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Transcript of MS Project Thesis Angshuman Sarkar MS111322
1
CHANGES IN DEMOGRAPHIC AND AGRICULTURAL FACTORS AND THEIR IMPACT ON CROPPING INTENSITY
AND NUTRIENT STATUS IN SOILS OF KALAPARA UPAZILA: A CASE STUDY
Course Title: Project Thesis
Course No. SS 5206
KHULNA UNIVERSITY
KHULNA
JULY, 2012
2
CHANGES IN DEMOGRAPHIC AND AGRICULTURAL FACTORS AND THEIR IMPACT ON CROPPING INTENSITY
AND NUTRIENT STATUS IN SOILS OF KALAPARA UPAZILA: A CASE STUDY
This project thesis paper has been prepared and submitted to Soil
Science Discipline, Khulna University, Khulna, as partial fulfillment of
the requirements for the degree of Master of Science in Soil Science.
Submitted By
……………………………………..
Angshuman Sarker
Student ID. MS 111322
Session: 2010-11
KHULNA UNIVERSITY
KHULNA
JULY, 2012
3
CHANGES IN DEMOGRAPHIC AND AGRICULTURAL FACTORS AND THEIR IMPACT ON CROPPING INTENSITY
AND NUTRIENT STATUS IN SOILS OF KALAPARA UPAZILA: A CASE STUDY
APPROVED AS TO STYLE AND CONTENT BY
……………………………………….
KhandokerQudrataKibria
Head and Associate Professor
Chairman of the Examination Committee
Soil Science Discipline
Khulna University, Khulna
KHULNA UNIVERSITY
KHULNA
JULY, 2012
4
CHANGES IN DEMOGRAPHIC AND AGRICULTURAL FACTORS AND THEIR IMPACT ON CROPPING INTENSITY
AND NUTRIENT STATUS IN SOILS OF KALAPARA UPAZILA: A CASE STUDY
Supervisor
……………………………………….
Md. Sanaul Islam
Associate Professor
Soil Science Discipline
Khulna University, Khulna
KHULNA UNIVERSITY
KHULNA
JULY, 2012
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CHANGES IN DEMOGRAPHIC AND AGRICULTURAL FACTORS AND THEIR IMPACT ON CROPPING INTENSITY
AND NUTRIENT STATUS IN SOILS OF KALAPARA UPAZILA: A CASE STUDY
Co-Supervisor
……………………………………….
Md. ZaberHossain
Assistant Professor
Soil Science Discipline
Khulna University, Khulna
KHULNA UNIVERSITY
KHULNA
JULY, 2012
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Contents
Contents i-iv
List of Tables iii
List of Figures iv
CHAPTER: 1. INTRODUCTION 01
1.1. Objectives 03
CHAPTER: 2. LITERATURE REVIEW 04
2.1. Coastal Areas of Bangladesh 05
2.1.1. Population pressure in coastal areas 06 2.1.2. Cultivable land in coastal areas 07
2.2. Cropping Patterns and Cropping Intensity in Bangladesh 07
2.2.1.Cropping Pattern and Cropping Intensity in Kalapara upazila 13
2.3.Nutrient status in soils of Bangladesh 14 2.3.1. Nitrogen 15
2.3.2. Phosphorus 16
2.3.3. Potassium 16
2.3.4. Sulphur 17
2.3.5. Zinc 18 2.3.6. Calcium and Magnesium 18
2.3.7. Boron 18
2.3.8. Other Micronutrients 19
2.4. Nutrient Status of Kalapara Upazila 19
2.5. Cropping Intensity and Its Effect on Nutrient Status 20 2.6. Soil Salinity 25
2.6.1. Present Soil Salinity Status in Coastal Area 25
2.6.2. Effect of Salinity on Fertility Status of Soil 27
CHAPTER 3. MATERIALS AND METHODS 30 3.1.Conceptualization and Work plan prepation Materials 30 3.2. Study Area 30
3.2.1. Area and Geographical Location 30
3.2.2. Demography 31
3.2.3. Topography and Relief 32 3.2.4. General Geology of the Study Area 32
7
3.2.5. Land Use Pattern 32
3.2.5.1. Cropland 33
3.2.5.2. Settlement 33 3.2.5.3. Fallow Land 34
3.2.6. Soil type 34
3.2.7. Climatic Condition 34
3.2.7.1. Rainfall 34
3.2.7.2. Temperature 34 3.2.7.3. Humidity 35
3.3. Selection of the Study Area 35
3.4. Data Collection 35
3.4.1. Cropping Intensity Determination 36 3.5. Data Interpretation 36
3.6. Data Processing and Analysis 36
CHAPTER 4. RESULTS AND DISCUSSION 37 4.1. Increase in population 37
4.2. Reduction of Cultivable land 38 4.3. Increase of Cropping Intensity 39
4.4. Increase of Salinity 39
4.5. Depletion of major Nutrient content 40
4.5.1. Nitrogen Depletion 40
4.5.2. Phosphorus Depletion 41 4.5.3. Potassium Depletion 42
4.5.4. Sulfur Depletion 43
4.5.5. Calcium Depletion 44
4.5.6. Zinc Depletion 45 4.5.7. Boron Depletion 45 CHAPTER 5. SUMMARY AND CONCLUSION 47
REFERENCES 48 - 60
8
List of Tables
2.1 Population growth trend in the coastal area 06
2.2 Some dominant cropping patterns under variable crop production environments 10
2.3 Cropping intensity rating 11 2.4 Last 10 year cropping intensity of Bangladesh 12 2.5 Major cropping patterns and cropping intensity in Kalapara 14 2.6 Nutrient status of Ganges tidal floodplain 20 2.7 Nutrient status of Kalapara upazila 20 2.8 Emergence of new nutrient deficiency with time 24 2.9 Extent of soil salinity during about last four decades (1973-
2009) in coastal areas 26
2.10 Estimation of salt affected areas(in ‘000’ ha) in Patuakhali 27 2.11 Agro-chemical characteristics of soil in some of the coastal
and offshore areas (saline belt) of Bangladesh 28
3.1 Represents increase of population in Union of Kalapara upazila after 10 years
32
3.2 Represents the cropland use of Kalapara upazila 33 3.3 Cropping intensity of Kalapara upazila 36
9
List of Figures
2.1 Land coverage status of major crops in Bangladesh 8
2.2 Acreage of different types of rice cultivated in Bangladesh 8
2.3 Land used under minor crops in Bangladesh 8
2.4 Nutrient input-output system 15
2.5 N+P+K input and output in Bangladesh 24
3.1 Location map of the study area 31
4.1 Population growth of five unions in Kalapara upazilla 37
4.2a Reduction of Cultivable land 38
4.2b Reduction of per capita land 38
4.3 Increase in Cropping Intensity 39
4.4 Increase in salinity 40
4.5 Depletion of Nitrogen 41
4.6 Depletion of Phosphorus 42
4.7 Depletion of Patassium 43
4.8 Depletion of Sulfer 43
4.9 Depletion of calcium 44
4.10 Depletion of Zink 45
4.11 Depletion of Boron 46
10
CHAPTER 1
INTRODUCTION
11
1. Introduction
Due to population increase, changes in the composition of the human diet and
increasing demand for bio-fuels, it is necessary to increase global crop production in
order to avoid a new era of malnutrition and hunger (Liu and Savenije,2008). The
food production increases in Arithmetic mean but population grows in Geometric
progression. So it is impossible to keep pace with the agricultural production and
increasing population. So far, the discussion on how to achieve the required increase
of crop production has been mainly restricted to the question of how many resources
(e.g. water, nutrients, energy, germplasm) are needed, and whether an extension of the
global cropland will be necessary or whether an increase of crop yields will be
sufficient (Neumann et al., 2010).
Cropping intensity is defined as the number of crops harvested per year and large
differences are reported in both space and time. Shifting cultivation is still practiced
by millions of farmers mainly in the tropics and subtropics and crop cultivation is
interrupted in these systems by fallow periods that may last decades (Hiernaux et al.,
2009). In contrast, up to four crops are harvested per year in very intensive land use
systems under similar climate conditions (Tanaka, 1995; Siebert et al., 2007). Crop
duration ratio is another indicator of land use intensity. Crop duration ratio is defined
as the fraction of the year in which the cropland is covered with crops (Siebert et al.,
2010).
According to the agricultural statistics database of the Food and agriculture
Organization of the united Nations FAO (2010), total cropland extent at the global
scale, computed as the sum of arable land and permanent crop area, is about 15.3
million km2. These statistics account for all cropland used at least once in a five-year
period, but neglect areas with longer fallow periods. The total harvested crop area
reported in the same database is 11.8 million km2 yr-1, indicating a global average
cropping intensity of 0.77 crop harvests per year. However, the extent of fallow land
is larger than the difference between global cropland extent and global harvested crop
areas because many areas are harvested more than once per year (Siebert et al., 2010).
With rising cropping intensities in South Asia, nutrient management is a major issue
being addressed by agricultural scientists for understanding any decline in yields.
Many long-term fertility experiments established in the region decades ago show no
evidence of yield decline at the farmers’ field level (Abrol et al., 1997).
12
The intensive cropping systems introduced by the Green Revolution impose much
heavier demands on crop nutrients than traditional systems had; nutrient deficiencies,
therefore, are a common problem. Intensive agricultural practices can also result in
changes in soil physical and chemical properties. In irrigated rice, the formation of a
plowpan is a frequent problem, impeding root growth and limiting access to nutrients.
Irrigation can also cause salinization or water-logging. The yield declines observed in
the IRRI long-term cropping trials are thought to result from anaerobic conditions in
irrigated rice production leading to changes in soil physical and chemical properties
which make it less able to supply nutrients to growing crops (Dey and Haq, 2009).
Climate change is an important issue nowadays. Various human activities are making
the world hot to hotter. The ultimate result is global warming, i.e. climate change.
Rising temperature in the atmosphere causes sea level rise and affects low lying
coastal areas and deltas of the world. In 1990, Intergovermental panel on climate
change estimates that with business-as-usual scenario of greenhouse gas emission, the
world would be 3.3°C warmer by the end of the next country, with a range of
uncertainty of 2.2 to 4.9°C. With rise in Sea level rise will cause river bank erosion,
salinity intrusion, flood, damage to infrastructures, crop failure, fisheries destruction,
loss of biodiversity, etc. along this coast. Salinity intrusion due to sea level rise will
decrease agricultural production by unavailability of fresh water and soil degradation.
Salinity also decreases the terminative energy and germination rate of some plants
(Warrick et al., 1993). Salinity is an environmental stress that limits growth and
development in plants. The response of plants to excess NaCl is complex and involves
changes in their morphology, physiology and metabolism (Hilal et al., 1998). Salinity
is a very serious constraint to crop plant growth in about 100 countries of the world
(Munns, 2002; Sadiq, 2003). It can inhibit plant growth by a range of mechanisms,
including low external water potential, ion toxicity and interference with the uptake of
nutrients (Munns and Schachtman, 1995; Taffouo et al., 2009). Salinity toxicity is a
worldwide agricultural and eco-environmental problem. It is one of the most
important problems in crop growth and production (Ashraf, 2009). Approximately
one-third of the world land surface is arid and semi-arid, of which one half is affected
by salinity (Liang et al., 1996). It is estimated that about a third of the world’s
cultivated land is affected by salinity. The problem of salinity is of special importance
in Egypt for both the old cultivated area as well as for the newly reclaimed lands. The
major constraints for plant growth and productivity are ion toxicity with excessive
13
uptake of mainly Cl- and Na+ as well as nutrients imbalance caused by disturbed
uptake or distribution of essential mineral nutrients (Hu and Schmidhalter, 2005).
