Dennis P. Garrity and Chun K. Lai

Shifting cultivators usually slash and burn secondary forests or fallows and prepare the land for food crops. Fallows, which restore soil fertility and suppress weeds, occur between periods of food crop cultivation.

Can shifting cultivation be "sustainable"?

Alternatives to Slash-and-Burn Consortium indicates that a remarkably wide range of smallholder land use options are agronomically sustainable, depending on the larger environmental and economic context. However, household labor and land constraints are often limiting factors to intensification options.

In the past, relatively low population density and abundant forest cover provided a favorable base for sustainable shifting cultivation practices with long fallow periods, ranging from 10 to 60 years.

In parts of Papua New Guinea, the forest vegetation is cut but the underbrush is not burned. The cut branches and leaves are laid along the contour to provide erosion control as well as to slowly release nutrients from the decaying biomass. Food crops are then planted using minimum tillage practices, such as dibble or digging sticks.

In our common quest toward developing more sustainable shifting cultivation practices, as well as alternatives to unsustainable slash-and-burn agriculture, most strategies now being employed are towards intensification.

One major challenge is to document and evaluate indigenous strategies for intensification of shifting cultivation through an integrated and iterative process of research and development. This process involves identifying promising indigenous practices, understanding them and the context in which they are used, validating their utility, extrapolating them to other locations, verifying them with key farmers in new areas, establishing their recommendation domains, and extending them more widely.

Much of Asia is dominated by mountainous topography populated by diverse ethnic minority communities. Expansive forests and sparse populations allowed these mountain-dwelling communities to practice various forms of shifting cultivation, which enabled them to coexist in relative harmony with their environments. The annual cycle of slashing and burning that characterizes land preparation in shifting cultivation systems, however, has often been drawn criticized as being inefficient and a leading cause of tropical deforestation.

Detailed anthropological studies, starting with work by Harold Conklin in the Philippines, evolved a much more favorable assessment of shifting cultivation. They presented strong evidence to show that it is a rational farming system in the context of constraints and opportunities inherent in remote upland areas. They pointed to its long history as evidence of sustainability.

These studies argued that shifting cultivation is a land-use practice that does not want to destroy forests, but instead it generally reflects an

• indigenous knowledge accumulated through centuries of trial and error,

• intricate balance between product harvest and ecological resilience, and

• impressive degree of agrodiversity.

More recent studies point to the custodial role often played by shifting cultivation communities in preserving forest ecosystems and natural species and to the tight linkages between biological and cultural diversity. This suggests that efforts in biodiversity conservation will remain ineffective, until they broaden their scope to also address cultural conservation.

One cross-cutting issue of direct relevance to research and development priorities in Asia is identifying and disseminating successful indigenous strategies for managing fallow land in more productive ways. This will enable an intensified land use that provides a higher output per unit of land, labor, or capital investment. The resulting increased productivity will more ably support the growing population densities of the uplands and alleviate the pressure to convert remnant forests into agricultural land.

The approaches that farmers use to change their fallow management in response to intensification pressures may generally be classified as innovations to achieve:

• More 'effective' fallows — where the biological efficiency of fallow function is improved, and the same or greater production benefits can be achieved in a shorter time frame (e.g. weed suppression or soil fertility replenishment)
• More 'productive' fallows — in which fallow length remains the same or is actually lengthened as the farmer adds value to the fallow by introducing more economic species, or
• Combination of the two — where both biophysical and economic benefits may be obtained.

One of the most promising approaches to identify biophysically workable and socially acceptable technologies is to document and understand case studies of indigenous adaptations that are successful.

Unfortunately, there is little documentation of such indigenous innovations for the formulation of the national and international research agenda or to inform policy makers. Indigenous innovations are generally unobserved or misinterpreted.

The Indigenous Fallow Management (IFM) Network has been attempting to build a community of workers to fill that gap. The publication 'Voices from the Forest' (Cairns, 2001) contains a large and fairly comprehensive review of many systems.

