Eucalyptus in agroforestry: its effects on agricultural production and economics

The economics of eucalyptus in agroforestry and its effects on agricultural crops have been studied with the help of observations made during the harvests in agricultural fields and from the information supplied by progressive farmers. Three rotations of eucalyptus in agroforestry were selected for comparative study of its returns and relative loss to the crops, in order to ascertain the optimum rotation: i.e. the one giving the maximum internal rate of return with minimum loss to agricultural crops.     

Tropical floodplain agroforestry systems in mid-Orinoco River basin,Venezuela

Agricultural studies in seasonally flooded areas in the tropics have been limited. Orinoco alluvial soils are more fertile than adjacent non-flooded soils, and have been considered as potential areas for further agricultural development. Traditional agroforestry practices offer some possibilities to overcome the most limiting factors of floodplain cultivation. Indigenous knowledge of these traditional agroforestry practices was assessed and some indicators of the system's nitrogen and biomass dynamics were monitored. Nitrogen inputs by sediment and plant residues were 1668 and 47 kg ha^–1, respectively. Traditional selection of sediment by tree-and-grass barriers and litter management strategies increase nutrient-use efficiency in floodplain agroecosystems.

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Resumen Estudios agrícolas en areas tropicales sujetas a inundación estacional han sido limitados. Los suelos aluviales o vegas del Orinoco son más fértiles que suelos cercanos no sujetos a inundación y por lo tanto han sido considerados como areas potenciales para desarrollos agrícolas. Prácticas tradicionales de agroforestería constituyen una alternativa en el control de importantes factores limitantes en la agricultura de vegas. El conocimiento técnico autóctono asociado con prácticas agroforestales tradicionales de vegas fue evaluado y algunos indicadores de la dinámica de nitrógeno y biomas adel sistema fueron monitoreados. La contribución de nitrógeno por sedimentos y hojarasca fue de 1668 and 47 kg ha^–1 respectivamente. La selección del tipo de sedimento a depositarse en la parcela agrícola, por medio de barreras de vegetación, y el manejo adecuado de resíduos orgánicos constituyen estrategias tradicionales que aumentan la eficiencia de uso de nutrientes en sistemas agrícolas de vegas.

     

Coating nursery containers with copper carbonate improves root morphology of five native Australian tree species used in agroforestry systems

Seedlings of the native Australian tree species Acacia holosericea, Casuarina cunninghamiana, Eucalyptus argophloia, E. camaldulensis and Melaleuca bracteata, were raised in nursery containers which were coated with CuCO₃ (50 g l^-1, in a water-based paint solution) or left uncoated for three months. Seedling growth of all species in the nursery was generally less in treated containers, although differences were relatively small. More importantly, CuCO₃ treatment reduced the occurrence of lateral roots growing down or coiling around container walls for both three- and six-month-old seedlings. Twenty-four months after planting both three- and six-month-old seedlings on a semiarid site in subtropical southeast Queensland, there was no effect of CuCO₃ treatment on height or basal diameter development of seedlings. However, sample excavations of root systems showed that the poor root morphology exhibited by untreated seedlings when in the nursery had persisted in the field. As such poor root form has the potential to reduce tree growth and wind firmness in the longer term, these results suggest that chemical root-pruning is a helpful nursery practice when raising seedlings for dryland afforestation, and in circumstances where it may be necessary to retain seedlings in the nursery for longer than normal to take advantage of infrequent rainfall events. This revised version was published online in June 2006 with corrections to the Cover Date.     

Indigenous agroforestry of Pohnpei

Plant species and cultivars of the indigenous agroforestry system of Pohnpei were surveyed in transects through 54 randomly-selected farms. The agroforestry system was characterized by extensive cultivation of yams (Dioscorea), aroids (Alocasia), and Piper methysticum under a permanent overstory of breadfruit, coconut, and forest remnant trees and a middle canopy of Hibiscus tiliaceus, Musa spp., and Morinda citrifolia. In the 10 ha of survey plots, 161 species were found, of which 102 were trees, shrubs, and crops and 59 were uncultivated herbaceous plants. Numbers of tree, shrub, and crop species per farm ranged from 16 to 37 with an average of 26. Twenty-eight breadfruit and 38 yam cultivars were found in the survey plots, showing that cultivar diversity is an important component of the biological diversity maintained and utilized in Pohnpeian agroforests.     