Living with salinity is the only way of sustaining agricultural production in the salt
affected soil (Al-Rawahy et al., 2011). Salinity stress causes a number of effects on
plants such as osmotic effects, ion toxicity and nutrient imbalance. During a long time
in salinity, therefore, the sodium toxicity cause to reduce the yield. There are
antagonistic effects on nutrient uptake by plants that cause nutrient disorders
particularly of K and Ca under salinity conditions (Castillo et al., 2003).
The hypothesis therefore, is that fast population growth, rapid urbanization, increasing
food demand, high cropping intensity, intensive cultivation practices and salinity in
the study area may also entail negative impacts on soil fertility and nutrition and
finally may perish sustainability in agricultural use. In this research work the focus
mainly would be on impact of forgoing factors on some specific nutrient status in
soils of studied unions of Kalapara Upazila.
1.1. Objective
Objectives of this research work are –
To assess the rate of change of the triggering factors in the study areas
To estimate the impact of the change of the factors on nutrient status in the studied
unions of Kalapara Upazila. .
14
CHAPTER 2
LITERATURE REVIEW
15
2. Review of Literature
Bangladesh is an agro-based developing nation where majority of the people directly
or indirectly depend of agriculture. Crop agriculture in Bangladesh is constrained
every year by challenges, such as a) Loss of Arable Land, b) Population Growth, c)
Climate Changes, d) Inadequate Management Practices, e) Unfair Price of Produces,
and f) Insufficient Investment in Research. Bangladesh has lost about l million ha of
arable land from 1983 to 1996. Virtually, no step has been taken by the government to
arrest this loss. The landuse policy prepared by the government several years back has
not yet been implemented. Population growth poses another great threat to crop
productivity. Besides, crop agriculture in Bangladesh has become regularly vulnerable
to the hazards of climate change–flood, drought, and salinity in particular (Mondal,
2010). Bangladesh has one of the highest population densities in the world. The
population of Bangladesh followed an exponentially increasing trend during the past
century. Growth rate of population at present stands 1.42 % (BBS, 2011). Population
is increasing at the rate of 2 million per year and the total population would be around
233 million by 2050 if the current growth rate continues. Such a growth rate of a
country of 1,43,000 sq. km is viewed as a great challenge not only to different
economic development activities but also as crisis to accommodation, environment
and meeting other basic needs (food, education, and health). The rapid growth of
population and land loss impedes the agriculture development of this country. For this
reason the net cropped sown area of the country is decreasing but the cropping
intensity is increasing over times (Mondal, 2010).
Increased crop productivity from the shrinking land resources is the urgent need to
meet the increased food demand of the swelling population of Bangladesh. Food
requirement of the country is estimated to be doubled in the next 25 years. To feed the
teeming million the land resources in Bangladesh is intensively used for crop
production. Since land is a scarce resource in Bangladesh, the only choice is to
increase in cropping intensity. This resulted in increasing demand for nutrients, which
was reflected in more nutrient deficiencies exhibited by the crops (Islam and Haq,
1999).
16
2.1. Coastal Areas of Bangladesh
The coastal areas of Bangladesh is different from rest of the country not only because
of its unique geo-physical characteristics but also for different sociopolitical
consequences that often limits people’s access to endowed resources and perpetuate
risk and vulnerabilities. Coastal areas include coastal plain islands, tidal flats,
estuaries, neretic and offshore waters. It extends to the edge of a wide (about 20 km)
continental self. A vast river network, a dynamic estuarine system and a drainage
basin intersect the coastal zone, which made coastal ecosystem as a potential source
of natural resources, diversified fauna and flora composition, though there also have
immense risk of natural disasters (Islam et al., 2006).
The coastal areas cover the nineteen districts in the south and south-east parts of
Bangladesh. It occupies 32% of the total area and 28% of the population of
Bangladesh (Islam, 2004). It covers an area from the shore of 37 to 195 km. whereas
the exposed coast is limited to a distance of 37 to 57 km (Islam et al., 2006). The
coastal belt of Bangladesh is divided into three distinct regions, that is, the western,
central and eastern regions. The western and central zones are very flat and low. The
land here is criss-crossed by numerous rivers and channels with a large number of
islands. The western zone of Satkhira, Khulna, Bagerhat, Perojpur is home to the
famous mangrove forest, the Sundarbans. A submarine canyon, Swatch of No Ground
runs NE-SW upto about 24 km. south of the western coast of the country. The central
region of Barguna, Patuakhali, Bhola, Barisal, Lakshmipur, Noakhali, Feni is
geomorphologically most active land formation process making a new shape of land
features. These areas are facing a lot of natural hazards that is salinity intrusion,
cyclones, and tidal surges, floods almost every year (Ahmed, 2011). People living in
different coastal areas have been suffering from lack of food security. There are many
reasons behind that such as lower crop productivity and less fertility in soil due to
increased salinity, increased cropping intensity, increased incidences of pests and
diseases, erratic rainfall, higher temperature, drought, tidal surges, cyclone,
submergence, large fallow lands/water bodies, land degradation, poor road network,
poor marketing facilities and unemployment with long-term cumulative effects of
soil-related constraints, climate risks and socio-economic problems (Miah, 2010).
17
2.1.1. Population Pressure in Coastal Areas
This coastal area represents an area of 47,211 km2, 32 percent of the country’s
geographical area, wherein 35 million people i.e. 28 percent of the country’s total
population live at 6.85 million households (Population census in 2001). In terms of
administrative consideration, 19 districts out of 64 are considered as coastal district. A
study of IPPC reveals that 20 percent and 40 percent of the world population live
within 30 kilometers and 100 kilometers of the coast respectively, which is very true
in regards to Bangladesh’s perspective (Inter Governmental Panel of Climate Change,
2001). Again, population growth rate in the coastal areas is higher than the national
average. In between 1991- 2001 the average population growth rate was 1.29, if so
continued then by 2020 the coastal population will be 44 million, more people will be
landless, and more people will be city bounded for livelihood earning. Official
poverty indicators show a slightly higher percentage of the population living below
the absolute poverty line in the coastal zone compared to the country as a whole (52
percent vs. 49 percent), while the GDP per capita and the annual GDP growth rates in
the coastal zone are more or less similar to the national averages(Ahmad, 2005).
Urban population in Bangladesh has increased at an annual exponential rate of 6.1
percent during the inter-census period of last forty years (1961-2001). Urban
population growth has been slightly lower in the coastal zone with annual growth rate
of 5.9 percent. With the increasing population, land is being converted from
productive purposes, such as crop cultivation, to other uses. Bangladesh is losing
good quality agricultural land by approximately 80,000 ha annually to urbanization,
building of new infrastructure and implementation of other development projects
(World Bank, 2005).
Table 2.1. Population growth trend in the coastal area
Year Population(million) Urban
population
(%) Coastal
rural
Costal
urban
Total
2001 27 8 35 23
2010 25 14 39 36
2020 22 22 44 50
(Source: Coastal livelihoods, ICZM, 2003)
18
2.1.2. Cultivable Land in Coastal Areas
The coastal area covers about 20% of the country and over thirty percent of the net
cultivable area. It extends inside up to 150 km from the coast. Out of 2.85 million
hectares of the coastal and offshore areas about 0.83 million hectares are arable lands,
which cover over 30% of the total cultivable lands of Bangladesh. A part of the
coastal area, the Sundarbans, is a reserve natural mangrove forest covering about
4,500 km2. The remaining part of the coastal area is used in agriculture. The
cultivable areas in coastal districts are affected with varying degrees of soil salinity.
The coastal and offshore area of Bangladesh includes tidal, estuaries and river
floodplains in the south along the Bay of Bengal. Agricultural land use in these areas
is very poor, which is roughly 50% of the country’s average (Petersen and Shireen,
2001). Observations in the recent past indicated that due to increasing degree of
salinity of some areas and expansion of salt affected area as a cause of further
intrusion of saline water, normal crop production becomes more restricted. In general,
soil salinity is believed to be mainly responsible for low land use as well as cropping
intensity in the area. Salinity in the country received very little attention in the past.
Increased pressure of growing population demand more food. Thus it has become
increasingly important to explore the possibilities of increasing the potential of these
(saline) lands for increased production of crops (Haque, 2006).
2.2. Cropping Pattern and Cropping Intensity in Bangladesh
Physiographically, Bangladesh has three categories of lands: floodplains (80%),
terraces (8%) and hills (12%). Crop cultivation is intense in floodplain soils. At
present, rice covers about 79.4 percent of cultivated land. Area coverage by other
crops is: pulses (4.64%), wheat (3.92%), oilseeds (3.77%), jute (3.71%), sugarcane
(1.23%), potato (1.11%), fruits (0.84%) and vegetables (1.39%) (Fig. 2.1) This
production system dominated by a single crop (i.e. rice) is neither scientific nor
acceptable from the economic point of view. It is therefore necessary to increase the
cultivation and production of other crops. However, considering the increasing
demand for food grains and with a view to ensuring food security (forecast for 2012),
production of rice will continue to have priority in the food grain production
programmes (Roy and Farid, 2011). Rice production systems make a vital
contribution to the reduction of hunger and poverty in Bangladesh. Total rice
19
production in Bangladesh was 10.32 million tons in the year 1975-76 when the
country's population was only 79.90 millions and cultivated rice area was 10.32
million ha (DAE, 2007). However, the country is producing 34.28 million tons rice in
the year of 2008-09, where Boro rice contributed more than 55% (18.5 million tons).
From the analysis of the last few years’ data we found that its contribution in total rice
production follows an increasing trend.
Fig. 2.1. Land coverage status of major crops in Bangladesh
(Source: Roy and Farid, 2011)
Recently, the rate is increasing rapidly due to adoption of high yielding rice varieties,
including modern rice cultivation technologies, improvement irrigation facilities and
applications of fertilizer and pesticides. It has been broadly divided into three classes
viz, aman (transplanted and broadcast varieties), boro, and aush according to the
season in which they are harvested, namely, in December-January, March-May and
July-August respectively. Again, of these varieties transplanted aman is the most
important and covers about 46.30% of the paddy area, followed by boro (26.85%),
aus (17.59%) and broadcast aman (9.26%) (Fig 2.2) (Basak, 2010).
Fig. 2.2. Acreage of different types of rice cultivated in Bangladesh
(Source: BBS, 2008)
20
Crops that are grown on less than one per cent of the gross cropped area (GCA) of a
country are considered minor crops. In Bangladesh gram, millets and maize, onion,
black gram, sweet potato, groundnut, green pea, sesame, linseed, garlic, pea and
barley, etc. are usually considered as minor crops (Fig. 2.3) In addition some crops,
including certain vegetables, spices, etc. occupy a very insignificant proportion of the
GCA (i.e., less than 0.10 per cent to each crop), and they account for 1.57 per cent
altogether (Mainuddin et al., 2011).
