Soil moisture conservation for drought management in bd

Welcome
Conservation of Soil Moisture for Drought Management in Bangladesh
Md. Altaf Hossain, PhD
Principal Scientific Officer
SRDI, Ministry of Agriculture
2/20/2019 1SRDI

Soil is one of the most important water storage in nature.
Water content in the soil is very significant parameter of water regime of
the country which significantly depends on soil area and quality of soil.
Lower acreage of soil and lower soil quality lead to less water content in
the country and vice versa.
Human activities (agriculture, forest management, soil sealing) are still
important factors of water regimes of land.
Mainly agriculture drives the soil water regime from positive or negative
points of view.

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The earth has a limited amount of water. That water keeps going around and around and
around and around and (well, you get the idea) in what we call the "Water Cycle".
This cycle is made up of a few main parts:
evaporation (and transpiration)
condensation
precipitation

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Drought is primarily an agricultural phenomenon that refers to conditions where plants face
certain levels of moisture stress that affect both vegetative growth and yield of the crops.
Decrease in rainfall and shortage of surface water and ground water recharge causes
depletion in soil moisture.
Changes in such factors develop due to changes in local, regional and global weather and
climate.
Bangladesh experienced severe drought in the of 1951, 1957, 1961, 1972, 1976, 1979, 1986,
1989 and 1997. Most of these droughts primarily occurred in pre-monsoon and post
monsoon seasons, but in some extreme cases the pre monsoon drought had extended to
the monsoon season due to delayed onset of monsoon rains (CDMP II, 2013).

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Seasons Period Weather Events Rainfall (%)
Summer
(Pre-monsoon)
March-May Nor' western Tornado,
Hail, Cyclone, Heat wave
19
Rainy Season
(Monsoon)
June-September Heavy rain, monsoon
depression, flood
71
Autumn
(Post-monsoon)
October-November Cyclone, Tornado 8
Winter December-February Abnormal dryness
(drought), cold wave
2
Bangladesh Meteorological Department
Seasonal variability of rainfall in Bangladesh

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Agricultural drought dominantly starts when the amount of water in
the soil is at the level of wilting point.
The physical definition of the wilting point is defined as the water
content at -1500 J/kg of suction pressure or negative hydraulic head
(WÖSTEN ET AL. 1999, GIVI ET AL. 2004, PATIL ET AL. 2012).
The soil types with higher total available water are generally more
conducive to high biomass productivity because they can supply
adequate moisture to plants during time when rainfall does not
occur. Sandy soils are more prone to drought and will quickly
(within a few days) be depleted of their available water when
evapotranspiration rates are high.

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Droughts often result in heavy crop damage and livestock losses, disrupt
energy production and hurt ecosystems. They cover wide areas of land and
often affect several neighboring regions or countries simultaneously.
Drought can lead to famines, loss of life, mass migration and conflicts.
Drought can wipe out development gains and accumulated wealth in
developing countries, especially for the poorest. In a number of countries,
drought wiped out significantly more than 5 % of the previous year`s GDP
(GUHA-SAPIR 2004).

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Soil water holding capacity (SWHC) is the portion of water that can be absorbed
by plant roots. Simply, more water saved by soils means better conditions for
nature and people.
SWHC is the amount of water stored, or released between field capacity and the
wilting point water content. The average total soil water content depends on its
textural characteristics mainly as follows: coarse sand 5 %(volume) , fine sand 15
%, loamy sand 17 %, sandy loam 20 %, sandy clay loam 16 %, loam 32 %, silt
loam 35 %, silty clay loam 20 %, clay loam 18 %, silty clay 22%, and peat 50%.
Firstly it depends on the soil use (agriculture, forestry, etc.), on farming systems
(soil tillage, cultivated plants, fertilizing, machines use, etc.) and on use of soil
conservation farming systems (approaches) in agriculture and forestry.

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Soil Moisture
(up to 100 cm)
Average moisture content (mm)
Silt loam Silty Clay loam Silty Clay/Clay
Available moisture 282 205 160
Readily available moisture 185 87 75
SRDI, 1983
Average moisture availability of soils under different textural classes in Ganges
River Floodplain
In silt loam soils short durated early rabi crops may be grown successfully without
irrigation

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Average moisture availability of soils under different textural classes in Barind Tract
Soil Moisture
(up to 100 cm)
Silt loam Silty Clay loam Clay loam Clay
Available moisture 240 155 152 165
Readily available moisture 135 60 90 80
SRDI, 1984
In silt loam soils (Kashimpur, Tejgaon) short durated early rabi crops may be
grown successfully without irrigation

