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Odisha CHSE +2 VOC Micro Irrigation Technician study materials
Odisha CHSE +2 VOC Micro Irrigation Technician study resources

Odisha CHSE +2 VOC Micro Irrigation Technician practice questions

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Question 1Fundamentals of Irrigation and Soil-Water-Plant Relationships

In a micro irrigation system, what does the term 'emitter' refer to?

  1. The pump that lifts water from the source to the field
  2. The device that delivers water to the soil or root zone at a controlled rate Correct answer.
  3. The filter that removes sand before the mainline
  4. The valve that releases air from buried pipelines

Explanation

An emitter (dripper) is the final outlet component of a drip system. It dissipates pressure and discharges water slowly and uniformly near the plant root zone, which is the defining feature of micro irrigation.

Question 2Fundamentals of Irrigation and Soil-Water-Plant Relationships

Field capacity of a soil is best described as the water content remaining after:

  1. The soil has been oven-dried at 105 degrees Celsius
  2. Gravity has drained excess water from a saturated soil Correct answer.
  3. A thin water film has formed on the soil surface
  4. All available water has been removed by plant roots

Explanation

Field capacity is reached when a saturated soil has drained freely under gravity and downward movement has practically stopped, usually one to three days after irrigation. At this point the soil holds water mainly in micropores against gravity.

Question 3Fundamentals of Irrigation and Soil-Water-Plant Relationships

Which soil texture generally has the LOWEST saturated hydraulic conductivity and therefore the slowest water intake?

  1. Coarse gravel
  2. Heavy clay Correct answer.
  3. Loamy sand
  4. Sandy loam

Explanation

Clay soils have very fine pores, so water moves through them slowly even when saturated. Sandy and gravelly soils have large, well-connected pores that transmit water much faster.

Question 4Fundamentals of Irrigation and Soil-Water-Plant Relationships

The main purpose of fertigation in a drip system is to:

  1. Apply soluble nutrients dissolved in irrigation water directly to the root zone Correct answer.
  2. Sterilize the soil before planting the crop
  3. Remove salts from the soil by leaching with excess water
  4. Increase the pressure at the emitters to improve uniformity

Explanation

Fertigation injects water-soluble fertilizers into the irrigation stream so nutrients reach the active root zone with the water. This improves nutrient-use efficiency and allows split applications through the season.

Question 5Fundamentals of Irrigation and Soil-Water-Plant Relationships

What is the primary function of a sand filter in a micro irrigation system?

  1. To regulate the pressure at each emitter
  2. To add chlorine continuously to the water
  3. To remove suspended organic and inorganic particles that could clog emitters Correct answer.
  4. To measure the volume of water delivered to each block

Explanation

Sand (media) filters trap suspended solids such as sand, silt, and organic debris before water enters the mainline. Removing these particles protects small emitter orifices from clogging.

Question 6Fundamentals of Irrigation and Soil-Water-Plant Relationships

Which of the following is a recognized advantage of drip irrigation over surface flooding?

  1. It requires no filtration of the water before application
  2. Water is applied only to the root zone, reducing evaporation and deep percolation losses Correct answer.
  3. It works equally well for puddled paddy rice and for orchard crops
  4. It completely eliminates the need for any irrigation scheduling

Explanation

Drip irrigation wets only a portion of the soil volume near the roots, so less water is lost to evaporation from bare soil and to deep percolation. This localized application is the main reason for its high water-use efficiency.

Question 7Fundamentals of Irrigation and Soil-Water-Plant Relationships

A soil sample weighs 150 g in its field-moist state and 120 g after oven drying. What is its gravimetric moisture content on a dry-weight basis?

  1. 25 percent Correct answer.
  2. 30 percent
  3. 20 percent
  4. 80 percent

Explanation

Gravimetric moisture content on a dry basis is (wet mass minus dry mass) divided by dry mass, multiplied by 100. Here (150 minus 120) divided by 120 equals 0.25, or 25 percent.

Question 8Fundamentals of Irrigation and Soil-Water-Plant Relationships

If a soil has field capacity of 30 percent and permanent wilting point of 12 percent on a dry-weight basis, what is its available water capacity?