Fig. 2.3. Land used under minor crops in Bangladesh
(Source: BBS, 2008)
A spatial and temporal arrangement of crops within a cropping year is largely
determined by physical, biological, and socio-economic factors. There are three
cropping seasons (Rabi, Kharif-I or Pre-Kharif, and Kharif-II) during a year in
Bangladesh (Banglapedia, 2006a). The major cropping pattern in Bangladesh
agriculture mostly consists of rice based cereal crops. More than 60% of the total
cropped area covered by Boro-T. aman rice cropping patterns in Bangladesh (FRG,
1997). Rice is grown in three seasons. Aman, grown during July/August to
December/ January, is part rain-fed (during early part of growth) and part dry season
crop (during flowering and harvest time). This is followed by boro, grown at present
under irrigated conditions during the laargely dry period from February/March to
April/May. Aus are grown in rainfed conditions; it falls in between boro and aman
season but may overlap with both. This means that the longer-duration varieties of
rice do not allow for more than two rice crops per season on the same land, although
other crops may be grown, depending on duration of the crop and other agronomic
factors. The growth in rice output over the last quarter of a century has been
characterized by increasing reliance on irrigated boro cultivation, using fertilizer-
21
intensive high-yielding varieties (HYVs). Boro rice now accounts for the bulk of rice
grown in the country (Asaduzzaman et al., 2010).
Table 2.2. Some dominant cropping patterns under variable crop production
environments
Rabi Kharif-I Kharif-II
Rainfed
condition
Wheat/Potato/Pulses/Oilseeds/Sugarcane Boro Aus/Jute Fallow
Irrigated
condition
Wheat/Boro/Wheat/Potato/ Tobacco/Vegetables Fallow T. Aus T.Aman
Fallow
(Source: Banglapedia, 2006a)
Depending on the land type, soil characteristics, and water availability, rice cropping
may be single, double, or triple. In general, double or triple rice cropping is practised
in high land areas. In medium lowlands, mixed cropping of Aus and broadcast Aman
is a common practice, while in deeply flooded lands, single cropping of broadcast
Aman (deepwater rice) in Kharif, or Boro in Rabi, is the common practice. Non-rice
crops are generally grown as a sequential or intercrop with rice. Most non-rice crops
are dryland crops, although some crops like jute (Deshi type), millets (Kaon), and
sugarcane can tolerate some degree of submergence at later stages of growth. Jute is
grown in the Kharif-I season, competes with Boro Aus for land, and is considered a
substitute crop for Boro Aus in cropping patterns. The dry (Rabi) season crops
included in cropping patterns may be early, middle, or late, depending upon land
types, recessions of floods, and dates of harvests of the preceding crops (Basak,
2010).
A change in cropping pattern thus implies a change in the proportion of area under
different crops. The cropping pattern in an area depends largely on agro-climatic,
technical and institutional factors (Vaidyanathan, 1987). The change of cropping
pattern is basically the results of the adoption of new crops and the intensification of
cultivation through multiple cropping. More precisely, changing in cropping pattern
over time are also function of changes in the extent and quality of irrigation and the
relative costs of and returns to competing crops and crop combinations (ghosh, 2011).
22
Cropping intensity, defined as the ratio of gross temporary cropped area to net
temporary cropped area per annum. Intensity of cropping represents the ratio of the
gross cropped area to the net temporary cropped area expressed in terms of
percentage. It indicates the extent to which the same area is used for cropping
(Ahmed, 1992).
Cropping intensities were calculated by the following formula as suggested by Sing (2004).
Intensity of cropping = X 100
Calculating cropping intensity
• Step1. Assign a number to each crop in the rotation based on its
crop type.
0 = summer fallow
1 = cool season crops (wheat, canola, lentil)
1 = short season crops (millet, green fallow)
1 = full season crops (corn, sunflower, sorghum, soybean)
• Step 2. Add the intensity values for all crops in the rotation and
divide by the number of years in the rotation to obtain an intensity
rating (Table 2.2)
Table 2.3. Cropping intensity rating
Examples of Cropping Intensity Rating
Rotation Rating Wheat-fallow 0.5 Wheat-corn-fallow 1.0 Wheat-corn-millet-fallow 1.0 Wheat-corn-pea 1.33 Springwheat-winter wheat-corn-sunflower 1.5 Spring wheat-corn-soybean 1.67 Corn-soybean 2.0 Winter wheat-sorghum-corn-soybean 2.33
(Source: Beck et al., 1998).
Total cropped area
Net cultivated area
23
Bangladesh faces formidable challenges to feed its population in the future from an
increasingly vanishing and degraded natural resource base for agriculture. The
agriculture is still an important segment of the country’s economy though the
contribution of broad agriculture sector in 2005-06 to GDP was 21.84%. Crops and
vegetables accounted for about 12% of GDP. About 52 percent of the total labor
forces of the country are engaged in agriculture (MOF, 2007). To feed the growing
population of Bangladesh (at the rate 1.59% per year) increased agriculture
production especially staple cereal rice is a must. In the year 2006-07, the staple
cereal rice was grown in 11.30 million hectare. HYV (High Yield Variety) rice was
produced on 8.50 million hectare. Of the total cropped area, 14.11 million hectares in
2004-05, the net cropped area was7.98 million hectare giving a cropping intensity of
1.77% (MOI, 2008). The Department of Agriculture Extension (DAE) claims that the
current cropping intensity is 195%.
Table 2.4. Last 10 years cropping intensity of Bangladesh
Year Total Land Area of the Country
Net Cultivable Land
% of Net Cultivable Land in Terms of Total Area
Net Area Sown
Total Cropped Area
Cropping Intensity (%)
2000-01 14.85 8.40 56.57 8.08 14.30 176.98
2001-02 14.84 8.48 57.14 8.08 14.30 176.98
2002-03 14.84 8.42 56.74 8.04 14.17 176.24
2003-04 14.84 8.40 56.60 8.03 14.23 177.21
2004-05 14.84 8.44 56.87 7.97 14.10 176.91
2005-06 14.85 8.29 55.82 8.03 14.20 180.00
2006-07 14.45 8.29 57.37 8.03 14.20 180.00
2007-08 14.85 9.09 61.21 8.23 16.50 179.00
2008-09 14.85 9.09 61.21 7.77 13.88 179.00
2009-10 14.85 9.23 62.15 7.69 13.91 180.88
(Source: BBS, 2010)
24
Bangladesh has made a remarkable progress in the last three decades towards
achieving self sufficiency in food grains due to substantial intensification of cropping,
introduction of high yielding crop varieties, and expansion of irrigated areas and
increased use of chemical fertilizers. Among the factors, contribution of fertilizers
leading to increased production is about 50 percent. But recently, declining or
stagnation of major crop yields have been recorded due to cumulative effects of many
soil-related constraints and climatic risks viz. depletion of soil organic matter,
imbalanced use of fertilizers, nutrient mining, degradation of soil physical and
chemical properties, erratic rainfall, temperature rise, droughts, floods, soil salinity,
water salinity, tidal surges, water-logging, cyclone, scanty use of bio and organic
fertilizers and poor management practices. The proportion of different nutrients used
in agriculture without soil testing in recent years is highly deleterious to soil
productivity. Nitrogen alone constitutes about 83 percent of total nutrient use in the
country, while the use of phosphorus and potassium is limited to only about 7.75 and
9.1 percent respectively (Miah, 2010).
2.2.1. Cropping Pattern and Cropping Intensity in Kalapara
Major crop cultivation in Kalapara is Transplant Aman (T- aman), Boro, potato and
vegetables. Sesame, linseed, sugarcane, kaon are extinct or nearly extinct crops of the
study area. Gher farming is done in some different land and also in some T-Aman
cropland. T-Aman is mainly the cultivated in the Kharif-2 season. At present, about
100% cropland is used for T- aman cultivation (Banglapedia, 2006).
The cropping pattern T. Aman – Fallow – Fallow has the highest coverage in the
Kalapara upazila. Some areas were cultivated for production of high yielding
varieties during Boro season, where the irrigation facilities were available either from
surface water or groundwater sources. The Boro area could be expanded by
introducing salt tolerant Boro Variety BRRI Dhan 47, where the water salinity ranges
upto 8 dS/m. Pulse followed by T. Aman pattern dominated in Kalapara upazila. The
highest cropping intensity of 199% was observed in Kalapara upazila followed by
other coastal upazilas (Bala and Hossain, 2009).
25
Table 2.5. Major cropping patterns and cropping intensity in of kalapara
upazila (2008)
Major cropping pattern % Coverage Cropping intensity (%)
T. Aman – Fallow – Fallow T. Aman – Khesari – Fallow/ T. Aus T. Aman – Mung – Fallow/ T. Aus T. Aman – Fallow – Aus T. Aman – Cowpea – Aus T. Aman – Cowpea – Fallow
27.7 18.9 6.8 13.0 12.7 11.0
199
(Source: Bala and Hossain, 2009)
2.3. Nutrient Status in Soils of Bangladesh
Soil Fertility capability of soils to supply elements essential for plant growth without
a toxic concentration of any element. It is the inherent capacity of a soil to supply 14
of the 17 essential nutrient elements to the growing crop. Fertility is the potential
nutrient status of a soil to produce crops. Soil productivity is a measure of the soils
ability to produce a particular crop or sequence of crops under a specified
management system (Banglapedia, 2006).
Nutrient status depends on nutrient balance of soil. Nutrient Balance is the sum of
nutrients inputs minus the sum of nutrients outputs; the balance may be positive or
negative. Positive balance indicates nutrient accumulation and negative balance shows
nutrient depletion (mining). To achieve sustainability, the quantity of nutrients inputs
and outputs could be equal. Nutrient mining may eventually cause soil degradation
and affect crop production. On the other hand, excess nutrient accumulation may lead
to soil and water pollution (BARC, 2005).
Input = Output: Sustainable system
Input > Output: Plant nutrient build-up/ Soil fertility increase. This may in Extreme
cases eventually lead to soil and water pollution.
Input < Output: Nutrient depletion or “nutrient mining”. May lead to serious soil
degradation.
In calculating nutrient balance, fertilizer, manure, BNF, deposition (rain),
sedimentation (flood) and irrigation water can be regarded as nutrients inputs, and the
crop produce, crop residues, leaching, gaseous losses (leaching and denitrification)
26
and soil erosion as nutrients outputs (Fig. 2.4 ) Hence, these major inputs and outputs
can be considered for calculating nutrient balance to understand partial or apparent
nutrient balance. Although the nutrient balance value tells us little about available
nutrient status of soils, it has important implications when considering the future long-
term total status of nutrients in soils. Nutrient balance values varied with locations,
cropping systems and nutrient management practices (BARC, 2005).
Fig. 2.4. Nutrient input-output system
(Source: FRG, 2005)
The role of macro and micronutrients is crucial in crop nutrition and thus important
for achieving higher yields. Nitrogen (N), phosphorus (P) and potassium (K), being
primary essential nutrient, have prime importance in crop nutrition (Raun and
Johnson, 1999). Bangladesh 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 (Kafiluddin, 2008).
2.3.1. Nitrogen
Nitrogen is generally considered as the key nutrient in Bangladesh agriculture because
of its low supply in the soils. Portch and Islam (1984) reported that 100% of
27
Bangladesh soils studied contained available N below critical level. Most of the
agricultural soils are critically deficient in this nutrient.
The main reasons for such deficiency are due to:
- Intense decomposition of organic matter
- Rapid removal of mineralized products under high leaching conditions and
- crop removal.
Total nitrogen content of Bangladesh soils range from 0.032% in the Shallow Red-
Brown Terrace Soils to 0.20% in Peat Soils. For wetland rice, soil test values for
nitrogen interpreted as low, medium and optimum are 0.090-0.180, 0.181-0.271 and
0.271- 0.360%, respectively (Kafiluddin, 2008).
