vanua Levu out-growers supplied some 10 tonnes of fruit, with another 109 tonnes coming from Rotuma in 1984 (McGregor 1984, 10). A major problem of this monocultural project has been the destruction of 25 per cent of the annual production by a fruit-sucking moth (Fiji Times 26 July 1988, 3).
In 1945 the Cook Islands began a large-scale Citrus Replanting Scheme, with the initial establishment by 1950 of 150 acres on Rarotonga and 50 acres on Aitutaki. which did include deliberate inter cropping with cover crops and multi-purpose trees. Crotalaria and tarapi grass were planted as green manure between rows to be ploughed under thrice yearly during inter-row cultivation, with leguminous dadap trees (Erythrina variegate) planted between alternate citrus trees to be trimmed to provide green manure. Shelterbelts of jambolan (Syzygium cumin)), Albizia falcataria, hibiscus (Hibiscus rosa-sinensis or H. tiliaceus - it was not made clear what species was planted), and hedge panax (Polyscias guilfoylei) were planted, with A. falcataria being grown to provide timber for citrus shipping-cases (Johnson 1951; Johnston 1967). Unfortunately, the scheme did not encourage self-reliance and has been less than successful. Many landowners have fallen into debt and have suffered widely fluctuating yields and returns.
In Nine, which has actively promoted the planting of extensive areas of limes (Citrus aurantiifolia), often as intercrops with coconuts and other crops, the export of limes and lime juice has been the second most important agricultural export after passion-fruit (Carter 1984, 298). Other countries that have tried to encourage limited intercropping of citrus include Tonga, Western Samoa, and French Polynesia.
Banana intercropping
Intercropping of bananas for export under coconuts, with cocoa, and to a lesser extent with subsistence ground crops and other trees, has been promoted from time to time in Fiji, Tonga, Western Samoa, and the Cook Islands, although recently there has been a trend towards more monocultural production.
In Fiji, the export banana industry was based on smallholder production, often under coconuts and other trees with root crops and supplementary crops cultivated in between, at least in the early stages of plantations. In the early 1960s, however, greater official emphasis was placed on monocultural production for expanding export markets in New Zealand and Japan. The major effort in this direction was the Lomaivuna Resettlement Scheme in south-east-central Viti Levu, which was designed to resettle some 200 landless families on 4ha (10-acre) allotments. The objective of the scheme was the monocultural production of bananas on 2 ha, with the balance being used for homestead and subsistence crops. As a banana scheme it failed because of serious outbreaks of black-leaf-streak fungal (Mycosphaerella musicola) and bunchy-top viral diseases, heavy nematode (Radolus similis) infestations, loss of trees rule to a series of tropical cyclones, the unsuitability of the soils and topography for banana cultivation, and the resultant poor quality of the fruit (Eaton 1988b). Because of these problems associated with monocultural banana production, export banana production in Fiji ceased in the early 1970s.
Intercropping of bananas for export with coconuts and staple root crops has also long been promoted in Tonga, Western Samoa, and the Cook Islands, and supported by considerable financial and technical support from the New Zealand marketing agent, Fruit Distributors Limited, and the New Zealand Government. As was the case in Fiji, banana production increased dramatically in the mid- and late 1960s in response to increasing market demands in New Zealand (partly due to the removal of an earlier quota system, after Fiji ceased export production), but then declined just as dramatically due to the same diseases as experienced in Fiji. Banana production in Tonga, for example, dropped 60 per cent in 1969, with further decreases in 1970 and 1971 (Thaman 1976).
In an attempt to combat declining production and improve export quality, the Departments of Agriculture in Tonga, Western Samoa, and the Cook Islands, with subsidization by Fruit Distributors Ltd and New Zealand AID, have all implemented planting or rehabilitation schemes. In Tonga, a Banana Rehabilitation Scheme, which required growers to plant one or more acres of at least 500 plants, with no intercropping, to control weeds to a reasonable standard, to practice desuckering and leaf-trimming, and to destroy bunchytopaffected plants, was instituted in the early 1970s (Thaman 1976). Despite continued efforts to rehabilitate banana production in Tonga, Western Samoa, and the Cook Islands, yields and fruit quality continued to deteriorate in all island groups during the 1960s and 1970s, with the major share of the New Zealand market being increasingly supplied by Ecuadorean bananas.
