Manioc is, by far, the most cultivated crop; it is the most important component of the local diet and also the most important crop economically and culturally Fraser a , Fraser et al. No other crop in the region is the focus of such elaborated knowledge, and such detailed, ingenious, and labor-intensive practices in cultivation and processing.
Our interviews indicate considerable variation in the number and size of swiddens that farmers open in a year. Normally it varies between 1 and 4, most often 2; size varies between 0.
Farmers have been making swiddens for manioc in this landscape for generations, and they consider that being self-sufficient in manioc flour is an important part of their identity. It is a behavior that is expected from a member of the community. Apart from its important subsistence and cultural value, farmers also cultivate manioc for sale, mostly as flour, and this is often their most important source of monetary income.
Although a cultivated swidden provides an opportunity to meet both subsistence and monetary needs, its success requires careful planning from the very beginning, with the decision of opening being crucial. Months ahead of opening, farmers are already thinking of their future swiddens, discussing them with their relatives, and considering why the swidden will be opened, how it will be opened, planted, and maintained, i.
Essentially, the decisions to open and abandon swiddens are the outcomes of balancing labor requirements with other demands.
Farmers say they open a new swidden when the older one s in cultivation become too burdensome to maintain, i. For nonanthropogenic upland soils NAS , this generally starts to occur after the first cropping cycle. Swiddens on NAS are dominated by bitter manioc, and farmers say that the length of the cropping cycle varies from six months to three years, depending on the landraces that are cultivated and the time it takes for harvesting.
Most often harvesting starts months after planting and lasts from a couple of months to more than a year. The opening of a swidden requires enormous effort because it is mostly manual labor and usually involves cutting dense vegetation. There is, however, considerable variation in opening and planting times, especially for crops other than bitter manioc, e. Many farmers consider that ADE is suitable for the cultivation of almost everything, in which whatever you plant grows owing to the relatively high fertility of these soils.
According to farmers, crops like watermelon, maize, or beans, which are commonly cultivated on the floodplains, can only be cultivated successfully on uplands when grown on ADE. For the decision about where to open their swiddens, farmers rely on their historical knowledge of the landscape, e. This reading is essential, especially because farmers recognize that environments are dynamic and that their properties or suitability for cultivation change over time.
Their decision to establish a new swidden, or on how to cultivate and manage it, reflects an integrated knowledge of the soil and vegetation, as affected by their management practices. Ease of access, proximity, and land tenure also play important roles in the decision about where to open a new swidden. Because most of the transportation of people and products is by foot or canoe, farmers prefer to establish their swiddens as close as possible to their houses or, in the case of bitter manioc, to the place where the manioc is processed into flour although the processed product of course also needs to be transported.
In most villages, the area used and managed by households is comprised of a mosaic of private lands, which can be formalized or not, and state-owned lands. Although population density is very low and land is not scarce in most villages, farmers say that access to land tends to be more regulated closer to habitation sites, in which both formal, e. Because ADE occur in relatively small areas, closer to habitation sites, and allow the cultivation of crops that cannot be cultivated elsewhere, access to these areas tends to be most regulated by both formal and informal land-tenure rules.
Farmers recognize the variation in soil properties and always associate them with vegetation differences in terms of 1 fallow development, 2 weeding requirements, or 3 crop suitability:. For the identification of soils, farmers use physical characteristics, especially texture and color. The term terra preta black earth is used in reference to soils that are darker and loose, and therefore does not always correspond to the scientific definition of anthropogenic soils.
People who live on ADE patches or who use them for agriculture or agroforestry are constantly in contact with archaeological artifacts, including lithic materials stone axes, mortars , earthworks ditches, excavated trails , and ceramic fragments. There is general agreement that these are remains of former indigenous residents, but there is no consensus about the origin of the soil itself.
Most farmers see ADE as a natural type of soil with specific properties, favored for habitation by indigenous people, which would explain the occurrence of the material artifacts. People actively manage soils in many ways albeit in very small areas and recognize that management can modify soil properties. In their explanations and practices for soil enrichment, fire always plays a central role.