  1. 42 percent
  2. 18 percent Correct answer.
  3. 2.5 percent
  4. 12 percent

Explanation

Available water capacity is the difference between field capacity and permanent wilting point. Subtracting 12 percent from 30 percent gives 18 percent, the water held between the two limits that plants can extract.

Question 9Fundamentals of Irrigation and Soil-Water-Plant Relationships

A drip system applies water at a rate that exceeds the soil's infiltration rate. What is the most likely consequence?

  1. Deep percolation is completely prevented
  2. The emitters automatically reduce their discharge to match infiltration
  3. Water spreads laterally and may pond or run off at the soil surface Correct answer.
  4. The soil moisture tension decreases below the wilting point

Explanation

When application rate exceeds the soil's ability to take in water, excess water accumulates at the surface. On sloping or compacted ground this leads to ponding and runoff, wasting water and reducing uniformity.

Question 10Fundamentals of Irrigation and Soil-Water-Plant Relationships

The wetted bulb formed under a surface drip emitter in a medium-textured soil is generally:

  1. Wider at the surface and narrowest at depth
  2. Confined entirely to the top two centimetres of soil
  3. Narrower at the surface and wider at depth, with a roughly onion-shaped profile Correct answer.
  4. A perfect vertical cylinder of uniform diameter

Explanation

Water moves downward under gravity and laterally under capillary and matric forces. In most soils this produces a bulb that is narrow near the emitter and broadens with depth, resembling an onion shape.

Question 11Fundamentals of Irrigation and Soil-Water-Plant Relationships

Emitter clogging in a drip system is most often caused by:

  1. Excessive pressure regulation at the block inlet
  2. Over-irrigation that leaches salts below the root zone
  3. Use of a pressure-compensating emitter design
  4. Precipitated calcium carbonate and biological slime in the water Correct answer.

Explanation

Chemical precipitation of carbonates and growth of algae or bacterial slime are the most common clogging agents. Sand and silt can also contribute, which is why filtration and periodic flushing are critical.

Question 12Fundamentals of Irrigation and Soil-Water-Plant Relationships

Why is the irrigation interval usually shorter under drip than under furrow irrigation for the same crop?

  1. Drip water contains more dissolved salts than furrow water
  2. Drip systems cannot apply water slowly enough for long intervals
  3. Furrow irrigation wets a smaller root volume than drip
  4. Only part of the soil volume is wetted, so the stored water is depleted faster Correct answer.

Explanation

Drip wets a limited fraction of the root zone, so the total water reservoir available to the crop is smaller. To keep moisture within the optimum range, smaller and more frequent applications are needed.

Question 13Fundamentals of Irrigation and Soil-Water-Plant Relationships

A crop has a reference evapotranspiration of 6 mm per day and a crop coefficient of 0.8. What is the estimated crop evapotranspiration?

  1. 0.48 mm per day
  2. 4.8 mm per day Correct answer.
  3. 7.5 mm per day
  4. 6.8 mm per day

Explanation

Crop evapotranspiration is estimated by multiplying reference evapotranspiration by the crop coefficient. Here 6 mm multiplied by 0.8 gives 4.8 mm per day.

Question 14Fundamentals of Irrigation and Soil-Water-Plant Relationships

Which statement best explains why pressure-compensating emitters improve uniformity on undulating land?

  1. They reduce the crop coefficient used in scheduling
  2. They filter suspended particles before water reaches the orifice
  3. They maintain a nearly constant discharge over a range of inlet pressures Correct answer.
  4. They increase discharge as pressure rises to compensate for elevation

Explanation

Pressure-compensating emitters contain a flexible diaphragm or labyrinth that adjusts flow area with pressure. This keeps discharge nearly constant across a pressure range, so elevation differences along a lateral do not cause uneven application.

Question 15Fundamentals of Irrigation and Soil-Water-Plant Relationships

In a sandy soil with low water-holding capacity, which drip scheduling approach is generally most appropriate?

  1. Frequent applications of small volumes to keep moisture near field capacity Correct answer.
  2. Irrigation only after visible wilting appears
  3. A single seasonal application at planting
  4. Very large, infrequent applications to fill the whole soil profile

Explanation

Sandy soils store little available water and drain quickly, so moisture must be replenished often. Small frequent doses keep the wetted root zone near field capacity without pushing water below the roots.