Traditional agroforestry practices in Zimbabwe

Traditional agroforestry systems in the communal areas of Zimbabwe are described. There are systems centered on main fields, on home gardens, on homesites and on grazing areas. In the main fields, the major tree-related management practice is the conservation of preferred indigenous fruit trees. Fruit trees are also the focus of forestry activities around the gardens and the homesite; but here it is the planting of exotic species. In a localized area of Zimbabwe Acacia albida is important in fields. There is almost no use of tree fallows in Zimbabwe. Trees in grazing areas have numerous roles, but at present there is little knowledge about traditional management practices in these areas. In the development of agroforestry systems in Zimbabwe it is suggested that those systems designed to improve fodder production will make a significant contribution to farm productivity because of the importance of cattle in the farming system and the present fodder shortage. Interventions involving the planting of fruit trees are likely to be very successful, as there is much interest in such planting. Another area that needs to be developed is that of tree plantings to improve soil fertility.     

Structure and function of traditional agroforestry systems in the western Himalaya. I. Biomass and productivity

Species composition, biomass, and productivity patterns of three types of traditional agroforestry systems, namely, agrisilvicultural, agrihorticultural, and agrihortisilvicultural, commonly practiced in the western Himalaya, were studied. Species composition in the systems varied depending upon the size of the land holdings, and the basic requirements of the farmer. Among three systems agrihortisilvicultural was highly diverse in vegetation, with as many as 13 tree and 5 agricultural crops mixed together. This system showed the highest productivity up to 25.8 t ha⁻¹ yr⁻¹, out of which 68 percent was contributed by the trees and the remainder by the annuals. Agrisilvicultural system having predominantly annuals had the lowest productivity of 20.4 t ha⁻¹ yr⁻¹ with only 27 percent contribution by the trees. Total aboveground biomass in agrihortisilvicultural or agrihorticultural system was around 48 t ha⁻¹ and it was about 2-fold higher than agrisilvicultural system. In fodder trees, a significant percentage of annual production, up to 48 percent, was allocated in current twigs, while in horticultural trees a major portion, up to 63 percent was partioned towards fruits. Implications of the results have been discussed in context with the growing problems of fuel, fodder, and packaging material in the western Himalaya.     

The role of extension in agroforestry development: evidence from western Kenya

The extension strategy used by the CARE International in Kenya Agroforestry Extension Project (AEP) is described. This strategy is evaluated in terms of documented changes in farmer's agroforestry practices and the importance of AEP relative to other changes in economic incentives, institutional support, and land use and tenure rules for agroforestry. The project served mainly to increase awareness of the multipurpose potential of agroforestry, expand available technical options, and strengthen local institutions. Its community-based extension approach was more suitable for local conditions than commodity-based, training-and-visit, farming systems, or media-based extension. Projects are encouraged to tailor extension design to local circumstances, use community participation to guide extension priorities, and use extensionists as catalysts and information brokers.Research undertaken while the author was a Principal Scientist at the International Council for Research in Agroforestry, Nairobi, Kenya.     

Improving multipurpose tree and shrub species for agroforestry systems

With the aid of an example of ICRAF's tree improvement research programme for the highlands of Eastern and Central Africa, a logical approach to selection and breeding of multipurpose trees and shrubs in agroforestry context is proposed. Criteria for selection of high priority species are proposed. Some species of high potential for agroforestry development in Sub Sahara Africa are proposed. The necessary sequential research steps are discussed.     

Farmer perspectives on agroforestry opportunities and constraints in cape verde

In the água de Gato Watershed on the island of Santiago, Cape Verde Islands, 51 farmers were surveyed regarding their attitudes and knowledge of agroforestry. The farmers identified eight constraints to agroforestry implementation, with virtually all indicating that a source of loan funds was the major concern. Space or land constraints and availability of tree seedlings were identified as constraints by 94% and 88%, respectively. Despite these concerns, 92% of the farmers expressed a willingness to adopt or improve agroforestry practices in the watershed, with 73% expressing a willingness to establish fruit trees, 53% willing to establish trees or shrubs for fuelwood, and 16% willing to plant trees for shade.     

