Md.Nurul Huda Al Mamun
INTRODUCTION
Bangladesh is the largest deltaic floodplain in the world with a total area of 14570 km2 of which 88892 km2 is occupied by major rivers and estuaries. The great delta is flat throughout and stretch from near the foothill of the Himalayas mountain in the north to a southern and irregular deltaic coastline that faces the bay of Bengal. The country is mostly surround by India except for a short (about 200 km) southeastern frontier with Myanmar. She lies between 20034″ and 26038″ north latitude, and 88001″ and 92041″ longitude. Bangladesh is one of the densely populated countries in the world with about 150 million people. The population density is around 974 people per km2 with annual growth rate of 1.54 percent. Agriculture is the life force of her economy. The country has been a food deficit area for long time and has about 8.2 million hectares of cultivated land with average cropping intensity of about 190 per cent (BBS 2008). Soil is the most important natural resource. The majority of the country’s soils are alluvial. Hill and terrace soils represent only 20 per cent of the country and 8-10 per cent of the cultivable land. Agro ecologically the country has been divided into thirty regions.
The rainfall ranges from 1500 mm in the North West to 5000 mm in the northeast. The rainfall along with depth and duration of flooding remain the critical factors for agriculture in the country. The critical aspects of rainfall in relation to the use of land for agriculture relate to the uncertainty of the onset and departure of the monsoon as well as the occurrence of drought, Bangladesh is really very lucky in having a hyper thermos temperature regime where agriculture production is possible all though the year. Bangladesh has more than 60% of the land area under agricultural use, against only 12% for the world. The country is really at odds in maintaining ecological balance on one hand and maintaining self sufficiency in food production for its burgeoning population on the other. Very few agrarian societies in the world have willfully employed such a high percentage of their land area under cultivation.
Bangladesh comprises hills, terraces and alluvial plains. The major portion of the Bengal Basin of the Sindhu-Ganges depression lies in Bangladesh. Recently formed delta and alluvial plains of the Ganges, Brahmaputra and Meghna rivers are the most extensive area of cropping practices (cropping intensity 180%, BBS 2009). However, most of the area suffers from a variable extent of soil and land constraints and natural hazards. The south-western part of Bangladesh mainly comprising Ganges river and tidal alluvial plains has a lower cropping intensity of 134% (BBS, 2009) along with severe constraints due to certain unfavorable soil and land characteristics and natural disasters like drought, flood, cyclonic storm surges, tornadoes, etc. The ingression of soil and water salinity from the Bay of Bengal causes adverse affect on cropping practices and other uses of land resource. This region thus needs special attention for its development and to mitigate constraints to use potentials. Keeping in view feed the hungry millions no area is separable for intensive use according to its potentials with adoption of suitable measures to overcome the constraints.
What is Soil
Soil is a natural body consisting of layers (soil horizons) of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics. It is composed of particles of broken rock that have been altered by chemical and environmental processes that include weathering and erosion. Soil differs from its parent rock due to interactions between the lithosphere, hydrosphere, atmosphere, and the biosphere. It is a mixture of mineral and organic constituents that are in solid, gaseous and aqueous states. Soil particles pack loosely, forming a soil structure filled with pore spaces. These pores contain soil solution (liquid) and air (gas).
This has been possible for the existence of the proverbially futile soils on the few vast flood plains that are annually replenished by siltation during flooding. Over 60% percentage of the population in Bangladesh depends direct or indirectly upon agriculture, while nearly 22% of the gross national product comes from this sector.
Bangladesh Soil
The major part of Bangladesh is on the delta formed by the three major rivers brahmaputra, ganges and meghna. These rivers and many of the country's other minor rivers originate outside the national boundary of the country and make up the Ganges-Brahmaputra-Meghna river system. The system drains a basin of some 1.76 million sq km and carry not only snowmelt water from the himalayas but also runoff water from some of the highest rainfall areas of the world. Over millennia, the sediments carried by the huge discharges of these rivers have built a broad delta, forming most of the large area of Bangladesh and the submerged delta-plain in the bay of bengal. These huge sediments are the major sources of formation of 80% soils of the country. The remaining 20% of soils have been formed in Tertiary and Quaternary sediments of hills (12 %) and in uplifted pleistocene terrace (8%).