Efforts in all three countries during the 1980s to rehabilitate production of bananas for export have continued to face problems of disease, cyclone damage, and marketing. Many of these often heavily capitalized efforts have been strongly monocultural; several have failed entirely; none has met with real success; and most banana schemes have contributed to agrodeforestation.
Vanilla intercropping
Smallholder vanilla production, with appropriate support plants, and often under coconuts or other trees, has been increasingly promoted by governments throughout the Pacific. The only areas where vanilla has become a significant export, however, are French Polynesia and Tonga. In French Polynesia, where it has been intercropped under coconuts and other trees using Tecoma stans as a support plant, exports dropped from 28 tonnes in 1970 to a low of 0.6 tonnes in 1981, but renewed interest in the crop had increased production to 14.7 tonnes by 1984 (Douglas and Douglas 1989, 149).
In Tonga, where vanilla is becoming an increasingly important export crop, there is widespread official advocacy for its planting under coconuts and other trees, using physic nut (Jatropha curcas) as the support plant. Vanilla, given its high returns per acre and negligible demands on soil fertility as an epiphytic member of the orchid family, seems to be the perfect plant for Tonga, where land scarcity is increasing. Vanilla has been a major export crop in the northern Vava'u group since the 1960s, and the Department of Agriculture has been seriously promoting its cultivation in all island groups within the Kingdom for the past 10 years. By 1984, there were reportedly 105 vanilla growers with 21.2 ha of vanilla in production, 37.2 ha planted but not yet in production, and another 3.7 ha planted with support plants in preparation for vanilla planting.
Two different models have been developed to determine how best to incorporate vanilla into the traditional mixed cropping system in the belief that Tongan farmers will manage their plantations better if vanilla is introduced into a system that is already familiar (Fa'anunu n.d.). Other countries, such as Fiji, Vanuatu, and Papua New Guinea, have small vanilla development programmes, and a small number of growers in Fiji are producing marketable yields.
Oil-palm intercropping
Papua New Guinea and the Solomon Islands are the only two countries growing oil-palm (Elaeis guineensis) on a commercial scale. Papua New Guinea has three schemes, the first and largest being the Hoskins Oil Palm Development Scheme started in West New Britain in 1967, on the basis of a balance between a company plantation and adjacent smallholders; the Sangara Scheme started in the Northern Province in 1977; and the Bialla Scheme started in West New Britain in 1980. On the Hoskins oil-palm resettlement scheme, smallholders were encouraged to intercrop subsistence crops between oil-palms in the early stages of plantation development. Consequently, in the late 1970s, 31 per cent of the settlers were able to practice market garden ing of traditional foods, and, given access to land, the farming systems of almost all settler groups had remained virtually intact with people growing their own food (Benjamin and Wapi 1982). In the Solomon Islands, however, the large-scale Guadalcanal Plains joint venture oilpalm development scheme is entirely monocultural, with little encouragement of intercropping or agroforestry practices (Carter 1984).
Kava intercropping
Kava (Piper methysticum) is an important crop in Vanuatu, Fiji, Tonga, Pohnpei, and to a lesser extent in Western Samoa. Given its shade tolerance and that it takes 3-6 years to mature, it is particularly amenable to intercropping both with short-term food crops and with coconuts and other trees.
In Vanuatu, where kava cultivation and consumption is, in many rural areas, highly ceremonial and very significant in garden magic, the plant is almost always intercropped amongst trees in polycultural gardens. Kava is also one of the main cash crops promoted as an intercrop with coconuts and in timber plantations of Cordia alliodora.
In Fiji, kava (known locally as yaqona) is a major cash crop for local sale and the major cash crop for villagers in some of the smaller outer islands and the interiors of the larger islands. Programmes to rehabilitate the copra industry have encouraged the establishment of other economic crops such as cocoa and kava underneath coconut palms. Some Fijian kava farmers are beginning to intercrop kava with Calliandra calothyrsus, a nitrogen-fixing species being promoted for agroforestry in Fiji by the Fiji-German Forestry Project. Throughout Fiji, kava is commonly intercropped with staple root crops, particularly taro (Colocasia esculenta). The kava is then allowed to mature amongst existing cultivated and protected trees after the root crops have been harvested.
