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Hedgerows/alley cropping to control soil erosion, Jamaica
The use of the hedgerow/alley system has been advocated by conservationists who have found it to be effective in minimizing soil erosion by reducing surface runoff velocities and prolonging infiltration rates. Hedgerows are also a good source of organic matter, nitrogen, phosphorous, potassium, and other micro-nutrients. The practice of hedgerows/alley cropping is currently being promoted in Southern Trelawny, Jamaica. The Southern Trelawny Environmental Agency (STEA), an NGO which has been technically supporting it, has reported a high acceptance level of this technology, due to the ease of implementation, its effectiveness in controlling soil erosion and the low financial cost.
The objectives of the technology are:
- to minimize soil erosion;
- to reduce rainfall run-off velocity;
- to prolong the infiltration rate;
- to provide organic matter to improve soil structure, and a source of phosphorous, potassium and other micro-nutrients;
- to fixate nitrogen where leguminous plants are used;
- to fiversify agricultural production;
- to increase carbon sequestration through the planting of trees and shrubs;
- to reduce deforestation through the provision of yam sticks.
Implementation of the Technology
On gentle slopes hedgerows are established about 2-6 meters apart. On steeper slopes, the hedgerows should be about 2 meters apart along the contour of the land. Within the rows, the distance between the trees varies, but may be as close as 5-10 centimeters on steep slopes.
At the seedling stage, temporary stakes are placed into the ground close to the young hedges and farm trash is placed on the up-slope side of the stakes to form barriers that control soil erosion. The stakes hold the barriers until the plants are mature enough to hold the barriers by themselves. As the hedges grow, they are periodically pruned to prevent the shading of crops in the alleys, and the pruning debris are used to further build up the trash barrier or as mulch on the farmed area between the hedgerows. In southern Trelawny, hedgerows are also being managed to produce yam sticks by leaving individual trees to grow at intervals of 2 meters. When the trees mature, the sturdy stems are cut and used as yam sticks. A variety of leguminous species can be used for nitrogen fixation. These include Leucaena leucocophala, Tephrosia candida, Desmodium rensonii, Flemingia macrophylla, Alnus nepalensis, and Calliandra calothyrsus.
The hedgerow/alley system of vegetative soil conservation is currently being promoted in Southern Trelawney, in Jamaica, part of the Cockpit Country buffer zone and one of the foremost regions in Jamaica for commercial yam production. The Calliandra calothyrsus, the hedgerow plant that is being promoted, does not occupy much farm space and its vertical root system penetrates deep into the soil where it provides support for the upper soil horizons and does not interfere with the root systems of cultivated crops. This allows farmers to plant food crops in close proximity to the Calliandra plants. Further advantages of the species are that the Calliandra tree grows well on a wide variety of soil types, with its rooting system stabilizing banks and ridges, its leaves can be used as animal fodder and enhances soil fertility through nitrogen fixation. Given the high level of interest expressed in this technology by small farmers, similar acceptance levels are likely in yam growing communities elsewhere, especially where soil loss from steep slopes is a problem. A key factor in ensuring similar level of success elsewhere lies in the promotion and management of the technology.
Monitoring of the Demonstration
Although there is no quantitative assessment of the impact of the project, qualitative assessment indicates positive physical and socio-economic impacts (Spence, 1999).
Accumulation of soil behind the barriers is a good indicator of the extent of reduced soil loss. Observation made of treated plots towards the end of the project indicated significant levels of soil accumulation behind the hedgerows while soil loss continued unabated on untreated plots. One farmer whose plot was used as a demonstration site explained that before the treatment of his land, soil-wash from his farm posed a hazard to traffic on the road below, but this is no longer the case since the treatment of his land. The hedgerow/alley technique was regarded by farmers as a vast improvement on their traditional use of contour drains, because although these drains reduced water velocity on the slopes they nevertheless channeled away substantial quantities of soil. The hedgerow/alley technique also resulted in improved water infiltration on slopes, which can enhance ground water discharge.