Fig. 1 General Soil Map of Bangladesh
Soil Resource of Bangladesh
Bangladesh though a small country, has surprisingly a wide range of soils. About 576 soil series have been identified which ranges from juvenile alluvium or manmade soil material deposits at one extreme to old, deeply weathered, red soils at the other with variation kinds of hydomorphic and drainage characteristics in between these soil series have been grouped in to 21 general soil types (Brammer, 1984). The general soil type is a local level of classification system designated in a very broad land of generalization for use of general purpose. This system provides an overview of the soil condition of the whole country or of a region within the country. The general principles taken to classify the soils are that they are first divided into broad categories. 1. The floodplains soils 2. The terrace sinlase 3. The hill soils. Although physiographically Bangladesh appears to be a relationally simple landmark, as many as 22 physiographic units has been identified. (FAO-UNDP,1988). The physiographic units are the identification of the land formation and the origin of the soil materials.
The tertiary hills belonging to the district of Chittagong,Chittagong hill tracts,Sylhet, the edge of the Garo hills in Mymensingh and Lalmai hills of Comilla occupy 12% of the country. They are composed mainly of unconsolidated and some consolidated rocks and sediments of mostly miocne and pliocne geological periods. The soils are mainly coarse textured and being located in a high rainfall area and are intensely leached and have developed strong acidity. The soils inherently have low fertility status and are degraded in many places for various reason. The reasons are surface erosion, jhum cultivation and deforestation shifting cultivation is practiced locally by tribal people living there.The Pleistocene terrace include mainly the Modhupur tract in greater Dhaka, Tangail and Mymensingh district and the Barind tract of greater Rajshahi, Bogra, Rangpur and Dinazpur districts and the Akhaura terrace of B baria district, which together occupy 8% area of the country. The soils of these tracts stand on the high land above the floodplain and have good external drainage. Because of origin of soils are mainly clay loam/clayey texture, contain numerous ferruginous concretions are relatively rich in free iron and aluminium oxides and have high phosphate fixing capacity.
The Gangetic alluvium is calcareous and may contain <15%>
COSTRAINT OF USE OF SOIL RESOURCE
Throughout human history, soil has been repeatedly ruined and destroyed. This is highly dangerous to a civilization, because soil is an essential resource that is useful in many ways. Some societies have even collapsed due to mistreatment of their soil resources, so modern people must be cautious to avoid a similar fate.
They have many limitations they are:
Soil Erosion
Soil erodibility is the inherent liability of the soil to erode. This is a function of the properties of the soil itself especially soil structure and texture (SRDI 1998). Erosivity is a term applied to rainfall referring to inherent characteristics of rainfall in terms of its potential to cause erosion.
Soil degradation
Soil degradation refers to the decline in the productive capacity of the soil. Used broadly it may subsume soil erosion, however more usually reference is made to soil erosion and degradation as two distinct but related phenomena. Soil degradation may be caused by preferential soil erosion where the most productive fraction of the soil is lost leaving the less fertile part. This may occur without visible or measurable physical loss, for example of soil depth, and can only be determined through comparative soil analysis.
Infiltration
Infiltration rate (also mistakenly known as percolation) is the rate at which water enters into the soil. When the rate of water supply (rainfall) exceeds the infiltration rate then runoff occurs and flows over the soil surface as overland flow, a critical parameter in soil erosion by water. Nutrient mining and land quality
It is essential to maintain an optimum fertility land in the soils for attaining sustainable agriculture production. In a low input agriculture the gradual net loss of nutrients from soils is everyday phenomenon. Agriculture in Bangladesh is practiced on moderately fertile soils of the without application of adequate quantity’s of farmland manures and chemical fertilizer. As a result, yield have started to become stagnant or even declining in many areas. But in some cases the decline in land productivity has been offset by higher fertilizer application. The decrease of yields has been estimated to be around one percent per year and in the more adversely affected areas if it is higher than that. There has been steady increase in the yields of HYV rice. Nutrient mining in Bangladesh soils has been noted as a serious and widespread problem ( Karim and Iqbal, 2001) estimated a total loss of 1.25 million tons of Nitrogen, phosphorus, potassium from the agriculture land of Bangladesh every year.
Environmental impact of Agriculture
The indiscriminate use of lands, imbalanced use of fertilizers, non-judicious use of agrochemicals and very low land-man ratio has created a threat to the agriculture of Bangladesh. To meet the over-growing needs of an extremely outsized population, the country's natural resource base is rapidly being outstripped by human induced environmental degradation, especially due to poor management of agricultural lands. Some of them are briefly enumerated below.