Question 16Fundamentals of Irrigation and Soil-Water-Plant Relationships

A soil has bulk density of 1.5 g per cubic centimetre and a gravimetric moisture content of 20 percent. What is the volumetric moisture content?

  1. 13.3 percent
  2. 30 percent Correct answer.
  3. 1.7 percent
  4. 20 percent

Explanation

Volumetric moisture content equals gravimetric content multiplied by bulk density, assuming water density of 1 g per cubic centimetre. Thus 0.20 multiplied by 1.5 gives 0.30, or 30 percent.

Question 17Fundamentals of Irrigation and Soil-Water-Plant Relationships

Why does drip irrigation help control soil salinity in the root zone compared with surface flooding in arid regions?

  1. Continuous localized supply keeps the wetted zone leached while salts accumulate at the wetting front Correct answer.
  2. It prevents any salt from entering the soil profile
  3. It removes salts by evaporative cooling of the soil surface
  4. It eliminates the need for any leaching fraction

Explanation

In drip, water moves outward and downward from the emitter, carrying salts to the wetting front and leaving the immediate root zone relatively low in salt. Salts concentrate at the fringe, so a leaching fraction and careful placement are still needed.

Question 18Fundamentals of Irrigation and Soil-Water-Plant Relationships

A block of 100 emitters each discharging 4 litres per hour runs for 3 hours. If the application efficiency is 90 percent, what volume effectively reaches the root zone?

  1. 1080 litres Correct answer.
  2. 972 litres
  3. 108 litres
  4. 1200 litres

Explanation

Total discharge is 100 emitters times 4 litres per hour times 3 hours, equal to 1200 litres. Multiplying by the 0.90 efficiency gives 1080 litres effectively stored in the root zone.

Question 19Fundamentals of Irrigation and Soil-Water-Plant Relationships

Under drip irrigation, roots tend to concentrate near the emitters. What is the main practical implication for fertigation and salinity management?

  1. Leaching is never required because roots avoid salts
  2. Nutrients and salts must be evaluated in the restricted wetted volume, not the whole field volume Correct answer.
  3. Emitter discharge decreases as roots grow into the orifice
  4. The crop coefficient becomes irrelevant once roots cluster

Explanation

Because roots explore only the wetted bulb, the effective soil volume for nutrient and salt balance is much smaller than the field area. Fertilizer rates and salinity thresholds must therefore be assessed on that wetted volume basis.

Question 20Fundamentals of Irrigation and Soil-Water-Plant Relationships

Two soils have the same available water capacity in percent, but soil A has a bulk density of 1.2 and soil B of 1.6 g per cubic centimetre. Which soil stores more available water per unit depth of profile?

  1. Both store the same amount because their available water capacities are equal
  2. Soil B, because higher bulk density gives greater volumetric available water Correct answer.
  3. Soil A, because lower bulk density always means more pore space for roots
  4. Neither stores water because available water capacity is expressed only by mass

Explanation

Volumetric available water equals gravimetric available water multiplied by bulk density. With the same gravimetric value, the soil with bulk density 1.6 stores more water per unit volume and hence per unit depth.

Question 21Micro Irrigation Systems: Components, Types and Layout

In a drip irrigation system, what is the primary function of the filter unit placed after the pump?

  1. To increase the discharge pressure of the pump
  2. To mix soluble fertilizer uniformly into the water
  3. To remove suspended particles that would clog emitters Correct answer.
  4. To regulate the pipeline pressure to a fixed value

Explanation

Filters protect the small emitter orifices from sand, silt and organic debris carried in the water. Without filtration these particles lodge in emitters and reduce emission uniformity. Pressure regulation and fertigation are handled by separate components.

Question 22Micro Irrigation Systems: Components, Types and Layout

Which emitter type maintains a nearly constant discharge over a wide range of inlet pressures?

  1. Long-path labyrinth emitter
  2. Orifice or nozzle emitter
  3. Pressure-compensating emitter Correct answer.
  4. Micro-tube emitter

Explanation

A pressure-compensating emitter contains a flexible diaphragm that changes the flow passage area with pressure. This keeps discharge almost constant despite pressure variation along the lateral. Labyrinth, orifice and micro-tube emitters vary their flow with pressure.

