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-

Irrigation

Methods

Sub-Surfa

ce Irrigation

Sprinkler or

Overhead Irrigation

Drip or

Trickle

Irrigation

Surface

Irrigation

Basin Irrigation

Furrow

Irrigation

Border

strip Irrigation

Check

Basin Irrigation

Flood Irrigation

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

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.

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

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

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

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

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.

3.What is AWD? Briefly explain AWD as a water saving technology in Bangladesh rice production.

Ans: Rice is the staple food of 164 million Bangladeshis, accounting for 77% of the total cropped area and two-thirds of the value-added of crop production, with an agrarian structure dominated by marginal and small farm holdings. During the past decades, rice production in Bangladesh experienced an impressive intensification. In the north and north-western divisions of Rajshahi and Rangpur, the increase in rice production is largely attributed to an unprecedented expansion of dry season cultivation, triggered by the liberalization policy for small-scale irrigation equipment. The change to dry season rice, constituting about 60% of national rice production, was largely due to groundwater irrigation by shallow tube wells (STW) and deep tube wells (DTW). This practice led to the massive extraction of groundwater, an overexploitation of groundwater, locally manifested by declining groundwater tables in Rajshahi. Correspondingly to the expansion of irrigation, demand for energy increased, as electricity or fuel are needed to lift groundwater to the surface. This also touches on the chronically deficient energy situation of Bangladesh.

To address problems of water scarcity, researchers had been looking for ways to decrease water consumption of the rice crop. Alternate Wetting and Drying (AWD) is a technology developed by the International Rice Research Institute (IRRI). The technology is based on the knowledge that rice tolerates up to 30% reduced water supply during the main growing period compared to conventional irrigation. To determine the timing of irrigation, the water level in the soil is monitored by a perforated plastic tube, which is inserted into the rice field. AWD requires irrigation when the water level drops to 15 cm below the soil surface. Under technical assistance from IRRI (Dr. Hamid Miah), a number of NGOs like RDRS implemented AWD technology in farmers’ field during boro rice season. This technology was piloted in 109 farmers’ field in 2009-2010, where farmers cultivated boro rice with reduced number of irrigations (11 irrigations instead of 17) and received almost the same yield as in the case without AWD system. This reduced irrigation saved 35% irrigation cost. However, it was observedthat weed infestation was occurred in AWD plots, which resulted in increased hired labourer cost for weeding.Although the number of irrigation was reduced significantly (30%) and the corresponding irrigation cost was reduced by 35%, the benefits went tothe pump owners due to a fixed rate arrangement system between pump owner and farmers settled at the beginning of the season. It means the user has to pay the full payment as agreed despite reduced number of irrigation provided.

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.”

• 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, -

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

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.

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.

Clay, Silt, Sand ,Loam ,Silty clay ,Sandy clay ,Clay loam ,Silt loam ,Sandy Loam ,Loamy sand,Silty clay loam ,Sandy clay loam