Whereas copra prices are dictated by outside market forces beyond the control of Fiji and its farmers, most of the kava produced is sold internally and has shown much greater price stability than copra. Of further significance is that almost all kava farms are Fijian-run. Sofer (1985) argues that the success of kava as a commercial crop in Fiji results from the familiarity of Fijian farmers with its husbandry. Also, kava provides higher returns to the grower, per unit of land, labour, and capital investment, than most alternative cash crops; it requires few outside inputs; its planting material is readily available and consists of parts of the plant not normally sold; it can be harvested or processed at any time; it is non-perishable and can be easily stored; and it is well-adapted to the environmental conditions and to the semisubsistence polycultural shifting agroforestry system in Fiji.
In Tonga, kavais also seen as an important local cash crop and is almost always planted under coconut palms and other useful trees.
Other commercial agroforestry intercrops
In Fiji, a number of successful smallholder papaya plantations, sometimes under coconuts or as part of diversified agricultural developments, supply the growing demand for the fruit in the country's tourist resorts. Unfortunately, a major 30-ha capital-intensive papaya plantation developed by the Native Land Development Corporation to air freight fruit to Japan has been a failure. Most recently, however, the Southern Development Company Ltd. the company responsible for directed smallholder tobacco production for Fiji's local cigarette manufacture, has attempted to diversify the production of its directed smallholder farmers into tomatoes, maize, chillies, mangoes, and papayas. Papayas seem to offer the greatest potential, with 18 farmers already growing the crop under the auspices of the company (Eaton 1988, 194-195).
Areas of improved mango varieties for export have also been planted by the Native Land Development Corporation and on the Government-run Yaqara Beef Cattle holding on Viti Levu as part of a diversification programme. Papua New Guinea, Vanuatu, Tonga, Western Samoa, and the Cook Islands have also experimented with improved mango cultivars, as well as avocados in efforts to diversify tree crop production.
Smallholder passion-fruit (Passiflora edulis) production, often as an intercrop with coconuts or other trees or on small plots within existing plantation areas, has been strongly promoted in Papua New Guinea, Fiji, Tonga, Western Samoa, and Nine, as part of agricultural diversification programmes. Results have been mixed. Hurricanes have damaged vines, market availability has been inconsistent, as has ability to supply, given low production because of poor management and insufficient labour to carry out daily the hand pollination of the flowers needed to obtain high yields. The industry has showed promise only in Fiji, where the production is run as a directed smallholder operation by a fruit processing and exporting company that provides most of the inputs, planting material, and research, extension, and managerial services, and in Nine, where passion-fruit is the most important agricultural export (Carter 1984).
In Fiji, the aid-funded Fiji-German Forestry Project, working together with Fiji's Forestry Department and the Extension Service of the Ministry of Primary Industries, is promoting a kind of alleycropping system through the introduction of hedgerows of Calliandra calothyrsus along the contours of sloping land used for various crops, particularly ginger. In less than two decades, ginger has grown to be Fiji's third-largest agricultural export earner, surpassed only by sugar and coconut products. A combination of the environmental requirements of ginger (high rainfall, fertile soils, good drainage, freedom from nematodes) and the low capital resources of the smallholders planting the crop has led to a "ginger frontier," where ginger is grown on plots newly cleared of forest for a few seasons and then moved on to still more recently cleared land, leaving behind a cleared, less fertile area (Overtop 1989, 83). The Calliandra hedgerows, which are recurrently pruned, are intended to slow erosion, which has been serious at times on the steep ginger-growing lands, to provide nutrients and firewood, and to serve as wind-breaks. Attempts to analyse the economic benefits of Calliandra hedgerows suggest that the labour costs of establishing the hedgerows are repaid in two years by savings on fertilizer (Künzel 1992, personal communication).