Article condensed by D.B. Magcale-Macandog and R.T. Yao from “Shifting Cultivation in Asia: Diversity, Change, Indigenous Knowledge and Strategies” by Dr. Dennis P. Garrity and Mr. Chun K. Lai. In: Shifting Cultivation: Towards Sustainability and Resource Conservation in Asia. International Fund for Agricultural Development, International Development Research Centre, Cornell International Institute for Food, Agriculture and Development, International Center for Research in Agroforestry, and International Institute of Rural Reconstruction. 2001.

About the authors:

Dr. Dennis P. Garrity is the Director General of the International Center for Research in Agroforestry (ICRAF).

Paul Burgers

Historically, in most traditional shifting cultivation systems, fallow vegetation was simply left to establish naturally after abandonment of a cropped field. In the recent decades, many households have shifted toward more active management of fallows to better serve the changing needs and priorities of the farming households.

Some of these managed fallow strategies still mimic natural vegetation succession. Usually, these strategies are based on species enrichment to increase the economic value of the fallow vegetation and have sometimes led to the development of semi-permanent tree-crop based systems (Raintree and Warner, 1987; Cairns and Garrity, 1999; Sanchez, 1999). Other management strategies focus on the intensification of the cropping period through the incorporation of species that enhance soil fertility restoration as the traditional fallow period is shortened. The different strategies are largely a result of the dynamic context in which people live. This context consists of changes in the biophysical, social, economic, and political environment.

People in the forest margins: pioneers and indigenous forest farmers

Forest farming communities in Southeast Asia can be broadly defined as consisting of two groups: “pioneers or colonists” and “indigenous forest farmers”.

The pioneer or colonist group includes households that have migrated to the upland areas for safety reasons due to political instability or wars. It also includes households that have migrated due to the deterioration of their livelihood to the point where upland migration is the only option. A third subset of this group consists of more voluntary “pioneers”, who see greater prospects for wealth accumulation in the uplands (White, 1991; Dietz et al., 1992). These more voluntary pioneers are, on the whole, relatively resource-rich migrants (usually through off-farm employment) who invest in forest conversion to establish perennial and annual cash crop gardens. These various pioneer households are generally unfamiliar with the natural environment in which they operate and do not rotate crops. They are more likely to abandon cropped fields once the soils have become badly and frequently irreversibly degraded (Fujisaka and Wollenberg, 1991; Sunderlin, 1997).

The second group, indigenous forest farmers, consists of communities that have practiced forest farming and lived in the forest margins for generations. They have gradually accumulated local ecological knowledge and experiences through decades of trial-and-error experimentation in and with the natural environment. They have learned to practice agriculture sustainably, enabling them to satisfy their livelihoods at the forest margins without causing large-scale deforestation. Slash-and-burn techniques are an integral part of this group’s rotational farming systems, which have featured short cropping periods followed by long forest fallows to restore soil fertility.

Fallow management strategies

Indigenous forest farming communities have developed fallow management strategies over time to adapt to changing environmental, economic, social, and political conditions. Three types of adaptive strategies have been distinguished: (1) improved fallows focusing on increasing the rate of restoration of soil fertility and other ecosystem properties following cropping such as reduction in pernicious weed populations; (2) enriched fallows focusing on increasing the direct economic benefits of the

natural fallow vegetation; and (3) a focus on integrating soil fertility and economic benefits through integration of livestock (Raintree and Warner, 1987; Cairns and Garrity, 1999; Sanchez, 1999).

Benefits and constraints of improved fallows

For households that rely solely on upland farming and live too far away from markets where they can easily sell their products or buy food and inputs for their agricultural system, soil fertility restoration for food cropping usually remains the dominant purpose of the fallow. The approaches that have been developed by the farming households to manage the fallow and its component species to enhance production of the cropping system can be summarized as follows: (1) restore soil fertility more completely during a fallow period of the same length,

(2) shorten the fallow period and increase the cropping intensity while maintaining the same level of soil fertility at the start of each cropping cycle, or (3) a combination of (1) and (2). For example, in Nagaland, northeast India, the stumps of the alder trees in the Alnus nepalensis-based fallow system are kept in the field during the cropping season so that during the fallow period, they will coppice rapidly, forming a closed canopy of nutrient-rich biomass that can be cut to enrich the soil before the next cropping phase. In northern Vietnam, the introduction of leguminous trees such as Tephrosia candida has enabled a decrease in fallow length from 10-15 to 4-6 years (Siem and Phien, 1993; Fagerstrom, 1999).