2.3.2. Phosphorus
Phosphorus is recognized as an important mineral element limiting crop growth and
production (Batten et al., 1984). It is generally considered as the second most limiting
nutrient after N for plant growth (Vance, 2001). The available P in Bangladesh soils
could be considered to be between low and medium. About 20.7% areas were
reported to be predominantly low in available P and 21.2% were medium in available
P which is limiting crop production. Therefore, one of the adverse effects in
agriculture practice in Bangladesh is phosphorus deficiency. Plants cannot live at
phosphate concentration below two parts per ten million in soil solution (Nautiyal et
al., 2000). For wetland rice, soil P contents of 6.0-12.0 μg g-1soil are considered as
low, 12.1-18.0 μg g-1 soil as medium and 18.0-24.0 μg g-1 soil as optimum. The
critical level of P by the Olsen method, which is extensively used for rice, has been
considered as 8.0 μg g-1soil in Bangladesh so long (Kafiluddin, 2008).
2.3.3. Potassium
Potassium is the seventh most common element in the Earth’s crust and is essential
for plant growth. Potassium, along with N and P, are the three major macronutrients
contributing to many functions in plants. The essentiality of this macronutrient was
known after Von Liebig’s published work in 1840 (Sparks, 2000). Potassium is one of
the major nutrients and absorbed in large quantities by crops. Intensive cropping with
modern rice varieties is responsible for increasing the K deficiency in soil (Tiwari,
28
1985). Most of the north-western parts of Bangladesh are deficient in potassium
(BARC, 2005). The critical levels of potassium for Bangladesh soils have been
determined 0.09-0.18 meq/100g soil as low, 0.18-0.27 meq/100g as medium, 0.27-
0.36 meq/100 g as optimum and above 0.36 meq/100 g high (Kafiluddin, 2008).
Regmi et al. 2002 reported that depletion of soil K and inadequate K fertilization
seem to be the primary reason of limiting and declining yield of the first rice and
wheat crop. Shah et al. 2008 reported that continuous omission of K in fertilizer
schedule for 23 yrs resulted in about 41% reduction of Boro rice yield over 100%
NPKSZn fertilization. The general recommended dose of K fertilizer for MV rice in
Bangladesh only around 35-40 kg K/ha (BARC, 1997), while an average rice yield
(4.0 t/ha) removes at least 70 kg K/ha from the soil. This level of K fertilization may
not be adequate for sustaining favorable K status of the soil in the long run.
2.3.4. Sulphur
Sulfur (S) deficiency has been recognized as a constraint on crop production all over
the world (Eriksen et al., 2004; Girma et al., 2005; Schonhof et al., 2007; Mascagni et
al., 2008) becoming a limiting factor to higher yields and fertilizer efficiency. Sulphur
has been recognized as the fourth major nutrient limiting crop production as early as
1980. In the past very little attention was paid to this nutrient until 1977 when sulphur
deficiency in wetland rice was first detected at the Bangladesh Rice Research Institute
(BRRI) farm and on nearby farmers’ fields (Kafiluddin, 2008). The main reasons are
the reduction of sulfur dioxide emission from power plants and various industrial
sources, the increasing use of high analysis low-S-containing fertilizers, the
decreasing use of S-containing fungicides and pesticides and high-yielding varieties
(Scherer, 2001; Eriksen et al., 2004). Until recently little attention has been given to
the problem of sulfur deficiency in soils. Intensive cropping has been resulting higher
removal of sulfur among the other nutrients rather its replenishment under natural
process (Balsa et al., 1996). In Bangladesh about 7 M ha (about 52%) of agricultural
lands are reported to consists of sulfur deficient soils in the Northern region of
Bangladesh (SRDI, 1999). The current intensive use of agricultural land for crop
production has extended the sulfur deficient areas to about 80% (Khan et al., 2007).
The critical level of sulphur for Bangladesh soils has been determined as 10 μg g-1
soil (Kafiluddin, 2008).
29
2.3.5. Zinc
The importance of zinc in crop nutrition has received considerable attention during
eighties in Bangladesh. This element deficiency has arisen in Bangladesh mainly due
to continuous mining of soil nutrients for increase cropping intensity (180% at
present). The availability of Zn in the soil varies widely depending on the soil
properties. The calcareous soils have low to medium extractable Zn content
(Jahiruddin and Islam, 1999). Zinc deficiency, together with sulphur deficiency, are
recognized as limiting factors in crop production in Bangladesh. About 1.75 Mha of
intensively cropped land are estimated to be affected by zinc deficiency, which
mainly affects rice and wheat (Ahsan and Beuter, 2000).
The incidence of zinc deficiency is widespread in most calcareous and alkaline soils.
The problem is more acute in wetland rice culture. The critical levels of available soil
zinc content as established by different extracting procedures are 1 ppm for light
textured soils and 2 ppm for heavy and calcareous soils. The critical level of Zn in
rice plant tissue is generally considered as 20 ppm. Yield responses of rice to zinc
fertilization have been well documented in different soils of Bangladesh where zinc
contents were below the critical level (Kafiluddin, 2008).
2.3.6. Calcium and Magnesium
The pH values of Bangladesh soils generally range between 5.8 and 7.0 with
exception observed in acid hill soils and calcareous soils. Thus, most of our soils have
adequate Ca and Mg saturation on the exchange surface. Recent investigations have
reflected that acid hill soils and Old Himalayan piedmont soils are extremely low in
exchangeable Ca and Mg. The critical levels for these two nutrients are as 2.00 and
0.5 meq100g -1 (Kafiluddin, 2008).
2.3.7. Boron
Although taken up in tiny quantities, boron deficiency may lead to serious
consequences regarding economic yield of various crops. Boron deficiency in
Bangladesh was first observed in reverine soils of Teesta on wheat causing sterility in
grains (Islam, 2006). Light textured soils of the country are deficient in available
boron where significant leaching loss of borate ions might have depleted soil boron
level. The available boron content of the major soils of Bangladesh varies between 0.1
and 1.9 ppm. But most of the light textured soils of Rangpur, Dinajpur and terrace
30
soils of Gazipur and hill soils of Srimangal contain low level of available B (0.1-0.3
ppm). The critical level of available soil boron used to interpret the soil test result is
0.2 ppm (Kafiluddin, 2008).
2.3.8. Other Micronutrients
Intensive cropping, imbalanced fertilization and no use of micronutrients, less or no
use of organic manures resulting the depletion of soil fertility in Bangladesh.
Consequently, micronutrients statuses have been decreasing day by day and finally
fertility status of Bangladesh soils have been declining. Micronutrients like Fe, Mn,
Cu, Mo and Cl have attracted less attention in Bangladesh agriculture. Generally they
are seldom needed to be applied in crop production in most soils. However, recently
Cu and Mn application in Calcareous Soils have appeared to be beneficial for higher
yield in some field trials. Recent studies have also indicated that Mo deficiency is
widespread in cabbage and legumes like groundnut acid soils. Appreciable yield
increases of these crops in presence of added molybdenum have also been recorded
(Kafiluddin, 2008).
2.4. Nutrient Status of Kalapara Upazila
This region occupies an extensive area of tidal floodplain land in the south-west of the
country. The greater part of this region has smooth relief having large areas of
salinity. There is a general pattern of grey, slightly calcareous, heavy soils on river
banks and grey to dark grey, non calcareous, heavy silty clays in the extensive basins.
Non calcareous Grey Floodplain soil is the major component of General Soil Types.
Acid sulphate soils also occupy significant part of the area where it is extremely
acidic during dry season. In general, most of the topsoils are acidic and subsoils are
neutral to mildly alkaline. Soils of the Sundarbans area are alkaline. General fertility
level is high with medium to high organic matter content and very high CEC and K
status but have limitations of high exchangeable Na and low Ca/Mg ratio. The Zn
status is low to medium and the B and S status is high (BARC, 2005).
31
Table 2.6. Nutrient status of ganges tidal floodplain
Major
Land
type
Soil
pH
Soil
OM
Nutrient status
N P K S Ca Mg Zn B Mo
Medium
Highland
(78%)
4.2-
8.1
L-M VL-
L
VL-L Opt-H Opt-
H
Opt-H Opt-
H
L-M Opt-
H
Opt
(Source: FRG, 2005)
Average Height of Kalapara upazila, in the northern edge is about 2m and in the
south is about lm high from mean sea level. But the maximum height is 6m. This area
lies in the southwestern part of Bangladesh and downstream of the well known
Ganges deltaic region. The area comprises a flat land with natural ground slopes are
found. Kalapara Upazila is a Ganges Floodplain (SRDI, 2001a). In Kalapara Upazila
most of the soil types are present deposits. In this region, pH varies from7.5-4.9. The
color of the soil is light grey, grey and black. The soil salinity varies from Moderate to
nil; (EC 0.37 to 15.2 dS m-1). The study areas are mainly located in Medium High
land. Here soil is rich in Calcium, Magnesium, Boron, Copper, and Sulphate and
moderately high in Manganese, Zinc and lower concentration of Phosphorus, Iron,
and Nitrogen (SRDI, 2001).
Table 2.7. Nutrient status of Kalapara Upazila
Depth Horizon pH Macro nutrient Micro nutrient
N% P S K Mg/100 Gm soil
Cu Fe B Mn Zn
Mg/L Mg/L 0-11 Ap1 5.6 0.09 1.90 67.0 0.07 5.82 180.0 0.92 12.1 0.68
0-17 Ap2 5.8 0.12 1.69 71.0 0.05 5.08 160.0 0.88 9.9 0.56
17-41 Ap3 7.9 0.09 0.96 24.0 0.17 1.72 11.0 1.44 2.3 0.16
41-79 Ap4 8.1 0.08 0.98 44.0 0.12 0.70 7.0 1.41 1.9 0.22
79-130
Ap5 8.3 0.06 0.75 38.0 0.11 0.64 8.0 1.46 1.6 0.22
(Source: SRDI, 2009)
2.5. Cropping Intensity and Its Effect on Nutrient Status Cropping intensity and sequencing have significant effects on soil structure or soil
tilth (Elliott, 1986). The intensive cropping systems introduced by the Green
32
Revolution impose much heavier demands on crop nutrients than traditional systems
had; nutrient deficiencies, therefore, a common problem. Intensive agricultural
practices can also result in changes in soil physical and chemical properties (Dey and
Haq, 2009). With rising cropping intensities in South Asia, nutrient management is a
major issue being addressed by agricultural scientists for understanding any decline in
yields. Many long-term fertility experiments established in the region decades ago
show no evidence of yield decline at the farmers’ field level (Abrol, et al., 1997).
Conventional tillage with intensive soil disturbance promotes rapid decrease of soil
organic matter and subsequent CO2 emission increase. A chemical, physical and
biological soil degradation process then develops, negatively affecting crop
productivity. Tillage is the principal agent producing soil disturbance and subsequent
soil structure modification, increasing potential soil organic matter loss by erosion and
biological decomposition (Langdale et al., 1992; Carter et al., 1994). Quantitatively,
the latter is thought to be the primary source of organic matter loss triggered by soil
tillage (Rasmussen et al., 1998).
Nitrogen, P, K, S and Zn, of which three major elements are most important both in
the terms of the extent of their deficiencies in the soils, and in terms of their potentials
for crop yield increases or losses. Nitrogen is the nutrient element limiting growth in
most of the rice soils (Savant and Datta, 1982), and there have been indications that
many rice soils of Bangladesh are becoming deficient in P, K, S and Zn (BARC,
2005). The decline in productivity of rice and wheat with continuous cropping was
related to deficiency of P, K, S, Zn and imbalanced nutrition (Kumar and Yadav,
2005).