Most people do not think that the ADE patches, large and relatively abundant in the landscape, were created by humans. Interestingly, their reasoning about the creation of ADE resembles the academic understanding of how these soils were formed, incorporating 1 the temporal dimension, 2 the magnitude of the historical human occupation of the landscape, and the practices of resource use and management that might have led to these transformations, i.
Apart from the recognition of variation in soil properties per se, farmers obtain a more complete understanding of soils by observing characteristics of the vegetation. In particular, the observations that relate to labor requirements are prominent. Farmers recognize the stage of development of the vegetation as a direct indicator of the amount of the labor required to open the swiddens and to maintain their productivity. Opening an older fallow, described locally with terms such as tall, thick, or old fallow, means cutting more and larger trees, which requires more labor.
On the other hand, farmers say that swiddens opened in older fallows tend to have less weed growth and higher productivity. When it comes to ADE, farmers recognize several contrasts with other upland soils. Farmers say that the vegetation grows faster on ADE, which implies higher weeding requirements, but they also mention that fallows on ADE are denser in the understory, have a higher abundance of palms and lianas, and do not grow as tall as fallows on NAS.
Fallows on ADE are thought to be hard to walk through, but at the same time they are easier to open because they tend to be softer, i. The fact that older fallows require less weeding and give higher yields is, however, not strongly emphasized when they talk about ADE. Farmers say that ADE always requires a lot of weeding, even if swiddens are opened from old fallows, and that ADE always produces well, even if swiddens are opened from young fallows Fig.
Also, farmers say that old fallows on ADE are harder to find, and therefore they have fewer options when choosing from fallows in different stages of development on ADE than they have with NAS.
The high weeding requirement for cultivation on ADE is the most common and salient consideration of farmers in their decisions about opening a swidden on these soils. We recorded some situations in which farmers opened swiddens on ADE but only managed to weed a fraction and had to abandon the remainder.
This reading of the fallow, therefore, enables farmers to project immediate and future labor requirements to obtain a potential yield. The diagrams in Figure 2 represent these differences schematically. As indicated, opening a new swidden is very labor intensive.
A few days or weeks before his puxirum, the farmer invites a number of fellow farmers to participate. The duration of the puxirum and the number of people involved depends on the age of the fallow and the size of the swidden. Thus, older fallows require longer puxiruns because they have larger trees and more of them have hard wood, which makes felling more laborious.
Shorter puxiruns involve farmers and can last for a few days, but in general a puxirum is thought to last only 1 day, from early morning to the middle of the afternoon, and can involve as many as 20 people. When opening a new swidden, the farmer will have to consider the number of days he will have to work outside his swidden in return for the puxirum, as well as the labor that he and his family will have to invest in weeding, harvesting, and other activities in the swidden.
Although puxiruns are still the most common form of organization of collective work, farmers say that puxiruns are gradually being replaced by wage labor. The owner of the swidden-to-be is the one who decides the exact size and location of the new swidden. After these steps, the vegetation is left to dry for some time before burning. Also, they say that the burned vegetation that is turned into ashes and also some charcoal allows cultivation; therefore they associate better burns with higher yields.
Farmers say that the main reason for making coivaras is to clean their swiddens better, i. Farmers also say that each coivara leaves charcoal and ashes accumulated, leading to local modifications in soil properties that are suitable for the cultivation of specific crops, such as banana Musa x paradisiaca L. Because farmers state that swiddens on ADE are opened from younger and softer fallows, and are also smaller than NAS swiddens, the labor required for opening swiddens on ADE tends to be lower, less often requiring puxiruns and coivaras.
Some swiddens on ADE, however, especially those under more intensive cultivation, may contain an abundance of very aggressive shrubs or treelets, e. Farmers report that planting a second time in the same swidden leads to reduced crop yields and higher weeding requirements.
