Alternate wetting and drying (AWD) is an irrigation practice for rice that saves water and reduces greenhouse gas emissions while maintaining yields. It involves periodically drying and re-flooding rice fields. In Bangladesh, boro rice is fully irrigated while aman rice is partly irrigated. Research shows AWD can save 15-30% of the estimated 3,000-5,000 liters of water needed to produce one kilogram of rice, without lowering yields. The practice involves irrigating until the water table is 20cm below ground, then allowing the field to partially dry before re-flooding. This technique is being validated in Bangladesh and could help conserve irrigation water and reduce environmental impacts.

1. 1.What is irrigation? Briefly explain the different types of irrigation are generally
followed in Bangladesh.
Ans: Irrigation:The artificial application of water to plant for its proper growth and
development is called irrigation. Its is supplied to supplement the water available
from rainfall, residual soil moisture and ground water contribution.
Methods of irrigation: There are a number of irrigation methods according to the
soil,physiography,sources and amount of water, types of crop ,labour cost capital
etc.The important methods of irrigation are shown in the Flow chart-

2. A. Surface irrigation: This methods of irrigation is widely used in Bangladesh. Surface
irrigation includes flood irrigation check basin irrigation, border stripe irrigation, furrow
irrigation and basin irrigation.
1.Flood Irrigation
In this methods, water is allowed from the irrigation channel into the entire field and it
slowly spread all the land. This methods is practiced where water is in abundance and
inexpensive. It is followed in smooth and even land
Advantage of flood irrigation:
Less time consuming
Cost of irrigation is minimum
There is no extra cost except land leveling
Labour requirement is minimum
Waste of land is minimum
Limitation of flood irrigation:
It is very inefficient methods
Only 20-25% of the supplied water is used by plant and rest amount is lost by different
process
It is not suitable in unleveled land
There of no control of water
There may be water logging in lower end of field
Possibility of soil erosion is high
Suitable crops: Rice,jute,Mustard,Pulses,Linseed etc

3. 2.Check Basin Irrigation: In this methods the field is divided into a number of plots and
leveled .It is also known as bed methods .water from the main channel is supplied to
the field channels one after another .Each field channel supplies water to adjacent
plots.
Advantages of Check Basin Irrigation:
Water can be supplied uniformly
Soil erosion is lower
Water loss is minimum
Water can be applied efficiently
Limitation of Check Basin Irrigation:
It is more costly than flood irrigation
More labour is required for field layout and irrigation
More land is wasted due to channel preparation
Movement of farm animals and implements is difficult
Intercultivation is difficult due to obstruction by bunds
Suitable crops: Wheet,T.Aman,Mustard
3.Border strip irrigation
Border strip irrigation methods involves irrigating a field by dividing it into long strip
separated by low parallel borders (bounds).the size of the strip ranges from 30-300 m in
length and 3-15 m in breadth. This methods for suitable for medium to heavy textured
souls but not for sandy soils.

4. Advantage of Border strip irrigation
Border can be used for growing crops
Efficient of water application is high
Construction of borders is easy and does not involve much cost
Labour requirement for irrigation is low than check basin irrigation
Limitation of Border strip irrigation:
Initial cost for land preparation and land grading is high
Excess water may accumulate at the tail end of the strip
It can be used in light textured soils
Suitable crops :Wheat, Oat, jowar,Mungbeen,upland rice etc
4.Furrow Irrigation: In furrow irrigation water is applied in small stream between the
rows of crop grown on ridges or furrow sides. This methods of irrigation is generally
used to irrigated row crops and vegetables.
Advantage of furrow irrigation:
Great saving of water over other flooding methods
Irrigation water can be used efficiently
Flow of water can be controlled
Furrow acts as drainage channel
Low cost for crops which are cultivated in ridge