Nitrogen is the most limiting nutrient in crop production all over the world. Nitrogen
deficiency occurs everywhere in Bangladesh. Understanding the behavior of N in soil
is essential for maximizing crop productivity and profitability on one hand and for
reducing the possible negative impact of N fertilization on the environment on the
other hand. The loss of N from the soil is mainly due to crop removal and leaching
(FRG, 2005). Phosphorus does not occur as abundantly in soils as N and K. Although
the total concentration of P in the soil varies between 0.02 and 0.10%, it has no
relationship with the availability of P to plants. The average concentration of P in soil
solution is about 0.05 ppm which varies widely among soils while the level of
organically bound P varies between a few ppm and 1000 ppm (FRG, 2005).
Phosphorus is removed or lost from the soil by: 1) crop uptake and removal; 2) runoff
33
and erosion and 3) leaching. Harvested crops remove phosphorus from the soil and
the farm. Phosphorus concentrations in plant tissues typically range from 0.1 to 0.5%
on a dry weight basis and most crops utilize or take up between 20 and 90 pounds of
P2O5 each year. Since soils are constantly subjected to changes due to the effects of
cropping practices, it is impossible to totally eliminate phosphorus losses from soil.
Water moving across the surface or through soils can remove both soluble (dissolved)
and particulate (eroded soil particles) forms of soil phosphorus. Phosphorus can also
loss by leaching (Mullin, 2009).
Potassium (K+) is an essential element for plant growth and development and is the
most abundant cation in plants, making up 3–5% of a plant’s total dry weight. Run-off
of drainage water and migration of elements and matter depends on the amount of
precipitation and cropping intensity. However, the results of a comparison of organic
and intensive cropping systems showed that cropping intensity had no influence on
potassium concentration in drainage and groundwater (Guzys, 2001). The balance of
potassium in both cropping systems was negative and the average amounts of K+
leached were 3.5-3.8 kg. Micronutrient S and Zn deficiencies in particular have an
adverse effect on yields, a common problem in intensive rice production, because
conditions in flooded paddies have a strong negative effect on their availability (Day
and Haq, 2009).
Rapid decline of Soil fertility is a problem of crop production in Bangladesh. Soil
fertility is a dynamic property which varies with crops, cropping intensity and input
use. More than 50% of our cultivated soil contains organic matter below the critical
level (1.5%). Annual depletion of plant nutrients in the intensively cropped area
ranges from 180 to more than 250 kg/ha. High and medium high land comprises 60%
of total cultivated land which is in most cases deficient in essential nutrients such as
nitrogen, phosphorus, potassium and Sulphur. The low organic matter content, higher
cropping intensity, improper cropping sequence and faulty management practices are
the major causes of depletion of soil fertility. Imbalance use of fertilizer is another
serious problem for the country. Nutrients present in soil, added as inorganic and
organic sources and the nutrient harvested by crops should be considered to develop a
cropping pattern based fertilizer recommendation. Available data indicate that the soil
fertility in Bangladesh is declining trend (Karim et al, 1994; Ali et al, 1997) which is
responsible for declining crop yields (Cassman et al, 1995).
34
About 60% of arable lands of Bangladesh are deficient in N, P, and K. Organic matter
content of soils is much below the critical level of 1.5%. Imbalance use of fertilizers,
unplanned cultivation and improper management of soil have already caused not only
stagnation but also declined in productivity of modern varieties. Intensive and
continuous rice-based crop culture, replacement of local rice varieties by modern
ones, decreasing jute cultivation, increasing adoption of power tillers for tillage
operations and increasing use of dung and organic waste as fuel have been negatively
affecting the status of soil organic matter. Increased cropping intensity and sustained
productivity of the soil are the important options to achieve self-sufficiency in food.
Sharp declining in soil fertility is a threat for sustainable crop production (Kashem et
al., 2007). In irrigated rice, the formation of a plowpan is a frequent problem,
impeding root growth and limiting access to nutrients. Irrigation can also cause
salinization or water-logging. The yield declines observed in the IRRI long-term
cropping trials are thought to result from anaerobic conditions in irrigated rice
production leading to changes in soil physical and chemical properties which make it
less able to supply nutrients to growing crops (Dey and Haq, 2009).
Depletion of soil fertility is mainly due to exploitation of land without proper
replenishment of plant nutrients. The problem is enhanced by intensive land use
without appropriate soil management. The situation is worse in areas where HYV
crops are being grown using low to unbalanced doses of mineral fertilizers, with little
or no organic recycling. Because of increasing cropping intensity (presently 198%)
and cultivation of modern varieties of crops, the net removal of plant nutrients is far
from the nutrient supply through fertilizers and manures. Nitrogen status in this
country’s soils resembles the results of SOM (Jahiriddin and Satter, 2010).
Ali et al. (1997) reported that the total carbon content on an average decreased by
11%, the total N by 12%, pH decreased by 4% and the exchangeable acidity increased
by 30%. The exchangeable K content in soil decreased by 31% and available P
showed a 9% decrease over 27 years (1967-1995). The annual removal of nutrients
from soil is higher compared to their addition. From an extensive review, Rijmpa and
Jahiruddin (2004) reported that the overall N balances of Bangladesh soil were
negative (-10 to –100 kg N ha-1
yr-1
depending on the nutrient management and
cropping systems), the P balances were near zero and the K balances were highly
negative (-100 to –225 kg ha-1
yr-1
) (Fig. 2.5).
35
Fig. 2.5. N + P + K inpute – outpute in Bangladesh
(Source: Jahiruddin and Satter, 2010)
Six mineral elements such as N, P, K, S, Zn and B are commonly deficient in
Bangladesh soils. Of them, nitrogen is the most limiting nutrient in Bangladesh
agriculture. Until 1980, deficiencies of three nutrients viz. N, P and K were identified
in Bangladesh soils. In early 1980s, S and Zn deficiencies in rice were observed. In
early 1990’s, the B deficiency of some crops was reported. There is sporadic
information of Cu, Mo and Mn deficiencies in crops. Deficiencies of Fe and Cl are
not yet reported in this country. Magnesium is reported to be deficient in Old
Himalayan Piedmont Plain and Tista Floodplain soils (Table 2.7) (Ferdoush et al.,
2003).
Table 2.8. Emergence of new nutrient deficiency with time
?
Mg Mg
B B B
Zn Zn Zn Zn
K K K K K K
P P P P P P P
N N N N N N N N
1951 1957 1960 1980 1982 1995 2000 2011
(Source: Jahiruddin and Satter, 2010)
36
2.6. Soil Salinity
Salinity is a major environmental constraint for crop production throughout the world
(Ashraf, 2004; Flowers, 2004; Munns et al., 2006). Salt-affected soils occupy more
than 7% of the earth land surface (Munns et al., 2006; FAO, 2008). Reduction in the
osmotic potential and toxic effect of excessive Na+ or Cl- on the plasma membrane
are the direct effects of salts on plant growth that reduce the availability of water to
plants. Now it is well known that salt stress causes a number of effects on plants such
as osmotic effects, ion toxicity, hormonal imbalance, generation of reactive oxygen
species and nutritional imbalance (Ashraf, 2004; Flowers and Flowers, 2005). Soil
salinity is a widespread problem, restricting plant growth and biomass production
especially in arid, semi-arid and tropical areas (Apse et al., 1999). On a global basis,
salt affected soils occupy an estimated 952.2 M ha of land, constituting nearly seven
per cent of total land area or nearly 33 per cent of the area of potential arable lands of
the world (Gupta and Abrol, 1990). Bangladesh covers more than 30% of the
cultivable lands of the country. About 53% of the coastal areas are affected by salinity
(Haque, 2006). Out of 2.86 Mha of coastal and offshore lands about 1.056 Mha of
lands are affected by different degrees of salinity. Out of 151 Upazilas (sub-districts)
in 19 districts coastal 93 Upazilas under 18 districts are affected by salinity. As the
cropping intensity and crop yields are well below the country average, the
contribution to agriculture sector is not proportional to its land mass. The reason
behind this is unfavourable agroecological conditions of the region. These include
coastal flooding in the monsoon, higher levels of soil salinity in the winter and higher
water salinity in winter reduces its potential for irrigation (Hussain, 2010).
2.6.1. Present Soil Salinity Status in Coastal Area
A direct consequence of sea level rise would be intrusion of salinity with tide through
the rivers and estuaries. It would be more acute in the dry season, especially when
freshwater flows from rivers would diminish. According to an estimate of the Master
Plan Organization, about 14,000km2 of coastal and offshore areas have saline soils
and are susceptible to tidal flooding. If some 16,000 sq km2 of coastal land is lost due
to a 45cm rise in sea level, the salinity front would be pushed further inland. The
present interface between freshwater and saline water lies around 120 to 160km
inland in the southwest, and this could well be pushed northward as far as central
Jessore region in the event of a sea level rise . Increase in salinity intrusion and
37
increase in soil salinity will have serious negative impacts on agriculture (Uddin et
al., 2011). In the winter months the areas suffer due to salinity related problems. In
absence of appreciable rainfall the soil in the coastal areas starts to desiccate, and
because of capillary actions salt comes up at the surface of the soil and accumulates in
the root zones of crops. Many of the crop varieties are not tolerant to salinity, and as a
result, a large area in the coastal districts becomes virtually unsuitable for a number of
crops, while the production of a few other crops is lesser under saline conditions.
Most of the land remains fallow in the dry season (January- May) because of soil
salinity, lack of good quality irrigation water and late draining condition. Farmers
cultivate mostly low yielding, traditional rice varieties during wet season. Only about
six percent of the land types in coastal area are highland and 13% medium low land.
The dominant land type in this region is medium highland, which is about 64%
(Hussain, 2010).
A comparative study of soil salinity maps of 1973, 2000 and 2009 shows the extents
of soil salinity intrusion in the coastal region. The map shows that about 0.223 million
ha (26.7%) new land is effected by various degrees of last four decades (Hussain,
2010).
Table 2.9. Extent of soil salinity during about last four decades (1973-2009) in
coastal areas
Yrar Total Salt affected area(‘000’
Salinity class S1 S2 S3 S4
1973 833.45 287.37 426.43 79.75 39.90
2000 1020.75 289.76 307.20 336.58 87.14
2009 1059.19 328.39 274.21 351.68 101.14
Percent increase (+) or decrease (-) during 2000-2009
+ 35.44 +38.63 -32.99 + 15.1 + 14.0
(Source: Ahsan and Sattar , 2010)
It was also found that about 0.0354 million hectares of new land is effected by various
degrees of salinity during last last 9 years only. Some of new land of Patuakhali,
Borguna, Barisal , Jhalakathi , pirojpur, Satkira, Jessore, Gopalgang and Madaripur
38
districts are affected by different degrees of salinity, which reduces agricultural
productivity remarkably (Hussain, 2010).
Table 2.10. Estimation of Salt affected areas (in ‘000’ ha) in Patuakhali
District
Year
Salinity Level* Salinity increase
over 4 decades
Remarks
patuakhali S 1 S2 S3* S4 Area (000’ha)
%
1973 68.50 46.60 0.00 0.00 43.28 37.60 Galachipa, Kalapara, Sadar,
Dashmina
2000 40.11 43.62 46.10 9.52
2009 57.73 39.90 44.98 15.77
(Souce: Miah, 2010)
2.6.2. Effect of Salinity on Fertility Status of Soil
Agriculture is a major sector of more than 30% of the cultivable land in Bangladesh is
in the coastal area. About 1.0 million ha of arable lands are affected by varying
degrees of salinity. Farmers grow mostly low-yielding, traditional rice varieties during
the wet season. Most of the lands remain fallow in the dry season (January–May)
because of soil salinity and the lack of good-quality irrigation water (Karim et al.,
1990; Mondal, 1997).
Nutrient uptake and accumulation by plants is often reduced under saline conditions
as a result of competitive process between the nutrient and a major salt species.
