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Land Degradation Situation in Bangladesh and Role of Agroforestry

M. K. HASAN
On Farm Research Division, Bangladesh Agricultural Research Institute, Gazipur, Bangladesh

A. K. M. ASHRAFUL ALAM*
School of Agriculture and Rural Development, Bangladesh Open University, Gazipur, Bangladesh

Abstract/ Executive Summary:

Degradation of land is a vital issue throughout the world with the particular references to Bangladesh as it a threat to agricultural productivity. Agroforestry, a land use system is being popular in many countries to protect the land from various types of degradation. Studies have proved that agroforestry can check soil erosion to some extent, increase soil fertility, reduce salinity, alkalinity, acidity and desertification etc. ultimately improve soil health which keep the land suitable for agricultural production. The article has drawn on the basis of various reviews focusing the land degradation situation of Bangladesh and potentialities of agroforsetry.

Keywords: Bed and flat planting; Water logging stress; Sesamum indicum L

Location: On Farm Research Division, Bangladesh Agricultural Research Institute, Gazipur, Bangladesh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Land degradation, Farming System

Objectives:

An effort was made to highlight the extent of land degradation situation in Bangladesh and the potentialities of agroforestry minimizing various types of land degradation so that it may serve as a tool to research, planning or development works.

Methodology:

EXTENT OF LAND DEGRADATION IN BANGLADESH Major types of land degradation that occurs in Bangladesh are- water erosion, soil fertility depletion, salinization, waterloggoing, pan formation, active flood plain etc. Among them, water erosion and fertility depletion are the main factors. The soils of hilly area are the most susceptible to water erosion in which sheet, rill and gully erosion occurs. About 75% of the hilly areas have very high susceptibility to erosion, 20% have high susceptibility and 5% have moderate susceptibility to erosion (BARC, 1999). Faulty 'Jhum' cultivation in hilly area causes gully erosion and losses of soil ranges from 10 to 120 t/ha/ yr. (Farid et al., 1992). Decline of soil fertility occurs through and combination of lowering of soil organic matter and loss of nutrients. The average organic matter content of top soils (high land and medium high land situation) have gone under from about 2% to 1% over the last 20 years due to intensive cultivation which means and decline by 20-46% ( Miah et al., 1993). Removal of nutrients is also and threat to the agriculture. The negative soil nutrient balance have found in the country and the net removal of major nutrients (N, P, K, S) are as high as ranges between 180 and 250 kg/ha/yr. (Karim et al., 1994). The extent of land degradation and its economic impact are given in the Table 2 and 3 respectively. BENEFICIAL EFFECTS OF AGROFORESTRY ON SOIL On the basis of various experimental evidences, Dwivedi (1992) pointed out some beneficial effects of agroforestry on soil, such as: (i) reduction of loss of soil as well as nutrients through reduction of run-off, (ii) addition of carbon and its transformation through leaf, twig, bark fall etc., (iii) nitrogen enrichment by fixation of nitrogen by nitrogen fixing trees, shrubs etc., (iv) improvement of physical conditions of soil such as water holding capacity, permeability, drainage etc., (v) release and recycling of nutrients by affecting biochemical nutrient cycling, (vi) more microbial associations and addition of more root biomass, (vii) moderately effect on extreme conditions of soil acidity and alkalinity (viii) creating more favourable microclimate by windbreak and shelterbelt effect and (ix) lowering effect on the water-table in areas where the water table is high. Agroforestry techniques involving planting multipurpose trees that are tolerant of the adverse soil conditions have been suggested as a management options for reclamation of problem areas (King and Chandler, 1978). Agroforestry for erosion control Young (1989) reported that trees and shrubs have several functions to control erosion like (i) to increase soil cover, by litter and pruning (ii) to provide partly permeable hedgerow barriers (iii) to lead to the progressive development of terraces, through soil accumulation upslope of hedgerows (iii) to increase soil resistance to erosion, by maintenance of organic matter (iv) to stabilize earth structures by root systems (v) to make productive use of the land occupied by conservation works. Alley cropping or hedgerow cultivation is very helpful in controlling of soil erosion in the hilly area. Hill Tract Development Board of Bangladesh identified five nitrogen fixing trees species like Leucaena leucocephala, Gliricidia sepium, Indigofera tysmani, Fleminigia spp. and Desmodium rensonii etc. and two grass species Vetiviera zizanoides and Thysanolaena maxima for controlling run off and erosion in the hilly region of Bangladesh ( Khisa et al., 2002).. Singh et al. (1990) found that runoff and soil loss were substantially reduced when small watersheds with agriculture were replaced either by trees and grasses (silvipasture) or with mechanical measures. In a study, Wiersum (1984) found that different agroforestry systems cause lowest soil erosion.

Source of Information: J Agric Rural Dev 4(1&2), 19-25, June 2006

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Achievement/Findings:

Land degradation is a global concern for agricultural productivity. It is the demand of time to check the further degradation and restore the degraded land. Agroforestry systems appear to have the potential to control erosion, improve soil fertility, and so lead towards sustainable land use. Agroforestry is being treated as and component of sustainable agriculture in many countries. Research is need in specific land degradation situation to generate appropriate technologies. Training should be provided to the agricultural researchers and extension personnel. Planning of agroforestry is to be framed out at the top level. Linkage with international organizations should be developed. Selection of suitable species, selection of appropriate technology, sufficient inputs and effective organization etc. should be kept in mind during the initiation of agoforestry programme minimizing the land degradation.

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