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-

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 IrrigationIn 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 consumingCost of irrigation is minimumThere is no extra cost except land levelingLabour requirement is minimumWaste of land is minimumLimitation 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 processIt is not suitable in unleveled landThere of no control of waterThere may be water logging in lower end of fieldPossibility of soil erosion is highSuitable 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 minimumWater can be applied efficientlyLimitation of Check Basin Irrigation:It is more costly than flood irrigationMore labour is required for field layout and irrigationMore land is wasted due to channel preparationMovement of farm animals and implements is difficult Intercultivation is difficult due to obstruction by bunds Suitable crops: Wheet,T.Aman,Mustard3.Border strip irrigationBorder 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 irrigationBorder can be used for growing cropsEfficient of water application is highConstruction of borders is easy and does not involve much costLabour requirement for irrigation is low than check basin irrigationLimitation of Border strip irrigation:Initial cost for land preparation and land grading is highExcess water may accumulate at the tail end of the stripIt can be used in light textured soilsSuitable crops :Wheat, Oat, jowar,Mungbeen,upland rice etc4.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 methodsIrrigation water can be used efficientlyFlow of water can be controlled Furrow acts as drainage channelLow 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 furrowMore cost for furrow makingIt is unsuitable for light irrigationExcessive water flow in the furrow can break the ridgeWeeds may grow I furrowsSuitable 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 irrigationA considerable amount of water is savedWater application efficiency is very highEntire area does not require leveling except basin areaDoes not hamper the fruit cropsNo land is wasted

Limitation of Basin irrigationThis methods is only suitable for trees and shrubsPrimary cost is highChannels 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 substancesTo control soil temperatureTo 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 productivityIt facilitates proper growth of crop plantsIt facilitates early ploughing and plantingIt facilitates proper root growth It increase soil erosionIt 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.

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 precipitationA portion of water finds its way over and through the surface soil to stream channelsOther 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 waterSources 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 productivityIt facilitates proper growth of crop plantsIt facilitates early ploughing and plantingIt facilitates proper root growth It increase soil erosionIt increase soil temperature It prevent the soil from water logging

Drainage improves the productivity of soils in the following way: Removes excess waterImproves soil structureIncrease the depth of root zoneImproves the air circulation in the soilImproves the organic matter decay and nitrificationReduce erosion; higher infiltration reduce soil erosion

Removes soluble salts from the root zone or soil profileIncrease soil temperatureDecreases CO2 accumulation and increase oxygen levelIncrease 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 structureSoil 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 classificationSoil 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

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.