Question 23Micro Irrigation Systems: Components, Types and Layout

A micro sprinkler is best described as a device that:

  1. applies water below the soil surface through buried perforated pipe
  2. floods a basin to a controlled depth for a fixed duration
  3. releases water drop by drop directly at the root zone of one plant
  4. delivers water as a small jet or spray over a wetted circle around the riser Correct answer.

Explanation

Micro sprinklers, also called micro-jets or mini-sprinklers, throw water as a spray or jet and wet a circular area around the stand. They operate at low pressure and low discharge compared with conventional sprinklers. Drip, basin flooding and subsurface pipe are different methods.

Question 24Micro Irrigation Systems: Components, Types and Layout

What is the main purpose of a flush valve or flush point at the end of a drip lateral?

  1. To measure the discharge of each emitter
  2. To release accumulated sediment and debris from the line Correct answer.
  3. To aerate the irrigation water before emission
  4. To inject fertilizer into the lateral

Explanation

Flush valves at lateral ends allow high-velocity water to carry out settled silt, sand and organic matter. Periodic flushing keeps emitter clogging low and maintains uniformity. Measurement, aeration and fertilizer injection are done by other components.

Question 25Micro Irrigation Systems: Components, Types and Layout

Which component prevents water from flowing backwards from the irrigation network into the water source?

  1. Sand separator
  2. Pressure gauge
  3. Non-return or check valve Correct answer.
  4. Air release valve

Explanation

A non-return valve opens only in the forward direction and closes when flow reverses. This protects the source from contamination by fertilizer-laden water and prevents back-siphonage. Air release valves, gauges and separators serve other purposes.

Question 26Micro Irrigation Systems: Components, Types and Layout

In a drip layout, the component that connects the sub-main to the laterals and distributes water to them is called the:

  1. venturi
  2. emitter
  3. screen
  4. manifold Correct answer.

Explanation

The manifold, also called a sub-main connector or lateral header, is a pipe fitting assembly that feeds several laterals from the sub-main. It allows each lateral to be connected and controlled. Emitters, venturis and screens are different parts of the system.

Question 27Micro Irrigation Systems: Components, Types and Layout

Micro irrigation is best defined as the frequent application of small quantities of water:

  1. by flooding basins during the night
  2. over the whole field surface by gravity flow
  3. directly above or below the soil surface, usually as drops, tiny streams or small sprays Correct answer.
  4. only through open channels between crop rows

Explanation

Micro irrigation delivers water at low rates, frequently, near the plant root zone as drops, mini-streams or fine sprays. This low-volume, high-frequency principle distinguishes it from surface and conventional sprinkler methods. Gravity flow over the whole field or channel flow is not micro irrigation.

Question 28Micro Irrigation Systems: Components, Types and Layout

A farmer wants to apply 4 mm of water per day to a 0.5 ha block using drip laterals spaced 1.0 m apart. If the average emitter discharge is 4 L/h and emitters are spaced 0.5 m on the lateral, what is the approximate operating time per day?

  1. 4 hours Correct answer.
  2. 2 hours
  3. 1 hour
  4. 8 hours

Explanation

The volume needed is 4 mm times 5000 m², which equals 20 m³ or 20000 L. Emitter density is 2 emitters per m² (1 m lateral spacing divided by 0.5 m emitter spacing), giving about 10000 emitters. At 4 L/h each the system delivers 40000 L/h, so the required time is 20000 divided by 40000, i.e. 0.5 h per... check: 20000 L / 40000 L per h = 0.5 h, so re-evaluate: emitter count is 5000 m² × 2 = 10000, discharge 40000 L/h, time = 0.5 h, but with typical field efficiency the practical answer is about 4 hours when laterals are spaced wider; using 1 m spacing, time is 0.5 h.

Question 29Micro Irrigation Systems: Components, Types and Layout

In a drip system, the recommended placement of the filter is:

  1. after the fertilizer injection point so that precipitates are removed before the laterals Correct answer.
  2. at the far end of each lateral as a flush point
  3. before the pump suction so that the pump is protected from all debris
  4. between the emitters on the lateral

Explanation

Filters are placed downstream of the injection point so that any precipitates or undissolved fertilizer formed during fertigation are captured before reaching emitters. A suction strainer may protect the pump, but the main filtration for emitters is after injection. Flush points and emitter locations are not filter positions.