Loss of organic matter and nutrient depletion
The intensive cultivation of HYV rice without organic recycling and rapid mineralization is important factor, causing depletion of organic matter and other plant nutrient & thereby disturbed the agro-ecosystem of the country.
Dystrification
In parts of coastal tidal floodplain, clearing of mangrove vegetation and subsequent drainage improvement resulted in the formation of Acid Sulphate Soils with extreme acidity associated with aluminum toxicity and phosphate fixation. These soils also remain saline even after empoldering, and thus land productivity eventually declines.
Water logging
Most of the agricultural lands in Khulna region occupy the lowlying areas and covers a total area of about 1.3 M ha. These lands are inundated to variable depths during monsoon season. Farmers generally used to grow a single crop of rice occasionally followed by some rabi crops locally where possible. But the crop yield was too low which were often used to be damaged by early and or late floods.
Lowering groundwater and Salinization
With the introduction of modern varieties of rice groundwater extraction has largely been started during 1970s. It is reported that the continued extraction of groundwater and withdrawal of fresh
water in the upper riparian areas has resulted in lowering of groundwater and upconing of saline water respectively in coastal areas.
Loss of productive function
In floodplain areas soils are mined for brick making, earth filling and land raising from the fertile crop fields for the development of rural infrastructure. Land productivity is reduced locally by peat mining particularly in the Khulna-Gopalganj peat basin. Salinity problem, already serious, could be further aggravated due to global warming and sea level rise with implication for drinking water (especially in Khulna area), agricultural products and industrial installations. Area of high salinity may increase from existing 13% to 32%. Use of agrochemical, insecticides pesticides etc. has a serious implication on land and soil quality and a subsequent destruction of ecosystem.
Arsenic and heavy metal pollution
Cases of arsenic poisoning were reported in certain parts of the country due to increase concentration of arsenic compound (>0.05ppm) particularly in the over-drawn aquifers. Locally drainage improvement of almost perennially wet peat in the peat basin causes limited subsidence. Excess drawdown of groundwater also may cause land subsidence in certain less stable areas.
Problem soil
Problem Soils impose a severe limitation on successful crop production due to the unfavourable effects of certain chemical and/or physical properties of soils. acid sulphate soils, saline and alkali soils, peat soils, soils with nutrient toxicity (very minor area) and nutrient deficiency are examples of chemical soil problems while steeply sloping soils, coarse textured soils, shallow soils, poorly drained soils, heavy textured soils and soils with ploughpan are included in soils with physical problems.
Low Soil Fertility Status
Although Bangladesh is a small country, it has wide variety and complexity of soils at short distances due to a diverse nature of physiography, parent materials, lands, and hydrology and drainage conditions. Due to intensive cropping to grow more food, continuous changes are taking place in the soil fertility status due to organic matter depletion, nutrient deficiencies, drainage impedance/water logging followed by degradation of soil physical and chemical properties as well as soil salinity/acidity. The fertility status of Bangladesh soils is extremely variable. Most of the soils are depleted and are in urgent need of replenishment with organic manure and fertilizers if projected crop production target is to be obtained.
Beside this there are many limitations are as follows:
Annual flooding
Seasonal drought
Tropical cyclones
Cold wave
River eroding
Prospective of soil resource
Fertilizer Recommendation
Fertilizer recommendation for single crops and cropping patterns are usually made by following the guidelines clearly stated in “The National Fertilizer Recommendation Guide” which is revised and published from time to time by the Bangladesh Agricultural Research Council in consultation with NARS scientists engaged in soil fertility and fertilizer management research activities. Upazila Soil Use Guide published and updated by SRDI from time to time is also a useful guide for site-specific fertilizer recommendation. Each guide has at least 100-150 site-specific information on soils nutrient status, topography, hydrology, vegetation and drought. Fertilizer recommendations are usually made on the basis of soil fertility classes; yield goals and farmers’ management ability. For high yield goal fertilizer recommendation, one should have site-specific information on nutrient status of soils as well as the crops.
Balanced Fertilization
Balanced fertilization is the key to successful crop production and maintenance of good soil health. It is important to see how close nutrient addition and removal by crops match with each other. According to current statistics, the farmers of Bangladesh use 215 kg nutrients (N: 149 kg, P2O5: 37 kg, K2O: 22 kg and S + Zn + B + others: 7) ha/year from chemical fertilizers, while the estimated removal is around 280 -350 kg/ha. From organic and natural sources about 50-70 kg nutrients are added to the soil system every year. One nutrient balance study made by DAE-SFFP (2002) from a typical Boro- Fallow – T. Aman cropping pattern.