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Soil Moisture
(up to 100 cm)
Silt loam Silty Clay loam Silty Clay/Clay
Old Brahmaputra Floodplain (AEZ 9)
Available moisture 290 222 169-160
Readily available moisture 135 83 38-30
Old Meghna Estuarine Floodplain (AEZ 19)
Available moisture 215 147.5 -
Readily available moisture 85 62.5 -
SRDI, 1986
Average moisture availability of soils under different textural classes in Old
Brahmaputra and Old Meghna Estuarine Floodplain
In silt loam soils short durated early rabi crops may be grown successfully without
irrigation

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Available soil moisture (mm), date of 1st stress and wilting point (SRDI, 1985)
Soil series Available
moisture
(up to 100
cm)
Readily
available
moisture
Moisture
available
with stress
Moisture
after
October
Moisture
after
November
Start of
stress
Start of
wilting
point
Amnura 218.0 116.2 101.8 218.0 117.6 06 Dec 12 Jan
Belabo 201.0 115.0 86.0 201.0 100.0 05 Dec 06 Jan
Chandra 175.5 91.7 83.8 175.0 75.1 24 Nov 29 Dec
Charkai 169.0 80.4 88.6 169.0 68.6 21 Nov 25 Dec
Ekdala 175.0 86.8 88.2 175.0 74.6 23 Nov 23 Dec
Gulta 174.0 86.6 87.4 174.0 73.6 23 Nov 27 Dec
Kahalu 165.0 80.0 85.0 165.0 64.6 20 Nov 24 Dec
Lauta 162.0 76.4 85.5 162.0 61.6 20 Nov 23 Dec
Nijhuri 177.0 91.3 85.7 177.0 76.6 24 Nov 28 Dec
Noadda 177.0 92.8 84.2 177.0 76.0 24 Nov 28 Dec
Short durated rabi crops may be grown in Belabo and Amnura series

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Land capability class Area (million ha) Percentage
I. Very good agricultural land 0.19 2
II. Good agricultural land 4.19 34
III. Moderate agricultural land 4.82 39
IV. Poor agricultural land 1.92 16
Source: FAO, 1988
Data revealed that moderately good and good agricultural lands together constitute
the bulk of the land area in Bangladesh.
It is interesting to note that about one-fourth of the agricultural land is of poor quality.
Care will be needed to manage these lands otherwise they may turn unproductive.
Quantified data for land and soil properties need to be developed for major crops for
sustainable production, development and conservation of the limited land resources
of the country.

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Conversion of agricultural land to non-agricultural land
Land use/
Land cover
Area (million hectare) Yearly average change (ha)
1976 2000 2010 1976-2000 2000-2010
Crop Land 9.761450 9.439541 8.751937 -13413 -68760
Forest 1.754917 1.311121 1.434136 -18492 12031
Mangrove 4.52444 4.86791 4.41455 1431 -4534
Aquaculture 0.000582 0.143506 0.175663 5955 3216
Salt Pan 0.011789 0.024306 36022 522 1172
Rural
Settlement
0.885637 1.458031 1.766123 23850 30809
Urban +
Industry
0.026799 0.047495 0.087616 862 4012
Land loss from crop agriculture at the rate of 0.73% per annum; per capita land being0.052ha
SRDI, 2013

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Center for Global Climate Change (2009)

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Techniques of Soil Moisture Conservation
The main objective of soil moisture conservation is to minimize the amount of water
lost from the soils through evaporation (water loss directly from the soil) and
transpiration (water loss occurring through the plants) – or combined, the
evapotranspiration.
Preserving soil moisture is important means to maintain the necessary water for
agricultural production, and also helps minimize irrigation needs of the crops. This is
especially important in areas where rainwater and/or groundwater resources for
irrigation are scarce or decreasing due to climate change or other causes.
There is a variety of methods that can be used to conserve soil moisture. Most of
these are relatively low cost and complexity approaches, primarily relying on the
presence of required materials and local technical capacity. Many of the methods
rely on providing some kind of cover for the soil to minimize evapotranspiration and
direct soil exposure to heat and sun. Generally, most methods used for soil quality
improvement and conservation, will also yield benefits to soil moisture
conservation.

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 Spreading manure or compost over the soil – this minimizes evapotranspiration
and also provides valuable nutrients to the soil through processes of
decomposition
Crop rotation – growing different types of crops every season helps improve soil
structure and thus water holding capacity.
Examples include rotating deep-rooted and shallow rooted crops that make use
of previously unused soil moisture, as plants draw water from different depth
levels within the soil. Crop rotation may also improve soil fertility and help
control pests and diseases.