Farmers who utilized the hedgerow/alley technique reported that when daily labour costs for maintenance of hedgerows are taken into account, the overall costs of establishing and maintaining the new technique was substantially less than those associated with contour trenches as a soil conservation measure. In this regard the production costs for yam farmers who adopted the technique were reduced.
At the community level, reduced inconveniences related to road blockage owing to erosion from farms and the related cost of clearing roads was yet another positive effect of the hedgerow/alley technique. In addition, reduced turbidity of streams has implications for reduction in the cost of water treatment for communities. At the time of the final evaluation of the project, 393 farmers had been exposed to detailed information regarding the use of the technique. This served to improve the level of environmental awareness among farmers in southern Trelawny and as such the technique holds great promise for the promotion of sustainable use of land resources by farmers.
Relevance of the Proposed FAO Intervention
At the end of South Trelawny Soil Conservation Project a large number of non targeted farmers in southern Trelawny expressed interest and desires to adopt the hedgerow/alley technique, but were unable to benefit due to unavailability of STEA’s resources to continue expansion of the intervention when the project ended. A stakeholder meeting held in May 2007 between the FAO Resident Representative in Jamaica, the National Consultant for the FAO project, The Director of STEA and community representatives from southern Trelawny, indicated the desire of farmers to continue adaptation of the hedgerow/alley technique. In this regard it is proposed that the funds available for fine-tuning and promoting good practice(s) identified in the first phase of the project should be allocated to the revival of the hedgerow/alley technique of vegetative soil conservation in southern Trelawny for the following reasons:
- Past evaluation of the technique indicates that it not only has the potential to reduce soil-loss associated with intense rainfall, but also include a wide range of environmental benefits.
- Farmers in southern Trelawny are extremely receptive to the innovation, but currently lack the resources for the implementation. Only a small proportion of the farmers in the area have benefited from the previous initiative and thus outreach and impact of the proposed FAO intervention is large.
Given the range of environmental and social benefits that can be derived from the intervention, there are good prospects for collaboration with other development partners.
References and Further Reading:
TCP/RLA/3101 Assistance to Improve Local Agricultural Emergency Preparedness in Caribbean Countries Highly Prone to Hydro-Meteorological Disasters – Jamaica, January 2007 FAO Regional Workshop on Disaster Risk Management – Final Report, April 2007. ftp://ftp.fao.org/docrep/fao/010/ai147e/ai147e00.pdf
Barker, D. (1998) Yam farmers on the Forest Edge of Cockpit Country: Aspects of Resource use and Sustainability, in Resource Sustainability and Caribbean Development, Duncan F.M. McGregor, David Barker and Sally Lloyd Evans (eds). University of the West Indies Press, Jamaica.
Evans, P. (1994) Agroforestry Development in Yam-growing areas of Central Jamaica. FAO, Rome.
Ross C. Gutteridge and H. Max Shelton (eds.), Forage Tree Legumes in Tropical Agriculture, The Tropical Grassland Society of Australia, Queensland, 1998
Spence, B. (1999) GEF Cockpit Country Conservation Project: Land Management Report
Spence B., (1995) Domestic Food Production and Small Farming in Jamaica
Spence B. et al (2005) Experiences and Behaviour of Jamaican Residents in Relation to Hurricane Ivan.
Report submitted to the Japan International Corporation Agency, 2005.
Thomas-Hope E. and B. Spence (2002) Promoting Agro-biodiversity under Difficulties: The Jamaica PLEC Experience. PLEC News and Views, #19, March 2002.
USDA Natural Resources Conservation Services, Alley Cropping Conservation Practice Job Sheet 311, April 2003 (revised edition)
USDA Forest Service, Agroforestry Notes, AFNI 2: Alley Cropping, January 1999
USDA Natural Resources Conservation Services, Alley Cropping: Practice Introduction, practice code 311
For more information please contact Stephan Baas at Stephan.Baas@fao.org
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