Soil Testing Facilities
For using balanced fertilization, Soil Resource Development Institute (SRDI) is providing soil testing facilities for farmers as well as crop growers in Bangladesh. It has 16 regional static laboratories and 10 Mobile Soil Testing laboratories (MSTL) namely Dhaka, Razshahi, comilla, Khulna, Mymensingh, Jamalpur, Bogra, Dinajpur, Jenida, Barisal, Noakhaly, Sylhet, Chittagong, Kustia and Faridpur.
Use of agricultural modern inputs
Modern inputs like improved varieties of seeds, fertilizers, insecticides and ground and surface water irrigation are being practiced. The use of modern technology and inputs is comparatively more intensive on soils of the Ganges river floodplain than on the tidal floodplain soils due to the problems of salinity and fresh water scarcity in the latter area and also lack of suitable salt tolerant varieties. About 70% area of Ganges floodplain could be brought under improved cropping practices. Crop screening, selection and introduction of salt tolerant varieties may increase crop yield. Traditional local varieties with poor yield have little possibility to improve the existing production system in the area. The chemical fertilizer, mainly urea is being used for moderate yield goal without knowing the site specific land and soil characteristics & existing nutrient status of the soils.
Land Use Program
Government of Bangladesh have initiated participatory bottom up planning process in the country with effect from July, 1997. It requires integrated and multi-disciplinary approach. GO/NGO's collaborative efforts will be necessary for successful implementation of land use program. Conservation of biodiversity, particularly the mangrove forest areas and promotional activities related to clientele driven technology dissemination program based on land and soil characteristics are being given top priority in the land use planning program of the region. There are sporadic success stories in co-operative farming and deserve fine-tuning and consolidation of activities for development of sustainable land use planning program.
Consideration
It is important to apply agrochemicals whenever necessary and appropriate use. Excess use of that agrochemical is now a coming disaster of our soil resource. The following measure should be taken for maintain soil fertility and sustainable agricultural production;
The Challenges-view points:
To address the challenges posed by local problems strategies for sustainable use of soil, land, water and other natural resources may be taken:
A. Policy issues
- Land zoning according to land potentials.
- Increasing trend of conversion of potential agricultural land into non-agricultural use to be minimized.
- Extensive motivation for rational use of water, fertilizers, insecticides and other inputs to restore environment and soil health (IPNS, water management, IPM).
- Marketing, price protection and preservation of agricultural commodities to be ensured.
- Illiteracy eradication and health care facilities to be enhanced.
- Rehabilitation of local drainage systems by dredging and excavation of major drainage ways is needed to mitigate the problem of drainage congestion, in combination with adaption of effective sediment/siltation control measures.
- Polder management such as maintenance of embankments, sluice gates, introduction of social forestry and development of green belt.
- Development of appropriate plans for natural disaster preparedness and post disaster rehabilitation programmes including agriculture.
- Protection of soil and water pollution from heavy metals.
- Conservation of bio-diversity and sustainable use of mangrove (Sundarbans) ecosystem.
B. Research and Technological Issues
- Effective technology transfer mechanism should be evolved to disseminate location specific agrotechnologies to the farmers.
- Use of soil test based inorganic and organic fertilizers is to be popularized.
- Development of appropriate soil management technology for irrigated rice or dryland crops on cracking heavy clays.
- Crop diversification in the western high Ganges floodplain and planned agro-fisheries in the lower areas in the east and south east.
- Groundwater abstraction should be limited to avoid abnormal drawdown to avoid inland ingression of fresh water-salt water interface and salinity upcoming.
- Development of soil tolerant germ plasm for coastal saline area is required.
- Development of appropriate technology on soil and water salinity management may be undertaken.
- Monitoring of coastal river water salinity for the demarkation of safe period of irrigation with brackish water.
- Groundwater control in the peat basin areas to avoid irreversible shrinkage of peat soils and cracking and subsidence of ground surface.
- The acid sulphate soils, active or potential, need special careful handling to avoid any further aggravation of the problems related to high acidity and aluminium toxicity.
- Effective protection of wildlife, especially of the endangered species such as The Royal Bengal Tiger, estuarine crocodiles, etc.
Beside this following measures should be considered:
-Farmer’s training for awareness of appropriate land use technique.
