Tag: humid tropics
Agroforestry – a policy imperative for Vietnam
Agroforestry has been traditionally practiced, although it does not go under the name ‘agroforestry’. The VAC-R-systems (vuon-ao-chuong-rung or garden-pond-livestock-forest) expanded largely in the 1960-90s. Taungya is often practiced to introduce reforestation by intercropping annu-al crops with tree seedlings during the first 1-3 years until the tree canopy has closed.‘Integrated agroforestry’ is originally used to denote the integration of trees and crops (in one field), such as intercropping, alley cropping, parkland – sometimes includ-ing livestock. Agroforestry in the northern uplands of Viet Nam can at best be described as temporarily integrated in transition from segregated mosaic monocultures of maize or cassava to timber-tree mono-plantation (typically Aca-cia, Eucalypts, Manglietia, Melia).
Agroforestry and the development of tropical forestry
This paper is divided into three parts. Part one deals specifically with deforestation. Deforestation is caused mainly by 1) conversion of forest lands into agricultural lands, 2) the quest for fuelwood and building poles, and 3) social and economic deprivation. The author warns of the dangers of confusing symptoms with cause of deforestation. Before embarking on the subject of agroforestry, the author, in the second part of this paper, gives a broad view of the ecological requirements of various plant species. The final, well detailed and comprehensive section deals specifically with agroforestry related aspects. A list of suitable agroforestry trees, shrubs and fodder crops is included.
Agroforestry and the sustained productivity of Asia’s humid uplands
The paper briefly characterizes the humid sloping uplands of Asia and then discusses the directions in which their land use systems are evolving. It emphasizes some solutions such as complex agroforests for the forest margins, reforestation through smallholder agroforestry in the grasslands and natural vegetative strips on hillslope farmlands.
Addressing key natural resources management challenges in the humid tropics through agroforestry research
The countries in tropical Asia have begun to lay the foundation for sustained economic growth. Their remarkable progress has been heralded as a source of encouragement for developing countries throughout the world. This optimism is well-deserved, but should not be misinterpreted as victory achieved. Hundreds of millions of people remain in poverty, and the momentum of development has frequently accelerated the degradation of the natural resource base. These pressures are particularly acute in uplands of the region. The rate of forest degradation and conversion has increased in recent years in those countries where significant forests remain.
Prioritization of tree species for agroforestry systems in the lowland Amazon forests of Peru
An analysis was made of information provided by farmers about products and services of tree species, and the preferred tree species for agroforestry systems in the Yurimaguas, Pucallpa and Iquitos areas of Peru. The methodology of the study was based on a process developed by the International Centre for Research in Agroforestry (ICRAF) and the International Service for National Agricultural Research (ISNAR), with modifications to adapt it to the study area. Farmers selected 58 species in Yurimaguas, 62 in Pucallpa and 100 in Iquitos; the selections included 41 plant families. Considering the number of species preferred by farmers and the number of people surveyed, farmers in the Yurimaguas area appeared to have greater knowledge about trees than farmers in the other 2 areas. Some 23 priory species in 17 families were selected for the development of agroforestry systems for this tropical humid lowland zone. The priority products of these 23 species are wood, energy and food. The highest-priority species for genetic improvement research for agroforestry systems are Bactris gasipaes, Cedrelinga catenaeformis, Inga edulis, Calycophyllum spruceanum and Guazuma crinita.
Dynamics of soil physical properties under alternative systems to slash-and-burn
A change from slash-and-burn to continuously cropped agricultural systems is occurring in heavily populated areas in the humid tropics. Well managed alternative systems to slash-and-burn can reduce soil structure deterioration, maintain soil fertility, and promote long-term productivity. The objectives of this paper are to describe the dynamics of soil physical properties under slash-and-burn and some alternative systems. Different land-clearing methods and post land-clearing management systems were evaluated on Typic Paleudults at Yurimaguas, Peru, for their effects on soil physical properties such as: bulk density, soil water characteristic, infiltration rate, aggregate stability, and penetrometer cone resistance. Mechanical clearing reduced the infiltration rate from 420 mm h1 before clearing to 35 mm h1 for the straight blade and 95 mm h1 for the shear-blade bulldozing. Straight-blade clearing damaged soil structure the most as indicated by a decrease in the percentage of larger soil aggregates. The practice of planting on raised beds prevented foot compaction of soil near the plants; bulk density was 1.14 and 1.29 Mg ha1 for bedded and flat planted soil, respectively. Of the various agroforestry systems evaluated (multistrata, peach palm production, shifting agriculture low input and high input continuous cropping) bulk density was lower after 4 years for the systems with trees or cover crops. Mean annual soil loss for alley cropping on sloping soils was 0.2 Mg ha1 year1 compared with 53 Mg ha1 year1 for two annual crops per year. The infiltration rate after 5 years of intensive grazing on five associations of legumes with grasses was reduced from 127 to 41 mm h1. Overgrazing caused severe soil compaction and reduced earthworm biomass. Research indicates that the greatest change in soil physical properties occurs during mechanical land clearing. Agroforestry systems improved soil physical properties when cover crops and trees were included in the system.
