Agroforestry Farming Systems Research Articles

Can agroforestry improve soil fertility and carbon storage in smallholder banana farming systems?

AbstractSoil fertility depletion is a major constraint to agricultural production for smallholder farming households in many sub‐Saharan countries, and it is worsened by climate variability. In order to sustain food security for a growing population, measures have to be taken against C and nutrient losses from soils. This study examines whether banana–coffee agroforestry systems can improve soil fertility and C pools in smallholder farms in E Africa amidst observed climate variability. We selected 20 farms in Central Uganda, where soil samples were obtained from the top and subsoil layers. Samples were analyzed for several soil fertility parameters including soil organic matter (SOM), total soil organic C, pH, total N, plant‐available P, exchangeable K, texture, and bulk density. Soil C stocks were calculated based on soil organic C concentrations and bulky density. We measured tree diameter and height and calculated aboveground plant biomass using allometric equations. Belowground biomass was estimated using equations based on the respective aboveground plant biomass. Our results show that banana–coffee agroforestry farming systems had significantly higher total SOM and total N compared to the banana monoculture. Similar trends were observed for soil C stocks and total C pools. The former contained 1.5 times higher soil C stocks than the latter. Likewise, the mean total C pools for the banana–coffee agroforestry farm plots were 26% larger than that under banana monoculture. However, exchangeable K was higher in the soil of banana monocultures. Plant‐available P levels were limiting under both farming systems. The study demonstrates that beyond socio‐economic benefits banana–coffee agroforestry farming systems have beneficial effects on soil fertility and C sequestration compared to banana monocultures in the study area. However, precautions to avoid P depletion have to be taken under current climate conditions.

Soil Classification and Carbon Storage in Cacao Agroforestry Farming Systems of Bahia, Brazil

Information concerning the classification of soils and their properties under cacao agroforestry systems of the Atlantic rain forest biome region in the Southeast of Bahia, Brazil is largely unknown. Soil and climatic conditions in this region are favorable for high soil carbon storage. This study is aimed to classify soils under cacao agroforestry and further, to quantify carbon stocks in these soil profiles. Soil classification was performed, and the amount of C stored was estimated, based on the thickness of the soil horizons, their bulk density, and total organic carbon stored. In the sites studied under cacao, four general classes of soils were identified: Ultisols, Oxisols, Alfisols, and Inceptisols. Carbon stocks in these soil profiles showed wide variation, ranging from 719.24 to 2089.93 Mg ha−1. Carbon stocks in soil surface and subsurface layers in different agroforestry systems with cacao (cacao cabruca, cacao × rubber tree, and cacao × erythrina) were comparable; however, total storage of organic C in these soils was higher than expected, compared to values reported for the International Soil Reference and Information Center (ISRIC), based on the FAO-UNESCO database, and were also higher than estimated regional soil data.

Evaluation of different agroforestry tree species for their suitability in the phytoremediation of seleniferous soils

AbstractSeven agroforestry tree species were grown in a clay loam soil treated with different levels of selenate‐Se, viz. 0, 1.25, 2.5 and 5.0 mg/kg supplied through sodium selenate. After 1 year of growth, a progressive decrease in dry matter of leaves, stem and roots was observed with increasing levels of applied Se. However, a significant decrease in dry matter yield was observed only at or above 2.5 mg Se per kg soil and shisham (Dalbergia sissoo) proved to be highly sensitive to the presence of selenate‐Se in the soil. On average, the largest above‐ground and below‐ground biomass was accumulated by arjun (Terminalia arjuna) and the lowest by the acacia tree (Acacia tortillas). The selenium content of leaves, stem and roots of all the tree species increased significantly with increasing levels of applied Se, although a large variation within species was observed. In the stem portion of different trees, the highest concentration of Se was found in dek (Melia azedarach) (5.1 mg/kg) and the lowest in mulberry (Morus alba) (2.6 mg/kg). The efficiency of selenium removal (including leaves, stem and roots) was the highest in arjun followed by eucalyptus (Eucalyptus hybrid) – Clone 10, mulberry, jambolin (Syzygium cumini), dek, shisham and acacia. Effective removal of Se takes place through the stem portion of different trees where it constitutes 30–50% of total Se. Large variation in Se uptake by different tree species suggests that trees vary in their potential for phytoremediation of seleniferous soils. In one growing season, shisham aged 24 years, poplar (Populus deltoides)– Clone G 48 (10 years old) and eucalyptus – Clone 10 (10 years old) could remove 2385, 1845 and 1407 g Se per hectare respectively. Corresponding reductions in Se capital of the soil varied between 24 and 37, 19 and 29 and 14 and 32%, respectively, in the surface layer (0–15 cm) alone or 7–11, 6–9 and 4–7% for the whole soil profile (0–120 cm). Removal further increased to 4207 g Se per hectare under an agroforestry farming system of poplar–mentha/wheat with Se being reduced from 43 to 65% for the surface layer and from 13 to 20% for the whole profile.

The Contribution of Farm Products to Farmer’s Livelihood and Household Consumption in Leyte, the Philippines

This paper describes the agroforestry farming systems through which crops, trees and small farm animals are produced and consumed by three farming families on Leyte Island, the Philippines, and the extent to which they contribute to the farmers’ livelihoods and wellbeing. A survey using semi-structured personal interviews was carried out to obtain data on cost savings of farm grown products consumed, health benefits derived and costs incurred in managing and maintaining each farm. There were notable differences in crop-tree arrangement and management methods used by the farmers. An estimate of the amount of product that was consumed by the households was conditional on crop choices and intensity of effort and inputs and offsets from off-farm income. Informal arrangements for bartering food, and coconut and bamboo product sharing for community use, made precise valuation of these products difficult, but comparative values against local market prices were placed on marketable produce. Labour and other inputs between the farms varied widely, depending on the type of product. In addition to crops grown as a source of income, portions of farm products were grown specifically for home consumption, and some non-consumable products were exchanged between households. The farmers had a basic understanding of the nutritional value and health benefits of all the food products they consumed for daily energy, health and medicinal purposes. They also believed that consuming their own farm-grown produce generated savings compared with quality and value of the same product from the local markets.