Therefore, a typical manioc swidden on NAS is used for one cropping cycle, which may last from one to three years. During the first months the swidden is weeded more intensively; then manioc harvesting starts, which may last from a few months to more than a year. Once harvesting is finished, farmers usually let the fallow vegetation grow. A swidden is, however, not abandoned completely; the fallows are also managed and contain many useful species, some of which were saved from cutting or burning during opening of the swidden, and others which may have been planted or spontaneously appeared and were favored during the period when the swidden was being managed more intensively.
On ADE, farmers say that they prefer planting crops that produce faster, including specific earlier maturing manioc landraces, so they can reduce the need to weed on these soils as much as possible. In NAS swiddens, replanting is not a common practice.
Farmers acknowledge changes in their cultivation systems to different extents and at different time scales. They consider these changes to affect their practices as well as the usefulness of their knowledge and associated cultural values. Changes in access to formal education are frequently mentioned by farmers because these can drive out-migration of children and teenagers and therefore change household labor availability Fig.
People along the Madeira River increasingly have access to formal education because of improvements in the infrastructure provided by the government. In almost every village there are schools for young children, but teenagers frequently have to move or travel on a daily basis to larger villages or cities in which there is available infrastructure for their continued education. The majority of the families interviewed had at least one son or daughter studying away from the village.
Farmers also acknowledge their increasing interaction with cities and their growing engagement with the market economy. They report a range of associated changes, such as increasing access to commercial opportunities through better transportation and market organization, e.
These include the reduction in the number of landraces cultivated, particularly manioc landraces, and the focus on a few improved, economically profitable ones; the increasing use of fertilizers and pesticides, especially in the cultivation of watermelon; and the increase in mechanization, although limited to weeding machines, chainsaws, and small tractors or motors.
The presence of these organizations varies strongly between villages, and farmers often complain about their absence or the lack of technical follow-up from extension agents.
Still, most of the farmers we interviewed said that they have accessed credit through these organizations. Most often, extension organizations tie this access to credit to the diversification of production activities, thereby stimulating farmers to buy technology packages that usually are associated with more intensive cultivation, e. These changes also change perceptions.
Farmers, particularly younger ones, consider traditional cultivation techniques old-fashioned, especially cultural and symbolic practices, e. The traditional collective puxiruns are gradually being replaced by the payment of daily wages.
Today not many people make swiddens, so when you invite someone you have to pay [with money]. Farmers say ADE cultivation has always been different than in other soils, tuned to the specific characteristics of this soil.
However, they acknowledge that the increasing adoption of cash crops and the intensification of production, through fallow shortening or semipermanent cultivation, have been particularly pronounced on ADE, especially over the last decades. Farmers recall that watermelon, for example, was only grown on floodplains until approximately 30 years ago, when they started planting it on ADE. In some villages, particularly those with better access to markets, watermelon became a major cash crop and led to higher pressure on ADE; farmers started using these areas almost every year, reserving them for watermelon only, and even started renting pieces of ADE land specifically for the cultivation of this crop.
This resulted, farmers say, in the weakening of the soil in some places, with declining yields and increasing need for fertilizers and pesticides. These areas now need to be left to fallow for longer periods so that they can recover their strength. The intrinsic characteristics of ADE, therefore, favored changes toward intensification and modernization of cultivation systems on these soils and attracted initiatives with similar approaches from extension organizations.
Our interviews showed that farmers along the Madeira River have an integrated understanding of soils and vegetation dynamics. This knowledge enables them to read the fallow and provides them with indicators of future crop yields and immediate and future labor requirements. They balance these with their crop production opportunities and livelihood needs. This forms the basis of their decision making, particularly that related to opening and abandoning swiddens.
Farmers know that increased fallow development is associated with increased crop yields and decreased labor requirements for weeding in shifting cultivation. Relationships between fallow development, labor, and yields appeared early in the shifting cultivation literature Nye and Greenland , Boserup , Clarke , although these have not been thoroughly addressed with empirical measurements Mertz , Nielsen et al.
We provide evidence from local rationales that the reading of the fallow is a major source of information upon which farmers rely to make their decisions in shifting cultivation. The high weed pressure on ADE has also been reported in other studies with a focus on the current cultivation of these soils German b , Major et al. Farmers recognize these different relationships in ADE and NAS and use them to decide about opening swiddens, predict future yields, and labor needs.