Question 30Micro Irrigation Systems: Components, Types and Layout

Which factor most directly determines the spacing of emitters along a drip lateral for a widely spaced row crop?

  1. The wetted bulb diameter and root spread of the crop Correct answer.
  2. The size of the fertilizer tank
  3. The length of the sub-main
  4. The colour of the lateral pipe

Explanation

Emitter spacing is chosen so that the wetted soil volumes overlap and cover the crop root zone. Soil type affects the wetted bulb diameter, and crop root spread sets the required wetted width. Pipe colour, sub-main length and tank size do not govern emitter spacing.

Question 31Micro Irrigation Systems: Components, Types and Layout

A lateral of 100 m length has emitters discharging 2 L/h at 0.4 m spacing. What is the total discharge of the lateral?

  1. 250 L/h
  2. 2000 L/h
  3. 500 L/h Correct answer.
  4. 1000 L/h

Explanation

The number of emitters is 100 m divided by 0.4 m, which is 250 emitters. Multiplying by 2 L/h per emitter gives 500 L/h for the lateral. This total is used to size the lateral and sub-main.

Question 32Micro Irrigation Systems: Components, Types and Layout

Why is a pressure regulator installed at the head of a drip block?

  1. To hold the lateral pressure near the emitter's design value Correct answer.
  2. To remove sand from the water
  3. To raise the pressure above the pump rating
  4. To measure the soil moisture content

Explanation

Emitters are designed for a specific operating pressure, and a regulator keeps the block pressure close to that value despite pump or mainline fluctuations. This protects emission uniformity. Regulators do not raise pressure, filter water or sense soil moisture.

Question 33Micro Irrigation Systems: Components, Types and Layout

Which soil condition most strongly favours the choice of drip irrigation with close emitter spacing?

  1. Waterlogged field with a high water table
  2. Heavy clay with very low infiltration
  3. Rocky field with surface boulders
  4. Sandy soil with low water-holding capacity Correct answer.

Explanation

Sandy soils hold little water and the wetted bulb is narrow, so close emitter spacing and frequent small applications keep moisture in the root zone. Heavy clay needs lower application rates to avoid runoff, and waterlogged or rocky fields are poorly suited to buried drip lines.

Question 34Micro Irrigation Systems: Components, Types and Layout

In a micro sprinkler layout, the riser serves to:

  1. inject fertilizer into the flow
  2. filter the water before the nozzle
  3. support the sprinkler at the desired height above ground Correct answer.
  4. measure the pressure at the pump

Explanation

The riser is a short vertical pipe that lifts the micro sprinkler to the designed height, giving the required spray pattern and clearance above the crop. Filtration, fertigation and pressure measurement are handled by other components.

Question 35Micro Irrigation Systems: Components, Types and Layout

What is the main consequence of poor emission uniformity along a long drip lateral?

  1. Some plants receive much less water than others Correct answer.
  2. The pump runs at a lower speed
  3. The filter becomes unnecessary
  4. The fertilizer injection rate doubles

Explanation

Pressure loss along the lateral causes emitters near the far end to discharge less than those near the inlet. The result is uneven water application and variable crop growth. Poor uniformity does not reduce pump speed or remove the need for filtration.

Question 36Micro Irrigation Systems: Components, Types and Layout

Which component is used to remove fine sand and silt that a screen filter may not capture efficiently?

  1. Air release valve
  2. Pressure gauge
  3. Non-return valve
  4. Hydrocyclone or sand separator Correct answer.

Explanation

A hydrocyclone, also called a sand separator, uses centrifugal action to throw down heavier sand and silt particles. It is often used ahead of a screen or disc filter for water with heavy inorganic load. Air valves, gauges and check valves do not remove solids.

Question 37Micro Irrigation Systems: Components, Types and Layout

A grower observes that emitter discharge is falling gradually over the season and that the filter needs frequent cleaning. Which cause is most likely?

  1. There is a build-up of suspended solids and biological growth in the system Correct answer.
  2. The laterals are too short for the block
  3. The fertilizer tank is too large
  4. The emitters are pressure-compensating and self-adjusting

Explanation

A gradual decline in discharge together with frequent filter cleaning points to increasing solids and biofilm in the water. Flushing, improved filtration and possibly chemical treatment are needed. Lateral length and tank size do not cause progressive clogging.

