The enigma of tropical homegardens

Agroforestry Systems - Tropical homegardens, one of the oldest forms of managed land-use systems, are considered to be an epitome of sustainability. Although these multispecies production systems...     

Acacia nilotica trees in rice fields: A traditional agroforestry system in central India

Time-tested, indigenous land-use systems can provide valuable information for the design of ecologically sustainable and socially acceptable agroforestry systems. One such traditional system is the growing of Acacia nilotica (L.) Willd. Ex Delile trees, locally known as babul, in rice fields of smallholder farmers in Madhya Pradesh State of Central India, an area with subhumid monsoon climate and hot summer. The functional characteristics of the system were collected through participatory rural appraisal involving intensive interactions with farmers in the region during six years, and through a structured-questionnaire survey in 25 villages, involving a total of 200 farm families. The farms had an average of 20 babul trees, ranging in age from <1 to 12 years, per hectare in upland rice fields, the tree-stand density being greater on smaller than on larger farms (>8 ha). Over a ten year rotation period, the trees provide a variety of products such as fuelwood (30 kg/tree), brushwood for fencing (4 kg/tree), small timber for farm implements and furniture (0.2 cu.m), and non-timber products such as gum and seeds. The babul + rice system was estimated to have a benefit/cost (B/C) ratio of 1.47 and an internal rate of return (IRR) of 33% at 12% annual discount rate during a ten-year period, though at a low level of income. Babul trees account for nearly 10% of the annual farm income of smallholder farmers (<2 ha). By practising the agroforestry (rice + babul) system, farmers get higher cash returns on a short-term (10-year) harvest cycle of trees, and the labour input (both family- and hired) on farms was distributed more uniformly throughout the year than in rice monoculture. Purchased inputs are seldom used in the system. The ease of management of the system, the self-generating and robust nature of the tree and the multiple products and services it provides, and easy marketability of the products are the major factors that encourage farmers to adopt the system. Furthermore, the farmers have secure ownership rights to their land, so that they are interested in long-term measures such as tree plantings on their farms. In spite of its long history and tradition as a sustainable approach to land use, the system has not attracted the attention of development agencies. More detailed investigations on its social, economic, and cultural attributes are warranted to not only improve this system, but provide insights into farmer adoption of agroforestry innovations.This revised version was published online in November 2005 with corrections to the Cover Date.     

Agroforestry education and training activities at the University of Florida

The interdisciplinary program in agroforestry was established at the University of Florida's Institute of Food and Agricultural Science in 1987 in response to the growing interest in the subject among students and faculty members from different units of the university. It is now an internationally recognized center for education, training, and research in the subject. Pursuant to the overwhelming student and faculty interest in agroforestry issues in developing countries of the tropics and subtropics, the program is particularly active in those areas. Educational activities of the Program are at the post-graduate level. In conjunction with the degree granted in one of the designated departments or other academic units, students can earn a Specialization or Minor in Agroforestry by fulfilling certain requirements. Research projects are undertaken in such diverse topics as biophysical processes, production/conservation technologies, and socioeconomic aspects. Training activities include various short-term courses for professionals involved in management, development/extension, or research related to agroforestry.     

Comparative growth performance of some multipurpose trees and shrubs grown at Machakos,Kenya

Growth rates of 29 multipurpose trees grown in an agroforestry arboretum for six years at a sub-humid to semi-arid climatic zone are presented. Exotic species such as Grevillea robusta, Sesbania grandiflora, Leucaena leucocephala, Cassia siamea and Sesbania sesban, some of which were outside their traditional climatic zones, had higher diameters, heights and bole volumes/tree (upto 130% more in certain cases) than of the indigenous species. However, poor performance of several species (both exotic and indigenous) would limit their agroforestry potentials at the evaluation site or other similar areas.     

Multipurpose leguminous trees and shrubs for agroforestry

These are various ways in which farmers deliberately incorporate trees and shrubs on farm production fields. Many of the species so incorporated are legumes. The role of such woody perennials in agroforestry systems can be productive and/or protective. Legumes offer by far the maximum range of choice of woody species for agroforestry in terms of their economic uses as well as ecological adaptibility. In addition to the several leguminous woody species that are well known in agroforestry, there are many more whose potentials have not yet been fully understood. An evaluation is presented of the agroforestry potentials of a few leguminous species from the point of view of their growth characteristics, ecological adaptability, combining ability with other species and uses/functions. The science of agroforestry is still in its infancy. There exists no research data on the various management aspects of these potentially promising group of plants. ICRAF, in its capacity as an international research council, has assembled several multipurpose leguminous trees and shrubs of agroforestry potential at the Council's recently-established Field Station in Machakos, Kenya, primarily for demonstration and training purposes. Initial results from these trials are presented in the paper.Adapted from a paper presented at the International Symposium on Nitrogen Fixing trees in the Tropics, 19–24 September, 1983 Rio-de-Janeiro, Brazil.     