5. Limitation of furrow irrigation:
It is not suitable for the crops which do not require ridge and furrow
More cost for furrow making
It is unsuitable for light irrigation
Excessive water flow in the furrow can break the ridge
Weeds may grow I furrows
Suitable Crops: potato,groundnut,sugarcane,coton,cabbage etc
5.Basin irrigation:
Basin methods is almost similar to check basin method where only the basins around the
plant are irrigated. Basins are generally round in shape and occasionally square or
rectangular. Basins are connected by an irrigation channel. This method is suitable for
fruit crops.
Advantage of Basin irrigation
A considerable amount of water is saved
Water application efficiency is very high
Entire area does not require leveling except basin area
Does not hamper the fruit crops
No land is wasted

6. Limitation of Basin irrigation
This methods is only suitable for trees and shrubs
Primary cost is high
Channels and basins restrict the movement of animals and farm machineries
Suitable crops :Mango,apple,oraqnge berry, olive etc.
2.Define Irrigation and Drainage. What are the importance of irrigation and drainage in
relation to crop production in Bangladesh.
Ans: Drainage: Advantage water is essential for crop plant but the excess water is harmful
for crops. So as the irrigation is needed to meet the water requirement ,the excess water
should also drain out immediately, the artificial removal of excess water from crop field is
called drainage.
Importance of irrigation to crop production:
To ensure the proper growth and development of plant by supplying adequate water.
To make the plant nutrient soluble so that they can be easily uptaken by plant
To accelerate the decomposition of organic substances
To control soil temperature
To soften tillage pans and clods
To control some destructives pests and diseases
To avoid short duration drought

7. Water for food production:
For vegetative growth and development, plants require, within reach of their roots, water
of adequate quality, in appropriate quantity and at the right time. Most of the water a plant
absorbs performs the function of raising dissolved nutrients from the soil to the aerial
organs, from where it is released to the atmosphere by transpiration: agricultural water use
is intrinsically consumptive. Crops have specific water requirements, and these vary
depending on local climatic conditions. Whereas an indicative figure for producing one
kilogram of wheat is about 1000 litres of water that is returned to the atmosphere, paddy
rice may require twice this amount.
Importance of drainage to crop production:
Drainage improves the soil structure and increases productivity
It facilitates proper growth of crop plants
It facilitates early ploughing and planting
It facilitates proper root growth
It increase soil erosion
It increase soil temperature
It prevent the soil from water logging

8. 5 importance of drainage:
1. Drainage ensures proper soil aeration is maintained in the field. Excess water (after a
rainfall for example), can cause standing water (or saturated soil) which will choke our
crops.
2. Drainage reduces soil and nutrient loss via runoff where water flows on the soil
surface, causing erosion.
5. Drainage can be such so that water and soil sediments are channelled and collected in
sediment ponds/basins/ditches, where collected water can be saved for future use
during periods of dry weather or the collected soil sediments returned back to the farm.

9. 4. What do you mean by Hydrology cycle? Briefly explain the hydrology cycle of water.
Ans: Hydrology treats the waters of the Earth, their occurrence, circulation, and
distribution, their chemical and physical properties,. However, hydrology for irrigation
includes those segments of the field pertinent to planning, designing, and operation of
irrigation projects for the control and use of water. The concepts of the hydrologic cycle
is useful to understand occurrence and distribution of precipitation.”

10. At beginning water evaporates from the oceans.
The resulting water vapor is transported by moving air masses.
Under the proper conditions, the water vapor is condensed to form clouds, which in turn
may result in precipitation
A portion of water finds its way over and through the surface soil to stream channels
Other water penetrates further into the ground to become part of the ground water
Consequently under the influence of gravity, both surface stream flow and ground water
move towards lower elevations and may eventually discharge into the ocean.
The greater part is retained in the soil near where it falls and is ultimately returned to
ocean
 A significant part is intercepted by vegetation
There are four phases of hydrologic cycle
 Precipitation (rain, hail, sleet or snow)
 Evaporation & transpiration
 Surface stream flow and
 Ground water
Sources of precipitation: The Hydrologic cycle- (rain, hail, sleet or snow)
Sources of irrigation water:
Surface – River ,dam, lake, ponds
Underground- Wells, STW, DTW, Canats, -