The homegarden agroforestry system of Bukoba district, North-Western Tanzania. 3. An economic appraisal of possible solutions to falling productivity

Homegardens of Bukoba are a traditional multi-storey agroforestry farming system based on mixed cropping and livestock keeping. Major crops are banana (Musa spp.) grown for food and coffee (Coffea canephora var.robusta) for cash. Livestock keeping is dominated by cattle. Over the last few decades the farming system in Bukoba has been pervaded by a host of constraints ranging from biological to socio-economic. Consequently farm productivity has declined and so has the economic welfare of the people in the area. A questionnaire survey was conducted in 1991 to 72 households in Bukoba district to compare three potential farming systems: the rehabilitation of the homegardens, the cultivation of two annual crops namely maize and beans as intercrops and the continuation of the current non-rehabilitated homegardens. Results strongly support the rehabilitation of homegardens by use of cattle manure and proper crop and livestock husbandry practices. Rehabilitated homegarden has the highest net present value and is not very sensitive to changes in prices of inputs and outputs.

The homegarden agroforestry system of Bukoba district, North-Western Tanzania. 1. Farming system analysis

Bukoba district is located in the north-western part of Tanzania and its economy is predominantly agricultural. Banana and coffee are, respectively, the most important food and cash crops. Population density is very high (500–1250 persons per km2 of cultivated land) and so is the pressure on land and other natural resources. Farm holdings (homegardens) are mostly smaller than a hectare and continue to fragment as population continues to grow. A homegarden is locally known as ‘Kibanja’ and it is both a social and economic unit of farm families in the district. Various crops, trees, shrubs, herbs and livestock are managed on the same piece of land mainly by family labour to provide food, cash, medicine, shade, poles, timber and some socio-cultural functions. This paper describes the homegarden agroforestry farming system of Bukoba, evaluates its viability and identifies critical constraints as well as research needs.

A decision support system for planning agroforestry systems

A decision support system for planning small-scale agroforestry systems was developed (DESSAP). The program generates a set of feasible alternatives of culture combinations based on specified constraints. The constraints include land, labor, and cash. Labor used include own and/or hired, and cash is money spent for different items and activities such as fertilizer, harvesting, etc. The program utilizes a multiple objective linear programming model coupled with a management tool to generate alternatives. The system can be used by planners, managers, trainers, extension personnel, farmers, etc., to determine the optimum and desirable alternative (s) for an agroforestry farming system.

Linking on-station research with on-farm testing: The case of agroforestry and organic matter-based cropping systems for the Rwanda farming systems improvement project

Hillside farming with its attendant erosion and decline in soil fertility is common-place in the area served by the Farming Systems Improvement Project. The project is designing land-use systems that would check erosion, increase soil organic matter and restore soil fertility. These systems will allow small farmers to increase or maintain product long-term basis without resorting to the use of high doses of inorganic fertilizers which are not readily available in the country. The use of leguminous shrubs and cover crops as nutrient sources — concepts embodied in agroforestry and organic farming systems — are options that landuse experts think might solve the problem. However, there is a dearth of knowledge about the biological feasibility of these interventions in the project area.

Agroforestry farming systems in the homesteads of Kerala, southern India

Kerala State on the southwestern coast of India in the tropical humid zone has a predominantly agricultural economy, a very high density of population and therefore high pressure on cultivable land. The farmers there undertake cultivation of an array of crops — tree crops, plantation crops, seasonals and biennials — all in intimate mixtures on the same piece of land around the homesteads. Farm animals and poultry and sometimes fisheries also are essential components of the system. The close association of agricultural crops, tree crops and animals in the homesteads represents an excellent example of sustainable and productive agroforestry homegardens. Optimum utilization of available resources of land, solar energy and technological inputs and an efficient recycling of farm wastes are important characteristics of the systems. This paper attempts to describe and evaluate the systems' stability, productivity and sustainability, and identify its merits and constraints as well as research needs.

Food, coffee and casuarina: an agroforestry system from the Papua New Guinea highlands

An agroforestry farming system is described from the Papua New Guina highlands (1400 to 2100 m) that has been developed by village growers since about 1960 and has expanded rapidly since about 1970. Major components of the system are numerous species of annual and perennial food crops (especially bananas), arabica coffee andCasuarina oligodon. It provides food, a cash crop and timber for construction and fuel. It is likely that returns on labour inputs are very favourable, but no formal assessments have been made. Evaluation of the system as a whole, and research on certain key components (casuarina ecology, banana cultivars, timing of operations) are suggested as high priority areas for systematic studies.

Approaches to the economic evaluation of agroforestry farming systems

The economics of agroforestry systems can be approached in a purely analytical fashion with mathematical equations and diagrams explaining the principles of analysis. This paper argues that such an approach may be useful for teaching purposes but has little practical relevance. There is an urgent need for a practical tool with which multi-disciplinary teams can asses agroforestry systems. The simplest and most common approaches to the economic analysis of farm management problems are various forms of budgeting. Recent advances in micro-computer technology provide the means by which the principles of partial budgeting can be adapted to the needs of agroforestry taking account of its multiple component nature, seasonal variability and long life span. The paper sets out the specifications for such an approach and indicates how it might be used.