Historical land use evolution in a tropical acid upland agroecosystem
Understanding the historical evolution of land use in humid tropical agroecosystems may assist in developing more appropriate farming systems better able to sustain dense human populations, alleviate deforestation and regenerate degraded land resources. We analyzed land use change over a 40 year period for a key acid upland farming systems research site (8 km × 10 km) undergoing rapid transformation in Claveria, Mindanao, Philippines. The landscape is dominated by small-scale cereal cropping on gently to steeply rolling volcanic Oxisols. The six slope classes identified (ranging from 0–3% to more than 60%) each occupied between 9 and 19% of the study area. Aerial photographs (1:15000) taken in 1949 and 1967, and a ground survey in 1988, were used to map land use patterns at three points in time. Settlement by in-migration began early in the twentieth century. By 1949 9% of the land was cultivated, but grassland (59%) and forest (14%) were the dominant land uses. From 1949 to 1967 the cultivated area doubled to 20%, and the proportion of grassland decreased to less than 50% of the land. The forested area remained unchanged. Subsequently, settlement by small-scale farmers accelerated. Between 1967 and 1988 the area cropped annually doubled again to 41%. Forest land declined drastically during this period to 1%, while perennial cropland (mainly coffee) increased to 30%. Land use on the steeply sloping lands (more than 15%) was particularly affected during the 21 year period: 27% was converted to field crop production, and 43% to perennial crops. More than 33% of the food crop area is now on steep slopes. The analysis of the historical evolution of land use may guide research priorities for developing sustainable technologies on sloping land based on agroforestry.
Alley farming as a potential agricultural production system for the humid and sub-humid tropics
It is widely recognized that the biggest challenge facing agricultural research in the Tropics is the development of farming systems capable of ensuring increased and sustained productivity with minimum degradation of the soil resource base. Reversing the trend of declining per capita food production in sub-Saharan Africa, therefore, does not depend solely on the development of improved and high-yielding crop varieties. Development of sustainable production systems is necessary to foster and maintain advantages derived from such improved varieties. The issue of sustainability has received considerable attention in recent years in agricultural research and development (CGIAR, 1990). The nature of much of the upland soils in the Tropics is such that over exposure and over cultivation can easily lead to their degradation. According to the Soil Management Support Services (1986), agricultural land in most humid and subhumid tropical regions is dominated by low activity clay (LAC) soils whose inherent characteristics and limitations make large upland areas dominated by these soils less suitable for conventional mechanized and high-chemical input farming methods. These soils have inherently low fertility, and are highly erodible when left unprotected. Nutrient loss through run off and erosion can, however, be kept to a minimum by using appropriate production systems that minimize disturbance and ensure a protective cover of the surface soil through live or dead mulches (Lai, 1986). Management of vegetation within the cropping system also could contribute to maintenance of soil fertility and enhance the stability of the cropping system (Juo & Lai, 1977; Lal et al., 1978). In the Tropics, trees have long been recognized as essential both for the stability of the environment and for maintenance of soil fertility for crop production. Trees have been recognized as major elements in soil fertility regeneration and conservation as reflected by their prominence in tradition.
Biodiversity: issues relevant to integrated natural resource management in humid tropics
Humanity stands at a defining moment in history. We are confronted with a perpetuation of disparities between and within nations, a worsening of poverty, hunger, ill health and illiteracy, and the continuing deterioration of the ecosystems on which we depend for our well-being. However, integration of environment and development concerns and greater attention to them will lead to the fulfillment of basic needs, improved living standards for all, better protected and managed ecosystems and a safer, more prosperous future.