However, this depends on the type of nutrients and composition of soil solution
(Grattan and Grieve 1999, Maas and Grattan 1999, Homaee et al., 2002). Although
plants selectively absorb potassium over sodium, Na+-induced K+ deficiency can
develop on crops under salinity stress by Na+ salt (Maas and Grattan 1999). Research
revealed that salinity inhibits the growth of plants by affecting both water absorption
and biochemical processes such as N and CO2 assimilation and protein biosynthesis.
Under saline conditions plants fail to maintain the required balance of organic and
inorganic constituents leading to suppressed growth and yield (Gunes et al., 1996).
Plant performance, usually expressed as a crop yield, plant biomass or crop quality
(both of vegetative and reproductive organs), may be adversely affected by salinity
induced nutritional disorders. These disorders may be as a result of the effect of
39
salinity on nutrient availability, competitive uptake, transport or partitioning within
the plant (Grattan and Grieve, 1999; Zhu, 2003; Ali et al., 2006; Nasim et al., 2008).
Saline conditions drastically change the environment of root aeration, osmotic
potential of soil solution and normal equilibrium of the dissolved ions. The
availability of most micronutrients to crop plants mainly depend upon the pH of the
soil solution as well as the nature of binding sites on organic and inorganic particle
surfaces. In saline and sodic soils, the solubility of micronutrients (Cu, Mn, Fe, Zn
and Mo) is particularly low, and plants growing on such soils often experience
deficiencies in these elements (Page et al., 1990).
Soil fertility is an important factor for crop production. In general the coastal regions
of Bangladesh are quite low in soil fertility. Thus in addition to salinity, plant
nutrients in soils affect plant growth. Soil reaction values (pH) range from 6.0-8.4
with the exception of Chittagong and Patuakhali, where the pH values range from 5.0-
7.8. Most of the soils are moderate to strongly alkaline, the pH values of the surface
soils being lower than those of the subsurface soils. In places with higher pH values,
micronutrients’ deficiencies are expected (Haque, 2006). The total N contents of the
soils are generally low, mostly around 0.1%. The low N content may be attributed to
low organic matter contents of most of the soils. Available P status of the soils ranges
from 15-25 ppm. Some deficient P soils are also found in Patuakhali, Barguna,
Satkhira and Chttagong districts. Widespread Zn and Cu deficiencies have been
observed in the coastal regions (Karim et al., 1990).
Table 2.11. Agro-chemical characteristics of soils in some of the coastal and offshore
areas (saline belt) of Bangladesh
District pH OM Total
N (%)
CEC
m.e.%
Na
m.e%
K
m.e.%
Ca
m.e.%
Mg
m.e.%
P
ppm
Zn
ppm
Cu
ppm
Satkhira 6.2-8.4 1.8-2.2 0.9-0.3 14.2-25.5 0.5-0.6 0.2-1.2 6.3-16.2 2.8-11.4 12-24 0.1-0.8 0.08-0.30
Khulna 6.2-7.9 0.1-0.3 0.1-0.3 18.2-40.6 1.6-33.3 0.3-1.0 8.3-22.5 2.6-18.3 8-36 Tr-0.8 Tr-0.20
Bagerhat 6.0-7.8 0.3-2.8 0.1-0.2 15.9-37.0 0.6-7.0 0.2-1.0 9.4-24.2 4.2-17.7 6-26 Tr-1.6 Tr-0.40
Patuakali 5.0-7.8 0.1-1.0 - - - 0.2-0.6 2.7-7.5 1.6-6.6 10-28 0.2-0.8 0.06-0.39
Barguna 6.3-8.0 1.2-2.3 0.1-0.1 12.0-22 2.5-21.7 0.2-0.7 11.5-28 3.9-18.2 4-28 0.2-0.8 -
Bhola 6.3-8.0 0.4-7.1 0.1-0.2 11.8-26 0.6-3.4 0.1-0.4 7.2-20.8 2-9.5 4-14 Tr-3.0 Tr-0.70 Chittagong 5.0-7.4 1.0-2.9 - - - 0.2-0.8 2.7-7.1 2.9-11.3 8-30 0.1-0.9 0.3-1.0
Noakhali 6.0-7.5 0.8-3.1 0.1-0.3 9.4-19.5 0.4-39 0.1-0.5 5.3-12.4 2.3-9.5 4-11 Tr-1.8 Tr-0.70
Feni 6.0-7.5 0.9-2.9 0.1-0.2 11.8-16.2 0.8-3.8 0.4-0.5 7.8-8.0 5.0-6.8 8-24 0.9 -
(Source: BARI, 1989)
40
The adverse effects of saline water intrusion will be significant on coastal agriculture
and the availability of fresh water for public and industrial water supply will fall.
Bangladesh’s economy and the coastal area of Bangladesh is very fertile for growing
rice. Increase in salinity intrusion and increase in soil salinity will have serious
negative impacts on agriculture. Presently practiced rice varieties may not be able to
withstand increased salinity. The food production does not seem to have a better
future in the event of a climate change. In Bangladesh, rice production may fall by
10% and wheat by 30% by 2050 (IPCC, 2007). It is very likely that the soil salinity
would increase due to climate change and consequential effects. Increased salinity
would significantly decrease food grain production. Reduction in food grain
production would put additional pressure to the food security of the country
(Habibullah et al., 1999).
41
CHAPTER 3
MATERIALS AND METHODS
42
3. Materials and Methods
Methodology is the guiding framework for researcher, which will be used to contain
and harmonize the scientific investigation. According to the Dictionary of Social
Science, “methodology is the systematic and logical study of the principals guiding
scientific investigation”. For good accomplishment of the research work, a well
arranged methodology is extremely needed. Methodology shows the total procedure
and working plan of the research work. It is divided into three phases:
conceptualization, data collection, and analysis. Methods involve processes or
techniques in which various stages or steps are followed to conduct the research work.
It is a logical as well as systematic part of the study to guide researchers to acquire
necessary data or information and produce logical explanation to resolve the research
goal.
3.1. Conceptualization and Work Plan Preparation
The conception about the cultivable land reduction, cropping intensity and nutrient
depletion was built up through literature review related papers, journals, books,
dissertation papers etc. The work plan about the research that developed goals and
objectives was prepared after achieving clear ideas. It refers to the process that how
the study would be conducted or the steps required for conducting the study. In this
phase, all the possible activities were incorporated. It emphasizes on the sequence of
the activities that should be undertaken one after another.
3.2. Study Area
3.2.1. Area and Geographical Location
Kalapara (also known as Khepupara) is an Upazila of Patuakhali District in the
Division of Barisal. The upazila occupies an area of 492.102 Sq. km. The study area
is located between 21.9861° N and 90.2422° E. The area is bounded by Amtali
upazila on the north, the Bay of Bangla on the south, Rabnabad channel and
Galachipa upazila on the east, Amtali upazila on the west. Kalapara Upazila consists
of 9 Union Parishads, 57 mouzas and 247 villages with 4 property offices.
Administration Kalapara thana was established in 1906 and was turned into an upazila
in 1983. The average population of each union, mouza and village are 202078 (BBS,
2011).
43
Fig.3.1. Location map of the study area
(Source: Banglapedia, 2006)
3.2.2. Demography
The total population of Kalapara upazilla was 2, 20,074 in the year 2001. As of the
2011 Bangladesh census, Kalapara has a population of 2, 82,000. Males constitute are
52.85% of the population, and females 48.15%. Kalapara has an average literacy rate
of 51.04% (7+ years), and the national average of 57.53% literate. The religious
picture is Muslim 74.29%, Hindu 25.35%, others 0.36%; Density of population of the
study area is 861 per sq. km, the growth rate is 39.10. The decadal population growth
rate is 16.35% and annual compound growth rate is 2.53% (BBS, 2011).
44
Table 3.1. Represents increase of population in Kalapara Upazila after 10 years
Name of Union
Population 2001 2011
Chakamaya 14859 19021 Teakhali 11893 15225 Lalua 14139 18099 Mithagonj 23964 31952 Nilgonj 25553 34710 Khaprabhanga 28124 35847 Latachapli 27004 36102 Dankhali 22716 30078 Dulasor 15199 19456 Total 183451 240490
(Source: Upazila Statistics Office, Kalapara, Patuakhali, 2011)
3.2.3. Topography and Relief
Average height of Kalapara Upazila, in the northern edge is about 2m and in the south
is about lm high from mean sea level. But the maximum height is 6m. The study area
lies in the southwestern part of Bangladesh and downstream of the well known
Ganges deltaic region. The area comprises a flat land with natural ground slopes are
found the main rivers are the Andharmanik, Agunmukha, Payra, Lohalia, Patuakhali
and Tentulia (Banglapedia, 2006).
3.2.4. General Geology of the Study Area
The physiographic condition of Kalapara Upazila is broadly characterized by tidal
flood plains having lower relief and crisscrossed by innumerable river channels. The
study Area is located in the south-west part of the Bengal Basin, a long established
area of subsidence and deposition containing an almost complete sequence from the
Cretaceous to Recent alluvium. The surface topography of the quaternary deposits is
very gentle. The whole of the south-west area is below elevation 17 m and 75% is
below 5m. The surface geology consists mainly of quaternary sediments, although
there are some tertiary deposits in the eastern flood belt. Clay soils are prevalent in the
low laying areas, and medium textured soils at the higher grounds (SRDI, 2001).
45
3.2.5. Land Use Pattern
The land use pattern of an area depends upon the climate, geology, soil, surface and
ground water availability and quality. Among the lands in Kalapara , there are 40,000
ha of cropland , 28 ha of gher, 386.20 ha of settlements and 70 ha of fallow land
(Upazila Agriculture Office, 2011).
3.2.5.1. Cropland
Major crop cultivation in kalapara is Transplant Aman (T- aman), Boro, potato and
vegetables. Sesame, linseed, sugarcane, kaun are extinct or nearly extinct crops of the
study area (Banglapedia, 2006). Gher farming is done in some different land and also
in some T-Aman cropland. T-Aman is mainly the cultivated in the Kharif-2 season.
At present, about in 100% cropland is used for T- aman cultivation. Boro is cultivated
in the Kharif-l season, Rabi crops are cultivated in the Rabi seasons and gher farming
is done rest of the year (SRDI, 2001)
Table 3.2. Represents the cropland use of Kalapara Upazila
Cropland information of 9 unions of Kalapara Upazila.
Name of Union Crop land (ha)
2001 2011 Chakamaya 3438 3364 Teakhali 3289 2774 Lalua 5219 3615 Mithagonj 7385 6466 Nilgonj 6343 5313
Khapravanga 5273 5379
Latachapli 5720 4794
Dhankhali 5929 5551 Dulasor 3251 2743
Total 45818 40000
(Source: Upazila Agriculture Office, Kalapara, patuakhali, 2011)
3.2.5.2. Settlement
In Kalapara Upazila, about 19% land is used for settlements. There are about 56
markets, 243 education centers (7 Kindergartens, 8 community primary schools, 80
reg. primary schools, 78 govt. primary schools, 8 lower secondary schools, 29
secondary schools, 27 madrasas and 6 colleges ), 443 religious centers (387 mosques,
46
45 temples , 3 church , 4 buddhist vihara and 2 pagoda), 30 health centers (2 hospital,
6 family planning centers and 22 community clinics), 5 Launch ghat, 7 union
complexes, 1 upazila complex, 1 customs office, 27 post offices, 1 food storehouse
are in the study area (BBS, 2011).