Shortening the fallow period carries the risk of ‘over-intensification’, degradation of the soil, and a decline in household food security. A simple model of crop fallow systems (Van Noordwijk, 1999) suggests that to obtain maximum crop yields per hectare in a sustainable way, soil fertility at the start of each new cropping cycle needs to be about 55% of the maximum value or higher. Effects on biodiversity are also a concern as fallows are “improved,” as the introduction of a single or several species for specific fallow purposes tends to reduce plant diversity of the fallows.

Benefits from and constraints to enriched fallows

Enriched fallows are observed in areas where livelihood needs and aspirations of the households change and economic considerations grow in importance. These are areas where links with urban areas and the monetary economy intensify, where there are large enough markets to sell agricultural surpluses, and where there are significant alternatives on-farm or off-farm employment opportunities. The growing need and desire to obtain cash income often result in a partial shift from subsistence farming to production of economically valuable annual crops and perennials for the market. In particular, when farming households largely depend on their off-farm income for their livelihood, fallow lands may be planted with trees that have long maturity periods as an investment strategy.

One of the management strategies for enriching fallows is to plant and promote the growth of economically valuable species in the fallow vegetation, including fruit and other non-timber tree species to obtain cash income (Wiersum, 1997a; Van Noordwijk and Swift, 1999). In some highly degraded lands of Sumatra, Indonesia, households have converted traditional fallows to multi-story tree-crop plantations of rubber, fruit trees, and rattan (Gouyon et al, 1993; Angelsen, 1995; Dove, 1998). Other management strategies include the planting of rattan in natural fallows in the Philippines and Indonesia (Godoy, 1990; Siebert and Belsky, 1994) and the enrichment of fallow vegetation with paper mulberry in northern Laos.

A system of relay-planting vegetables, coffee, and cinnamon in sequence is practiced in Kerinci, West Sumatra, Indonesia, to provide short-, medium-, and long-term cash income (Burgers and William, 2000). By imitating the crop-succession phases of a natural fallow, vegetables are planted first to provide the short-term cash income during the initial 2 years of establishment of forest-like structure of coffee-based system. After 2 years of coffee growth, vegetable growing is not feasible anymore due to overshadowing the coffee trees. At this time, cinnamon seedlings are planted in the coffee stand. After 3-4 years of earnings from the coffee harvest, the canopies of the cinnamon trees close and coffee can no longer be harvested. From this time on, the branches of some cinnamon trees are harvested to satisfy daily and/or weekly cash needs. The bark of all the trees (the main product) may be sold at once when a large sum of cash is needed.

Similar strategies are applied to establish smallholder rubber gardens in Sumatra (De Jong, 2001) and rattan and rubber forest gardens intercropped with rice in East Kalimantan, Indonesia (Mussche, 2001). Such succession-based systems provide households with cash income, while the architectural structure of these tree-based systems provides a certain degree of biodiversity. The systems also minimize erosion and surface run-off of water, thus protecting both the uphill areas and rice fields in the valleys (De Foresta and Michon, 1990; Wickramasinghe, 1997; Wiersum, 1997a; Dove, 1998; Tomich et al., 1998b). 

Despite the numerous benefits and the long-term steady cash flow provided by these systems, wider adoption of these strategies has been limited due to a number of factors. Foremost is the larger area of land required to satisfy cash income needs of the household, particularly during the establishment period of the trees, and the need to plant food crops. The area requirement can vary, depending on off-farm employment opportunities available to augment cash and food needs (Burgers and William, 2000; Sabirin and Hamdan, 2000). Another factor is the long waiting period before yields from the perennial crops can be harvested. During this waiting period, households would need other sources of income or food such as off-farm employment or planting of annual crops. A third factor is the increased dependence of households on market forces and increased exposure to risk due to price volatility of these cash crops when farmers plant food crops instead of non-food cash crops.