Despite the high weeding requirements on ADE, farmers value these soils because they offer important opportunities for diversification and intensification, i. Farmers say that the intensification of shifting cultivation is advantageous in situations in which they need to produce quickly, for subsistence or for the market, or when there are significant labor constraints for opening new areas.
Farmers along the Madeira River acknowledge numerous changes in their socioeconomic environment, on different spatial and temporal scales, which affect their shifting cultivation systems Fig. Among the most important current trends mentioned by farmers is the out-migration of teenagers to towns in pursuit of formal education and their abandonment of agricultural activities, resulting in increasing labor constraints.
The growing interaction with market economies and the incorporation of modern agricultural practices were also stressed by farmers in the interviews. They reported that more abundant transportation options and the development of market structures have increased opportunities to sell specific products, and that the role of agriculture is gradually shifting from for subsistence only toward partly subsistence and partly commerce-oriented cultivation.
These farmer-perceived changes in their context Fig. Improved transportation and market opportunities, farmers say, have contributed to the cultivation of new crops, a focus on fewer improved crop landraces, the growing use of fertilizers and pesticides, and incipient mechanization. Farmers also mention that access to these new management strategies is facilitated and stimulated by extension organizations through bringing knowledge, but mainly through access to credit.
In some villages with relatively good geographic and market access, farmers reported intensive cultivation of ADE, in some situations with no or extremely short fallow periods, and a pronounced focus on cash crops Junqueira et al. They say that this overintensification has resulted in degraded fallows, i. Given the intrinsic characteristics of ADE, shifting cultivation systems on these soils tend to be more prone to changes leading to intensification, which according to farmers is being driven mainly by increased market access and interventions from extension organizations.
This has implications for understanding the potential role of ADE in how farmers deal with change. On one hand, these soils can increase the opportunities for diversification of cultivation strategies Junqueira et al. On the other hand, they can attract certain forms of intensification that follow the typical green revolution path Evenson and Gollin , in which the goal of maximizing productivity occurs at the expense of a greater dependency of markets and external inputs, often with, on a slightly longer term, adverse environmental and social impacts Godfray et al.
In the consideration of ADE as a model for sustainability, intensification of production on these soils is assumed Glaser et al. Our study identified cases, e. To date, farmers and researchers have assumed that degradation of ADE, as well as NAS, can be solved with longer fallow periods allowing these soils to regain their fertility and to reduce weed pressure.
Hiraoka et al. In fact, we also identified many cases in which farmers manage ADE under moderately intensive systems that seem to be relatively sustainable in the long-term. However, with increasing market pressures and stimulus from the extension agency to cultivate ADE with nutrient-demanding crops with strong market demand, cases of overintensification on ADE are likely to occur more often, leading not only to depletion of soil nutrients, but also to increased use of agrochemicals.
This indicates that increasing intensification can be a potential threat to ADE and can undermine the importance of these soils for agricultural production, for the conservation of agrobiodiversity, and for local livelihoods.
We also found that farmer rationales for the use of ADE involves more than soil fertility per se, with its capacity to sustain more intensive cultivation. Farmers acknowledge changes in their social environment Fig. It is likely, therefore, that farmers will simultaneously maintain extensive long-fallow swiddens on soils with lower fertility, because of their lower labor demand, and smaller, more intensive short-fallow swiddens on ADE Junqueira et al.
This multifunctionality can be an effective strategy to cope with risk, particularly suited to the fragile market structures, insecure land tenure, and restricted access to credit that characterize most of rural Amazonia van Vliet et al. Future developments are difficult to predict in the dynamic context of rural Amazonia.