-Embankment in the costal area’s to protect cultivable land from salinity.
-Invent suitable saline tolerant crop variety.
CONCLUSION
Saving soil resources, for future generation, soil fertility should be ensured. For this why, timely supply and availability of fertilizers at reasonable prices at the doorsteps of the hard working farmers in the country can only ensure balanced fertilization that is very much needed for our depleted soils for optimum supply of nutrients for successful crop production and maintenance of soil health. The supply of nutrients to the soil – plant system comes from various sources, the most important sources being the organic manure and chemical fertilizers. The use efficiency of the chemical fertilizers are low and unsatisfactory because of imbalanced or under use/sometimes over use resulting in huge wastage which the country cannot afford. Therefore, the practice of balanced fertilization should receive top priority to sustain/increase crop productivity when food security is so crucial for poverty stricken people, when the country is facing challenges of increasing population and shrinking natural resources including agricultural land and also when there exists big gap between research and farmer’s yield. Conservation of bio-diversity and sustainable development of our ecosystem deserve special attention. The prosperity and further development of soil resources is a formidable task to be undertaken in an integrated and multi disciplinary approach.
REFERENCES
Bashar, M.A. 2001. Management of homestead: Plantation and agroforestry. Bangladesh
Observer. June 24 issue. Dhaka.
BBS (Bangladesh Bureau of Statistics), 2007. Statistical Yearbook of Bangladesh. Govt.
of Bangladesh. Dhaka.
BBS (Bangladesh Bureau of Statistics), 2008. Statistical Yearbook of Bangladesh. Govt.
of Bangladesh. Dhaka.
BBS (Bangladesh Bureau of Statistics), 2009. Statistical Yearbook of Bangladesh. Govt.
of Bangladesh. Dhaka.
Brammer, H. 1984. Disaster Preparedness Planning Precautionary and Rehabilitation
Measures for Agriculture, Bangladesh.
DAE-SFFP. 2002. Seminar on Soil Health Management: Department of Agricultural
Extension-Soil Fertility and Fertilizer Project Experience.
FAO-UNDP, 1988. Agroecological regions of Bangladesh. Report-2, FAO, Rome.
Huda, N and Roy, M.K. 2000. State of the forests. In Chowdhury, Q.I. (Edi.). State of
Environment Report. Forum of Environment Journalists of Bangladesh, Dhaka.
Karim, Z. and A. Iqbal. 2001. Impact of Land Degradation in Bangladesh. Bangladesh
Agricultural Research Council. Farm Gate. Dhaka. P. 60 and 160.
SRDI Staff, 1965-1986. Reconnaissance Soil Survey Reports of Various Districts. Soil
Resources Development Institute, Farm Gate. Dhaka.
Ullah, M. 2002. Biodiversity irreplaceable asset. Weekly Holiday. (8.2.2002 issue)
Center for sustainable development (CFSD). Dhaka.
Soil Resource of Bangladesh
Bangladesh though a small country, has surprisingly a wide range of soils. About 576 soil series have been identified which ranges from juvenile alluvium or manmade soil material deposits at one extreme to old, deeply weathered, red soils at the other with variation kinds of hydomorphic and drainage characteristics in between these soil series have been grouped in to 21 general soil types (Brammer, 1984). The general soil type is a local level of classification system designated in a very broad land of generalization for use of general purpose. This system provides an overview of the soil condition of the whole country or of a region within the country. The general principles taken to classify the soils are that they are first divided into broad categories. 1. The floodplains soils 2. The terrace sinlase 3. The hill soils. Although physiographically Bangladesh appears to be a relationally simple landmark, as many as 22 physiographic units has been identified. (FAO-UNDP,1988). The physiographic units are the identification of the land formation and the origin of the soil materials.
The tertiary hills belonging to the district of Chittagong,Chittagong hill tracts,Sylhet, the edge of the Garo hills in Mymensingh and Lalmai hills of Comilla occupy 12% of the country. They are composed mainly of unconsolidated and some consolidated rocks and sediments of mostly miocne and pliocne geological periods. The soils are mainly coarse textured and being located in a high rainfall area and are intensely leached and have developed strong acidity. The soils inherently have low fertility status and are degraded in many places for various reason. The reasons are surface erosion, jhum cultivation and deforestation shifting cultivation is practiced locally by tribal people living there.The Pleistocene terrace include mainly the Modhupur tract in greater Dhaka, Tangail and Mymensingh district and the Barind tract of greater Rajshahi, Bogra, Rangpur and Dinazpur districts and the Akhaura terrace of B baria district, which together occupy 8% area of the country. The soils of these tracts stand on the high land above the floodplain and have good external drainage. Because of origin of soils are mainly clay loam/clayey texture, contain numerous ferruginous concretions are relatively rich in free iron and aluminium oxides and have high phosphate fixing capacity.