Benefits from and constraints to livestock integration

Livestock are an extremely important component of farming systems for a number of reasons. First, they are an important source of cash income through the sale of animal products such as meat, milk, and skin (Hansen, 1997). Animals such as cattle and buffalo provide draft power in land preparation (cultivation and harrowing) and in transporting farm products and household supplies. They also play an important role in nutrient cycling in mixed crop-livestock systems, depending on what they are fed and whether or not manure is brought back into the field (Huxley, 1999).

Fallow species such as Leucaena leucocephala can be used as fodder for livestock. In eastern Indonesia, households use L. leucocephala as a fallow species in a rotational system with maize (Metzner, 1983; Yuksel and Aoetpaj, 1999). In addition to being a source of fodder, these trees also serve the purpose of enhancing soil fertility as they are able to fix nitrogen in the soil.

A number of factors hinder the integration of livestock into cropping systems. A major constraint is the investment needed to acquire them and any necessary feed, fencing materials, or grazing areas. Additional labor may be needed for herding and tethering the animals. Allowing animals to roam and graze freely in the farm may lead to overgrazing of young fallow vegetation, thereby reducing the regenerative processes of a natural fallow. Also, trampling may lead to soil compaction.

The key to success in the introduction of livestock as a means of improving fallow-based farming systems depends on how well they can be integrated into the system or segregated from crops (Cairns and Garrity, 1999). Karen communities in northern Thailand have successfully integrated cattle into their farming system. They allow the cattle to graze freely in the young fallow vegetation during the fallow period and herd the animals during the cropping season of rice (Burgers and Trakamsuphakon, 2001).

Evolving Soil Fertility Management Practices

Coen Reijntjes

Soil fertility management (SFM) is the basis for achieving sustainability of agricultural production systems. Many different practices influence soil fertility — fallowing, application of organic or synthetic fertilizer, green manuring, mulching, burning, soil tillage, soil and water conservation, crop rotation, and animal and tree integration.

Every farming system has its own unique way of SFM, depending on a combination of factors: the condition of the natural resource base; available land, labor, and capital resources; history of local farming; farmers’ knowledge, their motivation, skills, and degree of market orientation; relative prices of inputs; and agricultural policy.

Several broad categories of farming systems may be identified, each with characteristic SFM practices. These include

Shifting cultivation and fallow systems based on natural processes of soil fertility regeneration;

Interactive pastoral and fallow systems based on nutrient harvesting by animals and fallow vegetation;

Integrated and organic agriculture typified by recycling of nutrients; and

Modern agriculture in which synthetic fertilizers and mechanization control SFM.

Within and between these categories is a wide diversity of practices.

SFM practices are being continually modified as conditions change. As population pressure increases and land becomes scarce, SFM shifts from extensive to intensive. A framework of typologies of indigenous fallow management was developed based on case studies presented during the Conference on Indigenous Strategies for the Intensification of Shifting Cultivation in Southeast Asia held in Bogor, Indonesia. This framework provides a continuum of indigenous intensification strategies in shifting cultivation.

An example of evolving SFM is the intensification process of the Mangyan shifting cultivators in Mindoro, Philippines. The traditional strategies of using natural processes to manage crops and fallow vegetation provide options for increasing production in a sustainable way. One of these options is the replacement of slash-and-burn practices by slash-and-mulch practices.

Farmers are exploring alternative SFM strategies due to various factors. These driving forces of SFM evolution include the following:

population increase,

scarcity of arable land,

market,

decreasing yields, and

soil degradation.

Each SFM strategy fits but also needs specific conditions, farmers adopt those practices that best fit their conditions. Subsistence farmers in Nepal cannot afford and sometimes have no access to synthetic fertilizers, depending only on natural means of SFM such as use of green manure. Green manures or cover crops can successfully replace or complement synthetic fertilizers or slash-and-burn practices. Where labor is scarce or relatively expensive, farmers cannot afford the labor required for intensive recycling of organic waste. The relationship between different farming systems/SFM strategies and the different types of conditions under which farming is carried out in the mountain valleys was illustrated in Ecuador.

Today’s pressing issues are the ecological sustainability of agriculture and the search for ways to increase production. The Nutrient Monitoring (NUTMON) model nutrient balance study in Kenya showed that farmers who participated in nutrient management programs obtained about 30% of their income from nutrient mining.