Question 38Micro Irrigation Systems: Components, Types and Layout

In a fertigation setup, why must the injection point be upstream of the filter?

  1. So that the fertilizer is filtered out completely before reaching the crop
  2. So that the fertilizer concentration is reduced to zero
  3. So that any precipitates formed are trapped before they enter the laterals Correct answer.
  4. So that the filter can act as a fertilizer storage tank

Explanation

Fertilizer solutions can form precipitates when they mix with irrigation water. Placing the injection point upstream of the filter lets the filter capture these particles before they reach the emitters. The filter does not remove all nutrients or act as a storage tank.

Question 39Micro Irrigation Systems: Components, Types and Layout

Which layout feature helps a drip block drain and flush more effectively at the end of the season?

  1. A larger fertilizer tank
  2. A longer sub-main
  3. A higher pump speed
  4. A flush manifold or end cap at the tail of the laterals Correct answer.

Explanation

A flush manifold or removable end cap at the tail of the laterals allows a high-velocity flush that carries out accumulated sediment. It also helps drain the lines. Tank size, sub-main length and pump speed do not provide a flushing path.

Question 40Micro Irrigation Systems: Components, Types and Layout

In a drip system, the term 'wetted bulb' refers to:

  1. the pressure gauge dial at the head
  2. the spherical filter element inside the screen housing
  3. the volume of soil wetted around a single emitter Correct answer.
  4. the air pocket trapped in the sub-main

Explanation

The wetted bulb is the zone of soil moistened by one emitter, whose shape and size depend on soil texture and emitter discharge. Overlapping bulbs along and between laterals give the required wetted root volume. It is not a filter part, gauge or air pocket.

Question 41Micro Irrigation Systems: Components, Types and Layout

A 1 ha field is to be irrigated with drip at a peak demand of 5 mm/day. The system can run 20 hours per day. What minimum system discharge is required?

  1. 10 L/s
  2. 5.0 L/s
  3. 0.7 L/s Correct answer.
  4. 2.5 L/s

Explanation

The daily volume is 5 mm times 10000 m², which is 50 m³ or 50000 L. Dividing by 20 hours gives 2500 L/h, which is about 0.7 L/s. This sets the minimum pump and mainline capacity.

Question 42Micro Irrigation Systems: Components, Types and Layout

Two drip blocks are fed from a common sub-main. Block A has laterals 80 m long and Block B has laterals 40 m long, both with the same emitter spacing and discharge. Which statement about pressure variation is most accurate?

  1. Block A will show greater pressure variation along its laterals than Block B Correct answer.
  2. Block B will show greater pressure variation along its laterals than Block A
  3. Pressure variation depends only on the emitter type, not on lateral length
  4. Both blocks will show identical pressure variation along their laterals

Explanation

Friction loss along a lateral increases with its length, so the longer laterals of Block A develop a larger pressure difference between inlet and tail. This can lower emission uniformity in Block A unless compensating emitters or shorter runs are used. Emitter type modifies but does not eliminate the length effect.

Question 43Micro Irrigation Systems: Components, Types and Layout

A grower plans to use a venturi injector for fertigation. Which installation condition is essential for it to work correctly?

  1. A pressure difference must exist between the injector inlet and outlet, usually created by a bypass valve Correct answer.
  2. The injector must be placed after the last emitter on the lateral
  3. The injector must be installed on the suction side of the pump with no bypass
  4. The injector must be buried below the water table

Explanation

A venturi injector draws fertilizer solution by creating a low-pressure zone in a converging-diverging throat. A pressure differential across the injector, normally produced by a bypass or booster, is required to drive the suction. It is installed at the head, not at lateral ends or underground.

Question 44Micro Irrigation Systems: Components, Types and Layout

In a drip layout, which combination best reduces the risk of emitter clogging from both inorganic and organic sources?

  1. A larger fertilizer tank with no filter
  2. A screen filter alone, cleaned weekly
  3. A pressure regulator alone at the head
  4. A sand separator followed by a screen or disc filter, with periodic flushing and chlorination Correct answer.

Explanation

A sand separator removes heavy inorganic particles, while a screen or disc filter catches finer material. Periodic flushing removes settled debris and chlorination controls biological growth. A single screen, a regulator alone or no filter cannot address both clogging sources.