The Gangetic alluvium is calcareous and may contain <15%>
COSTRAINT OF USE OF SOIL RESOURCE
Throughout human history, soil has been repeatedly ruined and destroyed. This is highly dangerous to a civilization, because soil is an essential resource that is useful in many ways. Some societies have even collapsed due to mistreatment of their soil resources, so modern people must be cautious to avoid a similar fate.
They have many limitations they are:
Soil Erosion
Soil erodibility is the inherent liability of the soil to erode. This is a function of the properties of the soil itself especially soil structure and texture (SRDI 1998). Erosivity is a term applied to rainfall referring to inherent characteristics of rainfall in terms of its potential to cause erosion.
Soil degradation
Soil degradation refers to the decline in the productive capacity of the soil. Used broadly it may subsume soil erosion, however more usually reference is made to soil erosion and degradation as two distinct but related phenomena. Soil degradation may be caused by preferential soil erosion where the most productive fraction of the soil is lost leaving the less fertile part. This may occur without visible or measurable physical loss, for example of soil depth, and can only be determined through comparative soil analysis.
Infiltration
Infiltration rate (also mistakenly known as percolation) is the rate at which water enters into the soil. When the rate of water supply (rainfall) exceeds the infiltration rate then runoff occurs and flows over the soil surface as overland flow, a critical parameter in soil erosion by water. Nutrient mining and land quality
It is essential to maintain an optimum fertility land in the soils for attaining sustainable agriculture production. In a low input agriculture the gradual net loss of nutrients from soils is everyday phenomenon. Agriculture in Bangladesh is practiced on moderately fertile soils of the without application of adequate quantity’s of farmland manures and chemical fertilizer. As a result, yield have started to become stagnant or even declining in many areas. But in some cases the decline in land productivity has been offset by higher fertilizer application. The decrease of yields has been estimated to be around one percent per year and in the more adversely affected areas if it is higher than that. There has been steady increase in the yields of HYV rice. Nutrient mining in Bangladesh soils has been noted as a serious and widespread problem ( Karim and Iqbal, 2001) estimated a total loss of 1.25 million tons of Nitrogen, phosphorus, potassium from the agriculture land of Bangladesh every year.
Environmental impact of Agriculture
The indiscriminate use of lands, imbalanced use of fertilizers, non-judicious use of agrochemicals and very low land-man ratio has created a threat to the agriculture of Bangladesh. To meet the over-growing needs of an extremely outsized population, the country's natural resource base is rapidly being outstripped by human induced environmental degradation, especially due to poor management of agricultural lands. Some of them are briefly enumerated below.
Loss of organic matter and nutrient depletion
The intensive cultivation of HYV rice without organic recycling and rapid mineralization is important factor, causing depletion of organic matter and other plant nutrient & thereby disturbed the agro-ecosystem of the country.
Dystrification
In parts of coastal tidal floodplain, clearing of mangrove vegetation and subsequent drainage improvement resulted in the formation of Acid Sulphate Soils with extreme acidity associated with aluminum toxicity and phosphate fixation. These soils also remain saline even after empoldering, and thus land productivity eventually declines.
Water logging
Most of the agricultural lands in Khulna region occupy the lowlying areas and covers a total area of about 1.3 M ha. These lands are inundated to variable depths during monsoon season. Farmers generally used to grow a single crop of rice occasionally followed by some rabi crops locally where possible. But the crop yield was too low which were often used to be damaged by early and or late floods.
Lowering groundwater and Salinization
With the introduction of modern varieties of rice groundwater extraction has largely been started during 1970s. It is reported that the continued extraction of groundwater and withdrawal of fresh
water in the upper riparian areas has resulted in lowering of groundwater and upconing of saline water respectively in coastal areas.
Loss of productive function
In floodplain areas soils are mined for brick making, earth filling and land raising from the fertile crop fields for the development of rural infrastructure. Land productivity is reduced locally by peat mining particularly in the Khulna-Gopalganj peat basin. Salinity problem, already serious, could be further aggravated due to global warming and sea level rise with implication for drinking water (especially in Khulna area), agricultural products and industrial installations. Area of high salinity may increase from existing 13% to 32%. Use of agrochemical, insecticides pesticides etc. has a serious implication on land and soil quality and a subsequent destruction of ecosystem.