3.2.5.3. Fallow Land
The fallow lands of the study area are about 51ha. Most of this type of land use is
seen in Nilgonj, Chakamaya, dhankhali and Mithagonj. In lalua most of the land
remains submerged due to high and low tide. So, the soil salinity of lalua union is the
most than others (Upazila Agriculture Office, 2011).
3.2.6. Soil type
KalaparaUpazila is a Ganges Floodplain. In Kalapara Upazila most of the soil types
are present deposits. In this region, pH varies from7.5-4.9. The color of the soil is
light grey, grey and black. The soil salinity varies from Moderate to nil; (EC 0.37 to
11.2 dS m-1). The study areas are mainly located in Medium High land. Here soil is
rich in Calcium, Magnesium, Boron, Copper, and Phosphorus and moderately high in
Manganese, Zinc and lower concentration of Sulphate, Iron, and Nitrogen. There are
rnainly three types of soil present in kalapara upazila. They are ramgoti, Jhalokathi
and Barisal (SRDI, 2001).
3.2.7. Climatic Condition
3.2.7.1. Rainfall
The rain fall pattern is quite similar with the other location of the South-West coastal
Belt. The rainfall pattern raises up to 350 mm in the rainy season and in the dry
season the average rain fall is below 52 mm. But a heavy rainfall is common in the
study area and that occurs four or five times in a year. In 2001, the maximum rainfall
was 397 mm in June and the minimum rainfall was 0 mm in December. In 2011, the
maximum rainfall was 344 in August and the minimum rainfall was 0 January (BMD,
2011).
3.2.7.2. Temperature
Kalapara Upazila is located in coastal region and it falls on South-western climatic
sub-zone of Bangladesh. In 2001, the average maximum temperature was 36.6oC in
the month of April and average minimum temperature of 15.2oC in the month of
47
December. In 2011the average maximum temperature was 36.7oC in the month of
April and average minimum temperature of 11.5oC in the month of January (BMD,
2011).
3.2.7.3. Humidity
Humidity of the study area is completely high. In 2000, the maximum humidity was
88% in the month of July and lowest humidity is 68 % in the month of March .In
2010, the maximum humidity was 85% in the month of September and lowest
humidity is 71% in the month of March (BMD, 2011).
3.3. Selection of the Study Area
The following criteria are being considered for selecting the Kalapara Upazila as the
study area:
Kalapara Upazila is mostly affected by salinity intrusion, tidal surge and
impact of sea level rise, because the people of Kalapara are living beside the
coast of Bay of Bengal.
This region is a well crop productive area of the southwestern coastal
Bangladesh.
Cropland condition have greatly hampered by increasing population and
cropping intensity in study area
Croplands are severely affected by salinity intrusion.
Kalapara is severely affected by the devastating cyclone induced storm surge
3.4. Data Collection All data were collected from the various sources. They are as follows –.
Soil Nutrient data (2011) collection from Soil Resource Development
Institute, Patuakhali.
Soil Nutrient data (2001) collection from Soil Resource Development
Institute, Barisal.
Cropland and Crop production data collection from Upazila Agriculture
Office, Kalapara, patuakhali.
Demographic and Settlement information from Bangladesh Bureau of
Statistics, Kalapara
48
Bangladesh Bureau of Statistics, community series, Patuakhali Zila
Bangladesh Meteorological Department, Kalapara.
Internet/journal
Published/Unpublished report
Upazila Agriculture Office and Upazila Parisad, Kalapara Upazila, Patuakhali.
3.5. Cropping Intensity Determination
Data on cropping pattern and the land coverage for Aman, Aus, Boro and Vegetable
crops were collected from Upazila Agricure Office. Cropping intensities of five
different study unions of Kalapara Upazila were calculated by the following formula
as suggested by Sing (2004).
Cropping Intensity =Total cropped areaNet cultivated area × 100
Table 3.3. Cropping intensity of Kalapara Upazila
Union Net cultivated
area
Aman Aus , Boro Robi crops Total cropped
area
Cropping
Intensity
2001 2011 2001 2011 2001 2011 2001 2011 2001 2011 2001 2011 2001 2011
Chakamoia 3438 3364 3435 3364 75 215 50 103 1607 2975 5167 6657 150% 186%
Nilgonj 6313 5313 6310 5313 101 301 75 200 3295 4290 9781 10095 155% 190%
Latachapli 5720 4794 5697 4794 53 101 30 80 1923 2875 7703 7850 135% 164%
Dhankhali 5929 5551 5925 5551 65 190 70 125 3071 4507 9131 10373 154% 187%
Mithagonj 7385 6466 7383 6466 105 295 45 105 3172 4972 10705 11838 145% 183%
(Source: Upazila Agriculture Office, Kalapara, Patuakhali, 2011)
3.6. Data Interpretation
All data were compiled, processed and interpreted for discussion and analysis. The collected
secondary data were grouped, categorized and interpreted according to the objectives as well
as the indicators. Some data contains numeric and some contains narrative facts. For
measurable and indicative answer data have been grouped in the tabular forms.
3.7. Data Processing and Analysis
Data were statistically processed, analyzed and interpreted by using computer
programs- MS WORD and MS EXCEL 2007.
49
CHAPTER 4
RESULTS AND DISCUSSION
50
4. Results and Discussion
This chapter contains the presentation of results (data and information that was
collected and that was generated) and their analysis. The study was conducted at five
unions of Kalapara Upazila in Potuakhali District. In a view to meet the objectives of
the research paper the results were tabulated, interpreted and analyzed in the
following ways:
4.1. Increasing in Population
Fig. 4.1 presents the population growth of the studied unions of Kalapara upazilla
during 2001- 2011. The growth rate in 10-year period is 35.8% in Nilgonj, 33.6% in
Latachabli, 33.3% in Mitagonj, 32.4% in Dhankhali and 28% in Chakamoia,
respectively.
Data presentation in fig. 4.1 shows that the highest population growth rate was found
in Nilgonj whereas the lowest growth rate was observed in Chakamoia union. The
highest population growth of Nilgonj union might be due to migration of the rural
people to town areas to enjoy the urban facilities as it is the nearest union of the
pourashava likewise Latachabli is the most distant and remotest union from
pourashava. So, people intended to dwell in Dhankhali.
The total population of Kalapara upazilla was 2,20,074 in the year 2001 and 2,83,000
in 2011(BBS, 2011). Rapid population increase is one of the major problems of
Bangladesh. The population growth rate is about 1.42 %, which translates into about
two million additional new mouths every year need to be fed (BBS, 2011).
0
10000
20000
30000
40000
14859
2555322716
2700423964
19021
3471030078
3610231952
Popu
latio
n
Fig.4.1. Population growth of five unions in Kalapara upazilla
2001
2011
51
4.2. Reduction of Cultivable Land
Fig. 4.2a presents the shrinkage of cultivable land and Fig. 4.2b represents the per
capita land reduction of the studied unions of Kalapara upazilla during 2001- 2011. In
2001, the cultivable land of Chakamoia, Nilgonj, Dhankhali, Latachabli and Mitagonj
were estimated to be 3438 ha, 6333 ha, 5929 ha, 5720 ha, and 7385 ha respectively
whereas in 2011 cultivable land reduced by (2.15 %), (16.23 %), (6.37 %), (16.18 %)
and (12.44 %) ha in the respective unions.
The order of cultivable land reduction was Nilgonj> Latachabli> Mitagonj>
Dhankhali> Chakamoia. Thus the increased pressure on the cultivable land entailed
per capita land reduction. Homestead and other settlements in Nilgonj and Latachabli
occupied much valuable cultivable land higher than other unions. The population
added by 10-year time is 63,000; the average per capita land therefore, reduced in a
10-year time from 0.21ha to 0.14 ha. The per capita land reduction was observed in all
the studied unions provided that highest reduction in Nilgonj and the lowest reduction
in Chakamoia unions.
The country has a land area of 148.4 million hectares (Mha), population of over
142.32 million with a density of about 1000 persons per km2, which is one of the
highest in the world (BBS, 2011). With the growing population, and their increasing
needs in various sectors, land use patterns are undergoing a qualitative change in
which the area under the net cropped land is gradually shrinking (BARC, 2011).
0
2000
4000
6000
8000
3438
6343 5929 57207385
3364
53135551
47946466
Lan
d in
hec
tare
Fig. 4.2a. Reduction of Cultivable land
2001
2011
0
0.1
0.2
0.30.23 0.25 0.26
0.21
0.3
0.180.15
0.180.13
0.21
Per c
apit
a la
nd (h
a)
Fig. 4.2b Reduction of per capita land
2001
2011
52
4.3. Increase in Cropping Intensity
Fig. 4.3 represents the increase of cropping intensity in 10-year period of the studied
unions of kalapara upazila. In 2001, the cropping intensity of Chakamoia, Nilgonj,
Dhankhali, Latachabli and Mitagonj was 150%, 154%, 155%, 135% and 145%
respectively while in 2011 it was increased to 186%, 190%, 187%, 164% and 183%
of those unions. The order of increase cropping intensity was Nilgonj> Dhankhali>
Chakamoia > Mitagonj> Latachabli. Increased population and land shrinkage might
be the cause of increasing cropping intensity to meet up the food demand.
Increased crop productivity from the shrinking land resources is the urgent need to
meet the increased food demand of the swelling population of Bangladesh. Food
requirement of the country is estimated to be doubled in the next 25 years. To feed the
teeming million the land resources in Bangladesh is intensively used for crop
production (Islam and Haq, 1999). Since land is a scarce resource in Bangladesh, the
only choice is to increase in cropping intensity (Ahmed et al., 2001).The net cropping
intensity of Bangladesh in 2009-10 was 180.88% (BBS, 2010) and the highest
cropping intensity of 199% was observed in Kalapara upazila followed by other
coastal upazilas (Bala and Hossain, 2009).
4.4. Increase in Salinity
Fig. 4.4 showed the increasing trend of salinity of the studied unions of kalapara
upazilla. In 2001, the salinity of Chakamoia, Nilgonj, Dhankhali, Latachabli and
Mitagonj was 4.48 dS/m, 3.79 dS/m, 3.21 dS/m, 6.67 dS/m and 3.48 dS/m
respectively but in 2011 it was increased to 7.60 dS/m, 5.88 dS/m, 7.26 dS/m, 8.87
0%
50%
100%
150%
200%150% 154% 155%
135% 145%
186% 190% 187%164%
183%
Cro
ppin
g In
tens
ity (%
)
Fig.4.3. Increase in Cropping Intensity
2001
2011
53
dS/m and 6.91dS/m. The order of increasing salinity was Dhankhali> Chakamoia>
Mitagonj> Latachabli> Nilgonj. Due to salt water intrusion from river in Dhankhali
and chakamoia unions, were found to be the highest increase in salinity.
A comparative study of soil salinity maps of 1973, 2000 and 2009 shows the extents
of soil salinity intrusion in the coastal region. It was also found that about 0.0354
million hectares of new land is affected by various degrees of salinity during last 9
years only. Some of new land of Patuakhali, Borguna, Barisal, Jhalakathi, pirojpur,
Satkira, Jessore, Gopalgang and Madaripur districts are affected by differerent
degrees of salinity, which reduces agricultural productivity remarkably (Hussain,
2010). The study area is not out of this effect.
4.5. Depletion of Major Nutrients
Intensive cultivation practice and mismanagement of cultivable land reducing the
nutrient content of Kalapara Upazilla. The trends of major nutrients depletion are
discussed in this section.