Drawing from local knowledge and rationales, we showed how farmers whose livelihoods depend strongly on agricultural production interact with the heterogeneity and the dynamics of their agro-ecological and socioeconomic context, adapting their farming strategies accordingly Fig. They are likely to make well-informed decisions, given their integrated knowledge and understanding of the dynamic interactions of soils and vegetation. The observation that overintensification can lead to ADE degradation suggests the need to research the role of fallows in ADE resilience, as well as nutrient depletion and other biophysical and social consequences of intensified ADE production systems.
Our results also indicate that attempting to enhance productivity of ADE and of other soils while disregarding other biophysical and social components of the system may lead to biased support for farmers who practice shifting cultivation in Amazonia.
Exploring options to optimize the production of diverse and diversified systems, involving ADE as well as NAS, also requires attention. We thank the local residents of the villages along the middle and lower Madeira River for their invaluable help, support, and friendliness, without which this research would not have been possible. ABJ received PhD. We thank Simon Jeffery and two anonymous reviewers for improving an earlier version of this manuscript.
Adams, C. Murrieta, W. Neves, and M. Harris, editors. Amazon peasant societies in a changing environment: political ecology, invisibility and modernity in the rainforest. Almekinders, C. Fresco, and P. The need to study and manage variation in agro-ecosystems. Netherlands Journal of Agricultural Science Boserup, E.
The conditions of agricultural growth: the economics of agrarian change under population pressure. Chauvel, A. Lucas, and R. On the genesis of the soil mantle of the region of Manaus, Central Amazonia, Brazil. Experimentia Clarke, W. Maintenance of agriculture and human habitats within the tropical forest ecosystem. Human Ecology 4 3 Coomes, O. Grimard, and G.
This belief leads to overlooking farmer know-how, accumulated over generations to exploit natural resources while adapting itself to the mutations of the physical, social and economic environment. Research conducted in Phongsaly provides an idea about how complex and consistent a shifting cultivation system can be and how farmers optimise family labour but also limit their risks.
External interventions—policies, projects, etc. When these interventions overlook how diversified slash-and-burn agriculture is, they often lead to oversimplifying the farming systems, impoverishing people and exposing them to natural and economic risks. These actions are then counterproductive. In the interest of the Lao nation, as a community, the policies and their implementation should be rethought so as to hold highland farmers of ethnic minorities in higher esteem and to widen the viewpoint, currently limited to a caricature of the mountains and forest, upheld by the culturally and politically dominant lowland inhabitants.
For a resident of the lowlands, culturally used to distinguishing permanent farm areas—rice fields, gardens—from forest areas—protected forest or silviculture exploitation—images of slash-and-burn in uplands are traumatising see Fig.
As a result, it can seem obvious and natural to call on political powers to make the degrading practices stop Aubertin Some authors have put forward some convincing arguments Mellac et al. For lack of a study on and esteem for this farmer know-how, the public interventions for development have often led to results contrary to the political aims of environment preservation and poverty alleviation.
We then propose to evaluate the impact of locally implemented public programmes on farmer income. The methodology selected relies on the theory of differentiating agrarian systems Dufumier ; Mazoyer et al.
In the first zone, villages along the roadside or in the immediate vicinity of the city do substantial commercial trade with city dwellers and benefit from sustained attention from administrative services; that is the case for 16 out of 40 villages. The valleys, under meters in altitude, are very steep-sided; their V-shape limits the potential for irrigated paddy fields.
The schist or sandstone substrates create fairly deep, acid clayey or silty-clay soils, which are rather fertile but very heterogeneous Zhou et al. The very high inter-annual variability in rainfall , mm 5 strongly conditions how successful farming activities are. That system is a result of experience handed down from one generation of farmers to the next, and will serve as reference. The technical and economic findings are from families in the village of Samlang over the past three years.
The village proper is also used for animal raising, with poultry that wander among the houses, looking for consumable waste and rice bran. Pigs are left there to roam freely and search for their food, supplemented by input gathered on the fallow land. The upper part of the crown is sacred, and any economic activity whatsoever is banned.