However, in other places, nutrients are lost through the sediments washed out in soil erosion, as organic waste in city areas, leached into the groundwater and volatilized in the air. All these cause pollution.

Synthetic fertilizers are frequently used in an unbalanced, inefficient, and hence, polluting way, leading to soil degradation and declining yields. Each kilogram of synthetic fertilizer used corresponds to an approximately equivalent amount of nutrients contained in organic matter.

The drive toward modern, market-oriented farming is causing severe ecological degradation and economic marginalization. Market agriculture, migrant labor, and the desire to participate in the consumer culture are sapping the cultural and spiritual basis of traditional society and place a heavy burden on survival strategies. Reorientation toward traditional farming strategies or urbanization and the consequent weakening of indigenous culture seem to be the two development polarities available to indigenous communities and resource-poor farmers.

Evidences from case studies have shown that traditional farming strategies can still provide a sustainable basis for livelihood. Farmers can make their way between subsistence farming, market farming, and urban employment and succeed in intensifying land use while controlling ecological degradation. These farmers often complement natural methods of SFM with the judicious use of small amounts of synthetic fertilizers. There are, however, many cases where farmers have been less successful. They find themselves trapped in such poverty and ecological degradation that they are forced to migrate to the cities.

Integrated nutrient management (INM) or integrated plant nutrient systems (IPNS) refers to strategies that combine the use of internal and external sources of nutrients in a local situation. These strategies allow a more efficient, profitable and ecologically sustainable use of synthetic fertilizers and other external inputs in market agriculture, which, in turn, lowers the threshold for farmers working in less favorable conditions to become part of or remain within the market economy without degrading their system. Decreasing the cost of transport, marketing, inputs, and facilitating credit can help farmers become more competitive in the market.

Given the changing conditions, needs and insights, farmers have to constantly adapt their SFM practices. However, new practices have to accommodate not only the prevailing natural, economic and cultural conditions but also the way agriculture and society have evolved over time. Evaluation of learning processes can be enhanced by learning tools and dialogues that build on traditional practices and insights.

Article extracted from “Soil Fertility Under Pressure” by Mr. Coen Reijntjes, ILEIA Newsl. 13(3) 4. This article is also available online at: <http://www.oneworld.org/ileia/ newsletters/13-3/13-3-4.htm> Ð

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These traditional fallow systems have been modified over time. Several forces have driven the evolution of different fallow systems in the Philippines. Population pressure and the necessity to meet the food demands of the population have forced farmers to intensify the cropping phase and ultimately shorten the characteristic long period of fallow in the traditional sustainable shifting cultivation systems.

The main purpose of fallowing the land is to restore soil fertility levels. Improvement of fallow systems through the introduction of herbaceous legumes (Pueraria phaseoloides, Vigna radiata, Glycine max, Arachis hypogaea and Vigna sinensis), leguminous shrubs (Mimosa invisa and Calopogonium mucunoides) and fast-growing leguminous trees (L. leucocephala and Gliricidia sepium) has been observed in several fallow systems in the Philippines.

Soil fertility was restored in a much shorter time frame using legume-improved fallows, in contrast to the traditional fallow systems in which the native vegetation is allowed to regenerate naturally during the fallow period. Soil fertility recovery was hastened through the incorporation of leaves into the soil as green manure and mulch to protect the soil from erosion. Some nonleguminous shrubs such as Chromolaena odorata are allowed to proliferate in fallow areas due to their beneficial effect on the build up of organic matter in the soil.

The government’s concern for soil erosion control in the Philippine uplands was a major driving force in the widespread introduction and proliferation of hedgerow systems in the mid-1970s and early 1980s. Leguminous trees such as L. leucocephala and G. sepium are popular hedgerow species introduced in the sloping uplands at this time. Besides helping control erosion, they also serve as sources of organic material and nitrogen for the crops planted in the alleys between the hedgerows.

The Philippine fallow species can be classified into three categories: (1) tree-based; (2) shrub-based; and (3) grass/herb-based (Magcale-Macandog, Yao and Degal 1999).  Ð