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 Reduced tillage refers to any conservation system that minimizes the total
number of tillage primary and secondary operations for seed planting from that
normally used on field under conventional tillage (FAO 2015).
It is also called minimum tillage because it reduces the use of tillage to minimum
enough to meet the requirements of crop growth.
Reduced tillage is a conservation management strategy that leaves at least 30%
residue cover to minimize surface runoff and soil erosion, improve soil functions,
and sustain crop production.
These systems reduce surface runoff and soil erosion and improve or maintain crop
yields compared to conventional systems.

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Mulch tillage is a practice where at least 30% of the soil surface remains covered with
crop residues after tillage.
Tillage under this system is performed in a way that leaves or maintains crop residues
on the soil surface. Mulch tillage is an extension of reduced tillage and is also called
mulch farming or stubble mulch tillage.
The soil under mulch tillage is often tilled with chisel and disk plough instead of
mouldboard ploughs, and thus it minimizes soil inversion. The choice of implement for
mulch tillage is specific to each soil and management.
One of the advantages of mulch tillage over no-till is that it can control weeds better.
Soil erosion in mulch tillage is commonly lower compared to that in conventional tillage.

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Ridge tillage is a system in which 15- to 20-cm high permanent ridges are formed
by tillage during the second cultivation or after harvest in preparation for the
following year’s crop.
The ridges are maintained and annually re-formed for growing crops. Crops are
planted on the ridge tops, a practice known as ridge planting.
This system is designed to reduce costs of tillage, improve crop yields, and reduce
losses of surface runoff and soil. Ridge tillage can reduce soil erosion by as much
as 50% as compared to conventional tillage (GAYNOR AND FINDLAY 1995).

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 Organic farming is an agricultural system where no synthetic fertilizers or pesticides are
used to produce food and fiber in contrast to chemically-based conventional farming
systems.
It is also called biological or biodynamical agriculture because it improves soil biology,
enhances soil’s natural fertility, and promotes plant biodiversity.
It is a system that comprises a host of environmentally friendly agricultural practices to
sustain crop production.
Organic fertilization to add nutrients and mechanical and biological practices to control
pests are two key exclusive components of organic farming (REGANOLD ET AL. 1987).

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No. Agro-Ecological Region Dominant Land Type Low Water Consuming Cropping Pattern Total Water Use (Mm)
1 Old Himalayan Piedmont Plain
Highland
Medium Highland
Wheat-T. Aus-Fallow
Wheat-T. Aus-T. Aman
1,090
1,390
2 Active Tista Floodplain Medium Highland Wheat-T. Aus-T. Aman 1,390
3 Tista Meander Floodplain
Highland
Medium Highland
Wheat-T. Aus-Fallow
1,090
1,390
4 Karatoya-Bangali Floodplain Medium Highland Wheat-B. Aus-T. Aman 740
5 Lower Atrai Basin Lowland Boro-Fallow-Fallow 1,200
6 Lower Purnabhaba Floodplain Lowland Boro-Fallow-Fallow 1,200
7
Active Brahmaputra-Jamuna
Floodplain
Medium Lowland Boro-Fallow-Fallow 1,200
8
Young Brahmaputra and Jamuna
Floodplain
Medium Highland
Potato-T. Aus-Fallow
Blackgram/Boro-T. Aus-Fallow
1,280
9 Old Brahmapura Floodplain Medium Highland Boro-Fallow-T. Aman 1,500
10 Active Ganges Floodplain Medium Highland Blackgram/Wheat-B. Aus-Fallow 350
11 High Ganges River Floodplain
Highland
Medium Highland
Wheat-T. Aus-Fallow
1,090
1,290
12 Low Ganges River Floodplain Medium Highland
Pulses(Chickpea/Grasspea)-B. Aus-T.
Aman
1,060
13 Ganges Tidal Floodplain Medium Highland
Onion/Water melon/Mungbean/Cow
pea/Chilli-Fallow-T. Aman
400-600
14 Gopalgonj-Khulna Bils Medium Lowland Boro-Fallow-Fallow 1,200
15 Arial Bil Lowland Boro-Fallow-Fallow 1,200
16 Middle Meghna River Floodplain Medium Lowland Boro(Local)-Fallow-Fallow 1,000
17 Lower Meghna River Floodplain
Medium Highland
Medium Lowland
Boro-T. Aus-T. Aman
Boro-Fallow-T. Aman
2,250
1,500
18
Young Meghna Estuarine
Floodplain
Medium Highland Boro-Fallow-T. Aman (LIV) 1,200
19 Old Meghna Estuarine Floodplain Medium Lowland Boro-Fallow-T. Aman 1,500
20
Eastern Surma-Kushiyara
Floodplain
Lowland Boro-T. Aus (LIV)-T. Aman 2,200
21 Sylhet Basin Medium Lowland Boro-Fallow-Fallow 1,200
22
Northern and Eastern Piedmont
Plain
- - -
23 Chittagong Coastal Plain Medium Highland Fallow-T. Aus-T. Aman 1,050
24 St. Martin Coral Island - - -
25 Level Barind Tract Medium Highland Boro-Fallow-T. Aman 1,500
26 High Barind Tract Highland Boro-Fallow-T. Aman 1,500
27 Northern-Eastern Barind Tract Medium Highland Boro-Fallow-T. Aman 1,500
28 Madhupur Tract Medium Highland Boro-Fallow-T. Aman 1,500
29 Northern and Eastern Hills Highland Vegetables-T. Aus-T. Aman 1,350
30 Akhaura Terrace - - -
Low water consuming cropping patterns for different agro-ecological regions of Bangladesh (Iqubal et. el. 2008)