Every year, the active workers slash a single strip in the village land. In that strip, each family farms its own plot, which it owns: the field is always planted by the same farmer and then by his heirs. Each family owns a plot in each strip of the annual clearing; that system of family ownership is recent, but is derived from historical clan ownership, with similar features and consequences. Regulating this trend of reducing the surface area per active worker is complex, based on four successive mechanisms: loan of land between families, possible lengthening of crop period from one to two years, departure of part of the population, acceleration of rotations as a last resort Laffort et al.
The inflexibility of this land system tends to slow down the decrease in the fallow period, a characteristic response to demographic growth in many other shifting cultivation systems Foppes et al. This management favours the maintenance of fertility and satisfactory production levels, at the cost of expelling a fraction of the village population, essentially the younger generation, towards other zones.
The growth rate in the district was 1. This land tenure system, comparable to private property farmed by the owner, is unique for shifting forest agriculture.
It confers high security to each family in access to land, in particular in the long term. Farmers can plan on investing in their fields 6 so as to increase their productivity Ducourtieux et al. In the first year, glutinous rice dominates, associated with many crops maize, tubers and roots, cucurbits, crucifers, peppers, sunflower and groundnut.
In Samlang, all the work requires an average of days of work per active worker, i. It must be done according to a specific, restrictive schedule, or else weeds will put a strain on the yields of rice and associated crops.
For example, weeding done too late lets the weeds sprout and spread their seeds, complicating the management of grass cover during the subsequent weeding periods.
June, July and August weeding monopolises the entire workforce. The fallow land is the pasture area for large ruminants; cattle are limited to grazing grassy fallow whereas water buffaloes graze indifferently year round on shrubby, tree-covered and grassy fallow. There are more potentially farmable areas than actually farmed. The direct comparison of rice yields between lowlands—1. The progressive build-up of biomass resulting from photosynthesis on the fallow land has been proven, 12 but recent research work is challenging this oversimplified interpretation.
The yields are not directly proportionate to the fallow period Foppes et al. Furthermore, rapid rotations increase erosion, limiting future productive potential De Rouw et al. The role played by the fallow duration in the yield is itself the interaction of a substantial number of cumulative and synergetic factors, for which it is hard to isolate individual contributions. In addition to the build-up of biomass for mineral fertility and the soil structure, there is pest control.
The density of harmful insects and weeds in a slash-and-burn field decreases rapidly depending on how long the fallow period lasted before clearing Van Keer The author established that the constraints concerning yield are, in order of importance, the number of successive crop years, climatic hazards, the topographical position of the plot, 13 weeds and predators 14 Van Keer In Laos, farmers draw up a comparable list Roder et al.
Samlang farmers rank drought—once every three years—as the main problem, followed by parasitizing of roots, and rodents. On the contrary, each family is constantly adapting its actions based on the natural climate and socio-economic manpower, tools, markets, consumer needs, etc.
Cotton and tobacco have practically vanished from the fields since the arrival on the local market of low-cost manufactured products from China at the end of the s. On the other hand, some villages have developed maize or white rice farming as a raw material for the distillation and trade of alcoholic spirits in Phongsaly. Furthermore, every hour spent walking during the rainy season is lost for weeding.
Added to the marginal production gain that fallow periods over ten years procure Van Keer , the constraint of distance explains why villagers choose not to include in rotations the forest land within the village domain that is farthest away from the village. Out of the 24 forest villages in the study zone see Fig. The biodiversity is also observed on a large scale, with nearly sticky rice varieties identified for shifting cultivation in Northern Laos Roder et al.
For example, the sowing density will depend on the slope, with tubers being preferentially planted in large heaps of ashes or maize in the wettest part. On a larger scale, this well thought-out choice concerning land use can be observed in the development of terraced paddy fields in the scarce irrigable zones or in the choice of shady, damp plots that are not too high in altitude for growing cardamom Ducourtieux et al.
When the village clears several zones, in particular if there are two consecutive years of crops, each family first allocates its workforce to the plot considered potentially the most fertile.
It is usually the plot cleared that same year, but the choice is not systematic: seed quantities vary from one year and one plot to the next.
Furthermore, the initial distribution of labour can evolve over the year, depending on the problems encountered.
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