Arsenic and heavy metal pollution
Cases of arsenic poisoning were reported in certain parts of the country due to increase concentration of arsenic compound (>0.05ppm) particularly in the over-drawn aquifers. Locally drainage improvement of almost perennially wet peat in the peat basin causes limited subsidence. Excess drawdown of groundwater also may cause land subsidence in certain less stable areas.
Problem soil
Problem Soils impose a severe limitation on successful crop production due to the unfavourable effects of certain chemical and/or physical properties of soils. acid sulphate soils, saline and alkali soils, peat soils, soils with nutrient toxicity (very minor area) and nutrient deficiency are examples of chemical soil problems while steeply sloping soils, coarse textured soils, shallow soils, poorly drained soils, heavy textured soils and soils with ploughpan are included in soils with physical problems.
Low Soil Fertility Status
Although Bangladesh is a small country, it has wide variety and complexity of soils at short distances due to a diverse nature of physiography, parent materials, lands, and hydrology and drainage conditions. Due to intensive cropping to grow more food, continuous changes are taking place in the soil fertility status due to organic matter depletion, nutrient deficiencies, drainage impedance/water logging followed by degradation of soil physical and chemical properties as well as soil salinity/acidity. The fertility status of Bangladesh soils is extremely variable. Most of the soils are depleted and are in urgent need of replenishment with organic manure and fertilizers if projected crop production target is to be obtained.
Beside this there are many limitations are as follows:
Annual flooding
Seasonal drought
Tropical cyclones
Cold wave
River eroding
Prospective of soil resource
Fertilizer Recommendation
Fertilizer recommendation for single crops and cropping patterns are usually made by following the guidelines clearly stated in “The National Fertilizer Recommendation Guide” which is revised and published from time to time by the Bangladesh Agricultural Research Council in consultation with NARS scientists engaged in soil fertility and fertilizer management research activities. Upazila Soil Use Guide published and updated by SRDI from time to time is also a useful guide for site-specific fertilizer recommendation. Each guide has at least 100-150 site-specific information on soils nutrient status, topography, hydrology, vegetation and drought. Fertilizer recommendations are usually made on the basis of soil fertility classes; yield goals and farmers’ management ability. For high yield goal fertilizer recommendation, one should have site-specific information on nutrient status of soils as well as the crops.
Balanced Fertilization
Balanced fertilization is the key to successful crop production and maintenance of good soil health. It is important to see how close nutrient addition and removal by crops match with each other. According to current statistics, the farmers of Bangladesh use 215 kg nutrients (N: 149 kg, P2O5: 37 kg, K2O: 22 kg and S + Zn + B + others: 7) ha/year from chemical fertilizers, while the estimated removal is around 280 -350 kg/ha. From organic and natural sources about 50-70 kg nutrients are added to the soil system every year. One nutrient balance study made by DAE-SFFP (2002) from a typical Boro- Fallow – T. Aman cropping pattern.
Soil Testing Facilities
For using balanced fertilization, Soil Resource Development Institute (SRDI) is providing soil testing facilities for farmers as well as crop growers in Bangladesh. It has 16 regional static laboratories and 10 Mobile Soil Testing laboratories (MSTL) namely Dhaka, Razshahi, comilla, Khulna, Mymensingh, Jamalpur, Bogra, Dinajpur, Jenida, Barisal, Noakhaly, Sylhet, Chittagong, Kustia and Faridpur.
Use of agricultural modern inputs
Modern inputs like improved varieties of seeds, fertilizers, insecticides and ground and surface water irrigation are being practiced. The use of modern technology and inputs is comparatively more intensive on soils of the Ganges river floodplain than on the tidal floodplain soils due to the problems of salinity and fresh water scarcity in the latter area and also lack of suitable salt tolerant varieties. About 70% area of Ganges floodplain could be brought under improved cropping practices. Crop screening, selection and introduction of salt tolerant varieties may increase crop yield. Traditional local varieties with poor yield have little possibility to improve the existing production system in the area. The chemical fertilizer, mainly urea is being used for moderate yield goal without knowing the site specific land and soil characteristics & existing nutrient status of the soils.