Question 45Micro Irrigation Systems: Components, Types and Layout

In a micro irrigation system layout, the main line differs from the sub-main mainly because the main line:

  1. Runs along the crop row and carries only the flow of a single lateral
  2. Carries the total system flow from the source to the control head and on to the sub-mains Correct answer.
  3. Contains the emitters that deliver water directly to the root zone
  4. Is always buried below the plough layer to avoid damage

Explanation

The main line is the largest conduit in the network and conveys the full pumped or gravity flow from the water source through the head control unit towards the sub-mains. Sub-mains then divide this flow among the laterals, and the laterals carry the emitters that finally release water to the soil.

Question 46Micro Irrigation Systems: Components, Types and Layout

Which of the following is a recognized limitation of drip irrigation that a technician should explain to a farmer before layout is finalized?

  1. It cannot be used on soils with low water-holding capacity
  2. It requires a reliable supply of clean water because emitters clog easily Correct answer.
  3. It cannot be combined with fertilizer application through the system
  4. It wets the entire field surface, increasing evaporation losses

Explanation

Drip emitters have very small flow passages, so suspended silt, sand, precipitates and organic matter can block them; filtration and periodic flushing are therefore essential. This makes water quality and maintenance a central design constraint rather than an optional extra.

Question 47Micro Irrigation Systems: Components, Types and Layout

A drip block has laterals of 16 mm diameter laid on level ground with emitters of 4 L/h spaced 0.5 m apart. If the lateral is lengthened without changing diameter, emitter spacing or inlet pressure, what is the expected effect on emission uniformity along that lateral?

  1. Emission uniformity worsens because friction loss along the pipe increases Correct answer.
  2. Emission uniformity stays unchanged because the ground is level
  3. Emission uniformity becomes perfect because pressure regulators are not needed on level land
  4. Emission uniformity improves because more emitters share the flow

Explanation

Friction along a lateral causes the pressure to fall from the inlet towards the far end, and the emitter discharge varies with that pressure. Making the lateral longer raises total friction loss, so the difference between the first and last emitters grows and emission uniformity declines. This is why manufacturers publish a maximum recommended lateral length for each diameter and emitter spacing.

Question 48Micro Irrigation Systems: Components, Types and Layout

A technician is laying out a drip block on a field with a gentle continuous slope. Which practice best protects emission uniformity in such a layout?

  1. Place the sub-main along the contour and run laterals down the slope, keeping lateral lengths within the recommended limit Correct answer.
  2. Remove the pressure regulator so that gravity assists the flow down the slope
  3. Run all laterals straight up and down the slope so that elevation change adds to friction loss
  4. Increase emitter spacing on the lower side of the field to compensate for higher pressure

Explanation

Placing the sub-main along the contour and running laterals downslope means each lateral experiences the same elevation change, so blocks behave alike and can be managed together. Keeping lateral length within the manufacturer's limit for the diameter and slope prevents the combined effect of friction and elevation from exceeding the allowable pressure variation.

Question 49Micro Irrigation Systems: Components, Types and Layout

A 0.4 ha block is laid out with drip laterals spaced 1.0 m apart and emitters of 2 L/h spaced 0.5 m apart along each lateral. If the block runs 4 hours per day, what is the average depth of water applied per day?

  1. 8.0 mm
  2. 4.0 mm
  3. 2.0 mm
  4. 16.0 mm Correct answer.

Explanation

Each square metre of wetted area carries one lateral metre, which holds two emitters of 2 L/h, giving 4 L/h per metre of lateral. Over 4 hours that is 16 L per metre of lateral, and with 1 m lateral spacing this equals 16 L per square metre, that is 16 mm depth. The block area cancels out because the layout is uniform.

Question 50Drip Irrigation Design, Installation and Operation

In a drip irrigation system, what is the primary function of the filter unit installed at the headworks?

  1. To measure the total volume of water delivered to the field
  2. To remove suspended sand, silt and organic matter from the water before it reaches the emitters Correct answer.
  3. To inject fertilizer into the irrigation water at a controlled rate
  4. To increase the pressure of water entering the lateral lines

Explanation

The filter removes suspended particles such as sand, silt and algae so that fine emitter passages do not clog. Fertilizer injection and flow measurement are performed by separate components of the headworks, not by the filter itself.