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Increase in soil moisture storage capacity with
increase in soil organic carbon in 10 years tillage and
crop rotation study (Al-Kaisi et al., 2014)

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Farm Level Adaptation Options for Drought Management
 Adoption of varieties and species of crops with increased resistance to heat stress,
shock and drought.
 Probable change from boro to wheat/maize or other less water requiring crop
cultivation to reduce the demand of water during cultivation period.
 In case of seasonal shift of monsoon, consequent shift in planting date.
 Modification of crop calendars e.g. timing or location of cropping activities
according to water stress (with due consideration of livelihood adaptation)
 Mulching
 Top soil tillage (to avoid crack of topsoil)

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 Maintain data base at farm level by collecting yield data for different cultivars at
different region considering weather and soil sensitivity.
 Developing climate resilient cropping patterns suited to different regions In case of
seasonal shift of monsoon, consequent shift in planting date.
 Field level trials of the climate resilient cropping patterns and associated water
management systems.

Keeping Grower Shadow in the Field
Know the soil moisture condition using finger
feel method (dig-look-judge-respond):
• Dig- to see the soil below the field surface ( a
soil auger works well)
• Look- what is seen when looking at the soil?
• Judge- is the soil moisture sufficient?
• Respond- make appropriate changes to the
irrigation schedule
2/20/2019 SRDI 31

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Know your Conditions
 Know the soil: How many mm of water can be stored in the soil? Does the soil had a
hardpan layer that restricts root growth?
 Know the crop: what is the crop rooting depth? What is the drought tolerance of the
crop? Does the crop have any critical moisture requirement times?
Know the water supply: storage, surface or groundwater?
Know the irrigation system: is your irrigation system operating efficiently?
 Know the cropping systems: consider a combination of annuals and perennials that
will reduce water demand, and reduce risk of major crop loss.
Fertilizer use and Weed control
 Plan fertilizer program based on expected yields under drought condition
 Weed control is even more important as weeds often use moisture before crop
requirements are met

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Available soil moisture
remaining
Feel or appearance of soil
Light texture Medium texture Heavy texture
0 to 25 percent Dry, loose, flows through
fingers.
Powdery dry, sometimes
slightly crusted but easily
broken down into
powdery condition.
Hard, baked, cracked,
some times has loose
crumbs on surface.
25 to 50 percent Appears to be dry, will
not form a ball.* from
pressure.
Somewhat crumbly but
holds together
Somewhat pliable, will
ball under pressure.*
50 to 75 percent Tends to ball under
pressure, but seldom
holds together. slick
slightly with pressure.
Forms a ball somewhat
plastic, will sometimes
Forms a ball, ribbons out
between thumb and
forefinger.
75 percent to field
capacity
Forms weak ball, breaks Forms a ball, is very
pliable,
Easily ribbons out
between
easily, will not slick. in
clay.
slicks readily if relatively
high
fingers, has slick feeling.
At field capacity (100
percent)
Upon squeezing, no free
water appears on soil,
but wet outline of ball is
left on hand.
left on hand.
left on hand.
Saturated Water appears on ball
and hand.
Water appears on ball
and hand.
Water appears on ball
and hand.

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Soil moisture conservation for drought management in bd

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