Farmers’ local knowledge and topsoil properties of agroforestry practices in Sidama,Southern Ethiopia

Based on farmers’ knowledge and laboratory studies, the nutrient accumulation in the topsoil (0–20 cm) under Cordia africana Lam (Cordia), Millettia ferruginea Hochst (Millettia) and Eucalyptus camaldulensis Dehnhardt (Red gum) managed under two agroforestry practices on different farms at three sites was evaluated. The number of these trees on individual farms has increased during the last two decades. The number of stems ha⁻¹ of Red gum was higher on farms of wealthier households than on farms of poor and medium households at two of the sites, but, at one site the number of stems ha⁻¹ on farms of poor households was higher than on farms of wealthier households. Apart from the concentration of Na in the topsoil, there were significant variations in the analysed soil nutrients between the tree species. At all study sites, significantly higher concentration of P was observed under Millettia and Cordia than under Red gum. At one site, concentrations of available P under Cordia were nearly two-fold, and four and half-fold greater than under Millettia and Red gum, respectively. At one site, total N under Red gum was 14% and 24% lower than under Cordia and Millettia, respectively. In contrast, organic C content under Red gum was 11.6% greater than under Millettia and 23.8% greater than under Cordia. The pH under Millettia and Cordia were significantly higher than concentrations under Red gum at one site. Topsoil under Millettia and Cordia also had significantly higher levels of exchangeable Ca and Mg than Red gum.     

Benefit-cost analysis of selected agroforestry systems in Northeastern Thailand

Potential productivity and financial returns from selected agroforestry systems and traditional monocrops located in the Phu Wiang watershed were estimated from limited trials of cropping alternatives using cost-benefit analysis. The agroforestry systems studied consisted of combinations of Eucalyptus (Eucalyptus camaldulensis), Leucaena (Leucaena leucocephala), or Acacia (Acacia auriculiformis) inter-cropped with cassava (Manihot esculenta) or mungbean (Vigna radiata). Evidence from trials at short, 3-year rotations, demonstrate that early supplementary and complementary relationships between some system components can imply synergistic financial gains. Although these biological interactions turn competitive over time, in this case, the gains should be sufficient to make early adopters consider the agroforestry systems financially preferable to traditional monocrops.     

Tree seedling establishment in living fences: a low-cost agroforestry management practice for the tropics

Establishing trees in pastures can have production and conservation benefits, but is complicated by the presence of livestock. The need to protect seedlings from livestock increases tree establishment costs, which in turn, can deter landowners from planting trees. Living fences are a ubiquitous feature of pasture landscapes in the tropics that could help protect newly planted trees by preventing livestock trampling and browsing. This study quantified the effectiveness of a living fence in protecting tree seedlings during the first 2 years after planting. The four native tree species evaluated were: Cedrela odorata L., Pachira quinata (Jacq.) W.S. Alverson, Samanea saman (Jacq.) Merr., and Tabebuia rosea (Bertol.) A. DC. Results show that the living fence provided protection from livestock except in cases where tree species were highly palatable as forage (i.e. P. quinata). Trees planted into the living fence generally had greater survival (62 vs. 28%), relative growth (10.3 times initial height vs. 5.8 times initial height), and final height (191 cm vs. 108 cm) compared to those planted in open pasture after 2 years. However, survival and growth of trees planted into the fence remained lower than that observed at a nearby plantation with no livestock, regular weeding and no living fences. This study indicates that use of living fences as a protective barrier could be an effective low-cost approach for establishing trees in tropical pasture landscapes.

Modelling of rainfall interception loss in agroforestry systems

Two models of interception loss have been tested against new field data obtained in widely-spaced stands of Sitka spruce trees. The Gash model and a modified version of the Rutter model, have been used with data from an automatic weather station, to predict interception loss using parameters obtained from observations made in 1988 and 1989. The predictions for an eight-week period during 1987 were compared with measurements of interception loss. Good agreement between observed and predicted interception loss was obtained with both models over the whole period. The modified Rutter model gave better predictions than the Gash model for individual storm events and performed better at the wider spacings. The sensitivity of both models to the major characteristics of the tree stand structure in agroforestry systems was also investigated and it was shown that interception loss was most sensitive to boundary layer conductance and free throughfall coefficient.     

Development and validation of a simple approach to modelling tree shading in agroforestry systems

There have been a number of models developed which attempt to predict the shading patterns beneath individual tree or forest canopies. We describe a computer-based model which is able to estimate shading patterns through a discontinuous canopy of pruned trees. The model is designed to assist in the layout and management of agroforestry systems with widely spaced trees. The model was tested against data collected from a seven-year-old agroforestry system involving radiata pine, located near Canberra, Australia. The model was shown to slightly but consistently underestimate light penetration at ground level beneath the trees. However, the extent of bias (0.7% to 5%) was so small as to be of little significance in practice.     