11. 5. Define Drainage. What are the objective of drainage? How drainage improves the soil
productivity for better crop production?
Ans: Drainage: Advantage water is essential for crop plant but the excess water is harmful
for crops. So as the irrigation is needed to meet the water requirement ,the excess water
should also drain out immediately, the artificial removal of excess water from crop field is
called drainage.
Objective of drainage:
Drainage improves the soil structure and increases productivity
It facilitates proper growth of crop plants
It facilitates early ploughing and planting
It facilitates proper root growth
It increase soil erosion
It increase soil temperature
It prevent the soil from water logging
Drainage improves the productivity of soils in the following way:
Removes excess water
Improves soil structure
Increase the depth of root zone
Improves the air circulation in the soil
Improves the organic matter decay and nitrification
Reduce erosion; higher infiltration reduce soil erosion

12. Removes soluble salts from the root zone or soil profile
Increase soil temperature
Decreases CO2 accumulation and increase oxygen level
Increase the availability of nutrients to plants.
6. What do you mean by soil structure and soil texture? What are the texture
classification of soil?
Ans: Soil structure
Soil structure is the shape that the soil takes on based on its physical and chemical
properties. Each individual unit of soil in the overall structure is called a ped. Soil
structure is most easily determined by taking a sample of soil that has not been
disturbed and looking closely at its shape. The shape of the soil will fall into one of the
following categories: granular, crumb, blocky, platy, prismatic, columnar, single-grained,
or massive.
Soil texture:Soil texture is a soil property used to describe the relative proportion of
different grain sizes of mineral particles in a soil. Particles are grouped according to their
size into what are called soil separates. These separates are typically named clay, silt, and
sand. Soil texture classification is based on the fractions of soil separates present in a
soil. The soil texture triangle is a diagram often used to figure out soil textures.

13. Soil texture classification
Soil textures are classified by the fractions of each soil separate (sand, silt, and clay)
present in a soil.
Classifications are typically named for the primary constituent particle size or a
combination of the most abundant particles sizes, e.g. "sandy clay" or "silty clay."
A fourth term, loam, is used to describe a roughly equal concentration of sand, silt, and
clay, and lends to the naming of even more classifications, e.g. "clay loam" or "silt loam."
In the United States, twelve soil texture classifications are defined by the USDA:
Determining the soil textures is often aided with the use of a soil texture triangle.

14. Clay, Silt, Sand ,Loam ,Silty clay ,Sandy clay ,Clay loam ,Silt loam ,Sandy Loam ,Loamy
sand,Silty clay loam ,Sandy clay loam
3. AWD: Alternate wetting and drying (AWD) is a management practice in irrigated
lowland rice that saves water and reduces greenhouse gas (GHG) emissions while
maintaining yields. The practice of AWD is defined by the periodic drying and re-flooding
of the rice field.
Explain: Boro rice in Bangladesh is fully irrigated and the aman rice is partly irrigated. An
estimated 3,000 to 5,000 litres of water is required to produce one kilogram of rice.
Recent research at IRRI has proven that using Alternate Wetting and Drying (AWD), about
15-30%, if not more, could be saved without reduction in yield. Starting from about 15
days after transplanting, irrigate until the water table goes 20 cm below the ground level.
Dig a 20 cm deep hole in the rice field and install a perforated plastic pipe to monitor the
level of the water table after each irrigation. Continue the practice until flowering starts.
Keep 2-4 cm standing water from flowering to dough stage. This is now being valided in
Bangladesh by BRRI, BADC, BMDA and othe partners. The savings of irrigation water will
have impact on environment because of reduced withdrawal of ground water, reduction in
burning diesel. This may also reduce arsenic contamination in rice grain and straw.