Agroforestry in the South Pacific region — an overview

The developing countries of the Pacific Region consist of 27 countries and territories with a total nd area of 542 000 km² and over 5 million inhabitants. Though highly variable in physical characteristics and land-use pattern, these countries, in general, give a higher priority for production of export crops over other agricultural crops, so that they are net importers of food. Natural forests of the region are luxuriant and floristically rich, but the level of their commercial exploitation is low. Swidden cultivation is the mainstay of subsistence livelihood, but with the increase in population, the system is now causing severe environmental and land-use problems.The major agroforestry systems and practices in the region include various forms of combination of tree crops such as coffee, coconut and cacao with nitrogen fixing trees such as Casuarina, Gliricidia and Leucaena, and food crops (mostly tubers) such as cassava, taro, sweet potato and yams. Additionally, some improvements to swidden (shifting) cultivation are also being tried in several places, the most common being the u use of Casuarina oligodon before abandoning the swidden as in PNG highlands, and intercropping food crops in tree crop stands.Land tenure system in most of the countries is the traditional clan of extended family control over land. This can have either positive or negative influence on the adoption of agroforestry practices depending on the extent and duration of tenancy tenure enjoyed by the assignees of land.Several governments of the region are now promoting the agroforestry approach. In hilly areas with poor access, farmers are forced to produce most of their basic necessities locally. On the other hand, the lack of roads and communication facilities can pose a problem in marketing any surplus products they have.The immediate opportunity in agroforestry in the region lies in making better use of the unexplored potential of a large number of locally available trees and agricultural crops. Intercropping in tree crop stands and the taungya system seem to propromising m methods for the Pacific region.Researh Fellow, July–September, 1984     

Predicting the decomposition patterns of tree biomass in tropical highland microregions of Kenya

Decomposition- and nitrogen-release patterns of biomass from three agroforestry multipurpose trees (Calliandra calothyrsus, Cordia africana and Grevillea robusta) were investigated in four contrasting environments (microregions) in the Kenyan tropical highlands during two cropping seasons. Dried leafy biomass was placed in 2-mm litter bags, buried at 15-cm depth and recovered after 2, 4, 7, 10, 15 and 20 weeks. Decomposition patterns were best described by first-order exponential decline curves. The decomposition rate constants ranged from 2.1 to 8.2 yr^–1, and the rates of decomposition among the species were in the order: calliandra cordia > grevillea. There was a species-by-environment interaction during both seasons, but the nitrogen released did not follow such a pattern. Among the three tree species, calliandra released the highest amount of cumulative N, followed by cordia and grevillea. Using multiple regression techniques, decomposition pattern was described as a function of three groups of factors: biomass quality (N, C, lignin and polyphenol), climate (soil temperature and rainfall), and soil conditions (pH, soil organic C, total N and P). For all the species and factors combined, the adjusted R ² values were 0.88 and 0.91 for seasons 1 and 2, respectively. Among the three groups of factors, climate and biomass quality had the most influence on decomposition rates. Climatic factors accounted for 75% of the total rate of decomposition in season 1 (irregular season with less rainfall and more soil temperature fluctuations), whereas biomass quality factors were more influential in season 2 (regular season), accounting for 65% of the total variability.Florida Agricultural Experiment Station Journal Series No. R.-05555.     

Comparative functional genomic analysis of Pasteurellaceae adhesins using phage display

The Pasteurellaceae contain a number of important animal pathogens. Although related, the various members of this family cause a diversity of pathology in a wide variety of organ systems. Adhesion is an important virulence factor in bacterial infections. Surprisingly little is known about the adhesins of the Pasteurellaceae. To attempt to identify the genes coding for adhesins to some key components of the hosts extracellular matrix molecules, phage display libraries of fragmented genomic DNA from Haemophilus influenzae, Actinobacillus pleuropneumoniae, Pasteurella multocida and Aggregatibacter actinomycetemcomitans, were prepared in the phage display vector pG8SAET. The libraries were screened against human or porcine fibronectin, serum albumin or a commercial extracellular matrix containing type IV collagen, laminin and heparin sulphate. Four genes encoding putative adhesins were identified. These genes code for: (i) a 34 kDa human serum albumin binding protein from Haemophilus influenzae; (ii) a 12.8 kDa fibronectin-binding protein from Pasteurella multocida; (iii) a 13.7 kDa fibronectin-binding protein from A. actinomycetemcomitans; (iv) a 9.5 kDa serum albumin-binding protein from A. pleuropneumoniae. None of these genes have previously been proposed to code for adhesins. The applications of phage display with whole bacterial genomes to identify genes encoding novel adhesins in this family of bacteria are discussed.