深圳市植物物种指数与本地植物指数分析

以文献调研为主,结合野外踏查,对深圳市野生植物和常见栽培植物、建成区内本地植物和外来植物进行了统计分析,得出深圳市"植物物种指数"为0.789,"本地植物指数"为0.701;还分析了深圳植物的区系特点和外来植物的应用现状。       

Smallholder perceptions of agroforestry projects in Panama

The potential effects of agroforestry systems on conservation and development have been well documented. Panama has seen a substantial rise in the number of projects with an agroforestry component in the 1990s. There has been insufficient research on the actual impacts of these projects on smallholders and of farmers' attitudes towards these systems. This study explores the perceived socioeconomic and environmental impacts of five agroforestry projects in Panama. A total of 68 smallholders were administered semi-structured interviews. In addition, 13 agroforestry experts from NGOs, government departments and research institutes were interviewed, and their responses were compared with those of the smallholders. While the projects led to an increase in the standard of living by providing wood products and fruit for domestic consumption, farm income levels generally remained unchanged. This was due primarily to limited market development, the lack of marketing organizations and poor access roads. In terms of environmental impacts, the farmers' responses suggested a slight decline in slash-and-burn agriculture, and an increase in tree planting activities. Some environmental benefits were observed by farmers, including reduced soil erosion, increased soil fertility, and improved quality and quantity of water sources. Nevertheless, slash-and-burn agriculture was still the norm for the majority of farmers. Most farmers continued to harvest wood from primary and secondary growth to meet their domestic wood requirements, rather than relying on trees planted in agroforestry projects. The main obstacles preventing increased agroforestry adoption included insufficient agroforestry extension, inappropriate project design or management (such as top-down management approaches, and the use of food incentives), smallholders' economic constraints, and larger policy issues. Recommendations are proposed to improve project design and management, and to address the economic and policy constraints. This revised version was published online in June 2006 with corrections to the Cover Date.     

Agroforestry and its application in amelioration of saline soils in eastern China coastal region

Some environmental problems, especially soil salinity hinder the regional sustainable development of eastern China coastal region. Salinity mainly comes from tide weave, seawater flooding and seawater intrusion. Over exploitation of groundwater,which is the result of unfitful land use systems, leads to seawater intrusion and salt concentration increase. Agroforestry systems can enrich soil fertility and prevent soil salinization, furthermore help maintain biodiversity and enhance productivity. For the intergrated multiple ecosystems the most critical issue is to select optimum tree species and rationally arrange these plants. The basics of this multiple ecosystem is that different plants will occupy variable ecological niches within an area, both in space and in soil depth.Shelterbelts and trees intercropping with agricultural crops are major types of the multiple ecosystem. Shelterbelts can reduce wind speed and consequently lessen evaporation and erosion of the soil, increase pasture growth by up to 60% on exposed sites, increase crop yields by up to 25%. Besides intercropping with jujube, other agroforestry multiple ecosystem such as forestry plus agriculture,forestry plus agriculture plus fishery, and forestry plus animal husbandry are the most appropriate ways to utilise land resource in this region.     

Surveying farmers' agroforestry plots: experiences in evaluating alley-cropping and tree border technologies in Western Kenya

Evaluation of existing on-farm agroforestry plots should provide useful supplementary information for the design of improved agroforestry systems, in both research and development projects. Such evaluation has been little used, however, largely due to the methodological difficulties of surveying highly variable on-farm plots, and difficulties in identifying key variables for measurement. This paper describes a set of methods and tools used in evaluating plots of alley-cropping and tree borders around crop fields established by farmers working with the CARE Agroforestry Extension Project in western Kenya. Details of survey design, sampling, and implementation are discussed, and suggestions made for carrying out agroforestry surveys in other projects. A condensed version of the questionnaire is appended.     

Comparison of the erosion control potential of agroforestry systems in the Himalayan region

The great erosion control potential of agroforestry systems is generally recognized. However, insufficient data are available to be able to give absolute quantitative values for the erosion control potential of specific agroforestry systems or to compare their potential. To obtain such quantitative erosion data, long-term standard erosion measurements should be done in specific agroforestry systems. Such measurements may become very costly because the data need to be collected in a wide range of agroforestry systems on different sites over a long time. A further constraint is the reliability of such information: erosion figures may not be comparable because of discrepancy between the scale of measurement and the scale of the agroforestry system and the occurrence of different kinds of erosion. The methodology presented here enables a quick comparative estimation of the erosion (surface erosion, gully erosion and mass movement) control potential of different agroforestry systems. The erosion control value of agroforestry systems is related to their protective functions: the cover, barrier and soil reinforcement functions. The methodology involves identifying which features influence these different functions within a specific agroforestry system and subsequently evaluating the efficacy. The applicability of this methodology is demonstated with examples from various agroforestry systems in the Himalayan region.