Land Use Program
Government of Bangladesh have initiated participatory bottom up planning process in the country with effect from July, 1997. It requires integrated and multi-disciplinary approach. GO/NGO's collaborative efforts will be necessary for successful implementation of land use program. Conservation of biodiversity, particularly the mangrove forest areas and promotional activities related to clientele driven technology dissemination program based on land and soil characteristics are being given top priority in the land use planning program of the region. There are sporadic success stories in co-operative farming and deserve fine-tuning and consolidation of activities for development of sustainable land use planning program.
Consideration
It is important to apply agrochemicals whenever necessary and appropriate use. Excess use of that agrochemical is now a coming disaster of our soil resource. The following measure should be taken for maintain soil fertility and sustainable agricultural production;
The Challenges-view points:
To address the challenges posed by local problems strategies for sustainable use of soil, land, water and other natural resources may be taken:
A. Policy issues
- Land zoning according to land potentials.
- Increasing trend of conversion of potential agricultural land into non-agricultural use to be minimized.
- Extensive motivation for rational use of water, fertilizers, insecticides and other inputs to restore environment and soil health (IPNS, water management, IPM).
- Marketing, price protection and preservation of agricultural commodities to be ensured.
- Illiteracy eradication and health care facilities to be enhanced.
- Rehabilitation of local drainage systems by dredging and excavation of major drainage ways is needed to mitigate the problem of drainage congestion, in combination with adaption of effective sediment/siltation control measures.
- Polder management such as maintenance of embankments, sluice gates, introduction of social forestry and development of green belt.
- Development of appropriate plans for natural disaster preparedness and post disaster rehabilitation programmes including agriculture.
- Protection of soil and water pollution from heavy metals.
- Conservation of bio-diversity and sustainable use of mangrove (Sundarbans) ecosystem.
B. Research and Technological Issues
- Effective technology transfer mechanism should be evolved to disseminate location specific agrotechnologies to the farmers.
- Use of soil test based inorganic and organic fertilizers is to be popularized.
- Development of appropriate soil management technology for irrigated rice or dryland crops on cracking heavy clays.
- Crop diversification in the western high Ganges floodplain and planned agro-fisheries in the lower areas in the east and south east.
- Groundwater abstraction should be limited to avoid abnormal drawdown to avoid inland ingression of fresh water-salt water interface and salinity upcoming.
- Development of soil tolerant germ plasm for coastal saline area is required.
- Development of appropriate technology on soil and water salinity management may be undertaken.
- Monitoring of coastal river water salinity for the demarkation of safe period of irrigation with brackish water.
- Groundwater control in the peat basin areas to avoid irreversible shrinkage of peat soils and cracking and subsidence of ground surface.
- The acid sulphate soils, active or potential, need special careful handling to avoid any further aggravation of the problems related to high acidity and aluminium toxicity.
- Effective protection of wildlife, especially of the endangered species such as The Royal Bengal Tiger, estuarine crocodiles, etc.
Beside this following measures should be considered:
-Farmer’s training for awareness of appropriate land use technique.
-Embankment in the costal area’s to protect cultivable land from salinity.
-Invent suitable saline tolerant crop variety.
CONCLUSION
Saving soil resources, for future generation, soil fertility should be ensured. For this why, timely supply and availability of fertilizers at reasonable prices at the doorsteps of the hard working farmers in the country can only ensure balanced fertilization that is very much needed for our depleted soils for optimum supply of nutrients for successful crop production and maintenance of soil health. The supply of nutrients to the soil – plant system comes from various sources, the most important sources being the organic manure and chemical fertilizers. The use efficiency of the chemical fertilizers are low and unsatisfactory because of imbalanced or under use/sometimes over use resulting in huge wastage which the country cannot afford. Therefore, the practice of balanced fertilization should receive top priority to sustain/increase crop productivity when food security is so crucial for poverty stricken people, when the country is facing challenges of increasing population and shrinking natural resources including agricultural land and also when there exists big gap between research and farmer’s yield. Conservation of bio-diversity and sustainable development of our ecosystem deserve special attention. The prosperity and further development of soil resources is a formidable task to be undertaken in an integrated and multi disciplinary approach.
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Agricultural Research Council. Farm Gate. Dhaka. P. 60 and 160.
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Center for sustainable development (CFSD). Dhaka.
Great step as an agriculturist....
ReplyDeleteYou are right about the importance of land use and its effect on soil.
ReplyDeleteplease show the present status of soil salinity in babgladesh
ReplyDelete