4.5.1. Nitrogen Depletion
Fig. 4.5 demonstrates the depletion of nitrogen percentages of soil of the studied
unions of Kalapara upazilla during 2001- 2011. In 2001, the nitrogen status of
Chakamoia, Nilgonj, Dhankhali, Latachabli and Mitagonj were 0.099 %, 0.097%,
0.125 %, 0.118 % and 0.093% and the maximum value (0.125%) was found in
Dhankhali union while in 2011 and the levels were 0.057 %, 0.081%, 0.086 %, 0.076
% and 0.062 %.
0
2
4
6
8
10
4.483.79 3.21
6.67
3.84
7.6
5.887.26
8.87
6.91
Salin
ity (d
S/m
)
Fig. 4.4. Increase in Salinity
2001
2011
54
The maximum reduction of nitrogen was observed in Chakamoia union and the lowest
change was found in Nilgonj union. Nitrogen was reduced in 10-year period by the
sequence of Chakamoia> Latachabli> Dhankhali> Mitagonj> Nilgonj. Cultivable land
shrinkage and increasing cropping intensity of five unions might be the cause of
Nitrogen depletion in soil of those unions. Though population growth rate and
cropping intensity of Nilgonj was higher than other unions but nitrogen depletion rate
was found the lowest. It might be caused by high input of organic manure and
inorganic nitrogen fertilizer to get higher crop production to meet up the food demand
of boosting population.
Nitrogen is generally considered as the key nutrient in Bangladesh agriculture because
of its low supply in the soils. Portch and Islam (1984) reported that 100% of
Bangladesh soils contained available N below critical level. Nitrogen is the most
limiting nutrient in crop production all over the world. Nitrogen deficiency occurs
everywhere in Bangladesh (Kumar and Yadav, 2005). They conclude that the
depletion of N from the soil is mainly due to crop removal and leaching for increase
cropping intensity.
4.5.2. Phosphorus Depletion
In 2001, the phosphorus levels of Chakamoia, Nilgonj, Dhankhali, Latachabli and
Mitagonj were 7.63 ppm, 4.86ppm, 8.64 ppm, 2.56 ppm and 6.74 ppm while in 2011
the levels were 6.6 ppm, 0.5 ppm, 6.2 ppm,1- and 5.1 ppm. However, in 2011
phosphorus was depleted by the order of Nilgonj> Dhankhali> Mitagonj> latachabli>
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.099 0.097
0.1250.118
0.093
0.0570.071
0.0860.076
0.062N
itrog
en (%
)
Fig.4.5. Depletion of Nitrogen
2001
2011
55
Chakamoia (Fig. 4.6). Cultivable land shrinkage and increasing cropping intensity of
Nilgonj might be the cause of higher phosphorus depletion in Nilgonj.
Phosphorus is recognized as an important mineral element limiting crop growth and
production (Batten et al., 1984). It is generally considered as the second most limiting
nutrient after N for plant growth (Vance, 2001). Phosphorus depletion in soil due to
the current intensive use of agricultural land for crop production (Nautiyal et al.,
2000).
4.5.3. Potassium Depletion
Fig. 4.7 represented the depletion of potassium concentration in soils Kalapara
upazilla. In 2001, the potassium levels of Chakamoia, Nilgonj, Dhankhali, Latachabli
and Mitagonj were 0.42ppm, 0.47ppm, 0.37ppm, 0.31ppm and 0.35 ppm while in
2011 and the phosphorus levels were 0.3 ppm, 0.27 ppm, 0.29 ppm, 0.19 ppm and
0.24 ppm. The maximum depletion of potassium was observed in Nilgonj union and
the lowest depletion was found in Dhankhali union. Potassium depletion in Nilgonj
was mainly caused by high cropping intensity. Although cropping intensity of other
unions were also high but potassium level didn’t change more due to salinity.
0
2
4
6
8
10
Chakamoia Nilgonj Dhankhali Latacabli Mitagonj
7.63
4.86
8.64
2.56
6.746.6
0.5
6.2
1
5.1
Phos
phor
us c
onc.
(ppm
)
Fig. 4.6. Depletion of Phosphorus
2001
2011
56
Tiwari (1985) concluded that Intensive cropping with modern rice varieties is
responsible for increasing the K Depletion in soil. Most of the north-western parts of
Bangladesh are deficient in potassium (BARC, 2005).
4.5.4. Sulfur Depletion
Fig. 4.8. represents the depletion of potassium levels of soils of the studied unions of
kalapara upazilla. In 2001 the sulfur contents of Chakamoia, Nilgonj, Dhankhali,
Latachabli and Mitagonj was 61.1ppm, 59.03 ppm, 51.85 ppm, 48.32 ppm, and 54.5
ppm respectively where as in 2011 it decreased to 23.7 ppm, 20.5 ppm, 23.9ppm, 21.5
ppm and 25.4 ppm and sulfur depletion trend was Nilgonj > Chakamoia> Mitagonj>
Dhankhali> Latachabli.
The maximum depletion of Sulfur was observed in Nilgonj union and the lowest
depletion was found in Latacabli union. Sulfur depletion in Nilgonj was mainly
0
0.1
0.2
0.3
0.4
0.5 0.420.47
0.370.31
0.350.3
0.27 0.29
0.190.24
Pota
ssiu
m co
nc .
(ppm
)
Fig. 4.7. Depletion of Pottassium
2001
2011
0
10
20
30
40
50
60
70
Chakamoia Nilgonj Dhankhali Latacabli Mitagonj
61.1 59.0351.85
48.3254.5
23.7 20.5 23.9 21.525.4
Sulfu
r co
nc. (
ppm
)
Fig. 4.8. Depletion of Sulfur
2001
2011
57
caused by high cropping intensity. Intensive cropping has been resulting higher
depletion of sulfur among the other nutrients rather its replenishment under natural
process (Balsa et al., 1996). The current intensive use of agricultural land for crop
production has extended the sulfur deficient areas to about 80% (Khan et al., 2007).
Bangladesh is not free from this threat. About 7 M ha (about 52%) of agricultural
lands are reported to consists of sulfur deficient soils in the Northern region of
Bangladesh (SRDI, 1999).
4.5.5. Calcium Depletion
Fig. 4.9 presents the depletion of Ca contents in soils of the studied unions of
Kalapara upazilla. The contents of Ca in Chakamoia, Nilgonj, Dhankhali, Latachabli
and Mitagonj unions were 6.3 ppm, 4.3 ppm, 5.1 ppm, 5.91ppm and 4.58 ppm in 2001
but it decreased sharply in 2011 and the Ca contents were observed 4.4 ppm, 2.9 ppm,
4.5 ppm, 4.7 ppm and 2.58 ppm. The maximum depletion was found in Chakamoia
union and the lowest depletion was found in Dhankhali. Due to lower cropping
intensity and higher rate of increasing salinity, Ca depletion rate was also found lower
in Dhankhali union. Jahiruddin and Islam (1999) reported that Zinc depletion in
Bangladesh is mainly due to continuous mining of soil nutrients for increase cropping
intensity (180% at present).
0
1
2
3
4
5
6
7
Chakamoia Nilgonj Dhankhali Latachabli Mitagonj
6.3
4.35.1
5.91
4.584.4
2.9
4.5 4.7
2.58
Cal
cium
con
c. (p
pm)
Fig.4.9. Depletion of Calcium
2001
2011
58
4.5.6. Zinc Depletion
Fig. 4.10 shows the depletion of Zn contents in soils of the studied unions of Kalapara
upazilla. The contents of Zn in Chakamoia, Nilgonj, Dhankhali, Latachabli and
Mitagonj unions were 0.74 ppm, 0.79 ppm, 0.64 ppm, 0.68 ppm and 0.91 ppm in
2001 while in 2011 it decreased dramatically and the Zn contents were observed 0.45
ppm, 0.28 ppm, 0.45 ppm, 0.39 ppm and 0.42 ppm. The order of depletion was
Nilgonj > Chakamoia > Mitagonj > Latachabli > Dhankhali. Intensive cultivation of
crops in Nilgonj might be the fact that reduced the Zn level.
Zinc deficiency, together with sulphur deficiency, are recognised as limiting factors in
crop production in Bangladesh. About 1.75 Mha of intensively cropped land are
estimated to be affected by zinc deficiency, which mainly affects rice and wheat
(Ahsan and Beuter, 2000). Jahiruddin and Islam (1999) reported that Zinc depletion in
Bangladesh is mainly due to continuous mining of soil nutrients for increase cropping
intensity (180% at present). They also said that availability of Zn in the soil varies
widely depending on the soil properties and the calcareous soils have low to medium
extractable Zn content.
4.5.7. Boron Depletion
Fig. 4.11 demonstrates the depletion of Zn contents in Kalapara upazilla. The contents
of Boron in Chakamoia, Nilgonj, Dhankhali, Latachabli and Mitagonj unions were
0.56 ppm, 0.49 ppm, 0.41 ppm, 0.45 ppm and 0.59 ppm in 2001 but after 10 years
Boron contents were observed 0.27 ppm, 0.19 ppm, 0.31 ppm, 0.23 ppm and 0.29
0
0.2
0.4
0.6
0.8 0.740.79
0.64 0.680.6
0.45
0.28
0.450.39 0.42
Zinc
con
c. (p
pm)
Fig. 4.10. Depletion of Zinc
2001
2011
59
ppm and the order of Boron depletion was Nilgonj, Mitagonj> Chakamoia>
Latachabli> Dhankhali.
This might be the effect of high cropping intensity in Nilgonj and Mitagonj. Although
taken up in tiny quantities, boron deficiency may lead to serious consequences
regarding economic yield of various crops. Boron deficiency in Bangladesh was first
observed in reverine soils of Teesta on wheat causing sterility in grains. Boron
depletion in Bangladesh is mainly due to continuous mining of soil nutrients for
increase cropping intensity (Islam, 2006).
0
0.1
0.2
0.3
0.4
0.5
0.6
Chakamoia Nilgonj Dhankhali Latachabli Mitagonj
0.560.49
0.410.45
0.59
0.27
0.19
0.31
0.230.29
Bor
on c
onc.
(ppm
)
Fig. 4.11. Deplition of Boron
2001
2011
60
CHAPTER 5
Summary and Conclusion
61
5. Summary and Conclusion
Rapid population increase has been the most persistent problem of Bangladesh since
last 50 years or more. All the triggering factors discussed in the scope of this research
paper are the outgrowth of the biggest trigger factor ‘swelling population’. Growing
population entails increase in food demand, migration and settlement in town areas,
land use, cropping intensity and many such other factors that trigger nutrient depletion
or imbalance leading to degradation. That may halt sustainability in agricultural use of
the land of Kalapara upazila as this might be projected that the picture of other unions
are similar to the studied unions.
However, from the study it can be summarized that -
Population increased in all the studied unions but the highest population
growth was found in Nilgonj.
Estimated cultivable land reduction and cropping intensity both were highest
in Nilgonj.
The highest per capita land reduction was found in Mitagonj and the lowest of
the same was observed in Chakamoia unions.
The maximum depletion of P, K, Zn and B was observed in Nilgonj.
The maximum depletion of N, S and Ca found in Chakamoia.
Salinity was increased in all the studied unions
Study showed that land use patterns are undergoing a qualitative change in
Kalapara upazila as cultivable land is gradually shrinking. This research paper
projects that much alike in the other areas in Bangladesh, increasing food and
shelter demand of Kalapara upazila would be met by increasing cropping intensity
from the ever shrinking land resources without considering the nutrient balance in
the soil that may soon lead to the degradation. That is the ultimate threat is
imminent.
It can also be concluded from the observed facts of the nutrient status that Nilgonj and
Chakamoia are the most vulnerable unions among the studied ones.
62
CHAPTER 6
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63
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